Chapter: Neuroanatomy; Topic: Cranial Nerves; Subtopic: Trochlear Nerve and Its Anatomical Course
Key Definitions:
• Trochlear nerve (IV): The smallest cranial nerve that supplies the superior oblique muscle of the eye and is the only nerve to emerge dorsally from the brainstem.
• Intracranial course: The distance traveled by a cranial nerve within the cranial cavity before it exits through a foramen.
• Superior oblique muscle: An extraocular muscle responsible for depression and intorsion of the eyeball.
• Brainstem exit: The trochlear nerve uniquely emerges from the dorsal aspect of the midbrain and decussates completely before doing so.
Lead Question (NEET PG 2015):
1. The nerve which has the longest intracranial course is:
a) Fourth cranial nerve
b) Third cranial nerve
c) Sixth cranial nerve
d) Fifth cranial nerve
Answer: a) Fourth cranial nerve
Explanation: The trochlear nerve (cranial nerve IV) has the longest intracranial course among all cranial nerves. It arises from the dorsal aspect of the midbrain, decussates completely within the midbrain, and courses anteriorly around the brainstem to enter the cavernous sinus. It then enters the orbit through the superior orbital fissure to supply the superior oblique muscle. Despite being the thinnest cranial nerve, its long intracranial course makes it highly susceptible to trauma, especially in head injuries involving shearing forces.
Guessed Questions (Related to Trochlear and Other Cranial Nerves):
2. Which cranial nerve is the only one to emerge from the dorsal aspect of the brainstem?
a) Oculomotor nerve
b) Trochlear nerve
c) Abducent nerve
d) Optic nerve
Answer: b) Trochlear nerve
Explanation: The trochlear nerve is unique as it emerges dorsally from the midbrain, below the inferior colliculus. It completely decussates before exiting, supplying the contralateral superior oblique muscle.
3. Which cranial nerve has the longest extracranial course?
a) Facial nerve
b) Vagus nerve
c) Abducent nerve
d) Glossopharyngeal nerve
Answer: b) Vagus nerve
Explanation: The vagus nerve (cranial nerve X) has the longest extracranial course, extending from the medulla oblongata to the thoracic and abdominal organs, influencing heart rate, digestion, and respiratory function.
4. A lesion of the trochlear nerve leads to which of the following clinical features?
a) Diplopia on looking up
b) Diplopia on looking down and in
c) Loss of lateral gaze
d) Ptosis and mydriasis
Answer: b) Diplopia on looking down and in
Explanation: The trochlear nerve supplies the superior oblique muscle, which depresses and intorts the eyeball. Lesion results in vertical diplopia, especially noticeable when the patient looks down and in (e.g., reading or walking downstairs).
5. The trochlear nerve supplies which extraocular muscle?
a) Superior rectus
b) Inferior oblique
c) Superior oblique
d) Medial rectus
Answer: c) Superior oblique
Explanation: The trochlear nerve supplies only the superior oblique muscle, which acts to depress, abduct, and intort the eyeball, especially when the eye is adducted.
6. Which cranial nerve nucleus is located at the level of the inferior colliculus?
a) Oculomotor nucleus
b) Trochlear nucleus
c) Abducent nucleus
d) Facial nucleus
Answer: b) Trochlear nucleus
Explanation: The trochlear nucleus is situated in the midbrain at the level of the inferior colliculus. Fibers from this nucleus decussate in the midbrain before emerging dorsally to form the trochlear nerve.
7. A patient presents with head tilt to the opposite side and vertical diplopia. Which nerve is most likely affected?
a) Oculomotor nerve
b) Trochlear nerve
c) Abducent nerve
d) Trigeminal nerve
Answer: b) Trochlear nerve
Explanation: In trochlear nerve palsy, patients tilt their head to the side opposite the lesion to minimize diplopia caused by paralysis of the superior oblique muscle, which normally intorts the eye.
8. Which of the following cranial nerves decussates completely before emerging from the brainstem?
a) Optic nerve
b) Trochlear nerve
c) Abducent nerve
d) Facial nerve
Answer: b) Trochlear nerve
Explanation: The trochlear nerve is the only cranial nerve that undergoes complete decussation within the brainstem. Each trochlear nucleus supplies the contralateral superior oblique muscle.
9. Which nerve passes through the cavernous sinus along with the internal carotid artery?
a) Trochlear nerve
b) Abducent nerve
c) Optic nerve
d) Olfactory nerve
Answer: b) Abducent nerve
Explanation: The abducent nerve (VI) passes through the cavernous sinus close to the lateral wall of the internal carotid artery, making it vulnerable to injury in cavernous sinus thrombosis.
10. Which cranial nerve lesion produces both ptosis and mydriasis?
a) Trochlear nerve
b) Oculomotor nerve
c) Abducent nerve
d) Optic nerve
Answer: b) Oculomotor nerve
Explanation: The oculomotor nerve supplies the levator palpebrae superioris (eyelid elevation) and carries parasympathetic fibers to the sphincter pupillae. A lesion causes ptosis and pupil dilation (mydriasis).
11. The thinnest cranial nerve is:
a) Trochlear nerve
b) Oculomotor nerve
c) Abducent nerve
d) Optic nerve
Answer: a) Trochlear nerve
Explanation: The trochlear nerve is the smallest in diameter among cranial nerves but has the longest intracranial course. Despite its small size, it plays a crucial role in eye movement control, particularly in depression during adduction.
Chapter: Neuroanatomy; Topic: Cranial Nerves; Subtopic: Trigeminal Nerve – Anatomy and Functions
Key Definitions:
• Cranial nerves: Twelve pairs of nerves arising directly from the brain or brainstem, supplying structures of the head, neck, and thorax.
• Trigeminal nerve (V): The largest cranial nerve with both sensory and motor components, responsible for facial sensation and mastication.
• Gasserian (trigeminal) ganglion: A sensory ganglion located in Meckel’s cave, containing cell bodies of the trigeminal sensory neurons.
• Divisions of trigeminal nerve: Ophthalmic (V1), maxillary (V2), and mandibular (V3) divisions that transmit sensory information from face and oral cavity.
Lead Question (NEET PG 2015):
1. Largest cranial nerve is:
a) Trochlear
b) Trigeminal
c) Oculomotor
d) Vagus
Answer: b) Trigeminal
Explanation: The trigeminal nerve (cranial nerve V) is the largest of all cranial nerves. It is both sensory and motor in nature. The sensory root conveys sensation from the face, scalp, cornea, nasal and oral cavities, while the motor root supplies the muscles of mastication. It emerges from the pons as two roots — a large sensory and a smaller motor root. The trigeminal ganglion (Gasserian) lies in Meckel’s cave in the middle cranial fossa. Its extensive distribution explains its large size compared to other cranial nerves.
Guessed Questions (Related to Trigeminal Nerve and Cranial Nerves):
2. The trigeminal nerve is primarily responsible for which of the following functions?
a) Movement of the tongue
b) Facial sensation and mastication
c) Eye movement
d) Hearing
Answer: b) Facial sensation and mastication
Explanation: The trigeminal nerve carries sensory information from the face, scalp, and oral cavity, and motor fibers to muscles of mastication, such as masseter and temporalis, enabling chewing movements.
3. The sensory ganglion of the trigeminal nerve is located in:
a) Foramen ovale
b) Meckel’s cave
c) Cavernous sinus
d) Middle ear
Answer: b) Meckel’s cave
Explanation: The trigeminal (Gasserian) ganglion resides in a dural recess called Meckel’s cave, located in the middle cranial fossa near the apex of the petrous temporal bone, containing sensory neuron cell bodies.
4. Which branch of the trigeminal nerve has both sensory and motor components?
a) Ophthalmic
b) Maxillary
c) Mandibular
d) Zygomatic
Answer: c) Mandibular
Explanation: The mandibular division (V3) of the trigeminal nerve carries both sensory fibers (to lower face, jaw, and oral mucosa) and motor fibers to muscles of mastication and tensor tympani.
5. The sensory root of the trigeminal nerve originates from which part of the brainstem?
a) Midbrain
b) Pons
c) Medulla oblongata
d) Cerebellum
Answer: b) Pons
Explanation: The trigeminal nerve arises from the lateral aspect of the pons by a large sensory root and a small motor root. Its sensory fibers terminate in the trigeminal sensory nuclei extending through the brainstem.
6. A patient presents with loss of corneal reflex but normal vision. Which nerve is affected?
a) Optic nerve
b) Oculomotor nerve
c) Trigeminal nerve
d) Trochlear nerve
Answer: c) Trigeminal nerve
Explanation: The corneal reflex afferent limb is mediated by the ophthalmic division (V1) of the trigeminal nerve. Its loss indicates a lesion of V1 or its nucleus, even when vision remains intact.
7. Which of the following muscles is supplied by the mandibular division of the trigeminal nerve?
a) Orbicularis oculi
b) Masseter
c) Buccinator
d) Sternocleidomastoid
Answer: b) Masseter
Explanation: The mandibular nerve supplies muscles of mastication — masseter, temporalis, medial and lateral pterygoids — through its motor root, enabling closure and movement of the jaw.
8. The mandibular nerve exits the skull through which foramen?
a) Foramen rotundum
b) Foramen ovale
c) Foramen spinosum
d) Jugular foramen
Answer: b) Foramen ovale
Explanation: The mandibular division of the trigeminal nerve exits the cranial cavity via the foramen ovale in the sphenoid bone to enter the infratemporal fossa, where it branches extensively.
9. Which branch of the trigeminal nerve passes through the superior orbital fissure?
a) Ophthalmic
b) Maxillary
c) Mandibular
d) None
Answer: a) Ophthalmic
Explanation: The ophthalmic division (V1) of the trigeminal nerve traverses the superior orbital fissure to enter the orbit, supplying sensory innervation to the forehead, cornea, and upper eyelid.
10. In trigeminal neuralgia, pain is most commonly felt in which branch?
a) Ophthalmic
b) Maxillary
c) Mandibular
d) Maxillary and mandibular
Answer: d) Maxillary and mandibular
Explanation: Trigeminal neuralgia is characterized by intense, paroxysmal facial pain, commonly involving the maxillary (V2) and mandibular (V3) divisions due to compression or irritation of the trigeminal root.
11. A lesion in the mandibular nerve would result in which of the following clinical findings?
a) Loss of jaw jerk reflex
b) Ptosis
c) Loss of taste
d) Loss of hearing
Answer: a) Loss of jaw jerk reflex
Explanation: The jaw jerk reflex depends on the motor and sensory fibers of the mandibular nerve (V3). A lesion results in absence of this reflex and weakness of masticatory muscles on the affected side.
Chapter: Histology; Topic: Epithelium; Subtopic: Respiratory Epithelium of Nasopharynx
Key Definitions:
• Epithelium: A tissue composed of closely packed cells that form the covering of body surfaces and line internal cavities and organs.
• Ciliated columnar epithelium: A type of epithelial tissue with column-shaped cells bearing cilia, found in respiratory passages to move mucus and trapped particles.
• Nasopharynx: The upper part of the pharynx located behind the nasal cavity and above the soft palate, part of the respiratory tract.
• Respiratory epithelium: Pseudostratified ciliated columnar epithelium containing goblet cells for mucus secretion and airway protection.
Lead Question (NEET PG 2015):
1. Nasopharynx is lined by which epithelium?
a) Stratified squamous nonkeratinized
b) Stratified squamous keratinized
c) Ciliated columnar
d) Cuboidal
Answer: c) Ciliated columnar
Explanation: The nasopharynx is lined by pseudostratified ciliated columnar epithelium with goblet cells, also known as respiratory epithelium. This lining helps trap and transport dust particles and microorganisms through the coordinated beating of cilia, directing mucus toward the oropharynx. However, in areas exposed to greater mechanical stress (like the oropharynx), the lining transitions into stratified squamous nonkeratinized epithelium. The ciliated columnar epithelium of the nasopharynx is vital for maintaining clean and humidified air before it enters the lower respiratory tract.
Guessed Questions (Related to Nasopharynx and Epithelial Types):
2. The oropharynx is lined by which type of epithelium?
a) Ciliated columnar
b) Stratified squamous nonkeratinized
c) Simple cuboidal
d) Transitional
Answer: b) Stratified squamous nonkeratinized
Explanation: The oropharynx, subjected to friction from food passage, is lined by stratified squamous nonkeratinized epithelium, providing protection against mechanical wear during swallowing.
3. The laryngopharynx is continuous inferiorly with which structure?
a) Nasal cavity
b) Larynx
c) Esophagus
d) Trachea
Answer: c) Esophagus
Explanation: The laryngopharynx extends from the epiglottis to the cricoid cartilage, where it continues as the esophagus posteriorly and communicates with the larynx anteriorly for air passage.
4. Which type of epithelium lines the trachea?
a) Simple squamous
b) Pseudostratified ciliated columnar
c) Stratified squamous
d) Simple cuboidal
Answer: b) Pseudostratified ciliated columnar
Explanation: The trachea, like the nasopharynx, is lined by pseudostratified ciliated columnar epithelium containing goblet cells that secrete mucus, aiding in dust and microbe removal via the mucociliary escalator mechanism.
5. The olfactory region of the nasal cavity is lined by:
a) Stratified squamous
b) Pseudostratified columnar with sensory cells
c) Simple columnar
d) Transitional
Answer: b) Pseudostratified columnar with sensory cells
Explanation: The olfactory mucosa consists of pseudostratified columnar epithelium containing olfactory receptor neurons, supporting cells, and basal cells, specialized for smell perception.
6. In chronic smokers, the respiratory epithelium of the nasopharynx may undergo:
a) Hyperplasia
b) Dysplasia
c) Squamous metaplasia
d) Hypertrophy
Answer: c) Squamous metaplasia
Explanation: Chronic irritation from smoking can cause replacement of the normal ciliated columnar epithelium by stratified squamous epithelium — a protective adaptation called squamous metaplasia, reversible with cessation of insult.
7. The main function of the cilia in the nasopharyngeal epithelium is:
a) Humidification
b) Sound conduction
c) Mucus transport
d) Air filtration only
Answer: c) Mucus transport
Explanation: Cilia beat in a coordinated manner to move mucus loaded with dust and pathogens toward the pharynx, where it is swallowed, helping maintain respiratory hygiene and protection.
8. The eustachian tube opening in the nasopharynx is lined by:
a) Simple columnar
b) Ciliated columnar
c) Stratified squamous
d) Transitional
Answer: b) Ciliated columnar
Explanation: The pharyngeal opening of the eustachian tube in the nasopharynx is lined by ciliated columnar epithelium, facilitating air exchange between the nasopharynx and middle ear to equalize pressure.
9. A child presents with mouth breathing and recurrent ear infections. The cause is most likely hypertrophy of which structure?
a) Palatine tonsil
b) Pharyngeal tonsil
c) Lingual tonsil
d) Tubal tonsil
Answer: b) Pharyngeal tonsil
Explanation: Hypertrophy of the pharyngeal tonsil (adenoids) in the nasopharynx obstructs airflow and Eustachian tube openings, leading to mouth breathing and otitis media.
10. The epithelium of the nasopharynx transitions to stratified squamous at which level?
a) Soft palate
b) Nasal cavity
c) Laryngopharynx
d) Middle meatus
Answer: a) Soft palate
Explanation: At the level of the soft palate, where air and food pathways meet, the epithelium changes from respiratory (ciliated columnar) to stratified squamous to resist friction and mechanical stress.
11. Which structure is NOT lined by respiratory epithelium?
a) Nasopharynx
b) Trachea
c) Bronchi
d) Oropharynx
Answer: d) Oropharynx
Explanation: Unlike the nasopharynx and lower airways, the oropharynx is part of both respiratory and digestive tracts, hence lined by stratified squamous nonkeratinized epithelium to withstand food passage.
Chapter: Neuroanatomy; Topic: Cranial Nerves; Subtopic: Facial Nerve and Its Parasympathetic Branches
Key Definitions:
• Facial nerve (VII): A mixed cranial nerve with motor, sensory, and parasympathetic components that supplies muscles of facial expression, lacrimal glands, and salivary glands (except parotid).
• Geniculate ganglion: A sensory ganglion located at the sharp bend (genu) of the facial canal that gives rise to the greater petrosal nerve.
• Greater petrosal nerve: A branch of the facial nerve carrying preganglionic parasympathetic fibers to the pterygopalatine ganglion for lacrimal and nasal gland secretion.
• Pterygopalatine ganglion: A parasympathetic ganglion in the pterygopalatine fossa where fibers from the greater petrosal nerve synapse before supplying lacrimal and nasal glands.
Lead Question (NEET PG 2015):
1. Greater petrosal nerve is formed from?
a) Geniculate ganglion
b) Plexus around ICA
c) Plexus around middle meningeal artery
d) None of the above
Answer: a) Geniculate ganglion
Explanation: The greater petrosal nerve arises from the geniculate ganglion of the facial nerve within the facial canal. It carries preganglionic parasympathetic fibers originating from the superior salivatory nucleus. These fibers pass through the foramen lacerum, join with the deep petrosal nerve (sympathetic fibers) to form the nerve of the pterygoid canal (Vidian nerve), and reach the pterygopalatine ganglion. Postganglionic fibers then innervate the lacrimal gland and nasal mucosal glands. The geniculate ganglion, therefore, gives rise to this crucial branch involved in lacrimation and nasal secretion.
Guessed Questions (Related to Facial Nerve and Parasympathetic Pathways):
2. The greater petrosal nerve carries which type of fibers?
a) Somatic motor
b) Special sensory
c) Preganglionic parasympathetic
d) Postganglionic sympathetic
Answer: c) Preganglionic parasympathetic
Explanation: The greater petrosal nerve carries preganglionic parasympathetic fibers from the facial nerve to the pterygopalatine ganglion for lacrimal and nasal gland secretion, facilitating moisture of eye and nasal mucosa.
3. The deep petrosal nerve carries which type of fibers?
a) Sympathetic
b) Parasympathetic
c) Sensory
d) Motor
Answer: a) Sympathetic
Explanation: The deep petrosal nerve carries postganglionic sympathetic fibers from the internal carotid plexus. It joins the greater petrosal nerve to form the nerve of the pterygoid canal (Vidian nerve), influencing vasoconstriction in nasal mucosa.
4. The nerve of the pterygoid canal (Vidian nerve) is formed by the union of:
a) Lesser petrosal and auriculotemporal nerves
b) Greater petrosal and deep petrosal nerves
c) Chorda tympani and glossopharyngeal nerves
d) Lingual and maxillary nerves
Answer: b) Greater petrosal and deep petrosal nerves
Explanation: The Vidian nerve is formed by joining the greater petrosal (parasympathetic) and deep petrosal (sympathetic) nerves within the foramen lacerum, transmitting mixed autonomic fibers to the pterygopalatine ganglion.
5. Preganglionic parasympathetic fibers from the greater petrosal nerve synapse in which ganglion?
a) Otic ganglion
b) Submandibular ganglion
c) Pterygopalatine ganglion
d) Ciliary ganglion
Answer: c) Pterygopalatine ganglion
Explanation: The greater petrosal nerve synapses in the pterygopalatine ganglion, from which postganglionic fibers innervate the lacrimal gland and mucous glands of the nasal cavity and palate.
6. A lesion at the geniculate ganglion would result in loss of:
a) Taste sensation and lacrimation
b) Hearing
c) Salivation from parotid gland
d) Smell perception
Answer: a) Taste sensation and lacrimation
Explanation: The geniculate ganglion gives rise to both the greater petrosal nerve (for lacrimation) and chorda tympani (for taste). Damage at this level results in loss of taste from anterior tongue and dry eyes.
7. The lacrimal gland receives its secretomotor fibers via:
a) Auriculotemporal nerve
b) Zygomatic nerve
c) Maxillary nerve
d) All of the above
Answer: d) All of the above
Explanation: Postganglionic fibers from the pterygopalatine ganglion reach the lacrimal gland through branches of the maxillary and zygomatic nerves, finally joining the lacrimal branch of the ophthalmic nerve.
8. Which cranial nerve provides preganglionic fibers to the pterygopalatine ganglion?
a) Oculomotor nerve
b) Glossopharyngeal nerve
c) Facial nerve
d) Vagus nerve
Answer: c) Facial nerve
Explanation: The facial nerve provides preganglionic parasympathetic fibers to the pterygopalatine ganglion via its greater petrosal branch, mediating secretion from lacrimal and nasal glands.
9. A patient presents with dry eyes due to lack of tear secretion. The lesion is most likely in which nerve?
a) Greater petrosal nerve
b) Chorda tympani
c) Glossopharyngeal nerve
d) Deep petrosal nerve
Answer: a) Greater petrosal nerve
Explanation: The greater petrosal nerve provides parasympathetic supply to the lacrimal gland. Damage to it leads to decreased tear secretion and dryness of the conjunctiva (xerophthalmia).
10. The chorda tympani nerve joins which other nerve in the infratemporal fossa?
a) Auriculotemporal nerve
b) Lingual nerve
c) Inferior alveolar nerve
d) Buccal nerve
Answer: b) Lingual nerve
Explanation: The chorda tympani joins the lingual nerve in the infratemporal fossa to carry taste fibers from the anterior two-thirds of the tongue and parasympathetic fibers to the submandibular and sublingual glands.
11. The superior salivatory nucleus gives rise to parasympathetic fibers for which glands?
a) Parotid gland
b) Lacrimal, submandibular, and sublingual glands
c) Thyroid gland
d) Sebaceous glands
Answer: b) Lacrimal, submandibular, and sublingual glands
Explanation: The superior salivatory nucleus in the pons provides preganglionic parasympathetic fibers through the facial nerve to control secretions from lacrimal, submandibular, and sublingual glands.
Chapter: Neuroanatomy; Topic: Brain and Ventricular System; Subtopic: Third Ventricle and Its Embryological Derivation
Key Definitions:
• Ventricular system: A series of interconnected cavities within the brain filled with cerebrospinal fluid (CSF).
• Diencephalon: The part of the forebrain containing the thalamus, hypothalamus, epithalamus, and subthalamus; surrounds the third ventricle.
• Third ventricle: A midline cavity between the two halves of the diencephalon that communicates with the lateral ventricles and cerebral aqueduct.
• Cerebrospinal fluid (CSF): A clear fluid produced by the choroid plexuses that cushions the brain and spinal cord, circulating through the ventricles and subarachnoid space.
Lead Question (NEET PG 2015):
1. Third ventricle is the cavity of -
a) Mesencephalon
b) Rhombencephalon
c) Diencephalon
d) Telencephalon
Answer: c) Diencephalon
Explanation: The third ventricle is the cavity of the diencephalon. It lies in the midline between the two halves of the thalamus and hypothalamus. The lateral walls are formed by the thalami, the floor by the hypothalamus, and the roof by the tela choroidea. The third ventricle communicates with each lateral ventricle through the interventricular foramen (of Monro) and with the fourth ventricle via the cerebral aqueduct. It plays an essential role in CSF circulation and acts as a narrow passage connecting higher and lower brain centers.
Guessed Questions (Related to Brain Ventricles and Embryology):
2. The lateral ventricles are cavities of which part of the brain?
a) Telencephalon
b) Diencephalon
c) Mesencephalon
d) Rhombencephalon
Answer: a) Telencephalon
Explanation: The lateral ventricles are paired cavities within the cerebral hemispheres (telencephalon). They communicate with the third ventricle through the interventricular foramina (of Monro) and contain choroid plexuses that secrete CSF.
3. The fourth ventricle is the cavity of which embryonic structure?
a) Mesencephalon
b) Rhombencephalon
c) Diencephalon
d) Telencephalon
Answer: b) Rhombencephalon
Explanation: The fourth ventricle develops from the rhombencephalon (hindbrain) and lies between the pons and medulla anteriorly and the cerebellum posteriorly. It communicates with the subarachnoid space via the foramina of Luschka and Magendie.
4. The cerebral aqueduct connects which two ventricles?
a) Lateral and third ventricles
b) Third and fourth ventricles
c) Fourth ventricle and central canal
d) Lateral ventricles
Answer: b) Third and fourth ventricles
Explanation: The cerebral aqueduct (aqueduct of Sylvius), located in the midbrain, connects the third ventricle of the diencephalon to the fourth ventricle of the hindbrain, allowing CSF to flow downward.
5. The choroid plexus of the third ventricle is formed by:
a) Pia mater and ependyma
b) Arachnoid mater and dura mater
c) Ependyma only
d) Pia mater only
Answer: a) Pia mater and ependyma
Explanation: The choroid plexus is a vascular structure formed by invagination of pia mater covered by ependymal cells. It secretes CSF into the ventricles, maintaining intracranial pressure and nutrient balance.
6. Obstruction of the cerebral aqueduct results in which condition?
a) Communicating hydrocephalus
b) Non-communicating hydrocephalus
c) Subdural effusion
d) CSF leak
Answer: b) Non-communicating hydrocephalus
Explanation: Obstruction of the cerebral aqueduct prevents CSF drainage from the third to fourth ventricle, leading to enlargement of lateral and third ventricles — a form of non-communicating (obstructive) hydrocephalus.
7. The floor of the third ventricle is formed by:
a) Thalamus
b) Hypothalamus
c) Epithalamus
d) Corpus callosum
Answer: b) Hypothalamus
Explanation: The hypothalamus forms the floor and lower part of the lateral walls of the third ventricle, containing important structures like the optic chiasma, tuber cinereum, and mammillary bodies.
8. A lesion causing blockage of the foramina of Luschka and Magendie would lead to accumulation of CSF in:
a) Third ventricle only
b) Fourth ventricle
c) Subarachnoid space
d) Spinal canal only
Answer: b) Fourth ventricle
Explanation: Blockage of the foramina of Luschka and Magendie prevents CSF outflow from the fourth ventricle into the subarachnoid space, leading to dilation of the fourth ventricle and raised intracranial pressure.
9. Which part of the brain surrounds the lateral walls of the third ventricle?
a) Midbrain
b) Thalamus
c) Pons
d) Cerebellum
Answer: b) Thalamus
Explanation: The thalamus forms the lateral walls of the third ventricle, serving as a major relay station for sensory and motor pathways and enclosing the midline cavity of the diencephalon.
10. The central canal of the spinal cord is a continuation of which ventricular structure?
a) Third ventricle
b) Fourth ventricle
c) Lateral ventricle
d) Cerebral aqueduct
Answer: b) Fourth ventricle
Explanation: The central canal of the spinal cord continues downward from the fourth ventricle and carries CSF through the spinal cord, maintaining communication between the cranial and spinal compartments.
11. In a case of pineal tumor, obstruction of the aqueduct of Sylvius can cause dilation of which ventricle?
a) Fourth ventricle
b) Third and lateral ventricles
c) Only third ventricle
d) Lateral ventricles only
Answer: b) Third and lateral ventricles
Explanation: Pineal tumors compress the cerebral aqueduct, blocking CSF flow from the third to fourth ventricle. This causes accumulation and dilation of the third and both lateral ventricles, leading to obstructive hydrocephalus.
Chapter: Neuroanatomy; Topic: Cranial Nerve Nuclei; Subtopic: Oculomotor Nucleus and Its Location
Key Definitions:
• Oculomotor nerve (III): The third cranial nerve, responsible for most of the eye movements, eyelid elevation, and pupillary constriction.
• Oculomotor nucleus: The motor nucleus located in the midbrain that gives rise to the somatic motor fibers of the oculomotor nerve.
• Edinger–Westphal nucleus: The parasympathetic nucleus associated with the oculomotor nerve, controlling pupillary constriction and accommodation.
• Midbrain: The uppermost part of the brainstem containing nuclei for cranial nerves III and IV and serving as a pathway for motor and sensory tracts.
Lead Question (NEET PG 2015):
1. Oculomotor nucleus is located in -
a) Forebrain
b) Midbrain
c) Pons
d) Medulla
Answer: b) Midbrain
Explanation: The oculomotor nucleus is located in the midbrain at the level of the superior colliculus, near the midline, anterior to the cerebral aqueduct. It gives rise to fibers that form the oculomotor nerve, which exits the brainstem through the interpeduncular fossa. The associated Edinger–Westphal nucleus provides parasympathetic fibers to the sphincter pupillae and ciliary muscle. Together, these nuclei coordinate eye movements, eyelid elevation, and pupillary constriction, essential for visual focus and light reflexes.
Guessed Questions (Related to Oculomotor Nerve and Brainstem Nuclei):
2. The Edinger–Westphal nucleus is responsible for which of the following functions?
a) Eye abduction
b) Pupillary constriction
c) Eye depression
d) Eye elevation
Answer: b) Pupillary constriction
Explanation: The Edinger–Westphal nucleus provides preganglionic parasympathetic fibers that travel via the oculomotor nerve to the ciliary ganglion, which in turn innervates the sphincter pupillae for pupillary constriction.
3. The oculomotor nerve exits the brainstem through which area?
a) Pons
b) Interpeduncular fossa
c) Olive of medulla
d) Middle cerebellar peduncle
Answer: b) Interpeduncular fossa
Explanation: The oculomotor nerve emerges on the ventral aspect of the midbrain from the interpeduncular fossa, located between the cerebral peduncles, before entering the cavernous sinus and orbit.
4. A lesion in the oculomotor nerve results in which clinical feature?
a) Ptosis, mydriasis, and eye deviation down and out
b) Miosis, enophthalmos, and anhidrosis
c) Loss of corneal reflex
d) Nystagmus
Answer: a) Ptosis, mydriasis, and eye deviation down and out
Explanation: Oculomotor nerve palsy leads to paralysis of most extraocular muscles (except lateral rectus and superior oblique), causing the eye to deviate downward and outward, along with ptosis and a dilated pupil.
5. Which of the following cranial nerves emerges from the dorsal aspect of the brainstem?
a) Oculomotor nerve
b) Trochlear nerve
c) Abducent nerve
d) Trigeminal nerve
Answer: b) Trochlear nerve
Explanation: The trochlear nerve (cranial nerve IV) is the only cranial nerve to emerge dorsally from the brainstem, specifically from the dorsal midbrain below the inferior colliculus.
6. The oculomotor nerve supplies all extraocular muscles except:
a) Superior rectus
b) Lateral rectus
c) Inferior rectus
d) Medial rectus
Answer: b) Lateral rectus
Explanation: The oculomotor nerve innervates superior rectus, inferior rectus, medial rectus, and inferior oblique muscles. The lateral rectus is supplied by the abducent nerve (VI).
7. The oculomotor nerve nucleus lies at the level of which structure?
a) Superior colliculus
b) Inferior colliculus
c) Pons
d) Medulla oblongata
Answer: a) Superior colliculus
Explanation: The oculomotor nucleus lies in the midbrain at the level of the superior colliculus, adjacent to the midline, and anterior to the cerebral aqueduct.
8. Compression of the oculomotor nerve due to posterior communicating artery aneurysm leads to:
a) Miosis and enophthalmos
b) Ptosis and mydriasis
c) Diplopia only
d) Loss of corneal reflex
Answer: b) Ptosis and mydriasis
Explanation: Aneurysm of the posterior communicating artery compresses the oculomotor nerve, affecting parasympathetic fibers and causing pupillary dilation (mydriasis) and eyelid drooping (ptosis).
9. Which nucleus is involved in the accommodation reflex of the eye?
a) Oculomotor nucleus
b) Edinger–Westphal nucleus
c) Abducent nucleus
d) Trochlear nucleus
Answer: b) Edinger–Westphal nucleus
Explanation: The Edinger–Westphal nucleus mediates the parasympathetic component of the accommodation reflex by controlling ciliary muscle contraction and pupillary constriction for near vision.
10. A lesion in the midbrain affecting the oculomotor nucleus results in:
a) Contralateral lateral rectus paralysis
b) Ipsilateral oculomotor palsy
c) Bilateral visual loss
d) Horner’s syndrome
Answer: b) Ipsilateral oculomotor palsy
Explanation: A lesion involving the oculomotor nucleus or its fibers in the midbrain produces ipsilateral paralysis of the extraocular muscles supplied by CN III and loss of parasympathetic control to the pupil.
11. The parasympathetic fibers of the oculomotor nerve synapse in which ganglion?
a) Pterygopalatine ganglion
b) Otic ganglion
c) Submandibular ganglion
d) Ciliary ganglion
Answer: d) Ciliary ganglion
Explanation: The Edinger–Westphal nucleus sends preganglionic fibers via the oculomotor nerve to the ciliary ganglion, where they synapse before supplying the sphincter pupillae and ciliary muscle.
Chapter: Neuroanatomy; Topic: Cranial Nerves; Subtopic: Functional Classification of Cranial Nerves
Key Definitions:
• Sensory nerve: A nerve that carries afferent fibers transmitting impulses from sensory receptors toward the central nervous system.
• Motor nerve: A nerve that carries efferent fibers responsible for stimulating muscles and glands.
• Mixed nerve: A nerve containing both sensory and motor fibers, performing dual functions such as sensation and movement.
• Olfactory nerve (CN I): A pure sensory cranial nerve responsible for the sense of smell, composed of specialized bipolar neurons.
Lead Question (NEET PG 2015):
1. Which of the following is pure sensory nerve?
a) Trigeminal
b) Abducent
c) Trochlear
d) Olfactory
Answer: d) Olfactory
Explanation: The olfactory nerve (cranial nerve I) is a pure sensory nerve that carries impulses for the sense of smell. It consists of bipolar sensory neurons whose axons pass through the cribriform plate of the ethmoid bone to reach the olfactory bulb. From there, secondary neurons transmit signals to the olfactory cortex in the temporal lobe. In contrast, the trigeminal nerve is mixed, while the abducent and trochlear nerves are purely motor. The olfactory nerve’s sensory fibers are unique because they regenerate throughout life, unlike most other central nervous system neurons.
Guessed Questions (Related to Cranial Nerves):
2. Which of the following cranial nerves is purely motor?
a) Facial nerve
b) Oculomotor nerve
c) Abducent nerve
d) Trigeminal nerve
Answer: c) Abducent nerve
Explanation: The abducent nerve (cranial nerve VI) is a purely motor nerve that supplies the lateral rectus muscle, responsible for abducting the eye. Lesions lead to medial deviation (strabismus) and diplopia on lateral gaze.
3. Which of the following cranial nerves is mixed in function?
a) Glossopharyngeal nerve
b) Optic nerve
c) Trochlear nerve
d) Abducent nerve
Answer: a) Glossopharyngeal nerve
Explanation: The glossopharyngeal nerve (cranial nerve IX) carries both sensory and motor fibers — providing taste from the posterior third of the tongue, parasympathetic fibers to the parotid gland, and motor fibers to the stylopharyngeus muscle.
4. The optic nerve is a continuation of which structure embryologically?
a) Retina
b) Thalamus
c) Diencephalon
d) Cerebellum
Answer: c) Diencephalon
Explanation: The optic nerve is an outgrowth of the diencephalon and is covered by meninges. It transmits visual information from the retina to the lateral geniculate body in the thalamus.
5. Which cranial nerve does not arise from the brainstem?
a) Optic nerve
b) Trochlear nerve
c) Abducent nerve
d) Trigeminal nerve
Answer: a) Optic nerve
Explanation: The optic nerve originates from the diencephalon, not the brainstem. It is part of the central nervous system and carries visual impulses from retinal ganglion cells to the thalamus.
6. The sense of taste from the anterior two-thirds of the tongue is carried by which nerve?
a) Glossopharyngeal nerve
b) Facial nerve
c) Trigeminal nerve
d) Vagus nerve
Answer: b) Facial nerve
Explanation: The chorda tympani branch of the facial nerve carries special visceral afferent fibers for taste sensation from the anterior two-thirds of the tongue, synapsing in the nucleus tractus solitarius.
7. Damage to the abducent nerve results in which clinical manifestation?
a) Inability to move the eye laterally
b) Ptosis
c) Dilated pupil
d) Diplopia on upward gaze
Answer: a) Inability to move the eye laterally
Explanation: The abducent nerve supplies the lateral rectus muscle. Its palsy results in inability to abduct the eye, leading to convergent strabismus and diplopia during lateral gaze.
8. The trochlear nerve supplies which muscle of the eye?
a) Superior rectus
b) Superior oblique
c) Inferior rectus
d) Lateral rectus
Answer: b) Superior oblique
Explanation: The trochlear nerve (cranial nerve IV) is a pure motor nerve that supplies the superior oblique muscle, which depresses and intorts the eyeball when the eye is adducted.
9. Loss of smell (anosmia) occurs due to lesion in which nerve?
a) Optic nerve
b) Oculomotor nerve
c) Olfactory nerve
d) Trigeminal nerve
Answer: c) Olfactory nerve
Explanation: Damage to the olfactory nerve fibers or olfactory bulb can result in anosmia, often due to head trauma causing fracture of the cribriform plate or neurodegenerative conditions like Parkinson’s disease.
10. Which cranial nerve passes through the superior orbital fissure?
a) Olfactory nerve
b) Trochlear nerve
c) Optic nerve
d) Facial nerve
Answer: b) Trochlear nerve
Explanation: The trochlear nerve enters the orbit via the superior orbital fissure along with the oculomotor, abducent, and ophthalmic division of the trigeminal nerve to supply the superior oblique muscle.
11. A patient presents with loss of corneal sensation but normal blink reflex. Which nerve is affected?
a) Ophthalmic division of trigeminal
b) Facial nerve
c) Trochlear nerve
d) Abducent nerve
Answer: a) Ophthalmic division of trigeminal
Explanation: The ophthalmic division (V1) of the trigeminal nerve provides sensory fibers to the cornea. Its lesion causes loss of corneal sensation, while the blink reflex remains intact if the facial nerve (motor limb) is functional.
Chapter: Neuroanatomy; Topic: Venous Drainage of Brain; Subtopic: Great Cerebral Vein of Galen and Its Connections
Key Definitions:
• Great cerebral vein of Galen: A short midline vein formed by the union of two internal cerebral veins beneath the splenium of the corpus callosum that drains deep structures of the brain.
• Internal cerebral veins: Paired veins that drain deep cerebral structures including thalamus, caudate nucleus, and choroid plexus, joining to form the great cerebral vein.
• Straight sinus: A dural venous sinus formed by the union of the inferior sagittal sinus and the great cerebral vein, draining into the confluence of sinuses.
• Venous sinuses: Endothelial-lined spaces between layers of the dura mater that collect venous blood from the brain and drain into the internal jugular veins.
Lead Question (NEET PG 2015):
1. Great cerebral vein of Galen drains into -
a) Cavernous sinus
b) Basal vein
c) Internal cerebral vein
d) Straight sinus
Answer: d) Straight sinus
Explanation: The great cerebral vein of Galen is a short median vein formed by the union of the two internal cerebral veins beneath the splenium of the corpus callosum. It courses posteriorly to join the inferior sagittal sinus, forming the straight sinus. The straight sinus continues posteriorly to drain into the confluence of sinuses. The great vein drains deep structures of the cerebrum, such as thalami, basal ganglia, and deep white matter. Its blockage may cause venous congestion, hydrocephalus, or intracranial hypertension, particularly in neonates with vein of Galen malformations.
Guessed Questions (Related to Venous Drainage of Brain):
2. The internal cerebral veins are formed by the union of:
a) Thalamostriate and choroidal veins
b) Superior cerebral and inferior sagittal veins
c) Great cerebral and basal veins
d) Transverse and cavernous sinuses
Answer: a) Thalamostriate and choroidal veins
Explanation: Each internal cerebral vein is formed by the union of the thalamostriate vein and the choroidal vein near the interventricular foramen. These veins drain the thalamus, caudate nucleus, and choroid plexus before joining to form the great cerebral vein.
3. The straight sinus is formed by the union of:
a) Superior sagittal and transverse sinuses
b) Inferior sagittal sinus and great cerebral vein
c) Cavernous and petrosal sinuses
d) Sigmoid and occipital sinuses
Answer: b) Inferior sagittal sinus and great cerebral vein
Explanation: The straight sinus runs along the junction of the falx cerebri and tentorium cerebelli. It is formed by the union of the inferior sagittal sinus and the great cerebral vein, draining into the confluence of sinuses.
4. The basal vein of Rosenthal drains into which venous structure?
a) Cavernous sinus
b) Straight sinus
c) Great cerebral vein
d) Transverse sinus
Answer: c) Great cerebral vein
Explanation: The basal vein of Rosenthal, formed by the union of deep middle cerebral and anterior cerebral veins, drains the medial temporal lobe and basal forebrain structures and empties into the great cerebral vein of Galen.
5. A newborn with a vein of Galen malformation presents with heart failure. The underlying cause is:
a) Arteriovenous shunt increasing venous return
b) Obstruction of venous drainage
c) Thrombosis of superior sagittal sinus
d) Malformation of choroid plexus
Answer: a) Arteriovenous shunt increasing venous return
Explanation: Vein of Galen malformation is an arteriovenous fistula between cerebral arteries and the median prosencephalic vein, leading to increased venous return, high-output cardiac failure, and hydrocephalus in infants.
6. The superior sagittal sinus drains primarily into which sinus?
a) Sigmoid sinus
b) Straight sinus
c) Right transverse sinus
d) Cavernous sinus
Answer: c) Right transverse sinus
Explanation: The superior sagittal sinus drains posteriorly into the right transverse sinus at the confluence of sinuses, carrying venous blood from the superior cerebral veins and meninges.
7. The confluence of sinuses receives blood from all of the following except:
a) Superior sagittal sinus
b) Straight sinus
c) Transverse sinus
d) Cavernous sinus
Answer: d) Cavernous sinus
Explanation: The cavernous sinus does not drain into the confluence of sinuses. It drains via the superior and inferior petrosal sinuses into the sigmoid sinus and internal jugular vein.
8. In which dural fold is the straight sinus located?
a) Falx cerebri
b) Tentorium cerebelli
c) Falx cerebelli
d) Diaphragma sellae
Answer: b) Tentorium cerebelli
Explanation: The straight sinus lies at the junction of the falx cerebri and tentorium cerebelli. It drains posteriorly into the confluence of sinuses, conveying blood from deep cerebral structures.
9. The cavernous sinus receives blood directly from which vein?
a) Superior ophthalmic vein
b) Great cerebral vein
c) Straight sinus
d) Inferior sagittal sinus
Answer: a) Superior ophthalmic vein
Explanation: The superior ophthalmic vein drains blood from the orbit and communicates with the cavernous sinus, providing a route for infections to spread from the face or orbit to intracranial structures.
10. Obstruction of the straight sinus will primarily affect venous drainage from:
a) Cerebral cortex
b) Deep structures of brain
c) Orbit
d) Cerebellum only
Answer: b) Deep structures of brain
Explanation: The straight sinus receives blood from the great cerebral vein, which drains deep brain regions such as the thalamus, basal ganglia, and internal capsule. Its blockage leads to deep venous congestion and intracranial hypertension.
11. The internal cerebral veins drain which of the following structures?
a) Thalamus and caudate nucleus
b) Cerebral cortex
c) Cerebellum
d) Pons
Answer: a) Thalamus and caudate nucleus
Explanation: The internal cerebral veins drain deep gray matter structures, including the thalamus and caudate nucleus, as well as parts of the choroid plexus, converging posteriorly to form the great cerebral vein of Galen.
Chapter: Neuroanatomy; Topic: Venous Drainage of Brain; Subtopic: Superficial and Deep Cerebral Veins
Key Definitions:
• Superficial middle cerebral vein: A prominent vein on the lateral surface of the brain that drains the lateral aspect of the cerebral hemispheres into the cavernous sinus or sphenoparietal sinus.
• Cavernous sinus: A paired dural venous sinus located on either side of the sella turcica that receives venous blood from the orbit and superficial brain veins.
• Internal cerebral vein: A deep cerebral vein formed by the union of thalamostriate and choroidal veins that drains deep brain structures.
• Venous sinuses: Channels between the layers of the dura mater that collect venous blood from the brain and drain into the internal jugular veins.
Lead Question (NEET PG 2015):
1. Superficial middle cerebral vein drains into -
a) Internal cerebral vein
b) Cavernous sinus
c) Great cerebral vein of Galen
d) Straight sinus
Answer: b) Cavernous sinus
Explanation: The superficial middle cerebral vein runs along the lateral sulcus, draining blood from the lateral surface of the cerebral hemispheres. It usually empties into the cavernous sinus either directly or through the sphenoparietal sinus. Occasionally, it communicates with the superior sagittal sinus through the superior anastomotic vein (of Trolard) and with the transverse sinus through the inferior anastomotic vein (of Labbé). This venous network provides important collateral drainage pathways that protect against venous obstruction or increased intracranial pressure.
Guessed Questions (Related to Cerebral Venous Drainage):
2. The superior sagittal sinus drains primarily into which sinus?
a) Left transverse sinus
b) Right transverse sinus
c) Cavernous sinus
d) Sigmoid sinus
Answer: b) Right transverse sinus
Explanation: The superior sagittal sinus runs along the superior margin of the falx cerebri and usually drains posteriorly into the right transverse sinus, carrying venous blood from the cerebral cortex and meninges.
3. The great cerebral vein of Galen drains into which structure?
a) Inferior sagittal sinus
b) Straight sinus
c) Cavernous sinus
d) Sigmoid sinus
Answer: b) Straight sinus
Explanation: The great cerebral vein of Galen is formed by the union of the two internal cerebral veins and drains into the straight sinus, which continues posteriorly to the confluence of sinuses.
4. The inferior sagittal sinus joins with which vein to form the straight sinus?
a) Internal cerebral vein
b) Great cerebral vein of Galen
c) Superficial middle cerebral vein
d) Basal vein
Answer: b) Great cerebral vein of Galen
Explanation: The straight sinus is formed by the union of the inferior sagittal sinus and the great cerebral vein. It lies at the junction of the falx cerebri and tentorium cerebelli and drains deep cerebral venous blood.
5. The superior anastomotic vein (of Trolard) connects which two venous sinuses?
a) Cavernous and straight sinuses
b) Superior sagittal and superficial middle cerebral veins
c) Transverse and sigmoid sinuses
d) Inferior sagittal and occipital sinuses
Answer: b) Superior sagittal and superficial middle cerebral veins
Explanation: The vein of Trolard serves as a major communicating channel between the superficial middle cerebral vein and the superior sagittal sinus, assisting in collateral venous drainage of the cerebral cortex.
6. The inferior anastomotic vein (of Labbé) connects which venous structures?
a) Superficial middle cerebral vein and transverse sinus
b) Superior sagittal and straight sinuses
c) Cavernous and sigmoid sinuses
d) Internal cerebral vein and great vein of Galen
Answer: a) Superficial middle cerebral vein and transverse sinus
Explanation: The vein of Labbé connects the superficial middle cerebral vein to the transverse sinus, providing an alternate route for venous drainage from the lateral surface of the brain.
7. The cavernous sinus receives blood from all of the following except:
a) Superior ophthalmic vein
b) Superficial middle cerebral vein
c) Inferior petrosal sinus
d) Sphenoparietal sinus
Answer: c) Inferior petrosal sinus
Explanation: The inferior petrosal sinus drains the cavernous sinus into the internal jugular vein. It does not drain into it. The cavernous sinus receives blood from ophthalmic veins, superficial middle cerebral, and sphenoparietal sinuses.
8. The basal vein of Rosenthal drains into which vein?
a) Superior sagittal sinus
b) Cavernous sinus
c) Great cerebral vein of Galen
d) Straight sinus
Answer: c) Great cerebral vein of Galen
Explanation: The basal vein of Rosenthal drains deep cerebral structures including the medial temporal lobe and basal forebrain, joining the great cerebral vein before entering the straight sinus.
9. A thrombosis in the cavernous sinus may affect which cranial nerve first?
a) Optic nerve
b) Abducent nerve
c) Facial nerve
d) Hypoglossal nerve
Answer: b) Abducent nerve
Explanation: The abducent nerve (cranial nerve VI) lies freely within the cavernous sinus, close to the internal carotid artery, making it most vulnerable to compression or thrombosis of the sinus.
10. The vein of Galen malformation in infants can cause which of the following clinical findings?
a) Hydrocephalus
b) Cerebral ischemia
c) Hemianopia
d) Cerebellar ataxia
Answer: a) Hydrocephalus
Explanation: A vein of Galen malformation is a congenital arteriovenous communication that causes increased venous pressure and hydrocephalus due to impaired CSF absorption and high-output cardiac failure.
11. The internal cerebral vein is formed by the union of which two veins?
a) Thalamostriate and choroidal veins
b) Great cerebral and basal veins
c) Superior and inferior sagittal sinuses
d) Superficial middle and sphenoparietal veins
Answer: a) Thalamostriate and choroidal veins
Explanation: The internal cerebral vein is formed near the interventricular foramen by the joining of the thalamostriate and choroidal veins, which drain deep structures like the thalamus and caudate nucleus.
Chapter: Neuroanatomy; Topic: Cerebral Circulation; Subtopic: Blood Supply of Cerebral Hemispheres
Key Definitions:
• Cerebral hemisphere: The largest part of the brain divided into right and left halves, responsible for higher cognitive and motor functions.
• Anterior cerebral artery (ACA): A branch of the internal carotid artery supplying the medial surfaces of the frontal and parietal lobes.
• Middle cerebral artery (MCA): The largest branch of the internal carotid artery supplying the lateral surfaces of the cerebral hemispheres.
• Posterior cerebral artery (PCA): A branch of the basilar artery supplying the occipital lobe and inferomedial temporal lobe.
Lead Question (NEET PG 2015):
1. Major supply of medial surface of cerebral hemisphere:
a) Anterior cerebral artery
b) Posterior cerebral artery
c) Middle cerebral artery
d) Posterior inferior cerebellar artery
Answer: a) Anterior cerebral artery
Explanation: The anterior cerebral artery (ACA) primarily supplies the medial surface of the cerebral hemisphere, particularly the medial frontal and parietal lobes. It provides branches to the leg and foot areas of the motor and sensory cortices through the paracentral lobule. The ACA runs in the longitudinal fissure, anastomosing with its counterpart via the anterior communicating artery. Lesions of the ACA result in contralateral weakness and sensory loss predominantly affecting the lower limb, due to the topographic arrangement of the motor cortex (homunculus pattern).
Guessed Questions (Related to Cerebral Arterial Supply):
2. The lateral surface of the cerebral hemisphere is mainly supplied by:
a) Anterior cerebral artery
b) Middle cerebral artery
c) Posterior cerebral artery
d) Basilar artery
Answer: b) Middle cerebral artery
Explanation: The middle cerebral artery supplies the lateral convexity of the cerebral hemisphere, including areas for speech, upper limb, and face motor control. Occlusion causes contralateral hemiplegia affecting face and arm more than leg.
3. The visual cortex is supplied by which artery?
a) Middle cerebral artery
b) Posterior cerebral artery
c) Anterior cerebral artery
d) Basilar artery
Answer: b) Posterior cerebral artery
Explanation: The visual cortex in the occipital lobe receives blood from the posterior cerebral artery. Infarction leads to contralateral homonymous hemianopia with macular sparing if the macular region has collateral MCA supply.
4. Occlusion of the anterior cerebral artery causes weakness primarily in:
a) Contralateral upper limb
b) Contralateral lower limb
c) Ipsilateral lower limb
d) Face and tongue
Answer: b) Contralateral lower limb
Explanation: The ACA supplies the paracentral lobule, which controls motor and sensory functions of the lower limb. Occlusion results in contralateral paralysis and sensory loss mainly affecting the leg.
5. The artery supplying Broca’s and Wernicke’s areas is:
a) Anterior cerebral artery
b) Middle cerebral artery
c) Posterior cerebral artery
d) Internal carotid artery
Answer: b) Middle cerebral artery
Explanation: Broca’s and Wernicke’s speech areas are located on the lateral surface of the left hemisphere, supplied by the superior and inferior divisions of the middle cerebral artery, respectively. MCA stroke may cause aphasia.
6. The posterior cerebral artery is a branch of:
a) Internal carotid artery
b) Basilar artery
c) Middle cerebral artery
d) Vertebral artery
Answer: b) Basilar artery
Explanation: The posterior cerebral artery arises from the terminal bifurcation of the basilar artery. It supplies the occipital lobe, inferomedial temporal lobe, and thalamus through perforating branches.
7. A patient with right middle cerebral artery occlusion will present with:
a) Left-sided leg weakness
b) Left-sided face and arm weakness
c) Bilateral visual loss
d) Right-sided sensory loss
Answer: b) Left-sided face and arm weakness
Explanation: The MCA supplies the motor and sensory cortices for the face and upper limb. Contralateral weakness and sensory loss of these regions are classic features of MCA stroke.
8. The circle of Willis connects which arterial systems?
a) Internal carotid and vertebrobasilar systems
b) External carotid and vertebral systems
c) Jugular and vertebral systems
d) Dural sinuses and carotid system
Answer: a) Internal carotid and vertebrobasilar systems
Explanation: The circle of Willis provides an anastomotic connection between the carotid and vertebrobasilar circulations, ensuring collateral flow to cerebral tissue in case of vessel occlusion.
9. The paracentral lobule is mainly supplied by:
a) Anterior cerebral artery
b) Posterior cerebral artery
c) Middle cerebral artery
d) Basilar artery
Answer: a) Anterior cerebral artery
Explanation: The paracentral lobule lies on the medial surface of the hemisphere, supplied by the ACA. It represents the motor and sensory cortical areas for the lower limb in the somatotopic map.
10. Which artery supplies the thalamus?
a) Anterior cerebral artery
b) Posterior cerebral artery
c) Middle cerebral artery
d) Vertebral artery
Answer: b) Posterior cerebral artery
Explanation: The thalamus receives its arterial supply mainly from perforating branches of the posterior cerebral artery (PCA) and posterior communicating artery, which form part of the circle of Willis.
11. A lesion of the posterior cerebral artery typically causes which visual defect?
a) Bitemporal hemianopia
b) Contralateral homonymous hemianopia
c) Monocular blindness
d) Quadrantanopia
Answer: b) Contralateral homonymous hemianopia
Explanation: Damage to the visual cortex in the occipital lobe supplied by the posterior cerebral artery leads to contralateral homonymous hemianopia, often with macular sparing due to collateral MCA supply.