Chapter: Neurophysiology
Topic: Nerve Action Potentials & Nerve Conduction
Subtopic: Compound (Biphasic) Action Potential of Mixed Nerve
Keyword Definitions
Compound action potential (CAP) — Sum of many axons firing; extracellular recording from a mixed nerve; amplitude is graded.
Biphasic recording — Surface electrodes record a negative then positive deflection as the wave passes between and beyond them.
Monophasic recording — One electrode over injured/isoelectric region and one active; produces single main deflection.
All-or-none law — Property of single axons and muscle fibers; not of CAP, which is graded with recruitment.
Refractory period — Time after an AP when axons cannot (absolute) or need stronger stimuli (relative) to fire.
Mixed nerve — Contains myelinated and unmyelinated, motor and sensory fibers with different velocities and thresholds.
Recruitment — Progressive activation of more/larger fibers as stimulus strength increases, enlarging CAP.
Conduction velocity — Distance/time of AP propagation; higher in large, myelinated fibers (saltatory conduction).
Stimulus artifact — Brief deflection from the stimulus itself that precedes the true CAP.
Rheobase/Chronaxie — Minimal current for long duration (rheobase); and duration at 2× rheobase (chronaxie) describing excitability.
Lead Question - 2012
Biphasic action potential of mixed nerve except?
a) All or none phenomenon
b) Two or more positive peaks
c) Refractory period
d) Recorded on surface
Explanation: A compound (biphasic) action potential from a mixed nerve is recorded on the surface and often shows multiple peaks from groups of fibers with differing velocities. Although individual axons obey refractoriness, the CAP as a whole is graded and not all-or-none. Answer: a) All or none phenomenon.
1. CAP amplitude increases with stimulus strength primarily due to:
a) Bigger APs in each axon
b) Recruitment of additional axons
c) Shorter refractory period
d) Lower extracellular resistance
Explanation: Single axon AP size is constant (all-or-none). Increasing stimulus strength excites more axons (especially larger, lower-threshold myelinated fibers first), summating extracellularly to a larger CAP. This is recruitment, not bigger unit APs. Answer: b) Recruitment of additional axons.
2. Multiple peaks in a CAP reflect:
a) Temporal dispersion of fiber groups
b) Alternating depolarization and repolarization of one axon
c) Electrode artifact only
d) Hyperkalemia
Explanation: Mixed nerves contain fast large myelinated and slower small fibers. Their different conduction velocities cause temporal dispersion, producing distinct CAP peaks (e.g., Aα/β then Aδ). It is physiological, not merely artifact. Answer: a) Temporal dispersion of fiber groups.
3. Clinical: In demyelinating neuropathy, a motor nerve study most likely shows:
a) Increased conduction velocity
b) Temporal dispersion and conduction block
c) Higher CAP amplitude with faster latency
d) Normal distal latency
Explanation: Demyelination slows propagation, broadens the CAP (temporal dispersion), and may cause conduction block with reduced amplitude across segments. Distal latency is prolonged; velocity is reduced. Answer: b) Temporal dispersion and conduction block.
4. An extracellular biphasic CAP turns monophasic if:
a) Stimulus intensity is halved
b) One recording electrode is placed over an inactive/lesioned segment
c) Temperature increases
d) Ground electrode is removed
Explanation: Making one electrode indifferent (over electrically silent tissue) converts the recording to monophasic, producing a single main deflection. This is a classic teaching-lab maneuver (crush or ischemic block under one electrode). Answer: b) One recording electrode is placed over an inactive/lesioned segment.
5. Which statement about refractory period in nerve is TRUE?
a) CAP has no refractory behavior at any interval
b) Individual axons have absolute and relative refractory periods
c) Refractoriness depends only on extracellular K+
d) Refractory period occurs only in muscle
Explanation: Each axon shows absolute then relative refractoriness due to Na+ channel inactivation and K+ efflux. CAP refractoriness is less obvious because different axons recover at different times but can be demonstrated with double stimuli. Answer: b) Individual axons have absolute and relative refractory periods.
6. Local anesthetics reduce CAP amplitude by:
a) Blocking voltage-gated Na+ channels
b) Opening Cl− channels
c) Stimulating Na+/K+ pump
d) Inhibiting Ca2+ release from SR
Explanation: Local anesthetics (e.g., lignocaine) bind and block voltage-gated Na+ channels preferentially in small, myelinated pain fibers first, reducing the number of conducting axons and hence CAP amplitude and pain transmission. Answer: a) Blocking voltage-gated Na+ channels.
7. Strength–duration curve: a low chronaxie indicates:
a) Low tissue excitability
b) High tissue excitability
c) Only demyelination
d) Only temperature effect
Explanation: Chronaxie is the pulse duration needed at twice rheobase to excite tissue. Lower chronaxie signifies greater excitability (e.g., large myelinated axons). It is used to compare nerve/muscle excitability in disease and rehabilitation. Answer: b) High tissue excitability.
8. In a nerve conduction lab trace, the earliest deflection after the stimulus is most likely:
a) CAP negative peak
b) Stimulus artifact
c) F-wave
d) H-reflex
Explanation: The stimulus artifact is a brief, non-physiologic deflection due to the stimulus pulse that precedes the true CAP. F-waves and H-reflexes are later, long-loop responses. Recognizing artifact avoids misinterpretation. Answer: b) Stimulus artifact.
9. Cooling a nerve segment will:
a) Increase conduction velocity
b) Decrease conduction velocity and broaden CAP
c) Abolish refractory period
d) Convert biphasic to monophasic
Explanation: Lower temperature slows ion channel kinetics, reducing conduction velocity and increasing temporal dispersion, broadening the CAP. Extreme cooling can block conduction; it does not inherently change recording polarity. Answer: b) Decrease conduction velocity and broaden CAP.
10. Clinical: A patient with acute carpal tunnel shows reduced median motor CAP amplitude distally. This most likely reflects:
a) Primary demyelination only
b) Axonal loss or conduction block at the carpal tunnel
c) Pure muscle disease
d) Increased recruitment
Explanation: Reduced distal CMAP amplitude suggests fewer functioning axons reaching the muscle due to axonal loss or focal conduction block across the entrapment. Demyelination alone typically slows and prolongs latency with relative amplitude preservation. Answer: b) Axonal loss or conduction block at the carpal tunnel.
11. Antidromic sensory study records a larger CAP when:
a) The distance is shorter and fibers are well myelinated
b) The distance is longer only
c) Stimulation is subthreshold
d) Recording is across a joint in extreme flexion
Explanation: Shorter distances reduce temporal dispersion; intact myelination preserves synchrony, yielding larger sensory CAPs. Subthreshold stimulation fails to recruit fibers; joint extremes can compress nerves and reduce amplitude. Answer: a) The distance is shorter and fibers are well myelinated.
Chapter: Neuroanatomy
Topic: Dorsal Column Nuclei & Medial Lemniscus Pathway
Subtopic: Nucleus Gracilis/Cuneatus (aka “fasciculate” nuclei), Sensory Decussation & Clinical Correlates
Keyword Definitions
Fasciculus gracilis — Medial dorsal column carrying fine touch, vibration, proprioception from lower limb/trunk.
Fasciculus cuneatus — Lateral dorsal column carrying similar modalities from upper limb/upper trunk.
Nucleus gracilis — Relay nucleus in caudal medulla for fasciculus gracilis; gives internal arcuate fibers.
Nucleus cuneatus — Relay nucleus in caudal medulla for fasciculus cuneatus; projects to medial lemniscus.
Internal arcuate fibers — Axons from dorsal column nuclei that decussate in caudal medulla (sensory decussation).
Medial lemniscus — Ascending tract after decussation to VPL thalamus conveying touch, vibration, proprioception.
Accessory cuneate nucleus — Lateral to cuneate; origin of cuneocerebellar tract (ipsilateral proprioception to cerebellum).
Proprioception — Sense of joint position/movement; tested by joint position sense, Romberg.
Romberg test — Instability with eyes closed suggests proprioceptive deficit (e.g., dorsal column disease).
Tabes dorsalis — Neurosyphilis causing dorsal column degeneration; impaired vibration/position sense, positive Romberg.
Lead Question - 2012
Nucleus fasciculatus is seen in?
a) Frontal lobe
b) Medulla
c) Temporal lobe
d) Midbrain
Explanation: The dorsal column nuclei (gracilis and cuneatus—sometimes collectively termed “fasciculate” nuclei) lie in the caudal medulla. They receive input from the fasciculi gracilis and cuneatus and send internal arcuate fibers that decussate to form the medial lemniscus. Answer: b) Medulla.
1. Primary sensory modality conveyed by dorsal columns includes:
a) Pain and temperature
b) Fine touch, vibration, proprioception
c) Crude touch only
d) Auditory input
Explanation: Dorsal columns (gracilis, cuneatus) transmit fine touch, vibration, and proprioception. Pain and temperature ascend in the spinothalamic tract. Lesions produce loss of vibration/position sense and positive Romberg sign. Answer: b) Fine touch, vibration, proprioception.
2. Site of sensory decussation for the dorsal column–medial lemniscus pathway:
a) Spinal cord anterior white commissure
b) Caudal medulla (internal arcuate fibers)
c) Pons tegmentum
d) Midbrain colliculi
Explanation: Second-order neurons from nucleus gracilis and cuneatus cross midline as internal arcuate fibers in the caudal medulla, forming the medial lemniscus. Spinothalamic fibers decussate in the spinal cord. Answer: b) Caudal medulla (internal arcuate fibers).
3. The medial lemniscus terminates primarily in:
a) VPL nucleus of thalamus
b) VPM nucleus of thalamus
c) Pulvinar
d) LGB (lateral geniculate body)
Explanation: The medial lemniscus carrying body sensation projects to the VPL thalamus. Face tactile sensation via trigeminal lemniscus reaches VPM. From VPL, third-order neurons ascend to primary somatosensory cortex. Answer: a) VPL nucleus of thalamus.
4. A lesion limited to fasciculus gracilis causes deficits most prominent in the:
a) Ipsilateral upper limb
b) Ipsilateral lower limb
c) Contralateral upper limb
d) Contralateral lower limb
Explanation: Fasciculus gracilis carries input from the ipsilateral lower limb and lower trunk (below T6). Spinal cord dorsal column lesions are ipsilateral to deficits because crossing occurs in the medulla, not the cord. Answer: b) Ipsilateral lower limb.
5. Accessory cuneate nucleus projects to cerebellum via the:
a) Dorsal spinocerebellar tract
b) Cuneocerebellar tract
c) Ventral spinocerebellar tract
d) Rubrospinal tract
Explanation: Proprioceptive input from the upper limb reaches the accessory cuneate nucleus and ascends ipsilaterally via the cuneocerebellar tract to the inferior cerebellar peduncle, informing cerebellar coordination. Answer: b) Cuneocerebellar tract.
6. Clinical: A patient with sensory ataxia, positive Romberg, and impaired vibration in feet most likely has pathology in:
a) Lateral spinothalamic tract
b) Dorsal columns
c) Corticospinal tract only
d) Vestibular nuclei
Explanation: Loss of vibration/position sense with positive Romberg points to dorsal column disease (e.g., B12 deficiency, tabes dorsalis). Spinothalamic lesions cause pain/temperature loss instead. Answer: b) Dorsal columns.
7. In the caudal medulla, the gracile and cuneate tubercles on dorsal surface correspond to:
a) Inferior olivary nuclei
b) Nucleus gracilis and nucleus cuneatus
c) Hypoglossal nucleus only
d) Spinal trigeminal nucleus
Explanation: The dorsal elevations, gracile and cuneate tubercles, overlie the respective dorsal column nuclei, landmarks for the site where internal arcuate fibers originate. Answer: b) Nucleus gracilis and nucleus cuneatus.
8. Stroke of VPL thalamus most characteristically produces:
a) Ipsilateral facial analgesia
b) Contralateral loss of body vibration and proprioception
c) Ipsilateral limb ataxia from cerebellar lesion
d) Bilateral anosmia
Explanation: VPL relays contralateral body somatosensation (including dorsal column modalities). VPM serves face; cerebellar lesions cause ipsilateral ataxia via peduncles. Thus VPL stroke → contralateral tactile/vibration deficits. Answer: b) Contralateral loss of body vibration and proprioception.
9. Subacute combined degeneration (B12 deficiency) initially affects:
a) Anterior horn cells only
b) Dorsal columns and lateral corticospinal tracts
c) Medial longitudinal fasciculus
d) Optic radiations
Explanation: B12 deficiency causes demyelination of dorsal columns (sensory ataxia) and lateral corticospinal tracts (UMN signs). Early recognition prevents irreversible deficits. Answer: b) Dorsal columns and lateral corticospinal tracts.
10. A hemisection (Brown-Séquard) at T10 produces which dorsal column deficit below the lesion?
a) Contralateral loss of vibration/proprioception
b) Ipsilateral loss of vibration/proprioception
c) Bilateral pain loss only
d) No sensory deficit
Explanation: Dorsal column fibers ascend ipsilaterally and cross in the medulla; thus spinal hemisection causes ipsilateral loss of vibration and proprioception below the lesion, with contralateral pain/temperature loss (spinothalamic). Answer: b) Ipsilateral loss of vibration/proprioception.
11. Graphesthesia (recognizing numbers traced on skin) mainly tests integrity of:
a) Dorsal column–medial lemniscus pathway and cortical processing
b) Spinothalamic tract only
c) Vestibulospinal tract
d) Rubrospinal tract
Explanation: Graphesthesia requires intact dorsal column–medial lemniscus input to somatosensory cortex and association areas. Lesions in dorsal columns or parietal cortex impair stereognosis/graphesthesia despite normal strength. Answer: a) Dorsal column–medial lemniscus pathway and cortical processing.
Chapter: Neuroanatomy
Topic: Cerebral Cortex
Subtopic: Sulci and Gyri
Keywords:
Operculated sulcus: A sulcus covered partially by cortical opercula (frontal, parietal, temporal lobes).
Calcarine sulcus: Found in occipital lobe, related to primary visual cortex.
Collateral sulcus: Separates fusiform gyrus from parahippocampal gyrus.
Lunate sulcus: Seen in some primates, rare in humans.
Central sulcus: Separates frontal and parietal lobes.
Lead Question - 2012
Which of the following is an operculated sulcus ?
a) Calcarine
b) Collateral
c) Lunate
d) Central
Explanation: The central sulcus is an operculated sulcus, as parts of the frontal, parietal, and temporal lobes form opercula around the insula. Operculation is a covering phenomenon seen around the insula. Hence, the correct answer is Central sulcus.
Guessed Question 1
A lesion of the calcarine sulcus results in loss of:
a) Auditory perception
b) Visual field
c) Language comprehension
d) Motor function
Explanation: The calcarine sulcus contains the primary visual cortex (Brodmann area 17). A lesion leads to contralateral homonymous hemianopia. Thus, the answer is Visual field.
Guessed Question 2
The collateral sulcus is located in:
a) Occipital lobe
b) Temporal lobe
c) Parietal lobe
d) Frontal lobe
Explanation: The collateral sulcus is found in the temporal lobe, separating fusiform gyrus from parahippocampal gyrus. It plays a role in higher-order visual processing. Answer is Temporal lobe.
Guessed Question 3
Which sulcus separates motor and sensory cortices?
a) Calcarine
b) Central
c) Lunate
d) Collateral
Explanation: The central sulcus separates the precentral gyrus (motor cortex) from the postcentral gyrus (sensory cortex). This functional division is crucial in neurosurgery. Answer is Central sulcus.
Guessed Question 4
Lunate sulcus is considered a remnant of evolution, more prominent in:
a) Humans
b) Primates
c) Amphibians
d) Birds
Explanation: The lunate sulcus is more prominent in primates like apes and monkeys, rarely observed in humans. It demarcates visual areas in non-human primates. Answer is Primates.
Guessed Question 5
The insula is hidden deep to which sulcus?
a) Central
b) Lateral
c) Calcarine
d) Collateral
Explanation: The insula is buried deep within the lateral sulcus, covered by opercula of adjacent lobes. It is involved in autonomic and visceral functions. Answer is Lateral sulcus.
Guessed Question 6
Which artery supplies the region around the central sulcus?
a) Middle cerebral artery
b) Anterior cerebral artery
c) Posterior cerebral artery
d) Basilar artery
Explanation: The central sulcus is supplied by both anterior and middle cerebral arteries. The anterior cerebral supplies medial aspect, and MCA supplies lateral aspect. Answer is Anterior cerebral artery.
Guessed Question 7
A stroke involving the calcarine sulcus territory typically spares:
a) Central vision
b) Peripheral vision
c) Entire vision
d) Color vision
Explanation: A stroke involving posterior cerebral artery affecting calcarine cortex causes contralateral homonymous hemianopia with macular sparing, as macular area has dual supply. Answer is Central vision.
Guessed Question 8
The collateral sulcus is most closely associated with:
a) Olfactory processing
b) Visual memory
c) Auditory signals
d) Motor control
Explanation: The collateral sulcus is related to the fusiform and parahippocampal gyri, involved in recognition and visual memory processes. Answer is Visual memory.
Guessed Question 9
The central sulcus is also called:
a) Fissure of Rolando
b) Fissure of Sylvius
c) Fissure of Broca
d) Fissure of Wernicke
Explanation: The central sulcus is known as the fissure of Rolando, a landmark separating frontal and parietal lobes. Answer is Fissure of Rolando.
Guessed Question 10
Which sulcus lies in the occipital lobe and is crucial for vision?
a) Central
b) Calcarine
c) Collateral
d) Sylvian
Explanation: The calcarine sulcus in the occipital lobe contains the primary visual cortex. It is essential for processing vision. Answer is Calcarine sulcus.
Chapter: Neuroanatomy
Topic: Cranial Nerves
Subtopic: Oculomotor Nerve (III)
Keywords:
Oculomotor nerve: The third cranial nerve, motor to most extraocular muscles.
Parasympathetic fibers: Carried to ciliary ganglion for pupil constriction.
Inferior oblique muscle: Supplied by oculomotor nerve, elevates eye in adduction.
Superior orbital fissure: Route by which oculomotor enters orbit.
Pupil constriction: Mediated by sphincter pupillae via oculomotor parasympathetic supply.
Lead Question - 2012
All the following are characteristics of oculomotor nerve except:
a) Carries parasympathetic nerve fibres
b) Supplies inferior oblique muscle
c) Enters orbit through the inferior orbital fissure
d) Causes constriction of pupil
Explanation: The oculomotor nerve enters the orbit through the superior orbital fissure, not the inferior orbital fissure. It supplies extraocular muscles and parasympathetics to sphincter pupillae, causing pupillary constriction. Thus, the incorrect statement is Enters orbit through the inferior orbital fissure.
Guessed Question 1
A lesion of the oculomotor nerve results in:
a) Ptosis, mydriasis, eye down and out
b) Loss of corneal reflex
c) Diplopia only in horizontal gaze
d) Isolated nystagmus
Explanation: Oculomotor palsy produces ptosis (levator palpebrae), mydriasis (parasympathetics), and eye deviation down and out (unopposed lateral rectus and superior oblique). Correct answer is Ptosis, mydriasis, eye down and out.
Guessed Question 2
Parasympathetic fibers of oculomotor nerve synapse in:
a) Ciliary ganglion
b) Pterygopalatine ganglion
c) Otic ganglion
d) Submandibular ganglion
Explanation: The oculomotor nerve carries preganglionic parasympathetics that synapse in the ciliary ganglion, from where short ciliary nerves innervate sphincter pupillae and ciliary muscle. Correct answer is Ciliary ganglion.
Guessed Question 3
A patient with diabetes develops acute third nerve palsy but pupil is spared. This suggests:
a) Compressive lesion
b) Ischemic neuropathy
c) Tumor invasion
d) Inflammatory neuritis
Explanation: In ischemic oculomotor palsy (like in diabetes), central fibers are affected while peripheral parasympathetic fibers are spared, preserving pupillary function. Compressive lesions usually affect the pupil. Correct answer is Ischemic neuropathy.
Guessed Question 4
Which extraocular muscle is NOT supplied by oculomotor nerve?
a) Superior rectus
b) Inferior rectus
c) Superior oblique
d) Inferior oblique
Explanation: Oculomotor supplies all extraocular muscles except lateral rectus (abducens) and superior oblique (trochlear). Thus, correct answer is Superior oblique.
Guessed Question 5
The nucleus of oculomotor nerve is located in:
a) Midbrain at superior colliculus level
b) Midbrain at inferior colliculus level
c) Pons
d) Medulla
Explanation: The oculomotor nucleus is located in the midbrain at the level of the superior colliculus, ventral to the aqueduct. Correct answer is Midbrain at superior colliculus level.
Guessed Question 6
A compressive aneurysm of posterior communicating artery typically causes:
a) Pupil-involving oculomotor palsy
b) Pupil-sparing oculomotor palsy
c) Isolated superior oblique weakness
d) Bilateral ptosis without diplopia
Explanation: Aneurysms compress the superficial parasympathetic fibers of oculomotor nerve, leading to early pupillary involvement along with third nerve palsy. Correct answer is Pupil-involving oculomotor palsy.
Guessed Question 7
Which clinical sign is most specific for oculomotor nerve palsy?
a) Ptosis
b) Miosis
c) Lateral gaze palsy
d) Nystagmus
Explanation: Ptosis caused by paralysis of levator palpebrae superioris is a hallmark feature of oculomotor nerve palsy, often seen with diplopia and pupil dilation. Correct answer is Ptosis.
Guessed Question 8
The Edinger–Westphal nucleus provides fibers for:
a) Accommodation and pupillary constriction
b) Extraocular muscle contraction
c) Taste perception
d) Facial sensation
Explanation: The Edinger–Westphal nucleus, part of oculomotor complex, gives parasympathetic fibers that control accommodation reflex and pupillary constriction via ciliary ganglion. Correct answer is Accommodation and pupillary constriction.
Guessed Question 9
A patient presents with eye deviated down and out with dilated pupil. The most likely cause is:
a) Oculomotor nerve palsy
b) Trochlear nerve palsy
c) Abducens nerve palsy
d) Optic nerve lesion
Explanation: Down-and-out eye with dilated pupil indicates oculomotor palsy as lateral rectus and superior oblique act unopposed. Correct answer is Oculomotor nerve palsy.
Guessed Question 10
Which clinical test best assesses oculomotor function?
a) Ask patient to look laterally
b) Check convergence and accommodation
c) Assess corneal reflex
d) Test jaw movement
Explanation: Convergence and accommodation require action of medial rectus and ciliary muscle, both supplied by oculomotor nerve. Hence, testing accommodation is an effective way to assess its function. Correct answer is Check convergence and accommodation.
Chapter: Neuroanatomy
Topic: Cerebral Hemispheres
Subtopic: Corpus Callosum
Keywords:
Corpus callosum: Largest commissural fiber tract connecting right and left cerebral hemispheres.
Hemispheric connection: Corpus callosum unites the two hemispheres for integration.
Frontal lobe connection: Anterior part (genu) connects the two frontal lobes.
Commissural fibers: White matter tracts connecting similar cortical areas of both hemispheres.
Split-brain syndrome: Condition after corpus callosotomy leading to loss of hemispheric integration.
Lead Question - 2012
True about Corpus callosum :
a) Unite far area of two sides of brain
b) Connect two frontal lobe
c) Unite two hemisphere
d) All
Explanation: Corpus callosum is the major commissural bundle uniting the two hemispheres. It connects frontal lobes (via genu), parietal lobes (body), and occipital lobes (splenium). It enables interhemispheric communication. Hence, all the given statements are true, making the correct answer All.
Guessed Question 1
A lesion in the corpus callosum can lead to:
a) Split-brain syndrome
b) Horner’s syndrome
c) Parkinsonism
d) Hemiballismus
Explanation: Lesions in corpus callosum disrupt interhemispheric communication leading to split-brain syndrome. Patients may fail to name objects in the left visual field due to disconnection between hemispheres. Correct answer is Split-brain syndrome.
Guessed Question 2
Anterior part of corpus callosum (genu) primarily connects:
a) Occipital lobes
b) Frontal lobes
c) Temporal lobes
d) Thalamus
Explanation: The genu of corpus callosum bends forward and connects the two frontal lobes, enabling coordinated executive and motor function across hemispheres. Correct answer is Frontal lobes.
Guessed Question 3
The splenium of the corpus callosum connects:
a) Frontal lobes
b) Parietal lobes
c) Occipital lobes
d) Temporal lobes
Explanation: The posterior part of corpus callosum is the splenium, which connects occipital lobes and allows integration of visual information between hemispheres. Correct answer is Occipital lobes.
Guessed Question 4
Which imaging modality best visualizes corpus callosum abnormalities?
a) CT scan
b) MRI
c) Ultrasound
d) PET scan
Explanation: MRI is the most sensitive imaging modality for detecting corpus callosum malformations, agenesis, or demyelination. It clearly shows its structure and fiber connections. Correct answer is MRI.
Guessed Question 5
Congenital absence of corpus callosum is associated with:
a) Agenesis syndromes
b) Huntington’s disease
c) Amyotrophic lateral sclerosis
d) Multiple sclerosis
Explanation: Agenesis of corpus callosum is a congenital malformation, often linked with developmental delay, seizures, and midline anomalies. Correct answer is Agenesis syndromes.
Guessed Question 6
Which part of corpus callosum connects parietal lobes?
a) Genu
b) Body
c) Splenium
d) Rostrum
Explanation: The central part or body of corpus callosum mainly connects parietal lobes, allowing somatosensory integration across hemispheres. Correct answer is Body.
Guessed Question 7
Damage to corpus callosum may impair:
a) Interhemispheric communication
b) Reflex arcs
c) Spinal cord conduction
d) Basal ganglia circuits
Explanation: Corpus callosum is essential for communication between hemispheres. Its damage leads to disconnection syndromes, affecting coordinated tasks involving both sides of the body. Correct answer is Interhemispheric communication.
Guessed Question 8
Which condition is treated by partial corpus callosotomy?
a) Intractable epilepsy
b) Multiple sclerosis
c) Meningitis
d) Brain abscess
Explanation: In refractory epilepsy, partial callosotomy prevents seizure spread between hemispheres, reducing drop attacks. Correct answer is Intractable epilepsy.
Guessed Question 9
Which fibers are carried by corpus callosum?
a) Commissural fibers
b) Association fibers
c) Projection fibers
d) Reticular fibers
Explanation: Corpus callosum carries commissural fibers connecting identical cortical areas of both hemispheres. Association fibers connect areas within the same hemisphere, while projection fibers connect cortex with lower centers. Correct answer is Commissural fibers.
Guessed Question 10
In MRI, corpus callosum appears as:
a) Hypointense on T1, Hyperintense on T2
b) Hyperintense on T1, Hypointense on T2
c) Isointense on both T1 and T2
d) Variable with pathology
Explanation: On MRI, corpus callosum is typically hypointense on T1 and hyperintense on T2 due to its myelinated white matter. Signal changes vary with demyelination or agenesis. Correct answer is Hypointense on T1, Hyperintense on T2.
Chapter: Neuroanatomy
Topic: Cerebellum
Subtopic: Cerebellar Cortex
Keywords:
Cerebellar cortex: Three-layered structure of cerebellum responsible for motor coordination.
Molecular layer: Outer layer containing stellate and basket cells.
Purkinje cells: Principal output neurons of cerebellar cortex.
Granule cells: Smallest excitatory neurons forming parallel fibers.
Golgi cells: Inhibitory interneurons regulating granule cell activity.
Clinical relevance: Damage to cerebellar cortex causes ataxia, tremor, and dysmetria.
Lead Question - 2012
What are the cellular contents of cerebellar cortex?
a) Cortical cells
b) Glomus cells
c) Principle cells
d) Intercalated cells
Explanation: The cerebellar cortex has three layers containing five neuron types: Purkinje cells, granule cells, basket cells, stellate cells, and Golgi cells. Purkinje cells are the principal output neurons. Correct answer is Principle cells referring to Purkinje cells, essential for inhibitory output to deep cerebellar nuclei.
Guessed Question 1
Which is the only excitatory neuron of the cerebellar cortex?
a) Purkinje cells
b) Granule cells
c) Basket cells
d) Golgi cells
Explanation: Among cerebellar neurons, granule cells are the only excitatory type, releasing glutamate. Purkinje, basket, stellate, and Golgi cells are inhibitory GABAergic neurons. Correct answer is Granule cells.
Guessed Question 2
Purkinje cells exert their effect through:
a) Excitatory input to thalamus
b) Inhibitory output to deep cerebellar nuclei
c) Excitatory connections with cortex
d) Inhibitory effect on spinal cord
Explanation: Purkinje cells are GABAergic and provide the sole output from the cerebellar cortex, inhibiting deep cerebellar nuclei. This helps fine-tune motor control. Correct answer is Inhibitory output to deep cerebellar nuclei.
Guessed Question 3
Which cells in molecular layer form synapses on Purkinje cell dendrites?
a) Basket and stellate cells
b) Granule cells
c) Golgi cells
d) Glial cells
Explanation: The molecular layer contains basket and stellate cells which are inhibitory interneurons. They synapse on Purkinje cell dendrites and modulate their activity. Correct answer is Basket and stellate cells.
Guessed Question 4
Which neurotransmitter is released by Purkinje cells?
a) Glutamate
b) GABA
c) Dopamine
d) Glycine
Explanation: Purkinje cells are large inhibitory neurons of cerebellum releasing GABA. This inhibition regulates output from deep cerebellar nuclei and maintains motor coordination. Correct answer is GABA.
Guessed Question 5
Damage to Purkinje cells results in:
a) Ataxia
b) Rigidity
c) Hemiballismus
d) Tremor at rest
Explanation: Purkinje cell loss impairs inhibitory regulation, causing cerebellar ataxia with uncoordinated gait, intention tremor, and dysmetria. Unlike Parkinsonism, rigidity and resting tremor are absent. Correct answer is Ataxia.
Guessed Question 6
Which layer of cerebellar cortex contains Purkinje cell bodies?
a) Molecular layer
b) Purkinje cell layer
c) Granular layer
d) White matter
Explanation: Purkinje cells lie in a single row between the molecular and granular layers, forming the Purkinje cell layer. Their dendrites extend into molecular layer. Correct answer is Purkinje cell layer.
Guessed Question 7
Golgi cells provide inhibitory input to:
a) Purkinje cells
b) Basket cells
c) Granule cells
d) Stellate cells
Explanation: Golgi cells are inhibitory interneurons located in the granular layer. They regulate granule cell activity through inhibitory synapses, modulating parallel fiber output. Correct answer is Granule cells.
Guessed Question 8
Which afferent fibers excite Purkinje cells via climbing fibers?
a) Mossy fibers
b) Corticospinal fibers
c) Vestibulospinal fibers
d) Olivocerebellar fibers
Explanation: Climbing fibers arise from inferior olivary nucleus and directly synapse on Purkinje cell dendrites with strong excitatory input. Mossy fibers excite granule cells instead. Correct answer is Olivocerebellar fibers.
Guessed Question 9
Mossy fibers primarily synapse with:
a) Purkinje cells
b) Granule cells
c) Golgi cells
d) Stellate cells
Explanation: Mossy fibers form excitatory synapses with granule cells in the cerebellar granular layer. These granule cells then send parallel fibers to excite Purkinje cells indirectly. Correct answer is Granule cells.
Guessed Question 10
Clinical feature of midline cerebellar lesion (vermis) is:
a) Truncal ataxia
b) Intention tremor
c) Hemiballismus
d) Resting tremor
Explanation: Lesions in vermis affect axial muscles leading to truncal ataxia, wide-based gait, and imbalance. Intention tremor is seen in hemispheric lesions. Correct answer is Truncal ataxia.
Chapter: Anatomy
Topic: Abdominal Aorta
Subtopic: Branches of Abdominal Aorta
Keywords:
Abdominal aorta: Main arterial trunk of abdomen extending from diaphragm to bifurcation at L4.
Lateral branches: Paired arteries including renal, suprarenal, and gonadal arteries.
Anterior branches: Unpaired visceral arteries such as celiac, superior mesenteric, and inferior mesenteric arteries.
Posterior branches: Paired parietal arteries supplying abdominal wall, like lumbar arteries.
Clinical relevance: Aneurysms, occlusions, and variations in aortic branching cause surgical significance.
Lead Question - 2012
All are lateral branches of abdominal aorta, EXCEPT
a) Right testicular artery
b) Left renal artery
c) Inferior mesenteric artery
d) Middle suprarenal artery
Explanation: The abdominal aorta gives anterior, lateral, and posterior branches. Lateral branches include renal, suprarenal, and gonadal arteries. Inferior mesenteric artery is an anterior visceral branch. Correct answer is Inferior mesenteric artery, as it is not a lateral branch.
Guessed Question 1
Which of the following is an anterior visceral branch of abdominal aorta?
a) Renal artery
b) Suprarenal artery
c) Superior mesenteric artery
d) Gonadal artery
Explanation: The anterior visceral branches of abdominal aorta include celiac trunk, superior mesenteric artery, and inferior mesenteric artery. Renal, gonadal, and suprarenal arteries arise laterally. Correct answer is Superior mesenteric artery.
Guessed Question 2
The abdominal aorta terminates at which vertebral level?
a) L2
b) L3
c) L4
d) L5
Explanation: The abdominal aorta runs from T12 to L4, where it bifurcates into right and left common iliac arteries. Correct answer is L4.
Guessed Question 3
Which of the following arteries arises as a paired lateral branch?
a) Inferior phrenic artery
b) Median sacral artery
c) Gonadal artery
d) Celiac trunk
Explanation: Gonadal arteries (testicular or ovarian) are paired lateral branches of abdominal aorta. Median sacral is unpaired posterior, celiac trunk is anterior, inferior phrenic is paired but superior. Correct answer is Gonadal artery.
Guessed Question 4
Which artery supplies suprarenal glands directly from abdominal aorta?
a) Superior suprarenal artery
b) Middle suprarenal artery
c) Inferior suprarenal artery
d) None
Explanation: Middle suprarenal artery arises directly from the abdominal aorta as a paired lateral branch, while superior comes from inferior phrenic and inferior comes from renal. Correct answer is Middle suprarenal artery.
Guessed Question 5
Which is the first unpaired anterior branch of abdominal aorta?
a) Superior mesenteric artery
b) Inferior mesenteric artery
c) Celiac trunk
d) Gonadal artery
Explanation: The first anterior branch of abdominal aorta is the celiac trunk at T12 level, followed by superior mesenteric and inferior mesenteric arteries. Correct answer is Celiac trunk.
Guessed Question 6
Which branch of abdominal aorta supplies midgut?
a) Inferior mesenteric artery
b) Superior mesenteric artery
c) Celiac trunk
d) Renal artery
Explanation: Midgut (from duodenum distal to bile duct entry to proximal 2/3rd of transverse colon) is supplied by superior mesenteric artery. Correct answer is Superior mesenteric artery.
Guessed Question 7
Aneurysm of abdominal aorta is most common at which level?
a) Above renal arteries
b) Below renal arteries
c) At celiac trunk
d) At bifurcation
Explanation: Abdominal aortic aneurysm most commonly occurs below renal arteries (infrarenal segment). It is clinically important due to risk of rupture. Correct answer is Below renal arteries.
Guessed Question 8
Which artery is a posterior parietal branch of abdominal aorta?
a) Lumbar artery
b) Gonadal artery
c) Superior mesenteric artery
d) Middle suprarenal artery
Explanation: Lumbar arteries are paired posterior parietal branches supplying abdominal wall and muscles. Correct answer is Lumbar artery.
Guessed Question 9
Which abdominal aortic branch supplies hindgut?
a) Superior mesenteric artery
b) Inferior mesenteric artery
c) Celiac trunk
d) Renal artery
Explanation: Inferior mesenteric artery supplies hindgut structures including distal 1/3rd transverse colon, descending colon, sigmoid colon, and rectum. Correct answer is Inferior mesenteric artery.
Guessed Question 10
Occlusion of which artery causes ischemia in kidneys?
a) Renal artery
b) Inferior mesenteric artery
c) Median sacral artery
d) Gonadal artery
Explanation: Renal arteries are paired lateral branches of abdominal aorta supplying kidneys. Their occlusion leads to renal ischemia and hypertension. Correct answer is Renal artery.
Chapter: Radiology
Topic: Skull Base Imaging
Subtopic: Craniovertebral Junction (CVJ) Lines
Keywords:
Chamberlain’s line: Radiological line from hard palate to posterior margin of foramen magnum.
McGregor’s line: Line from hard palate to lowest point of occiput, used to assess basilar invagination.
Basilar invagination: Upward displacement of vertebral elements into foramen magnum.
Craniovertebral junction (CVJ): Region between skull base and cervical spine including atlas and axis.
Clinical relevance: Radiological lines are essential for diagnosing CVJ anomalies like atlantoaxial dislocation.
Lead Question - 2012
Chamberlain’s line is ?
a) Palate to occiput
b) Palate to temporal
c) Palate to foramen magnum
d) Palate to parietal
Explanation: Chamberlain’s line is drawn from the posterior edge of the hard palate to the posterior margin of the foramen magnum (opisthion). It is used to assess basilar invagination. The tip of the odontoid should not project more than 3 mm above this line. Correct answer is Palate to foramen magnum.
Guessed Question 1
McGregor’s line is drawn from hard palate to which landmark?
a) Posterior margin of foramen magnum
b) Inferior occiput
c) External occipital protuberance
d) Clivus
Explanation: McGregor’s line runs from the posterior edge of the hard palate to the lowest point of the occipital bone. Odontoid projecting >4.5 mm above this line indicates basilar invagination. Correct answer is Inferior occiput.
Guessed Question 2
In Chamberlain’s line, how much odontoid process protrusion above the line is considered abnormal?
a) 2 mm
b) 3 mm
c) 5 mm
d) 6 mm
Explanation: Normally, the tip of the dens should not lie more than 3 mm above Chamberlain’s line. If it projects beyond this, basilar invagination should be suspected. Correct answer is 3 mm.
Guessed Question 3
Which pathology is best assessed using Chamberlain’s line?
a) Chiari malformation
b) Basilar invagination
c) Hydrocephalus
d) Pituitary adenoma
Explanation: Chamberlain’s line is used in radiology to evaluate basilar invagination, where the odontoid process migrates upward into the foramen magnum. Correct answer is Basilar invagination.
Guessed Question 4
McGregor’s line is considered more reliable than Chamberlain’s line because?
a) Includes clivus
b) Uses occipital bone landmark
c) Uses odontoid directly
d) Longer reference line
Explanation: McGregor’s line is preferred because the inferior occiput is more easily visible on X-rays than opisthion. Hence, it is considered more practical. Correct answer is Uses occipital bone landmark.
Guessed Question 5
Which radiological line connects nasion to tuberculum sellae?
a) Chamberlain’s line
b) McGregor’s line
c) Twining’s line
d) McRae’s line
Explanation: Twining’s line runs from the nasion to tuberculum sellae and is useful in skull radiology. Chamberlain and McGregor relate to craniovertebral junction. Correct answer is Twining’s line.
Guessed Question 6
McRae’s line is drawn across which structure?
a) Foramen magnum
b) Hard palate
c) Occipital condyles
d) Clivus
Explanation: McRae’s line extends from basion to opisthion across the foramen magnum. The odontoid tip should lie below this line in normal anatomy. Correct answer is Foramen magnum.
Guessed Question 7
Which radiological line is most useful in detecting atlantoaxial dislocation?
a) Chamberlain’s line
b) McGregor’s line
c) McRae’s line
d) All of the above
Explanation: Atlantoaxial dislocation and basilar invagination require combined use of Chamberlain, McGregor, and McRae’s lines. Each provides complementary assessment. Correct answer is All of the above.
Guessed Question 8
Odontoid lying more than 4.5 mm above McGregor’s line suggests?
a) Chiari malformation
b) Basilar invagination
c) Syringomyelia
d) Hydrocephalus
Explanation: Protrusion of dens >4.5 mm above McGregor’s line is pathological and diagnostic of basilar invagination. Correct answer is Basilar invagination.
Guessed Question 9
McRae’s line is abnormal if?
a) Odontoid tip lies above line
b) Odontoid tip lies below line
c) Occiput overlaps clivus
d) Clivus angle decreases
Explanation: McRae’s line should always lie above the dens tip. If the odontoid projects above this line, it suggests basilar invagination. Correct answer is Odontoid tip lies above line.
Guessed Question 10
Which condition is commonly associated with basilar invagination?
a) Rheumatoid arthritis
b) Diabetes mellitus
c) Hypertension
d) COPD
Explanation: Basilar invagination is frequently associated with rheumatoid arthritis, congenital anomalies, and Paget’s disease due to weakening of craniovertebral junction structures. Correct answer is Rheumatoid arthritis.
Chapter: Anatomy
Topic: Nose and Paranasal Sinuses
Subtopic: Osteocartilaginous Junction
Keywords:
Osseocartilaginous junction: The anatomical transition zone between bony and cartilaginous parts of the nose.
Nasion: Junction of frontal bone and nasal bones, an external landmark.
Rhinion: Lower end of nasal bones, where bone meets cartilage.
Radix: Root of the nose, depression between forehead and nose.
Columella: Soft tissue between nostrils, separating nasal vestibules.
Clinical relevance: Important in nasal fractures, rhinoplasty, and septal surgeries.
Lead Question - 2012
Osseocartilagenous junction is present at ?
a) Nasion
b) Rhinion
c) Radix
d) Columella
Explanation: The osseocartilaginous junction lies at the rhinion, where the nasal bone meets the upper lateral cartilage. This is clinically important in trauma assessment and nasal surgeries. Correct answer is Rhinion.
Guessed Question 1
Which external landmark corresponds to the junction of frontal bone and nasal bones?
a) Nasion
b) Rhinion
c) Radix
d) Columella
Explanation: The nasion marks the point where the two nasal bones meet the frontal bone. It is used in cephalometry and as a surgical landmark. Correct answer is Nasion.
Guessed Question 2
The radix of the nose is located at?
a) Upper nasal root
b) Mid-nasal dorsum
c) Lower end of septum
d) Alar cartilage junction
Explanation: The radix refers to the root of the nose, situated between the forehead and the dorsum of the nose, often depressed in profile. Correct answer is Upper nasal root.
Guessed Question 3
The soft tissue that separates the nostrils externally is called?
a) Septum
b) Columella
c) Alar base
d) Vestibule
Explanation: The columella is the soft tissue and cartilage that separates the nostrils externally. It is important in cosmetic and reconstructive nasal surgeries. Correct answer is Columella.
Guessed Question 4
Osseocartilaginous junction is a common site for?
a) Septal hematoma
b) Nasal fracture
c) Epistaxis (Little’s area)
d) Foreign body impaction
Explanation: The osseocartilaginous junction at the rhinion is often involved in nasal fractures due to trauma, as it forms a weak point between rigid bone and flexible cartilage. Correct answer is Nasal fracture.
Guessed Question 5
In rhinoplasty, altering the nasal dorsum often involves working at?
a) Nasion
b) Rhinion
c) Columella
d) Alar rim
Explanation: Rhinoplasty commonly involves reshaping the dorsum, where the rhinion marks the osseocartilaginous junction, critical for aesthetic nasal contour. Correct answer is Rhinion.
Guessed Question 6
A blow to the mid-nasal region most likely fractures at?
a) Rhinion
b) Nasion
c) Columella
d) Radix
Explanation: The rhinion is the weakest point of the nasal dorsum where bone meets cartilage, making it the most common fracture site in trauma. Correct answer is Rhinion.
Guessed Question 7
Which landmark is most useful for radiographic assessment of nasal fractures?
a) Columella
b) Rhinion
c) Radix
d) Nasion
Explanation: The nasion is an external landmark used in radiographs for nasal bone fractures. It provides a reliable point for alignment and surgical planning. Correct answer is Nasion.
Guessed Question 8
Epistaxis in Little’s area arises near which junction?
a) Osseocartilaginous junction
b) Septal cartilage only
c) Inferior turbinate junction
d) Maxillary sinus ostium
Explanation: Little’s area (Kiesselbach’s plexus) is located at the anterior septum, close to the osseocartilaginous junction, making it a frequent site of anterior epistaxis. Correct answer is Osseocartilaginous junction.
Guessed Question 9
Basal cell carcinoma of the nose commonly affects?
a) Rhinion
b) Columella
c) Nasal ala
d) Nasion
Explanation: Basal cell carcinoma frequently affects sun-exposed areas such as the nasal ala and dorsum, sparing deeper structures initially. Correct answer is Nasal ala.
Guessed Question 10
Septoplasty commonly corrects deviation at?
a) Columella
b) Rhinion
c) Nasion
d) Posterior choana
Explanation: Septoplasty often addresses deviations near the osseocartilaginous junction (rhinion), as this area frequently causes airway obstruction. Correct answer is Rhinion.
Chapter: Embryology
Topic: Germ Cell Development
Subtopic: Origin and Migration of Primordial Germ Cells
Keywords:
Primordial germ cells: Precursors of gametes (sperm and ova) that originate outside the gonads.
Yolk sac: Extraembryonic structure providing nutrition and site of origin of primordial germ cells.
Genital ridge: Area where primordial germ cells migrate and form future gonads.
Neural crest: Source of melanocytes, craniofacial structures, and peripheral neurons, not germ cells.
Somatopleuritic mesoderm: Contributes to body wall and limbs, not germ cell origin.
Clinical relevance: Errors in germ cell migration can lead to gonadal dysgenesis or germ cell tumors.
Lead Question - 2012
Primordial germ cells are derived from:
a) Neural crest
b) Genital ridge
c) Somatopleuritic mesoderm
d) Yolk sac
Explanation: Primordial germ cells originate in the endoderm of the yolk sac, migrate through the dorsal mesentery, and settle in the genital ridge to form gonads. This migration is crucial for gametogenesis. Correct answer is Yolk sac.
Guessed Question 1
At what week do primordial germ cells migrate to the genital ridge?
a) 2nd week
b) 4th week
c) 6th week
d) 8th week
Explanation: Primordial germ cells migrate from the yolk sac to the genital ridge by the 6th week of embryonic development. Their arrival triggers differentiation into oogonia or spermatogonia. Correct answer is 6th week.
Guessed Question 2
Failure of primordial germ cell migration can result in?
a) Turner's syndrome
b) Germ cell tumors
c) Neural tube defects
d) Holoprosencephaly
Explanation: If primordial germ cells fail to migrate properly, ectopic germ cells may persist and transform into germ cell tumors like teratomas, often seen in sacrococcygeal regions. Correct answer is Germ cell tumors.
Guessed Question 3
The genital ridge differentiates into?
a) Kidneys
b) Gonads
c) Adrenal cortex
d) Pancreas
Explanation: The genital ridge, after receiving migrating primordial germ cells, develops into testes in males or ovaries in females depending on genetic and hormonal influences. Correct answer is Gonads.
Guessed Question 4
Which structure guides the migration of primordial germ cells?
a) Amnion
b) Dorsal mesentery
c) Neural crest
d) Umbilical cord
Explanation: Primordial germ cells migrate via the dorsal mesentery of the hindgut to reach the genital ridge. This pathway is essential for normal gonadal development. Correct answer is Dorsal mesentery.
Guessed Question 5
Which tumor commonly arises from misplaced primordial germ cells?
a) Osteosarcoma
b) Teratoma
c) Medulloblastoma
d) Neuroblastoma
Explanation: Teratomas arise from pluripotent primordial germ cells that fail to reach their destination. They can contain tissues from all germ layers. Correct answer is Teratoma.
Guessed Question 6
Primordial germ cells first appear in which layer?
a) Mesoderm
b) Endoderm
c) Ectoderm
d) Neural crest
Explanation: Primordial germ cells originate from the endoderm of the yolk sac wall before migrating to the genital ridge. Correct answer is Endoderm.
Guessed Question 7
Abnormal location of primordial germ cells can lead to?
a) Gonadal dysgenesis
b) Renal agenesis
c) Adrenal hyperplasia
d) Anencephaly
Explanation: Misplaced germ cells that fail to colonize the genital ridge may result in gonadal dysgenesis or infertility. Correct answer is Gonadal dysgenesis.
Guessed Question 8
Which signaling pathway is critical for primordial germ cell specification?
a) Sonic Hedgehog
b) BMP (Bone Morphogenetic Protein)
c) Notch
d) Wnt
Explanation: Bone Morphogenetic Protein (BMP) signaling from extraembryonic tissues plays a central role in specifying primordial germ cells. Correct answer is BMP.
Guessed Question 9
In which clinical condition are primordial germ cells absent in the gonads?
a) Klinefelter syndrome
b) Turner syndrome
c) Androgen insensitivity
d) Down syndrome
Explanation: In Turner syndrome (45,X), streak ovaries form due to failure of primordial germ cell colonization. Correct answer is Turner syndrome.
Guessed Question 10
Primordial germ cells give rise to?
a) Spermatogonia and Oogonia
b) Sertoli and Granulosa cells
c) Leydig and Theca cells
d) Adrenal cortical cells
Explanation: Primordial germ cells differentiate into spermatogonia in males and oogonia in females, initiating gametogenesis. Correct answer is Spermatogonia and Oogonia.