Brain and Neuroanatomy Practice Questions

Q: What is the site of lesion in a patient with alexia without agraphia?

Splenium. Alexia without agraphia (also known as pure word blindness) is a classic disconnection syndrome [1]. It occurs when a patient can write (agraphia is absent) but cannot read what they have written or any other printed text. 1. Why Splenium is the correct answer: The lesion typically involves the left primary visual cortex (causing a right homonymous hemianopia) and the Splenium of the corpus callosum. * Because the left visual cortex is damaged, visual information from the right field is lost. * Visual information from the intact right visual cortex (left field) needs to cross over to the left angular gyrus (the language processing center) to be interpreted as words [1]. * This crossover occurs through the Splenium. A lesion here disconnects the visual input from the language center, rendering the patient unable to read, despite having intact writing abilities (controlled by the left hemisphere). 2. Why other options are incorrect: * Fusiform gyrus: Located on the basal surface of the temporal and occipital lobes; lesions here typically lead to prosopagnosia (inability to recognize faces). * Inferior occipital gyrus: While part of the visual processing pathway, a localized lesion here would cause field defects but not the specific disconnection syndrome of alexia without agraphia. * Psalternum: Also known as the commissure of the fornix; it connects the two hippocampi and is involved in memory pathways, not visual-language integration. Clinical Pearls for NEET-PG: * Classic Triad: Right homonymous hemianopia + Alexia + Intact writing. * Vascular Supply: This syndrome is most commonly associated with a stroke involving the Left Posterior Cerebral Artery (PCA). * Angular Gyrus Lesion: In contrast, a lesion of the left angular gyrus results in Alexia WITH Agraphia (Gerstmann Syndrome).

Q: Which of the following fibres do not pass through the posterior limb of the internal capsule?

Corticopontine fibres. The **Internal Capsule** is a massive bundle of projection fibers divided into several parts. Understanding the specific topography of these fibers is a high-yield topic for NEET-PG. [1] ### **Why "Corticopontine fibres" is the Correct Answer** While the question is slightly nuanced, it refers to the **Frontopontine** fibers. These specific corticopontine fibers pass through the **Anterior Limb** of the internal capsule, not the posterior limb. Other corticopontine fibers (like parietopontine or occipitopontine) pass through the retrolentiform and sublentiform parts. Since "Corticopontine" is often used synonymously with the major frontopontine tract in exam contexts, it is the most appropriate outlier for the posterior limb. ### **Analysis of Other Options** * **Sublentiform & Retrolentiform fibres:** These are technically distinct anatomical divisions, but in many clinical descriptions, they are considered extensions or components of the "posterior" aspect of the internal capsule. They carry visual (optic radiation) and auditory (acoustic radiation) pathways. * **Dorsal column fibres:** These represent the **Sensory Radiation** (Third-order neurons from the VPL/VPM of the Thalamus). These fibers, which carry conscious proprioception and discriminative touch, pass through the **Posterior Limb** to reach the postcentral gyrus. [1] ### **High-Yield NEET-PG Pearls** * **Anterior Limb:** Contains Frontopontine fibers and Anterior Thalamic radiation. * **Genu:** Contains **Corticobulbar** (Corticonuclear) fibers. [1] * **Posterior Limb:** Contains **Corticospinal** fibers (Motor) and Superior Thalamic radiation (Sensory). [1] * **Blood Supply:** The posterior limb is primarily supplied by the **Lenticulostriate arteries** (branches of MCA) and the **Anterior Choroidal artery**. A stroke here typically results in contralateral pure motor hemiplegia. [1]

Q: Which sensation is not represented in the sensory cortex?

Olfaction. **Explanation:** The **Primary Somatosensory Cortex (Postcentral Gyrus, Brodmann areas 3, 1, 2)** is responsible for processing general somatic sensations [1]. **Why Olfaction is the correct answer:** Olfaction (smell) is a special sense, not a general somatic sensation. Unlike almost all other sensory modalities, olfactory pathways are unique because they **do not relay in the thalamus** before reaching the primary cortical area [2]. The primary olfactory cortex is located in the **rhinal cortex (uncus)** and the piriform lobe of the temporal lobe, rather than the sensory cortex (parietal lobe) [2]. Therefore, it is not represented in the somatosensory cortex. **Analysis of Incorrect Options:** * **A, B, & C (Pain, Temperature, and Touch):** These are all forms of **General Somatic Afferent (GSA)** sensations. They are carried via the Spinothalamic tracts (Pain and Temperature) and the Dorsal Column-Medial Lemniscal pathway (Fine touch/Pressure) [1]. These pathways relay in the **Ventral Posterior Lateral (VPL) nucleus** of the thalamus and project directly to the **Postcentral Gyrus** (Sensory Cortex) for conscious perception [1]. **High-Yield NEET-PG Pearls:** * **Thalamic Exception:** Olfaction is the only sense that bypasses the thalamus to reach the cortex directly. * **Sensory Homunculus:** The representation of body parts in the sensory cortex is disproportionate, with the largest areas dedicated to the face, lips, and hands. * **Lesion Localization:** A lesion in the postcentral gyrus results in **contralateral** loss of discriminative touch and proprioception, though crude pain and temperature may still be felt at the thalamic level.

Q: Which artery or arteries supply the occipital cortex?

Posterior Cerebral Artery (PCA). The **Posterior Cerebral Artery (PCA)** is the primary vessel responsible for the blood supply to the **occipital lobe**, including the primary visual cortex (Brodmann area 17) [1]. As the terminal branch of the basilar artery, the PCA curves around the midbrain to supply the medial and inferior surfaces of the temporal and occipital lobes. Specifically, the **calcarine artery**, a branch of the PCA, runs in the calcarine sulcus to supply the visual cortex [1]. **Analysis of Options:** * **Option A (Correct):** The PCA supplies the entire medial surface of the occipital lobe and the majority of its lateral surface [1]. * **Option B (Incorrect):** The **Middle Cerebral Artery (MCA)** supplies the majority of the lateral surface of the cerebral hemispheres (frontal, parietal, and temporal lobes) but does not extend significantly into the occipital cortex. * **Option C (Incorrect):** While the MCA and PCA have a watershed zone at the occipital pole, the primary and functional supply of the occipital cortex is attributed to the PCA. * **Option D (Incorrect):** The **Anterior Cerebral Artery (ACA)** supplies the medial surface of the frontal and parietal lobes up to the parieto-occipital sulcus. **Clinical Pearls for NEET-PG:** 1. **Macular Sparing:** In PCA occlusion, there is often "contralateral homonymous hemianopia with macular sparing." The macula is spared because the **occipital pole** (where the macula is represented) has a dual blood supply from both the **PCA and MCA** [1]. 2. **Visual Agnosia:** Damage to the visual association areas in the occipital lobe (supplied by PCA) can lead to the inability to recognize objects despite intact sight. 3. **Calcarine Artery:** This is the most important branch of the PCA for visual function; its occlusion leads to cortical blindness [1].

Q: Which thalamic nucleus forms the Papez circuit?

Anterior nucleus. The **Anterior Nucleus of the Thalamus** is the correct answer because it serves as a vital relay station in the **Papez Circuit**, which is the fundamental anatomical pathway for emotional expression and memory consolidation within the limbic system [1]. The flow of the Papez circuit is as follows: **Hippocampus** → (via Fornix) → **Mammillary bodies** → (via Mammillothalamic tract) → **Anterior Nucleus of Thalamus** → (via Internal capsule) → **Cingulate Gyrus** → (via Entorhinal cortex) → **Hippocampus** [1]. **Analysis of Incorrect Options:** * **B. Medial Geniculate Nucleus (MGN):** This is the thalamic relay station for the **auditory pathway**. (Mnemonic: **M**edial for **M**usic). * **C. Lateral Geniculate Nucleus (LGN):** This is the thalamic relay station for the **visual pathway**. (Mnemonic: **L**ateral for **L**ight). * **D. Posterior Nucleus:** This part of the thalamus (including the Pulvinar) is primarily involved in sensory integration and higher-order visual processing, not the Papez circuit. **High-Yield Clinical Pearls for NEET-PG:** * **Korsakoff Syndrome:** Damage to the mammillary bodies and the mammillothalamic tract (often due to Thiamine/B1 deficiency) disrupts this circuit, leading to anterograde amnesia and confabulation. * **Input/Output:** The Anterior nucleus receives its primary input from the **Mammillothalamic tract** and projects mainly to the **Cingulate gyrus** [1]. * **Function:** The Papez circuit is essential for converting short-term memory into long-term memory.

Q: What is the term for the arrangement of cerebellar grey matter?

Arbor vitae. The correct answer is **B. Arbor vitae.** ### **Explanation** The **Arbor vitae** (Latin for "Tree of Life") refers to the characteristic branching pattern of the **white matter** within the cerebellum, as seen in a sagittal section [1]. While the question asks for the arrangement of cerebellar matter, it specifically refers to the tree-like appearance created by the deep white matter tracts as they branch out into the overlying cerebellar cortex (grey matter) [1]. This arrangement is essential for carrying sensory and motor information to and from the cerebellar cortex. ### **Analysis of Incorrect Options** * **A. Folium:** This refers to a single leaf-like fold of the cerebellar cortex. The surface of the cerebellum is folded into many parallel ridges called folia, which increase the surface area of the grey matter [1]. * **C. Declive & D. Culmen:** These are specific anatomical parts of the **Vermis** (the midline structure connecting the two cerebellar hemispheres) [1]. The Culmen is the highest point of the vermis, and the Declive is the sloping portion posterior to it [1]. They are part of the Lobulus Centralis and Monticulus, respectively. ### **High-Yield NEET-PG Pearls** * **Deep Cerebellar Nuclei:** Remember the mnemonic **"Don't Eat Greasy Food"** (Lateral to Medial): **D**entate, **E**mboliform, **G**lobose, and **F**astigial nuclei [1]. * **Layers of Cerebellar Cortex:** From outer to inner: Molecular layer → Purkinje cell layer (middle) → Granular layer (inner) [1]. * **Clinical Correlation:** Lesions to the midline structures (Vermis/Culmen/Declive) typically result in **truncal ataxia**, whereas lesions to the cerebellar hemispheres result in **ipsilateral limb ataxia** and intention tremors [1].

Q: Which of the following vessels does not contribute to the formation of the Circle of Willis?

Anterior choroidal artery. The **Circle of Willis (Circulus Arteriosus)** is a vital polygonal anastomotic network located at the base of the brain in the interpeduncular fossa [2]. It provides collateral circulation between the internal carotid and vertebrobasilar systems [2]. ### **Explanation of Options** * **Correct Answer (A): Anterior choroidal artery.** This is a branch of the **Internal Carotid Artery (ICA)**. While it arises near the Circle of Willis, it does not form part of the actual hexagonal ring. It primarily supplies the internal capsule, optic tract, and choroid plexus. * **Option (B): Anterior cerebral artery (ACA).** This is a terminal branch of the ICA and forms the **anterolateral** segment of the circle. * **Option (C): Posterior cerebral artery (PCA).** This is the terminal branch of the Basilar artery and forms the **posterior** segment of the circle. * **Option (D): Anterior communicating artery.** This is a small bridge connecting the two ACAs, forming the **anterior** boundary of the circle. ### **Components of the Circle of Willis** To remember the components, visualize the ring from anterior to posterior: 1. **Anterior communicating artery** (1) 2. **Anterior cerebral arteries** (2) 3. **Internal carotid arteries** (2) 4. **Posterior communicating arteries** (2) 5. **Posterior cerebral arteries** (2) ### **High-Yield NEET-PG Pearls** * **Most common site for Berry Aneurysms:** Junction of the **Anterior Communicating Artery** and Anterior Cerebral Artery [1]. * **Rupture of Berry Aneurysm:** Leads to **Subarachnoid Hemorrhage (SAH)**, classically described as the "worst headache of life." * **Middle Cerebral Artery (MCA):** Despite being the largest terminal branch of the ICA, the **MCA is NOT part of the Circle of Willis**. This is a frequent "trap" in exams.

Q: Which of the following is true regarding Dandy-Walker syndrome?

All of the above. **Explanation:** **Dandy-Walker Malformation (DWM)** is a congenital brain malformation involving the cerebellum and the surrounding fluid-filled spaces. It is primarily characterized by a **classic triad**: 1. **Cystic expansion of the fourth ventricle** into the posterior fossa. 2. **Agenesis or hypoplasia of the cerebellar vermis** (mid-cerebellum). 3. **Enlargement of the posterior fossa** with upward displacement of the tentorium cerebelli and transverse sinuses. **Why Option D is correct:** * **Option A:** Approximately 70–90% of patients develop **obstructive hydrocephalus**, often due to atresia of the foramina of Luschka and Magendie or associated aqueductal stenosis [2]. * **Option B:** The hallmark of the syndrome is the ballooning of the fourth ventricle into a large posterior fossa cyst. * **Option C:** The cerebellar vermis (the midline structure) is typically small, rotated, or partially/completely absent. **High-Yield Clinical Pearls for NEET-PG:** * **Key Presentation:** Macrocephaly (due to hydrocephalus), delayed motor milestones, and signs of cerebellar dysfunction (ataxia, nystagmus). * **Imaging:** MRI is the gold standard. Look for the "keyhole" appearance of the fourth ventricle and an elevated torcula (torcular-lambdoid inversion). * **Differential Diagnosis:** * *Mega Cisterna Magna:* Large posterior fossa but the vermis and fourth ventricle are normal. * *Arachnoid Cyst:* Displaces the cerebellum rather than showing vermian hypoplasia. * **Associations:** Often associated with **corpus callosum agenesis** [1], cardiac defects, and polydactyly. Note: While the provided references primarily discuss related posterior fossa anomalies like Chiari malformations, they highlight the specific associations of hydrocephalus and vermian/corpus callosal anomalies seen in these complex congenital syndromes [1][3].

Q: The pineal gland is located on the posterior wall of which ventricle?

Third ventricle posterior wall. The pinneal gland (epiphysis cerebri) is a small, cone-shaped endocrine structure located in the midline of the brain. It is embryologically derived from the neuroectoderm and is situated in the posterior wall of the third ventricle. Specifically, it is attached to the diencephalon by a stalk that divides into two laminae: the superior lamina (containing the habenular commissure) and the inferior lamina (containing the posterior commissure). The pineal gland sits in the depression between the two superior colliculi. Analysis of Options: * Option C (Correct): The pineal gland forms part of the epithalamus, which constitutes the posterior boundary/wall of the third ventricle. * Option A (Incorrect): The floor of the third ventricle is formed by structures of the hypothalamus, including the optic chiasma, tuber cinereum, infundibulum, and mammillary bodies. * Option B (Incorrect): The anterior wall is formed by the lamina terminalis, the anterior commissure, and the column of the fornix. * Option D (Incorrect): The roof is formed by a layer of ependyma covered by the vascular fringe of the tela choroidea. High-Yield Clinical Pearls for NEET-PG: * Melatonin: The pineal gland secretes melatonin, which regulates the circadian rhythm (sleep-wake cycle). * Brain Sand (Acervuli Cerebri): With age, the gland accumulates calcium and magnesium salts. These are radio-opaque and serve as a useful midline marker on skull X-rays and CT scans. * Parinaud Syndrome: A pineal gland tumor (Pinealoma) can compress the superior colliculi and the pretectal nucleus, leading to "Upward Gaze Palsy." [1]

Q: Which of the following cranial nerve nuclei is not a part of the special visceral afferent (SVA) column?

Trochlear nerve. ### Explanation The **Special Visceral Afferent (SVA)** column is responsible for the special senses associated with the gastrointestinal tract, specifically **taste (gustation)** and **smell (olfaction)**. In the brainstem, the SVA fibers for taste are carried by the **Nucleus Tractus Solitarius (NTS)**—specifically its rostral part (gustatory nucleus). **1. Why Trochlear Nerve is the Correct Answer:** The **Trochlear nerve (CN IV)** is a pure motor nerve. It belongs to the **General Somatic Efferent (GSE)** column. Its sole function is to provide motor innervation to the Superior Oblique muscle of the eye. It has no sensory component, and therefore, no involvement in the SVA column. **2. Analysis of Incorrect Options:** * **Facial Nerve (CN VII):** Carries SVA fibers for taste from the anterior 2/3 of the tongue [1]. * **Glossopharyngeal Nerve (CN IX):** Carries SVA fibers for taste from the posterior 1/3 of the tongue [1]. * **Vagus Nerve (CN X):** Carries SVA fibers for taste from the epiglottis and vallecula [2]. * *Note: All three nerves (VII, IX, X) terminate in the rostral portion of the Nucleus Tractus Solitarius.* **3. NEET-PG High-Yield Pearls:** * **Nucleus Tractus Solitarius (NTS):** The "S" in Solitarius stands for **S**ensory. It handles **SVA** (Taste: VII, IX, X) and **GVA** (Visceral sensation: IX, X). * **Trochlear Nerve Unique Facts:** It is the only cranial nerve that emerges from the **dorsal** aspect of the brainstem, has the **longest intracranial course**, and is the **thinnest** cranial nerve. * **SVA Summary:** Includes CN I (Olfactory) and the taste components of CN VII, IX, and X.

Question 1

What is the site of lesion in a patient with alexia without agraphia?

Accepted Answer

Splenium

Answer

Fusiform gyrus

Answer

Inferior occipital gyrus

Answer

Psalternum

Question 2

Which of the following fibres do not pass through the posterior limb of the internal capsule?

Accepted Answer

Corticopontine fibres

Answer

Sublentiform fibres

Answer

Retrolentiform fibres

Answer

Dorsal column fibres

Question 3

Which sensation is not represented in the sensory cortex?

Accepted Answer

Olfaction

Answer

Pain

Answer

Temperature

Answer

Touch

Question 4

Which artery or arteries supply the occipital cortex?

Accepted Answer

Posterior Cerebral Artery (PCA)

Answer

Middle Cerebral Artery (MCA)

Answer

MCA + PCA

Answer

Anterior Cerebral Artery (ACA)

Question 5

Which thalamic nucleus forms the Papez circuit?

Accepted Answer

Anterior nucleus

Answer

Medial geniculate nucleus

Answer

Lateral geniculate nucleus

Answer

Posterior nucleus

Question 6

What is the term for the arrangement of cerebellar grey matter?

Accepted Answer

Arbor vitae

Answer

Folium

Answer

Declive

Answer

Culmen

Question 7

Which of the following vessels does not contribute to the formation of the Circle of Willis?

Accepted Answer

Anterior choroidal artery

Answer

Anterior cerebral artery

Answer

Posterior cerebral artery

Answer

Anterior communicating artery

Question 8

Which of the following is true regarding Dandy-Walker syndrome?

Accepted Answer

All of the above

Answer

Mostly presents with hydrocephalus

Answer

Characterized by cystic expansion of the fourth ventricle

Answer

Associated with mid-cerebellar hypoplasia

Question 9

The pineal gland is located on the posterior wall of which ventricle?

Accepted Answer

Third ventricle posterior wall

Answer

Third ventricle floor

Answer

Third ventricle anterior wall

Answer

Third ventricle roof

Question 10

Which of the following cranial nerve nuclei is not a part of the special visceral afferent (SVA) column?

Accepted Answer

Trochlear nerve

Answer

Facial nerve

Answer

Vagus nerve

Answer

Glossopharyngeal nerve

Brain and Neuroanatomy — MCQs

Brain and Neuroanatomy — MCQs

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