Brain and Neuroanatomy — MCQs

A 58-year-old male with a history of diabetes mellitus, hypertension, and hypercholesterolemia presents with loss of sensation below the level of the umbilicus. There is no motor loss and his bowel and bladder function are intact. An MRI scan revealed spinal infarction affecting the posterior white columns in the tenth thoracic segment of the spinal cord. Which of the following sensations would be intact in this patient?

Q170Easy

Two internal cerebral veins fuse to form which of the following veins?

Brain and Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 161: All are parts of the corpus callosum except?

A. Forceps minor
B. Forceps major
C. Tapetum
D. Indusium griseum (Correct Answer)

Explanation: The **Corpus Callosum** is the largest commissural fiber bundle connecting the two cerebral hemispheres. It consists of four main anatomical parts: the **Rostrum, Genu, Body (Trunk), and Splenium**. ### Why Indusium Griseum is the Correct Answer: The **Indusium griseum** is not a part of the corpus callosum itself; rather, it is a thin layer of vestigial gray matter (primitive cortex) that lies **on top** of the superior surface of the corpus callosum. It contains two longitudinal bands of white matter called the **medial and lateral longitudinal striae** (Striae of Lancisi). While anatomically related by position, it is functionally part of the limbic system (hippocampal formation), not the commissural fibers of the corpus callosum. ### Explanation of Incorrect Options: * **Forceps minor:** These are the fibers of the **Genu** that curve forward to connect the frontal lobes. * **Forceps major:** These are the fibers of the **Splenium** that curve backward into the occipital lobes. * **Tapetum:** These are fibers arising from the **Body and Splenium** that form the roof and lateral wall of the posterior and inferior horns of the lateral ventricle. ### High-Yield NEET-PG Pearls: * **Blood Supply:** Primarily by the **Anterior Cerebral Artery** (pericallosal and callomarginal branches). The splenium also receives supply from the posterior cerebral artery. * **Clinical Correlation:** **Marchiafava-Bignami disease** is a rare neurological condition characterized by primary demyelination and necrosis of the corpus callosum, often seen in chronic alcoholics. * **Surgical Note:** A **Callosotomy** (splitting the corpus callosum) is sometimes performed to treat refractory generalized epilepsy to prevent the spread of seizures between hemispheres.

Question 162: The ventricles of the brain are lined by which type of cells?

A. Ependymal cells (Correct Answer)
B. Astrocytes
C. Oligodendrocytes
D. Podocytes

Explanation: The correct answer is **A. Ependymal cells.** **Why Ependymal cells are correct:** The ventricles of the brain and the central canal of the spinal cord are lined by a specialized layer of simple cuboidal to columnar epithelium known as **Ependyma**. These cells are derived from the neuroectoderm. Their apical surfaces often possess **microvilli and cilia**, which facilitate the movement and circulation of Cerebrospinal Fluid (CSF). Specialized ependymal cells, in association with capillaries, form the **Choroid Plexus**, which is responsible for the active secretion of CSF. **Why the other options are incorrect:** * **B. Astrocytes:** These are star-shaped glial cells that form the blood-brain barrier (BBB) and provide structural and metabolic support to neurons [3]. They do not line the ventricular cavities. * **C. Oligodendrocytes:** These cells are responsible for the **myelination** of axons within the Central Nervous System (CNS) [1]. (Note: Schwann cells perform this function in the PNS). * **D. Podocytes:** These are specialized epithelial cells found in the **Bowman’s capsule of the kidney**, forming the filtration slits of the renal glomerulus. They have no anatomical presence in the brain. **High-Yield Clinical Pearls for NEET-PG:** * **Tanycytes:** Specialized ependymal cells found in the floor of the 3rd ventricle that transport hormones from CSF to the hypophyseal portal system. * **Blood-CSF Barrier:** Formed by the **tight junctions** between the epithelial cells of the choroid plexus (unlike the BBB, which is formed by endothelial tight junctions). * **Ependymoma:** A tumor arising from these cells, most commonly found in the 4th ventricle in children, often leading to obstructive hydrocephalus [2].

Question 163: Cerebellar glomeruli are seen in which layer of the cerebellum?

A. Molecular layer
B. Purkinje layer
C. Granular layer (Correct Answer)
D. None of the above

Explanation: Explanation: The **Cerebellar Glomerulus** is a complex synaptic structure located exclusively within the **Granular layer** (the innermost layer) of the cerebellar cortex. It serves as the primary processing station for incoming mossy fiber inputs [1]. **1. Why the Granular Layer is Correct:** The glomerulus is a functional unit where the large, bulbous terminal of an afferent **mossy fiber** synapses with the dendrites of numerous **Granule cells**. This complex is encapsulated by the processes of **Golgi cells** (inhibitory interneurons) [2]. This arrangement allows for the divergence of sensory information from a single mossy fiber to thousands of granule cells. **2. Why Incorrect Options are Wrong:** * **Molecular Layer:** This is the outermost, relatively cell-poor layer. It contains the axons of granule cells (parallel fibers), dendrites of Purkinje cells, and inhibitory interneurons like **Stellate and Basket cells** [1]. * **Purkinje Layer:** This is the middle, monolayered zone containing the large, flask-shaped cell bodies of **Purkinje cells**. While their dendrites extend into the molecular layer and their axons into the white matter, the glomerular synapses do not occur here [1]. **3. NEET-PG High-Yield Facts:** * **Components of a Glomerulus:** 1) Mossy fiber terminal (excitatory), 2) Granule cell dendrites (excitatory), and 3) Golgi cell axons (inhibitory) [2]. * **Climbing Fibers:** Unlike mossy fibers, climbing fibers (from the inferior olive) bypass the glomeruli and synapse directly onto Purkinje cell dendrites in a 1:1 ratio [2]. * **Cells of the Cerebellum:** All cells in the cerebellar cortex are **inhibitory (GABAergic)** except for the **Granule cells**, which are excitatory (Glutamatergic) [2].

Question 164: Which of the following is NOT a type of cell found in the cerebral cortex?

A. Cajal cells
B. Pyramidal cells
C. Stellate cells
D. Purkinje cells (Correct Answer)

Explanation: The cerebral cortex is organized into six distinct layers (neocortex) containing specific neuronal types. Understanding the localization of these cells is a high-yield topic for NEET-PG. ### **Why Purkinje Cells is the Correct Answer** **Purkinje cells** are the hallmark neurons of the **cerebellum**, not the cerebral cortex [1]. They are large, flask-shaped GABAergic neurons located in the middle layer (Purkinje cell layer) of the cerebellar cortex [1]. They provide the sole output from the cerebellar cortex to the deep cerebellar nuclei. ### **Analysis of Incorrect Options** * **A. Cajal cells (Cells of Cajal-Retzius):** These are spindle-shaped neurons found in the most superficial layer (Layer I - Molecular layer) of the cerebral cortex. They are crucial during embryonic development for the proper lamination of the cortex. * **B. Pyramidal cells:** These are the most numerous neurons in the cerebral cortex. They serve as the primary excitatory (glutamatergic) output neurons. Large pyramidal cells (Cells of Betz) are specifically found in Layer V of the motor cortex. * **C. Stellate cells:** Also known as granule cells, these are small, star-shaped interneurons. They are most abundant in Layer IV (Internal granular layer), which serves as the primary recipient of sensory input from the thalamus. ### **High-Yield Clinical Pearls for NEET-PG** * **Betz Cells:** The largest pyramidal cells, found in the primary motor cortex (Brodmann area 4), giving rise to the corticospinal tract. * **Layer IV:** This layer is highly developed in sensory areas (e.g., visual cortex) but nearly absent in motor areas [2]. * **Gennari's Band:** A macroscopic white line seen in the visual cortex (Layer IV), representing myelinated thalamocortical fibers. * **Purkinje vs. Purkinje:** Do not confuse **Purkinje cells** (cerebellum) with **Purkinje fibers** (specialized conduction cells in the heart).

Question 165: Cross section of the midbrain at the level of the superior colliculus shows which of the following structures?

A. Red nucleus and trochlear nerve nucleus
B. Red nucleus and abducent nerve nucleus
C. Red nucleus and optic nerve nucleus
D. Red nucleus and occulomotor nerve nucleus (Correct Answer)

Explanation: ### Explanation The midbrain is anatomically divided into two main levels based on the cranial nerve nuclei present: the level of the **inferior colliculus** and the level of the **superior colliculus**. **Why Option D is Correct:** At the level of the **superior colliculus** (the rostral part of the midbrain), the characteristic features include: 1. **Red Nucleus:** A large, vascularized mass of gray matter involved in motor coordination. 2. **Oculomotor Nerve Nucleus (CN III):** Located in the periaqueductal gray matter, ventral to the aqueduct. 3. **Edinger-Westphal Nucleus:** The parasympathetic component of CN III [1]. 4. **Pretectal Nucleus:** Involved in the pupillary light reflex [1]. **Analysis of Incorrect Options:** * **Option A:** The **Trochlear nerve nucleus (CN IV)** is located at the level of the **inferior colliculus**. It is the only cranial nerve to exit from the dorsal aspect of the brainstem. * **Option B:** The **Abducent nerve nucleus (CN VI)** is located in the **Pons** (specifically the lower pons, forming the facial colliculus), not the midbrain. * **Option C:** There is no "optic nerve nucleus" in the midbrain. The **Optic nerve (CN II)** is a tract of the diencephalon; its fibers terminate in the Lateral Geniculate Body (LGB) and the superior colliculus [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Weber’s Syndrome:** A lesion at the level of the superior colliculus involving the fascicles of CN III and the crus cerebri (corticospinal tract), leading to ipsilateral CN III palsy and contralateral hemiplegia. * **Benedikt’s Syndrome:** Involves the **Red Nucleus** and CN III fibers, resulting in ipsilateral CN III palsy and contralateral tremors/ataxia. * **Rule of 4s:** Midbrain contains nuclei for CN III and IV; Pons contains V, VI, VII, and VIII; Medulla contains IX, X, XI, and XII.

Question 166: Cerebrospinal fluid (CSF) is absorbed by which of the following structures?

A. Choroid plexus
B. Arachnoid granulations (Correct Answer)
C. Dura mater
D. Pia mater

Explanation: The circulation of Cerebrospinal Fluid (CSF) follows a specific physiological pathway: production, circulation, and absorption. **Why Arachnoid Granulations are correct:** CSF is primarily absorbed into the venous system through **arachnoid granulations** (and their smaller counterparts, arachnoid villi) [2]. These are protrusions of the arachnoid mater that pierce the dura mater to project into the **Superior Sagittal Sinus** and other dural venous sinuses [3]. Absorption occurs via a pressure gradient; when CSF pressure exceeds venous pressure, the vacuoles within these granulations transport CSF into the blood [1]. **Analysis of Incorrect Options:** * **A. Choroid Plexus:** This is the site of CSF **production**, not absorption [2], [3]. It is located in the lateral, third, and fourth ventricles and consists of tufts of capillaries covered by ependymal cells. * **C. Dura Mater:** This is the tough, outermost meningeal layer. While it contains the venous sinuses into which CSF is drained, the dura itself does not possess the specialized transport mechanisms for absorption. * **D. Pia Mater:** This is the delicate, innermost layer closely adherent to the brain surface. It plays a role in the blood-brain barrier but is not involved in the bulk drainage of CSF. **High-Yield Clinical Pearls for NEET-PG:** * **Normal Pressure Hydrocephalus (NPH):** Caused by impaired CSF absorption at the arachnoid granulations. It presents with the classic triad: *Urinary incontinence, Gait ataxia, and Dementia* ("Wet, Wobbly, and Wacky"). * **Flow Pathway:** Lateral ventricles → Foramen of Monro → 3rd ventricle → Aqueduct of Sylvius → 4th ventricle → Foramina of Luschka/Magendie → Subarachnoid space → Arachnoid granulations [2]. * **Rate of Production:** Approximately 0.3–0.5 ml/min (roughly 500 ml/day), though the total volume present at any time is only about 150 ml [3].

Question 167: Which of the following brainstem nuclei is not derived from the alar plate?

A. Inferior olivary nucleus
B. Substantia nigra
C. Red nucleus
D. Hypoglossal nucleus (Correct Answer)

Explanation: ### Explanation The development of the brainstem is organized around the **sulcus limitans**, which divides the neural tube into a dorsal **alar plate** (sensory functions) and a ventral **basal plate** (motor functions). **Why the Hypoglossal Nucleus is the Correct Answer:** The **Hypoglossal nucleus (CN XII)** is a General Somatic Efferent (GSE) nucleus located in the medulla. Since it provides motor innervation to the muscles of the tongue, it is derived from the **basal plate**. In the brainstem, basal plate derivatives are located medially, while alar plate derivatives are pushed laterally as the fourth ventricle opens. **Analysis of Incorrect Options:** * **Inferior Olivary Nucleus:** Although motor-related in function (coordinating movement via the cerebellum), these nuclei develop from the **rhombic lips** of the alar plate. They migrate ventrally to their final position in the medulla. * **Substantia Nigra & Red Nucleus:** Both are midbrain structures. Despite their motor functions in the extrapyramidal system, embryological studies indicate they originate from the **alar plate** (specifically the marginal zone) and migrate ventrally into the tegmentum. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Basal vs. Alar:** **B**asal = **B**efore (Front/Motor); **A**lar = **B**after (Back/Sensory). * **Medial vs. Lateral:** In the mature brainstem, motor nuclei (basal plate) are **medial** to the sulcus limitans, while sensory nuclei (alar plate) are **lateral** [1]. * **Pure Alar Plate Derivatives:** Sensory nuclei of cranial nerves, Pontine nuclei, Inferior olive, and the Cerebellum. * **Pure Basal Plate Derivatives:** Motor nuclei of CN III, IV, VI, and XII (GSE column).

Question 168: Which of the following is NOT true regarding the blood supply of the cerebral hemispheres?

A. The Middle Cerebral Artery (MCA) is the main supplier of the superolateral surface.
B. The Anterior Cerebral Artery (ACA) is the main supplier of the inferior surface. (Correct Answer)
C. The Posterior Cerebral Artery (PCA) is the main supplier of the inferior surface.
D. All three arteries supply each surface.

Explanation: To master the blood supply of the cerebral hemispheres, it is essential to map each artery to its specific territory. This question tests your knowledge of the distribution of the three major cerebral arteries: ### **1. Why Option B is the Correct Answer (The False Statement)** The **Anterior Cerebral Artery (ACA)** primarily supplies the **medial surface** of the cerebral hemisphere (up to the parieto-occipital sulcus) and a thin strip (1 inch) of the superolateral surface. It does **not** supply the majority of the inferior surface. The inferior surface is predominantly supplied by the **Posterior Cerebral Artery (PCA)** and the **Middle Cerebral Artery (MCA)**. ### **2. Analysis of Other Options** * **Option A (True):** The **MCA** is the largest branch and supplies the bulk of the **superolateral surface**, except for the narrow peripheral strips supplied by the ACA and PCA. * **Option C (True):** The **PCA** is indeed the main supplier of the **inferior surface** (specifically the temporal and occipital lobes) and the medial surface of the occipital lobe (visual cortex). * **Option D (True):** While each artery has a dominant territory, all three (ACA, MCA, PCA) contribute to the blood supply of every surface (Superolateral, Medial, and Inferior) at the peripheral margins where their territories overlap [1], [2]. ### **3. High-Yield Clinical Pearls for NEET-PG** * **Motor Homunculus:** The ACA supplies the "leg and foot" area (paracentral lobule). An ACA stroke leads to contralateral lower limb weakness. * **MCA Stroke:** Most common site of stroke. It affects the "face and arm" area and includes **Broca’s and Wernicke’s areas** (dominant hemisphere), leading to aphasia. * **Macular Sparing:** In PCA territory infarcts involving the visual cortex, macular vision is often spared because the **MCA** provides collateral supply to the occipital pole. * **Charcot’s Artery:** The lenticulostriate branches of the MCA are the "arteries of cerebral hemorrhage," frequently involved in hypertensive strokes.

Question 169: A 58-year-old male with a history of diabetes mellitus, hypertension, and hypercholesterolemia presents with loss of sensation below the level of the umbilicus. There is no motor loss and his bowel and bladder function are intact. An MRI scan revealed spinal infarction affecting the posterior white columns in the tenth thoracic segment of the spinal cord. Which of the following sensations would be intact in this patient?

A. Position sense
B. Pain (Correct Answer)
C. Touch
D. Vibration

Explanation: ### Explanation The patient presents with a spinal infarction localized to the **posterior white columns** (Dorsal Columns) at the T10 level. To answer this question, one must distinguish between the different sensory pathways of the spinal cord. **1. Why "Pain" is the Correct Answer:** Pain and temperature sensations are carried by the **Lateral Spinothalamic Tract** [1], while crude touch and pressure are carried by the **Anterior Spinothalamic Tract**. These tracts are located in the lateral and anterior funiculi of the spinal cord, respectively. Since the infarction is restricted to the posterior columns, the spinothalamic tracts remain functional. Therefore, the patient will still be able to perceive pain [2]. **2. Why the Other Options are Incorrect:** * **A, C, and D (Position sense, Touch, and Vibration):** These sensations are specifically mediated by the **Dorsal Column-Medial Lemniscal (DCML) pathway**, which consists of the Fasciculus Gracilis and Fasciculus Cuneatus. The DCML is responsible for: * **Fine (discriminative) touch** * **Conscious Proprioception** (Position sense) * **Vibration sense** * **Two-point discrimination** Because the MRI confirms damage to the posterior white columns, all these modalities will be lost below the level of the lesion. **Clinical Pearls for NEET-PG:** * **T10 Landmark:** The umbilicus corresponds to the T10 dermatome [1]. * **Blood Supply:** The posterior columns are supplied by the **Posterior Spinal Arteries**. An infarct here is rarer than an Anterior Spinal Artery syndrome (which spares the dorsal columns but causes motor and pain loss). * **Tabes Dorsalis:** A classic neurosyphilis manifestation that selectively involves the destruction of the posterior columns, leading to sensory ataxia and loss of vibration/position sense.

Question 170: Two internal cerebral veins fuse to form which of the following veins?

A. Middle cerebral vein
B. Anterior cerebral vein
C. Great cerebral vein (Correct Answer)
D. Inferior cerebral vein

Explanation: The **Great Cerebral Vein (of Galen)** is a short, thick venous trunk formed by the union of the **two internal cerebral veins**. This union occurs just below and behind the splenium of the corpus callosum. The great cerebral vein then travels posteriorly to join the inferior sagittal sinus, ultimately forming the **straight sinus**. **Analysis of Options:** * **Great Cerebral Vein (Correct):** It is the definitive vessel formed by the fusion of the internal cerebral veins. It drains the deep structures of the forebrain. * **Middle Cerebral Vein (Incorrect):** This is a superficial vein (Superficial Middle Cerebral Vein) or a deep vein (Deep Middle Cerebral Vein). The deep middle cerebral vein joins the anterior cerebral vein to form the **Basal Vein of Rosenthal**, not the Great Cerebral Vein. * **Anterior Cerebral Vein (Incorrect):** This vein accompanies the anterior cerebral artery and joins the deep middle cerebral vein to form the Basal Vein of Rosenthal. * **Inferior Cerebral Vein (Incorrect):** These are small veins that drain the undersurface of the hemispheres and empty into the cavernous and transverse sinuses. **High-Yield Facts for NEET-PG:** * **Internal Cerebral Veins:** Formed at the interventricular foramen (of Monro) by the union of the **thalamostriate vein** and the **choroid vein**. * **Basal Vein of Rosenthal:** Formed by the union of the anterior cerebral vein, deep middle cerebral vein, and inferior striate veins. It eventually drains into the Great Cerebral Vein. * **Vein of Galen Malformation:** A high-yield clinical condition in pediatrics involving an AV malformation that can lead to high-output heart failure in neonates. * **Straight Sinus:** Formed by the Great Cerebral Vein and the Inferior Sagittal Sinus.

Practice by Chapter

Cerebral Hemispheres

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Diencephalon

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Brainstem

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Cerebellum

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Basal Ganglia

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Limbic System

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Ventricular System and CSF

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Blood Supply of the Brain

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Cranial Nerves and Nuclei

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Functional Systems and Pathways

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Applied Neuroanatomy

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Neuroimaging Correlations

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