Brain and Neuroanatomy Practice Questions

Q: Lesion of the posterior inferior cerebellar artery in the brain involves/affects which of the following structures?

All of the above. The question refers to **Lateral Medullary Syndrome (Wallenberg Syndrome)**, which occurs due to the occlusion of the **Posterior Inferior Cerebellar Artery (PICA)** or the vertebral artery. This syndrome is a high-yield topic for NEET-PG as it involves a specific cluster of neuroanatomical structures located in the posterolateral part of the medulla. ### **Explanation of Structures Involved:** The PICA supplies the lateral territory of the medulla. A lesion here affects: * **Spinal tract and nucleus of the Trigeminal nerve:** This leads to loss of pain and temperature sensation on the **ipsilateral** side of the face. * **Nucleus and Tractus Solitarius:** This results in the loss of taste sensation (ageusia). * **Lateral Spinothalamic Tract:** This results in the loss of pain and temperature sensation on the **contralateral** side of the body. Since all three structures are located in the lateral medulla and are supplied by the PICA, **Option D (All of the above)** is the correct answer. ### **Clinical Pearls for NEET-PG:** * **Nucleus Ambiguus involvement:** This is the "hallmark" of Wallenberg syndrome, leading to paralysis of the palate, pharynx, and larynx (symptoms: dysphagia, dysarthria, and loss of gag reflex). * **Horner’s Syndrome:** Occurs due to damage to the descending sympathetic fibers. * **Vestibular Nuclei:** Damage leads to vertigo, nausea, and nystagmus. * **Rule of 4s:** Remember that PICA/Lateral Medullary syndrome **spares** the medial structures (Motor/Hypoglossal nerve and Medial Lemniscus), which are instead affected in Medial Medullary Syndrome (occlusion of the Anterior Spinal Artery).

Q: Which part of the brain is the olive located in?

Medulla. The **Olive** (or olivary body) is a prominent oval elevation located on the anterolateral surface of the **Medulla Oblongata**. It is situated lateral to the pyramid, separated from it by the anterolateral (pre-olivary) sulcus. **1. Why Medulla is Correct:** The olive is produced by the underlying **Inferior Olivary Nucleus**, a large mass of gray matter. This nucleus is a vital part of the extrapyramidal system, receiving inputs from the spinal cord and cerebral cortex and sending "climbing fibers" to the cerebellum via the inferior cerebellar peduncle. These fibers are essential for motor learning and coordination. **2. Why Other Options are Incorrect:** * **Cerebellum:** While the olive sends major projections to the cerebellum, it is anatomically located in the brainstem (medulla). * **Midbrain:** Key landmarks here include the superior and inferior colliculi (posteriorly) and the cerebral peduncles (anteriorly). * **Pons:** Characterized by the transverse pontine fibers and the basilar groove; it lies superior to the medulla. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Cranial Nerve Exit:** The **Hypoglossal nerve (CN XII)** emerges from the sulcus *between* the pyramid and the olive (pre-olivary sulcus). * **Post-olivary Sulcus:** The Glossopharyngeal (IX) and Vagus (X) nerves emerge lateral to the olive. * **Superior Olivary Nucleus:** Unlike the inferior nucleus in the medulla, the superior olivary nucleus is located in the **Pons** and is part of the auditory pathway (involved in sound localization). Do not confuse the two!

Q: Which of the following statements is true about the subarachnoid space?

It surrounds the conus medullaris.. ### Explanation **1. Why Option A is Correct:** The subarachnoid space is the interval between the arachnoid mater and the pia mater. It contains cerebrospinal fluid (CSF) and major blood vessels [2]. In the spinal column, the spinal cord ends at the level of **L1–L2** (the **conus medullaris**). Since the subarachnoid space extends down to the level of the **S2 vertebra**, it completely surrounds the conus medullaris and continues inferiorly as the lumbar cistern. **2. Why the Other Options are Incorrect:** * **Option B:** The subarachnoid space is **internal** (deep) to the subdural space [2]. The layers from superficial to deep are: Dura mater → Subdural space (potential) → Arachnoid mater → Subarachnoid space → Pia mater. * **Option C:** The subarachnoid space is located between the **arachnoid mater and the pia mater**. The pia mater is the innermost layer that is closely adherent to the brain surface; there is no space between the pia and the brain itself. * **Option D:** The space between the dura mater and the arachnoid mater is the **subdural space**, not the subarachnoid space [2]. **3. NEET-PG High-Yield Clinical Pearls:** * **Lumbar Puncture:** Performed in the **lumbar cistern** (subarachnoid space) between **L3-L4 or L4-L5** to avoid injuring the conus medullaris. * **Subarachnoid Hemorrhage (SAH):** Usually results from a ruptured **Berry aneurysm** in the Circle of Willis [3]. It presents as the "worst headache of life" (thunderclap headache). * **Cisterns:** The subarachnoid space enlarges at certain areas to form cisterns (e.g., Cisterna Magna, Interpeduncular cistern). * **Arachnoid Villi:** These are the sites where CSF is reabsorbed into the dural venous sinuses [1].

Q: The paracentral lobule is located in which part of the cerebral hemisphere?

Medial surface. **Explanation:** The **paracentral lobule** is a U-shaped convolution located on the **medial surface** of the cerebral hemisphere [1]. It surrounds the indentation produced by the central sulcus. It is anatomically continuous with the precentral and postcentral gyri of the superolateral surface and is bounded inferiorly by the cingulate sulcus [2]. **Why the correct answer is right:** * **Medial Surface:** The paracentral lobule is a key landmark of the medial surface. It is divided into an anterior part (part of the frontal lobe/motor cortex) and a posterior part (part of the parietal lobe/sensory cortex). It represents the **motor and sensory innervation for the lower limb, foot, and perineum (including sphincters).** [1] **Why the other options are wrong:** * **Superolateral Surface:** While the precentral and postcentral gyri are here, the paracentral lobule itself is tucked onto the medial aspect. * **Orbital Surface:** This is the inferior aspect of the frontal lobe, containing the olfactory bulb and gyrus rectus. * **Tentorial Surface:** This is the inferior aspect of the temporal and occipital lobes, resting on the tentorium cerebelli. **High-Yield Clinical Pearls for NEET-PG:** * **Blood Supply:** The paracentral lobule is supplied by the **Anterior Cerebral Artery (ACA)**. * **Clinical Correlation:** An ACA infarct or a parasagittal meningioma typically presents with **contralateral hemiparesis and hemisensory loss specifically involving the lower limb**, often accompanied by urinary incontinence (due to involvement of the cortical center for micturition). * **Functional Areas:** The anterior part corresponds to Brodmann area 4 (motor), and the posterior part corresponds to areas 1, 2, and 3 (sensory) [1].

Q: A patient with a small lacunar infarction complains of left hemisensory loss involving the face, arm, and leg equally. On exam, the patient has hemisensory loss to pin prick, temperature, and proprioception on the entire left side including the trunk. Which thalamic subnucleus is likely affected contralaterally?

Ventral posterolateral. ### Explanation **1. Why Ventral Posterolateral (VPL) is Correct:** The patient presents with **Pure Sensory Stroke (PSS)**, a classic lacunar syndrome most commonly caused by a small infarct in the **thalamus**. The VPL nucleus is the primary relay station for somatosensory pathways from the body (Spinothalamic tract and Dorsal Column-Medial Lemniscus). * **VPL (Ventral Posterolateral):** Receives sensory input from the **body and limbs** [2]. * **VPM (Ventral Posteromedial):** Receives sensory input from the **face** (via the Trigeminal nerve). In clinical practice and NEET-PG scenarios, a lacunar infarct involving the **ventroposterior complex (VPL + VPM)** results in a dense hemisensory loss involving the face, arm, and leg equally, as described in the question [1]. **2. Why Other Options are Incorrect:** * **Pulvinar:** Involved in visual processing and salience; damage does not cause primary sensory loss. * **Lateral Geniculate Nucleus (LGN):** The relay center for the **visual pathway**. Damage leads to contralateral homonymous hemianopia. * **Medial Geniculate Nucleus (MGN):** The relay center for the **auditory pathway** ("M" for Music/Medial). **3. Clinical Pearls for NEET-PG:** * **Pure Sensory Stroke:** Usually due to occlusion of the **thalamogeniculate branches** of the Posterior Cerebral Artery (PCA). * **Pure Motor Hemiparesis:** The most common lacunar syndrome; involves the **Posterior limb of the Internal Capsule** (Lenticulostriate arteries). * **Dejerine-Roussy Syndrome:** A late complication of thalamic stroke characterized by "thalamic pain"—severe, paroxysmal pain on the hemisensory-depleted side. * **Rule of Thumb:** If sensory loss involves the **Body**, think **VPL**; if it involves the **Face**, think **VPM** (M for Mouth/Makeup).

Q: A 63-year-old male presented with sudden onset of weakness of the face and tongue and dysarthria, suggestive of a lesion involving the corticobulbar tract. MRI revealed an ischemic stroke in a certain part of the internal capsule. Which of the following parts of the internal capsule was most likely affected?

Genu. **Explanation:** The **Internal Capsule** is a compact bundle of white matter fibers that serves as a major highway for motor and sensory information between the cerebral cortex and the brainstem/spinal cord. **Why Genu is the Correct Answer:** The **Genu** (meaning "knee") is the bend of the internal capsule located between the anterior and posterior limbs. It specifically contains the **Corticobulbar (corticonuclear) tract** [1]. These fibers originate in the motor cortex and descend to synapse on the motor nuclei of cranial nerves in the brainstem [1]. Therefore, a lesion in the genu manifests as "bulbar" symptoms: contralateral weakness of the lower face (CN VII) and tongue (CN XII), along with dysarthria and dysphagia. **Analysis of Incorrect Options:** * **Anterior Limb:** Primarily contains frontopontine fibers and thalamocortical projections (part of the limbic system). Lesions here do not typically cause motor deficits. * **Posterior Limb:** Contains the **Corticospinal tract** (motor fibers for the trunk and limbs) and general sensory fibers [1]. A lesion here would result in contralateral hemiplegia (body) and hemianesthesia, rather than isolated facial/tongue weakness. * **Both Genu and Posterior Limb:** While a large stroke could involve both, the clinical presentation described (face, tongue, and dysarthria) specifically isolates the corticobulbar fibers found in the genu. **High-Yield NEET-PG Pearls:** 1. **Genu:** Corticobulbar tract (Cranial nerves) [1]. 2. **Posterior Limb:** Corticospinal tract (Body motor) + Sensory radiations. 3. **Blood Supply:** The genu is primarily supplied by the **Lenticulostriate arteries** (branches of the Middle Cerebral Artery). 4. **Retrolentiform part:** Contains optic radiations (visual defects). 5. **Sublentiform part:** Contains auditory radiations.

Q: Auditory cortex is present in which Brodmann area?

Area 41. ### Explanation **Correct Option: A (Area 41)** The **Primary Auditory Cortex** is located in the superior temporal gyrus (specifically in the Heschl’s gyri) and corresponds to **Brodmann area 41**. It is the first relay station in the cortex for processing auditory information received from the medial geniculate body (MGB) of the thalamus. It is organized tonotopically, meaning different frequencies are mapped to specific areas of the cortex. **Analysis of Incorrect Options:** * **Area 42:** This is the **Auditory Association Cortex** (Secondary Auditory Cortex). While it also processes sound, it is involved in more complex analysis, such as interpreting the meaning of sounds or music. * **Area 44:** This corresponds to **Broca’s Area** (specifically the pars opercularis), located in the frontal lobe. It is responsible for motor speech production. Damage here leads to Broca’s (non-fluent) aphasia. * **Area 48:** This is the **Retrosubicular area**, located on the medial surface of the temporal lobe. It is involved in the hippocampal formation and memory, not primary auditory processing. **High-Yield Clinical Pearls for NEET-PG:** * **Wernicke’s Area:** Located in **Area 22** (posterior part of superior temporal gyrus). It is crucial for language comprehension. * **Pathway:** Remember the mnemonic **"M"** for **M**edial Geniculate Body = **M**usic (Auditory), and **"L"** for **L**ateral Geniculate Body = **L**ight (Visual). * **Lesion:** Unilateral destruction of Area 41 does not cause total deafness because auditory input from each ear is projected bilaterally to both hemispheres; however, it leads to difficulty in localizing sound.

Q: Facial colliculus is seen in which part of the brainstem?

Pons. The **Facial Colliculus** is a prominent elevation found on the **floor of the fourth ventricle** (rhomboid fossa) in the **lower part of the Pons**. ### 1. Why Pons is Correct The facial colliculus is an anatomical landmark formed by the **axons of the Facial nerve (CN VII)** as they loop around the **nucleus of the Abducens nerve (CN VI)**. This specific looping mechanism is known as the *internal genu* of the facial nerve. Because this anatomical arrangement occurs within the tegmentum of the pons, it is a characteristic feature of the pontine brainstem. ### 2. Why Other Options are Incorrect * **Midbrain:** The dorsal surface of the midbrain is characterized by the superior and inferior colliculi (corpora quadrigemina), not the facial colliculus. [1] * **Medulla:** The floor of the fourth ventricle in the medulla contains the hypoglossal and vagal triangles, but not the facial colliculus. * **Interpeduncular fossa:** This is a space located on the ventral (anterior) surface of the midbrain between the two cerebral peduncles; it contains the exit point of the Oculomotor nerve (CN III). ### 3. Clinical Pearls for NEET-PG * **Foville’s Syndrome:** A lesion involving the facial colliculus results in **ipsilateral facial nerve palsy** (lower motor neuron type) and **ipsilateral abducens nerve palsy** (inability to abduct the eye). * **Location:** It is specifically located in the **medial eminence** of the pontine part of the fourth ventricle, medial to the sulcus limitans. * **Rule of 4:** Remember that Cranial Nerves V, VI, VII, and VIII are associated with the Pons.

Question 1

Lesion of the posterior inferior cerebellar artery in the brain involves/affects which of the following structures?

Accepted Answer

All of the above

Answer

Spinal tract of the trigeminal nerve

Answer

Tractus solitarius

Answer

Spinothalamic tract

Question 2

Association fibers are also known as which of the following?

Accepted Answer

Forceps major

Answer

Uncinate

Answer

Cingulum

Answer

Longitudinal fasciculus

Question 3

Which part of the brain is the olive located in?

Accepted Answer

Medulla

Answer

Cerebellum

Answer

Midbrain

Answer

Pons

Question 4

Which of the following statements is true about the subarachnoid space?

Accepted Answer

It surrounds the conus medullaris.

Answer

It is outside the subdural space.

Answer

It is located between the pia mater and the brain surface.

Answer

It is located between the dura mater and the arachnoid mater.

Question 5

The hypothalamo-hypophyseal tract is present in which of the following structures?

Accepted Answer

Infundibular stalk

Answer

Pars intermedia

Answer

Pars nervosa

Answer

All of the above

Question 6

The paracentral lobule is located in which part of the cerebral hemisphere?

Accepted Answer

Medial surface

Answer

Superolateral surface

Answer

Tentorial surface

Answer

Orbital surface

Question 7

A patient with a small lacunar infarction complains of left hemisensory loss involving the face, arm, and leg equally. On exam, the patient has hemisensory loss to pin prick, temperature, and proprioception on the entire left side including the trunk. Which thalamic subnucleus is likely affected contralaterally?

Accepted Answer

Ventral posterolateral

Answer

Pulvinar

Answer

Lateral geniculate

Answer

Medial geniculate

Question 8

A 63-year-old male presented with sudden onset of weakness of the face and tongue and dysarthria, suggestive of a lesion involving the corticobulbar tract. MRI revealed an ischemic stroke in a certain part of the internal capsule. Which of the following parts of the internal capsule was most likely affected?

Accepted Answer

Genu

Answer

Anterior limb

Answer

Posterior limb

Answer

Both genu and posterior limb

Question 9

Auditory cortex is present in which Brodmann area?

Accepted Answer

Area 41

Answer

Area 42

Answer

Area 44

Answer

Area 48

Question 10

Facial colliculus is seen in which part of the brainstem?

Accepted Answer

Pons

Answer

Midbrain

Answer

Medulla

Answer

Interpeduncular fossa

Brain and Neuroanatomy — MCQs

Brain and Neuroanatomy — MCQs

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