Neuroanatomy Practice Questions

Q: A 4-month-old infant, who underwent surgical treatment for myelomeningocele, presents with progressive hydrocephalus. A CT scan at birth revealed herniation of the cerebellar tonsils through the foramen magnum, consistent with Arnold-Chiari malformation. Which of the following is also commonly associated with this syndrome?

Abnormal elongation of the medulla and lower cranial nerves. Explanation: **Arnold-Chiari Malformation (Type II)** is a congenital anomaly of the hindbrain characterized by the downward displacement of the cerebellar tonsils, vermis, and brainstem through the foramen magnum [2]. **Why Option C is Correct:** The hallmark of Chiari Type II is the caudal displacement of the medulla oblongata and the fourth ventricle into the cervical spinal canal [4]. This mechanical "dragging" or downward shift results in the **abnormal elongation of the medulla** and the stretching of the **lower cranial nerves** (CN IX, X, XI, and XII) as they must travel superiorly to exit their respective cranial foramina. This displacement often leads to obstructive hydrocephalus due to the narrowing of the aqueduct of Sylvius or obstruction of the fourth ventricle outlets [2]. **Why Incorrect Options are Wrong:** * **Option A & B:** Holoprosencephaly (failure of prosencephalon cleavage) and fusion of lobes are defects of the **forebrain** (prosencephalon). Arnold-Chiari is a defect of the **hindbrain** (rhombencephalon). * **Option D:** Pituitary gland abnormalities are associated with midline defects like Septo-optic dysplasia, not typically with the hindbrain herniation seen in Chiari malformations. **NEET-PG High-Yield Pearls:** * **Chiari Type I:** Downward herniation of cerebellar tonsils only; often asymptomatic until adulthood; associated with **syringomyelia** [3]. * **Chiari Type II:** Herniation of tonsils, vermis, and medulla; almost always associated with **lumbar myelomeningocele** and hydrocephalus [1], [2]. * **Radiological Sign:** "Beaked midbrain" (tectal plate peaking) and a small posterior fossa [2]. * **Clinical Presentation:** In infants, it may present with stridor, weak cry, and feeding difficulties due to lower cranial nerve stretching.

Q: Which one of the following structures is a part of the diencephalon?

Thalamus. **Explanation:** The brain develops from three primary vesicles: the forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon). The prosencephalon further divides into the **telencephalon** and the **diencephalon**. **Why Thalamus is Correct:** The **diencephalon** forms the central core of the brain and consists of four main components: the **thalamus**, hypothalamus, epithalamus, and subthalamus [1]. The thalamus acts as the major relay station for almost all sensory information (except olfaction) heading to the cerebral cortex [1]. **Why Other Options are Incorrect:** * **Caudate Nucleus:** This is a component of the **basal ganglia**, which develops from the **telencephalon** [2]. * **Cerebral Hemispheres:** These represent the largest part of the brain and are derived entirely from the **telencephalon**. * **Hippocampus:** Part of the limbic system located in the temporal lobe, the hippocampus is a **telencephalic** structure. **High-Yield NEET-PG Pearls:** 1. **Cavity Association:** The cavity of the diencephalon is the **third ventricle**. 2. **Boundary:** The boundary between the telencephalon and diencephalon is the *foramen of Monro* (interventricular foramen). 3. **Optic Nerve:** Interestingly, the **optic nerve (CN II)** and retina are embryologically outgrowths of the diencephalon; thus, the optic nerve is considered a tract of the CNS rather than a true peripheral nerve. 4. **Internal Capsule:** The diencephalon is separated from the lentiform nucleus by the posterior limb of the internal capsule.

Q: Which of the following sites is not involved in a posterior cerebral artery infarct?

Anterior cerebral artery territory. The **Posterior Cerebral Artery (PCA)** is the terminal branch of the basilar artery and is the primary blood supply to the posterior aspect of the brain. To identify the correct answer, one must understand the anatomical distribution of the PCA. **Why Option D is Correct:** The **Anterior Cerebral Artery (ACA)** and the PCA are distinct branches of the Circle of Willis. The ACA supplies the medial surface of the frontal and parietal lobes. An infarct in the PCA territory cannot involve the ACA territory unless there is a global hypoxic event or multiple vessel occlusions [1]. Therefore, the ACA territory is anatomically independent of the PCA. **Why the other options are incorrect:** * **Midbrain (A):** The PCA gives off small perforating branches (paramedian and short circumflex) that supply the midbrain. A PCA stroke often results in Weber’s syndrome (CN III palsy with contralateral hemiplegia). * **Thalamus (B):** The thalamoperforating and thalamogeniculate branches of the PCA supply the bulk of the thalamus [1]. Infarction here leads to Dejerine-Roussy syndrome (thalamic pain syndrome). * **Temporal Lobe (C):** The PCA supplies the inferior and medial surfaces of the temporal lobe (including the hippocampus). Damage here can lead to memory deficits. **High-Yield NEET-PG Pearls:** 1. **Visual Field Defect:** The most common finding in a PCA infarct is **contralateral homonymous hemianopia with macular sparing** (due to collateral supply to the occipital pole from the MCA). 2. **Alexia without Agraphia:** Occurs when the PCA infarct involves the dominant occipital lobe and the splenium of the corpus callosum. 3. **Cortical Blindness (Anton Syndrome):** Bilateral PCA infarction leads to blindness where the patient denies being blind.

Q: Which of the following is NOT typically seen in a cerebellar lesion?

Resting tremors. The cerebellum is the primary center for coordinating voluntary movements, maintaining posture, and regulating muscle tone. It functions as a "comparator," ensuring that motor output matches the intended movement. [1] **Why Resting Tremors is the Correct Answer:** Resting tremors are a hallmark of **Basal Ganglia** lesions (specifically the substantia nigra in Parkinson’s disease). They occur when the limb is at rest and disappear during voluntary movement. [2] In contrast, cerebellar lesions cause **Intention Tremors**, which appear only when the patient attempts a purposeful movement and worsen as the limb approaches its target. **Explanation of Incorrect Options:** * **Ataxia (A):** This is the most common sign of cerebellar dysfunction. It refers to a lack of muscle coordination resulting in a broad-based, "drunken" gait and clumsy movements. [1] * **Nystagmus (B):** Vestibulocerebellar lesions disrupt the coordination of eye movements, leading to involuntary, rhythmic oscillations of the eyeballs (usually horizontal). [1] * **Past Pointing (D):** Also known as **Dysmetria**, this is the inability to judge distance. In the "finger-nose test," the patient overshoots (hypermetria) or undershoots the target due to a lack of inhibitory control from the cerebellum. [1] **High-Yield Clinical Pearls for NEET-PG:** * **DANISH Mnemonic:** Common cerebellar signs include **D**ysdiadochokinesia, **A**taxia, **N**ystagmus, **I**ntention tremor, **S**lurred speech (Scanning speech), and **H**ypotonia. [1] * **Ipsilateral Rule:** Unlike cerebral lesions, cerebellar lesions manifest symptoms on the **same side** (ipsilateral) as the lesion. * **Midline vs. Lateral:** Midline (vermis) lesions cause truncal ataxia; Lateral (hemisphere) lesions cause limb ataxia. [1]

Q: Damage to which Brodmann area is responsible for motor aphasia?

Area 44. **Explanation:** **Motor aphasia** (also known as Broca’s aphasia or expressive aphasia) results from damage to **Broca’s area**, located in the inferior frontal gyrus of the dominant hemisphere [1]. This region corresponds to **Brodmann areas 44 (pars opercularis) and 45 (pars triangularis)**. Patients with lesions here understand language but struggle to produce speech, characterized by "broken," non-fluent, or telegraphic speech [1]. **Analysis of Options:** * **Area 44 (Correct):** This is the primary component of Broca’s area. It coordinates the complex motor sequences required for speech production [1]. * **Area 22 (Incorrect):** This corresponds to the superior temporal gyrus, part of **Wernicke’s area** [1]. Damage leads to sensory (receptive) aphasia, where speech is fluent but lacks meaning ("word salad"). * **Area 39 (Incorrect):** This is the **angular gyrus** [1]. Lesions here result in Gerstmann syndrome (agraphia, acalculia, finger agnosia, and left-right disorientation) or alexia with agraphia. * **Area 40 (Incorrect):** This is the **supramarginal gyrus**. It is involved in phonological processing and emotional responses to words; damage can contribute to conduction aphasia. **Clinical Pearls for NEET-PG:** * **Blood Supply:** Broca’s area is supplied by the **superior division** of the Middle Cerebral Artery (MCA). Wernicke’s area is supplied by the **inferior division** of the MCA. * **Arcuate Fasciculus:** The white matter tract connecting Broca’s and Wernicke’s areas [1]. Damage causes **conduction aphasia** (impaired repetition). * **Handedness:** In 95% of right-handed and 70% of left-handed individuals, the left hemisphere is dominant for language [2].

Question 1

A 4-month-old infant, who underwent surgical treatment for myelomeningocele, presents with progressive hydrocephalus. A CT scan at birth revealed herniation of the cerebellar tonsils through the foramen magnum, consistent with Arnold-Chiari malformation. Which of the following is also commonly associated with this syndrome?

Accepted Answer

Abnormal elongation of the medulla and lower cranial nerves

Answer

Holoprosencephaly (fusion of the frontal lobes)

Answer

Observed fusion of the temporal, parietal, and occipital lobes

Answer

Partial or complete absence of the pituitary gland

Question 2

Which one of the following structures is a part of the diencephalon?

Accepted Answer

Thalamus

Answer

Caudate nucleus

Answer

Cerebral hemispheres

Answer

Hippocampus

Question 3

Which of the following sites is not involved in a posterior cerebral artery infarct?

Accepted Answer

Anterior cerebral artery territory

Answer

Midbrain

Answer

Thalamus

Answer

Temporal lobe

Question 4

Which of the following is NOT typically seen in a cerebellar lesion?

Accepted Answer

Resting tremors

Answer

Ataxia

Answer

Nystagmus

Answer

Past pointing

Question 5

Damage to which Brodmann area is responsible for motor aphasia?

Accepted Answer

Area 44

Answer

Area 22

Answer

Area 39

Answer

Area 40

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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