Neuroanatomy for Radiologists — MCQs
Frontal gyrus lesion leads to?
Which of the following is the MOST accurate statement about CSF?
Which of the following most likely causes a communicating (nonobstructive) hydrocephalus?
Visual loss due to cerebral degeneration is related to which artery?
What are the effects of a lesion in Brodmann area 22?
Characteristic of venous blood flow of lower limb in duplex Doppler is?
Intra-tumoral calcification in the brain is seen in all except?
Which of the following brain tumors is typically hyperdense on CT scan?
A 7-year-old child presents with a posterior fossa mass characterized by cyst formation. On CT, the mass appears hypodense, while on T2-weighted MRI, it is hyperintense. Post-gadolinium administration, a nodular enhancement is observed. What is the most likely diagnosis?
What is the investigation of choice for entrapment neuropathy?
Neuroanatomy for Radiologists Indian Medical PG Practice Questions and MCQs
Question 1: Frontal gyrus lesion leads to?
- A. Nominal aphasia
- B. Akinetic mutism
- C. Wernicke's aphasia
- D. Broca's aphasia (Correct Answer)
Explanation: ***Broca's aphasia*** - A lesion in the **frontal gyrus**, specifically **Broca's area** (Brodmann areas 44 and 45), leads to Broca's aphasia [1]. - This condition is characterized by **non-fluent speech**, difficulty with articulation, and telegraphic sentences, while comprehension remains relatively intact [1]. *Nominal aphasia* - This is also known as **anomic aphasia**, characterized primarily by difficulty with **word finding** (naming objects). - It results from lesions in various cortical areas, but typically not isolated to Broca's area in the frontal gyrus. *Akinetic mutism* - This condition involves a state of **unresponsiveness** where the patient is awake but does not move or speak. - It usually results from lesions in the **cingulate gyrus**, basal ganglia, or medial frontal lobes, often bilateral, not typically a solitary frontal gyrus lesion. *Wernicke's aphasia* - Wernicke's aphasia results from damage to **Wernicke's area**, located in the **posterior superior temporal gyrus** [1]. - It is characterized by **fluent but nonsensical speech** with impaired comprehension [1].
Question 2: Which of the following is the MOST accurate statement about CSF?
- A. Formed by the choroid plexus in the ventricles. (Correct Answer)
- B. Normally contains no neutrophils
- C. pH is less than that of plasma
- D. Removal of CSF during dural tap can cause a headache due to the change in pressure.
Explanation: ***Formed by the choroid plexus in the ventricles.*** * The **choroid plexus**, located in the ventricles of the brain, is primarily responsible for the production of **cerebrospinal fluid (CSF)**. * Specialized epithelial cells of the choroid plexus filter blood plasma to produce CSF, which then circulates through the central nervous system. *Normally contains no neutrophils* * Normal CSF should contain **virtually no neutrophils**; their presence typically indicates an inflammatory or infectious process, such as **bacterial meningitis**. * While normal CSF doesn't have neutrophils, this option isn't as broadly accurate as the choroid plexus statement because the presence of other cell types like lymphocytes in small numbers is normal. *pH is less than that of plasma* * The pH of CSF is typically **slightly lower than that of plasma** (around 7.31 compared to 7.40), but the statement "less than" is broad and the degree of difference can be variable and is a less defining characteristic than its formation site. * This slight difference in pH is important for regulating **respiration** through chemoreceptors, but it's not the most accurate or fundamental statement about CSF properties. *Removal of CSF during dural tap can cause a headache due to the change in pressure.* * A **post-dural puncture headache** (PDPH) is a well-known complication of a dural tap (lumbar puncture), caused by the leakage of CSF from the puncture site, leading to **intracranial hypotension**, not simply a change in pressure. * This decrease in CSF volume and pressure causes a traction on pain-sensitive structures within the cranium, resulting in a headache that is typically **worse when upright** and relieved by lying down.
Question 3: Which of the following most likely causes a communicating (nonobstructive) hydrocephalus?
- A. Tuberculous meningitis
- B. Stenosis of the duct of Sylvius
- C. Blockage of the arachnoid granulations (Correct Answer)
- D. Ependymoma of the fourth ventricle
Explanation: ***Blockage of the arachnoid granulations*** - **Communicating hydrocephalus** occurs when CSF flow from the ventricles is unobstructed, but its **reabsorption** into the venous system is impaired [1] - **Arachnoid granulations** (pacchionian bodies) are responsible for reabsorbing CSF into the dural venous sinuses [1] - Blockage (e.g., due to **subarachnoid hemorrhage**, chronic **meningitis**, or venous thrombosis) prevents proper reabsorption, leading to CSF accumulation [2] - This is the **direct pathophysiologic mechanism** of communicating hydrocephalus *Tuberculous meningitis* - This can cause **communicating hydrocephalus** through inflammation and fibrosis of the **basilar meninges**, which obstructs the arachnoid granulations and impairs CSF reabsorption - It is a clinically important cause, especially in endemic regions - However, it works through the mechanism of arachnoid granulation blockage, making it an indirect cause - Less commonly, it can cause obstructive hydrocephalus if inflammatory exudates block the basal cisterns [2] *Stenosis of the duct of Sylvius* - Also known as **aqueductal stenosis**, this is a classic cause of **non-communicating (obstructive) hydrocephalus** - It blocks the flow of CSF from the third to the fourth ventricle, leading to dilation of the lateral and third ventricles - CSF cannot communicate between the ventricular system and subarachnoid space *Ependymoma of the fourth ventricle* - An **ependymoma** in this location causes **non-communicating (obstructive) hydrocephalus** [2] - The tumor physically blocks the outflow of CSF from the fourth ventricle through the foramina of Luschka and Magendie into the subarachnoid space - Ependymomas are the most common posterior fossa tumor in children **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1256-1257. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 703-704.
Question 4: Visual loss due to cerebral degeneration is related to which artery?
- A. Anterior cerebral artery
- B. Internal carotid artery
- C. Posterior cerebral artery (Correct Answer)
- D. Middle cerebral artery
Explanation: ***Posterior cerebral artery*** - The **posterior cerebral artery** supplies the **occipital lobe**, which contains the **primary visual cortex** [1], [2]. - **Infarction** or **degeneration** in this territory can directly lead to **visual field defects** or **cortical blindness** [3]. *Anterior cerebral artery* - The **anterior cerebral artery** supplies the **frontal lobes** and medial aspects of the **parietal lobes**, which are not primarily involved in visual processing [4]. - Occlusion typically causes **contralateral leg weakness** and **sensory loss**, and **behavioral changes**. *Internal carotid artery* - The **internal carotid artery** bifurcates into the **anterior** and **middle cerebral arteries** but does not directly supply the primary visual cortex for central vision [4]. - While it can cause **amaurosis fugax** (transient monocular vision loss) due to retinal ischemia, it is not responsible for cortical visual degeneration. *Middle cerebral artery* - The **middle cerebral artery** supplies the majority of the **lateral surface of the cerebral hemispheres**, including portions of the **temporal** and **parietal lobes** [4]. - While it can cause **homonymous hemianopia** if it affects the **optic radiations** in the temporal or parietal lobes, it does not directly supply the primary visual cortex in the occipital lobe where cerebral degeneration causing visual loss is localized.
Question 5: What are the effects of a lesion in Brodmann area 22?
- A. Expressive aphasia
- B. Receptive aphasia (Correct Answer)
- C. Poor repetition of language
- D. Poor naming
Explanation: ***Receptive aphasia*** - A lesion in **Brodmann area 22**, specifically in **Wernicke's area**, leads to **receptive aphasia** (Wernicke's aphasia). - This condition is characterized by **impaired comprehension** of spoken and written language, **fluent but paraphasic speech**, and **poor repetition**. - This is the most comprehensive answer as it describes the entire clinical syndrome. *Expressive aphasia* - **Brodmann areas 44 and 45** (Broca's area) in the frontal lobe are associated with expressive aphasia (Broca's aphasia). - Patients have good comprehension but struggle to produce fluent speech, with effortful, telegraphic output. *Poor repetition of language* - While poor repetition is indeed a feature of Wernicke's aphasia, this option describes only one component of the syndrome rather than the complete clinical picture. - **Conduction aphasia** (from arcuate fasciculus lesions) is characterized by poor repetition with **relatively preserved** comprehension and fluent speech, distinguishing it from Wernicke's aphasia. - "Receptive aphasia" is the more complete answer. *Poor naming* - Difficulty with naming, or **anomia**, is a common feature across various types of aphasia, including both receptive and expressive aphasia. - It reflects disruption in language networks involving the **temporal and parietal lobes** but is not specific to Brodmann area 22 lesions.
Question 6: Characteristic of venous blood flow of lower limb in duplex Doppler is?
- A. Biphasic (Correct Answer)
- B. Non phasic
- C. Monophasic
- D. Triphasic
Explanation: ***Biphasic*** - Normal venous blood flow in the **major lower limb veins** (femoral, popliteal) on duplex Doppler is characteristically **biphasic**, showing variations with respiration. - This biphasic pattern reflects the influence of the **thoracoabdominal pump**, where inspiration decreases intrathoracic pressure and increases intra-abdominal pressure, thus impeding venous return, and expiration reverses this action. - The two phases correspond to **acceleration during expiration** and **deceleration during inspiration**. *Non phasic* - **Non-phasic** (continuous) flow usually indicates a **proximal obstruction** such as deep vein thrombosis (DVT). - This pattern means the respiratory variations are absent due to the blockage preventing normal pressure changes from affecting venous return. - Loss of phasicity is an important sign of venous pathology. *Monophasic* - **Monophasic** flow shows only one phase (forward flow) without clear respiratory variation. - While monophasic flow can be **normal in smaller peripheral veins** (e.g., calf veins), in major lower limb veins it may suggest **partial obstruction** or poor respiratory effort. - It lacks the distinct respiratory modulation seen with biphasic flow. *Triphasic* - **Triphasic** flow is characteristic of **arterial waveforms** in peripheral arteries, showing rapid antegrade flow, brief reversal during early diastole, and slower forward flow during late diastole. - This is not a normal finding for venous blood flow and represents arterial rather than venous physiology.
Question 7: Intra-tumoral calcification in the brain is seen in all except?
- A. Craniopharyngioma
- B. Meningioma
- C. Oligodendroglioma
- D. Hemangioblastoma (Correct Answer)
Explanation: **Explanation:** The correct answer is **Hemangioblastoma**. In neuroradiology, identifying the presence or absence of calcification is a high-yield diagnostic marker for intracranial tumors. **1. Why Hemangioblastoma is the correct answer:** Hemangioblastomas are highly vascular, WHO Grade 1 tumors typically located in the posterior fossa (cerebellum). Characteristically, they present as a **cystic lesion with a highly enhancing mural nodule**. Crucially, hemangioblastomas **do not calcify**. Their primary imaging features are related to vascularity (flow voids on MRI) and associated erythropoietin production, which may lead to polycythemia. **2. Why the other options are incorrect:** * **Oligodendroglioma:** This is the "classic" answer for calcified brain tumors. Calcification is seen in **70–90%** of cases, often described as chunky or ribbon-like. * **Craniopharyngioma:** In the pediatric population (adamantinomatous type), calcification is a hallmark, occurring in approximately **90%** of cases. It follows the "90% rule": 90% are cystic, 90% calcify, and 90% enhance. * **Meningioma:** These are extra-axial tumors that frequently show calcification (about **20–25%**). When the calcification is diffuse and gritty, they are histologically termed "Psammomatous meningiomas." **NEET-PG High-Yield Pearls:** * **Mnemonic for Calcified Brain Tumors (Old Men Are Posh):** **O**ligodendroglioma, **M**eningioma, **A**strocytoma, **P**ineal tumors/ **P**apilloma (Choroid plexus). * **Most common calcified tumor in children:** Craniopharyngioma. * **Most common calcified tumor in adults:** Oligodendroglioma. * **Hemangioblastoma Association:** Frequently associated with **Von Hippel-Lindau (VHL) syndrome**; look for retinal angiomas and renal cell carcinoma in clinical stems.
Question 8: Which of the following brain tumors is typically hyperdense on CT scan?
- A. Ependymoma
- B. Medulloblastoma (Correct Answer)
- C. Oligodendroglioma
- D. Astrocytoma
Explanation: **Explanation:** The density of a tumor on a non-contrast CT (NCCT) scan is primarily determined by its **cellularity** and the **nuclear-to-cytoplasmic (N:C) ratio**. **1. Why Medulloblastoma is correct:** Medulloblastoma is a "Small Round Blue Cell Tumor." These tumors are characterized by extremely high cellular density and very little cytoplasm. Because DNA and cellular proteins attenuate X-rays more than water or lipids, the high concentration of cells makes the tumor appear **hyperdense** relative to the normal brain parenchyma on NCCT. This is a classic radiological hallmark of medulloblastoma, typically seen in the midline (cerebellar vermis) of pediatric patients. **2. Analysis of Incorrect Options:** * **Ependymoma:** Usually appears isodense or heterogeneous on CT. While they often contain calcifications (which are hyperdense), the soft tissue component itself is not typically hyperdense. * **Oligodendroglioma:** These are known for having the highest incidence of **calcification** (up to 90%), which is hyperdense. However, the tumor mass itself is usually hypo-to-isodense. * **Astrocytoma:** Most low-grade astrocytomas are **hypodense** due to high water content and associated edema. High-grade gliomas (GBM) are usually heterogeneous due to necrosis and hemorrhage. **3. High-Yield Clinical Pearls for NEET-PG:** * **Hyperdense tumors on CT (Mnemonic: "M-L-G"):** **M**edulloblastoma, **L**ymphoma (Primary CNS), and **G**erm cell tumors/Meningioma. * **Medulloblastoma:** Most common malignant brain tumor in children; associated with "drop metastases" (seeding via CSF). * **Calcification Mnemonic:** "Old Elephants Can't Dance" (**O**ligodendroglioma, **E**pendymoma, **C**raniopharyngioma, **D**ysembryoplastic Neuroepithelial Tumor).
Question 9: A 7-year-old child presents with a posterior fossa mass characterized by cyst formation. On CT, the mass appears hypodense, while on T2-weighted MRI, it is hyperintense. Post-gadolinium administration, a nodular enhancement is observed. What is the most likely diagnosis?
- A. Medulloblastoma
- B. Ependymoma
- C. Astrocytoma (Correct Answer)
- D. Cysticercosis
Explanation: **Explanation:** The clinical presentation and imaging findings are classic for a **Juvenile Pilocytic Astrocytoma (JPA)**, which is the most common brain tumor in children. **1. Why Astrocytoma is correct:** JPA typically arises in the cerebellum (posterior fossa). The pathognomonic radiological appearance is a **large cystic lesion with a brightly enhancing mural nodule**. * **CT:** The cyst is hypodense (fluid-filled). * **MRI T2:** The cyst fluid is hyperintense (similar to CSF). * **Post-Contrast:** The mural nodule shows intense enhancement, while the cyst wall usually does not (unless it contains neoplastic cells). **2. Why other options are incorrect:** * **Medulloblastoma:** This is the most common *malignant* pediatric brain tumor. It typically appears as a **solid, hyperdense mass** on CT (due to high cellularity) arising from the roof of the 4th ventricle (midline/vermis). It rarely shows large cyst formation. * **Ependymoma:** These typically arise from the floor of the 4th ventricle and are characterized by **"plasticity"** (squeezing through the foramina of Luschka and Magendie). Calcification is very common (50%), and they are usually heterogeneous rather than purely cystic with a nodule. * **Cysticercosis:** While cystic, Neurocysticercosis (NCC) usually presents as multiple small parenchymal cysts (vesicular stage) with a visible "scolex" (dot sign) and is not typically a large posterior fossa mass in a child. **3. High-Yield Clinical Pearls for NEET-PG:** * **JPA Location:** Cerebellum is most common; also associated with **Optic Gliomas** in Neurofibromatosis Type 1 (NF1). * **Histology:** Look for **Rosenthal fibers** (corkscrew-shaped eosinophilic bundles) and bipolar cells with long processes (pilocytic). * **Prognosis:** Excellent (WHO Grade I); surgical resection is often curative. * **Key Differentiator:** If a similar "cyst with a nodule" is seen in an **adult**, the diagnosis is likely **Hemangioblastoma** (associated with von Hippel-Lindau syndrome).
Question 10: What is the investigation of choice for entrapment neuropathy?
- A. CT scan
- B. MRI scan (Correct Answer)
- C. Clinical examination
- D. SPECT scan
Explanation: **Explanation:** **Why MRI is the Correct Answer:** MRI is the investigation of choice for entrapment neuropathy because of its superior **soft-tissue contrast resolution**. It allows for the direct visualization of the nerve itself (MR Neurography). In entrapment syndromes, MRI can detect both **morphological changes** (nerve thickening, flattening, or displacement) and **signal intensity changes** (increased T2/STIR signal indicating intraneural edema or inflammation). Furthermore, MRI is excellent at identifying the extrinsic cause of compression, such as ganglion cysts, tumors, or anatomical variants. **Analysis of Incorrect Options:** * **CT Scan:** While CT is excellent for bone pathology, it has poor soft-tissue resolution and cannot visualize the internal structure of nerves or subtle inflammatory changes. * **Clinical Examination:** While clinical assessment (history and physical exams like Tinel’s or Phalen’s sign) is the first step in diagnosis, it is a **clinical tool**, not an "investigation." It cannot definitively localize the site or cause of compression as accurately as imaging. * **SPECT Scan:** This is a functional nuclear medicine imaging technique used primarily for bone turnover or myocardial perfusion; it has no role in the routine evaluation of peripheral nerves. **High-Yield Facts for NEET-PG:** * **Gold Standard for Function:** While MRI is the investigation of choice for *imaging*, **Electromyography (EMG) and Nerve Conduction Studies (NCS)** remain the gold standard for assessing the *physiological severity* of the nerve injury. * **MR Neurography:** Uses dedicated sequences (like 3D T2-weighted STIR) to suppress fat and vessel signals, making the nerve appear "bright" against a dark background. * **Common Sites:** Carpal Tunnel Syndrome (Median nerve) is the most common entrapment neuropathy, followed by Cubital Tunnel Syndrome (Ulnar nerve).
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