Neuroradiology Practice Questions

Q: Which imaging modality is least useful in a case of CNS neoplasm?

Ultrasound. **Explanation:** The primary challenge in imaging the adult Central Nervous System (CNS) is the **intact calvarium (skull)**, which acts as a physical barrier to sound waves. **Why Ultrasound is the Correct Answer:** Ultrasound relies on the transmission of high-frequency sound waves. In adults, the thick, mineralized bone of the skull reflects almost all ultrasound waves, preventing visualization of the underlying brain parenchyma. While ultrasound is useful in neonates (via the open anterior fontanelle) or intraoperatively (once a bone flap is removed), it is the **least useful** modality for the initial diagnosis or screening of a CNS neoplasm in a standard clinical setting. **Analysis of Other Options:** * **MRI (Gold Standard):** This is the investigation of choice for CNS neoplasms due to its superior soft-tissue contrast, multiplanar imaging capabilities, and ability to visualize the posterior fossa without bony artifacts. * **CT Scan:** Often the first-line investigation in emergency settings. It is highly sensitive for detecting calcification (e.g., in oligodendrogliomas), acute hemorrhage, and gross mass effect or midline shift. * **Radiograph (X-ray):** While largely replaced by CT/MRI, radiographs can still show indirect signs of chronicity, such as "copper beaten skull" (increased intracranial pressure), pineal gland displacement, or erosion of the sella turcica. Thus, it remains more informative than a non-penetrative ultrasound. **NEET-PG High-Yield Pearls:** * **IOC for most CNS tumors:** MRI with Gadolinium contrast. * **Best for Calcification:** CT scan (e.g., Craniopharyngioma, Oligodendroglioma). * **Intraoperative Ultrasound:** Used by neurosurgeons to locate subcortical tumors in real-time after craniotomy. * **Neurosonogram:** Only useful in infants until the **anterior fontanelle** closes (usually by 12–18 months).

Q: What is the characteristic 'soap bubble' appearance seen in meningoencephalitis?

Cryptococcus. **Explanation:** **Cryptococcus neoformans** is the most common fungal infection of the CNS, typically seen in immunocompromised patients (e.g., HIV/AIDS). The characteristic **'soap bubble' appearance** on MRI (T2-weighted images) occurs due to the spread of the fungus from the subarachnoid space into the **Virchow-Robin (perivascular) spaces**. As the organisms multiply, they secrete a gelatinous polysaccharide capsule, causing these spaces to dilate and form small, non-enhancing cystic clusters in the basal ganglia and thalamus. **Analysis of Incorrect Options:** * **Mucormycosis:** Typically presents as an aggressive, angioinvasive infection originating in the sinuses. It often shows bone destruction and cerebral infarction/hemorrhage rather than cystic clusters. * **Tubercular Meningitis:** Characterized by thick, **basal exudates** and intense meningeal enhancement. It commonly leads to hydrocephalus and infarcts (due to vasculitis) or "tuberculomas" (ring-enhancing lesions). * **HSV Encephalitis:** Classically involves the **temporal lobes** and limbic system. On MRI, it shows T2/FLAIR hyperintensity and edema in these regions, often with hemorrhagic transformation, but not a 'soap bubble' pattern. **High-Yield NEET-PG Pearls:** * **Diagnosis:** India Ink preparation of CSF shows a "halo" (capsule); Latex Agglutination test for cryptococcal antigen is highly specific. * **Imaging:** Look for "Gelatinous pseudocysts" in the basal ganglia. * **Treatment:** Induction with Amphotericin B + Flucytosine, followed by Fluconazole. * **Key Sign:** Unlike most infections, Cryptococcal pseudocysts typically show **minimal or no peripheral enhancement** because of the lack of an inflammatory response in immunocompromised hosts.

Q: All of the following cause basal ganglia calcification except?

Wilson's disease. **Explanation:** Basal ganglia calcification (BGC) is a common radiological finding that can be physiological (age-related) or pathological. **Why Wilson’s Disease is the Correct Answer:** Wilson’s disease is characterized by the toxic accumulation of **copper** in the liver and brain (specifically the lentiform nucleus). On MRI, it typically presents with **T2-hyperintensity** (gliosis and edema) and the classic "Face of the Giant Panda" sign in the midbrain. It does **not** typically cause calcification; rather, it causes tissue necrosis and cystic changes. **Analysis of Other Options:** * **Hyperparathyroidism:** Both hyper- and hypoparathyroidism (and pseudohypoparathyroidism) are classic endocrine causes of BGC due to abnormalities in calcium-phosphate metabolism. * **Leigh’s Disease (Subacute Necrotizing Encephalomyelopathy):** While primarily known for symmetric T2-hyperintensities in the basal ganglia, chronic stages of mitochondrial disorders like Leigh’s disease or MELAS can occasionally manifest with dystrophic calcification. * **Cysticercosis:** While Neurocysticercosis (NCC) most commonly presents as parenchymal cysts or "starry sky" calcifications in the cortex, it can involve the basal ganglia, leading to focal calcified granulomas. **High-Yield Clinical Pearls for NEET-PG:** * **Fahr’s Syndrome:** An idiopathic, familial condition presenting with massive, symmetric basal ganglia calcification. * **Most Common Cause:** Physiological calcification (usually in the globus pallidus) is the most common cause in patients >40 years. * **Infections:** The "TORCH" group (especially CMV and Toxoplasmosis) are major causes of intracranial calcification in neonates. * **Wilson’s Disease MRI:** Look for the "Double Panda Sign" (Giant Panda in midbrain + Miniature Panda in pons).

Q: A round hyperdense lesion on NC-CT located in the 3rd ventricle is most likely to be which of the following?

Colloid cyst. **Explanation:** The correct answer is **Colloid cyst**. This is a classic "spotter" in neuroradiology based on its characteristic location and density. **1. Why Colloid Cyst is Correct:** A colloid cyst is a benign, mucin-containing lesion typically located at the **Foramen of Monro** in the anterior-superior aspect of the **3rd ventricle**. On a Non-Contrast CT (NC-CT), it classically appears as a **well-circumscribed, hyperdense (bright) round lesion**. The hyperdensity is due to the high protein content or inspissated (thickened) gelatinous material within the cyst. Its strategic location can cause sudden obstructive hydrocephalus by blocking the flow of CSF. **2. Why the Other Options are Incorrect:** * **Arachnoid Cyst:** These are CSF-filled sacs. On CT, they are **hypodense** (isodense to CSF) and do not show hyperdensity. * **Epidermoid Cyst:** These typically occur in the cerebellopontine angle. On CT, they are **hypodense** and have a "cauliflower-like" appearance that fills cisterns rather than appearing as a smooth round 3rd-ventricle mass. * **Subependymal Giant Cell Astrocytoma (SEGA):** While located near the Foramen of Monro, SEGA is a solid tumor associated with **Tuberous Sclerosis**. It is usually iso-to-hypodense on NC-CT and shows **strong contrast enhancement**, unlike the simple hyperdensity of a colloid cyst. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Symptom:** "Drop attacks" or positional headaches (relieved by lying down) due to intermittent CSF obstruction. * **MRI Appearance:** Variable signal on T1/T2 depending on protein concentration, but most commonly hyperintense on T1. * **Treatment:** Surgical excision or endoscopic drainage to prevent sudden death from acute hydrocephalus.

Q: What is the most common CNS tumor that shows calcification?

Craniopharyngioma. **Explanation:** The correct answer is **Craniopharyngioma**. In the context of CNS tumors, the distinction between "most common to calcify" and "highest percentage of calcification" is a frequent source of confusion in NEET-PG. **1. Why Craniopharyngioma is correct:** Craniopharyngioma is a benign, Grade I tumor arising from Rathke’s pouch. It is the most common CNS tumor to show calcification overall, particularly in the pediatric population. Approximately **90% of pediatric craniopharyngiomas** (Adamantinomatous type) show calcification on CT scans. While the adult (Papillary) type calcifies less frequently, the sheer frequency and density of calcification in the pediatric subgroup make it the top answer for this general question. **2. Why other options are incorrect:** * **Oligodendroglioma:** This tumor has the **highest percentage** of calcification among primary intra-axial tumors (70–90%). However, because it is much rarer than craniopharyngiomas or meningiomas, it is not the "most common" tumor encountered with calcification. * **Meningioma:** These frequently show psammomatous calcification (20–25%), but the incidence is significantly lower than in craniopharyngiomas. * **Pilocytic Astrocytoma:** While it can show calcification (approx. 10–20%), it is not a hallmark feature compared to the others. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Calcified Brain Tumors:** "Old Men Are Pushing Crates" (**O**ligodendroglioma, **M**eningioma, **A**strocytoma, **P**ineal tumors, **C**raniopharyngioma). * **CT vs. MRI:** CT is the gold standard for detecting tumor calcification. * **Craniopharyngioma Triad:** Visual field defects (bitemporal hemianopia), endocrine dysfunction (growth retardation/DI), and calcified suprasellar mass. * **Adamantinomatous type:** Shows "machinery oil" fluid within cysts and "wet keratin" on histology.

Q: Sphenoid wing dysplasia is seen in which of the following conditions?

Neurofibromatosis. **Explanation:** **Sphenoid wing dysplasia** is a characteristic skeletal manifestation of **Neurofibromatosis Type 1 (NF-1)**. It involves the partial or complete absence of the greater wing of the sphenoid bone. This defect leads to an expansion of the superior orbital fissure, resulting in a communication between the orbit and the middle cranial fossa. Radiologically, this produces the classic **"Bare Orbit Sign"** on a frontal skull X-ray or CT scan. Clinically, it may present as pulsating exophthalmos due to the transmission of cerebrospinal fluid (CSF) pulsations to the orbital contents. **Analysis of Incorrect Options:** * **A. Von Hippel Lindau (VHL):** A phakomatosis characterized by hemangioblastomas (cerebellum/retina), renal cell carcinoma, and pheochromocytoma. It does not involve sphenoid bone defects. * **C. Sturge-Weber Syndrome:** Characterized by a facial port-wine stain (trigeminal distribution) and leptomeningeal angiomatosis. Classic imaging finding is **"tram-track" cortical calcifications**, not bone dysplasia. * **D. Bournville’s Disease (Tuberous Sclerosis):** Features include cortical tubers, subependymal nodules (SEN), and subependymal giant cell astrocytomas (SEGA). Skeletal findings usually involve sclerotic bone islands, not dysplasia of the sphenoid. **High-Yield Clinical Pearls for NF-1:** * **Diagnostic Criteria (NIH):** Café-au-lait spots (≥6), Lisch nodules (iris hamartomas), Axillary/Inguinal freckling (Crowe sign), Optic nerve gliomas, and Neurofibromas. * **Skeletal Findings:** Sphenoid wing dysplasia, pseudoarthrosis of the tibia, and severe kyphoscoliosis. * **Imaging:** "Bare orbit sign" is a favorite NEET-PG image-based question.

Q: Schuller's view is for which anatomical structure?

Mastoid air cells. **Explanation:** **Schuller’s View** is a lateral oblique radiographic projection of the skull specifically designed to visualize the **mastoid air cells**. 1. **Why it is correct:** In this view, the X-ray beam is angled 25–30° cranio-caudally to avoid superimposition of the two petrous bones. It provides a clear lateral view of the mastoid air cell system, the tegmen tympani (middle ear roof), and the relationship of the lateral sinus to the mastoid. It is the gold standard conventional radiograph for assessing the degree of mastoid pneumatization (cellular, diploic, or sclerotic) and detecting bone destruction in chronic otitis media. 2. **Why other options are incorrect:** * **Sphenoid Sinus:** Best visualized using the **Waters’ view** (with open mouth) or a **Lateral view** of the skull. * **Frontal Sinus:** Best visualized using **Caldwell’s view** (occipito-frontal), which demonstrates the sinus without petrous bone interference. **High-Yield Clinical Pearls for NEET-PG:** * **Stenver’s View:** Oblique view used to visualize the **petrous apex**, internal auditory canal, and labyrinth. * **Towne’s View:** Antero-posterior view used to visualize the **mastoid antrum** and the petrous pyramids. * **Waters’ View:** The primary view for **Maxillary sinuses**. * **Law’s View:** A lateral oblique view (15° angle) also used for mastoids, but Schuller’s (25-30°) is more common in exams. * **Modern Practice:** While these views are high-yield for exams, **HRCT of the Temporal Bone** has largely replaced conventional radiography in clinical practice for ear pathologies.

Q: A 56-year-old man with a history of poorly controlled hypertension presents to the accident and emergency department with sudden onset weakness on the left side. What initial investigation would you request?

CT head. **Explanation:** The clinical presentation of sudden-onset focal neurological deficits (left-sided weakness) in a patient with hypertension is highly suggestive of an **acute stroke**. In the emergency setting, the primary goal is to differentiate between an **ischemic stroke** and a **hemorrhagic stroke**, as the management for each is diametrically opposed. **Why CT Head is the correct answer:** A **Non-Contrast Computed Tomography (NCCT) Head** is the gold standard initial investigation for suspected stroke. Its primary utility lies in its **high sensitivity for detecting acute intracranial hemorrhage**, which appears hyperdense (white). It is fast, widely available, and essential to rule out a bleed before initiating thrombolytic therapy (like tPA) or anticoagulation. **Why other options are incorrect:** * **MRI:** While Diffusion-Weighted Imaging (DWI) MRI is more sensitive for detecting early ischemic changes (within minutes), it is time-consuming, less available, and more expensive. In the "Time is Brain" window, CT is preferred for its speed. * **X-Ray:** Conventional skull X-rays have no role in the evaluation of acute stroke as they cannot visualize brain parenchyma or hemorrhage. * **D-dimer assay:** This is used to rule out venous thromboembolism (PE/DVT) and has no diagnostic value in the acute management of a stroke. **High-Yield Clinical Pearls for NEET-PG:** * **NCCT Findings:** In acute ischemia, the CT may appear normal for the first 6–12 hours. Early signs include the **"Hyperdense MCA sign"** (thrombus in the vessel) and loss of insular ribbon. * **Hemorrhage:** Appears **hyperdense** (60–80 HU) on CT. * **Ischemia:** Appears **hypodense** (dark) on CT as edema develops. * **Door-to-CT time:** Ideally should be within **20 minutes** of arrival.

Q: Which of the following conditions can cause a "bare orbit"?

Metastasis. The **"Bare Orbit" sign** is a classic radiological finding on a frontal skull X-ray or CT scan characterized by the **absence of the innominate line** (the greater wing of the sphenoid bone). This occurs due to the destruction or hypoplasia of the sphenoid wing, leading to an empty-appearing orbit. ### Why Metastasis is Correct **Metastasis** (particularly from neuroblastoma in children or lung/breast cancer in adults) is a common cause of aggressive bony destruction. When the greater wing of the sphenoid is destroyed by a neoplastic process, the normal bony landmarks disappear, resulting in the "bare orbit" appearance. ### Why Other Options are Incorrect * **Pseudotumor cerebri:** This involves idiopathic intracranial hypertension. While it may cause an empty sella or slit-like ventricles, it does not cause bony destruction of the sphenoid wing. * **Optic nerve glioma:** This typically causes **enlargement of the optic canal** rather than generalized destruction of the sphenoid wing. * **Osteomyelitis:** While it can cause bone erosion, it is a rare cause of a classic "bare orbit" compared to neoplastic or congenital conditions. ### High-Yield Pearls for NEET-PG * **Most Common Cause:** The most classic association for "bare orbit" in radiology exams is **Neurofibromatosis Type 1 (NF1)**, due to congenital sphenoid wing dysplasia. * **Differential Diagnosis for Bare Orbit:** 1. Neurofibromatosis Type 1 (Sphenoid dysplasia) 2. Langerhans Cell Histiocytosis (LCH) 3. Metastatic disease (Neuroblastoma) 4. Post-surgical changes (Craniotomy) * **Clinical Correlation:** In NF1, this finding is often associated with **pulsatile exophthalmos** because the brain pulsations are transmitted directly to the orbit through the bony defect.

Question 1

Which imaging modality is least useful in a case of CNS neoplasm?

Accepted Answer

Ultrasound

Answer

Radiograph

Answer

CT scan

Answer

MRI

Question 2

What is the characteristic 'soap bubble' appearance seen in meningoencephalitis?

Accepted Answer

Cryptococcus

Answer

Mucormycosis

Answer

Tubercular

Answer

HSV

Question 3

All of the following cause basal ganglia calcification except?

Accepted Answer

Wilson's disease

Answer

Hyperparathyroidism

Answer

Leigh's disease

Answer

Cysticercosis

Question 4

A round hyperdense lesion on NC-CT located in the 3rd ventricle is most likely to be which of the following?

Accepted Answer

Colloid cyst

Answer

Arachnoid cyst

Answer

Epidermoid cyst

Answer

Giant cell astrocytoma

Question 5

What is the most common CNS tumor that shows calcification?

Accepted Answer

Craniopharyngioma

Answer

Oligodendroglioma

Answer

Meningioma

Answer

Pilocytic astrocytoma

Question 6

Sphenoid wing dysplasia is seen in which of the following conditions?

Accepted Answer

Neurofibromatosis

Answer

Von Hippel Lindau's disease

Answer

Sturge Weber syndrome

Answer

Bournville's disease

Question 7

Schuller's view is for which anatomical structure?

Accepted Answer

Mastoid air cells

Answer

Sphenoid sinus

Answer

Frontal sinus

Answer

None of the above

Question 8

After head injury, a biconvex, lenticular shaped hematoma on CT scan is characteristic of which of the following?

Accepted Answer

Extradural haemorrhage

Answer

Subdural haemorrhage

Answer

Intracerebral hematoma

Answer

Diffuse axonal injury

Question 9

A 56-year-old man with a history of poorly controlled hypertension presents to the accident and emergency department with sudden onset weakness on the left side. What initial investigation would you request?

Accepted Answer

CT head

Answer

MRI

Answer

X-Ray

Answer

D-dimer assay

Question 10

Which of the following conditions can cause a "bare orbit"?

Accepted Answer

Metastasis

Answer

Pseudotumor cerebri

Answer

Optic nerve glioma

Answer

Osteomyelitis

Neuroradiology — MCQs

Neuroradiology — MCQs

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