Neuroradiology — MCQs

A mother presents with a one-and-a-half-year-old child who has a one-month history of increasing proptosis of the left eye. Examination reveals a left eye white reflex. A computed tomography scan of the orbit shows a left orbital mass with calcification, mainly centered within the globe. What is the most likely diagnosis?

Neuroradiology Indian Medical PG Practice Questions and MCQs

Question 41: What condition is characterized by a 'tram track' appearance on a CT scan of the head?

A. Sturge-Weber Syndrome (Correct Answer)
B. Von Hippel-Lindau Syndrome
C. Tuberous sclerosis
D. Neurofibroma

Explanation: **Explanation:** **Sturge-Weber Syndrome (SWS)**, also known as encephalotrigeminal angiomatosis, is a neurocutaneous disorder characterized by a capillary-venous malformation (leptomeningeal angioma). The classic **'tram track' appearance** on a non-contrast CT scan is caused by **gyriform calcifications** in the underlying cerebral cortex (usually the parietal and occipital lobes). These calcifications occur due to chronic ischemia and venous stasis resulting from the overlying angioma. On CT, these appear as curvilinear, parallel radio-opaque lines following the cerebral gyri. **Analysis of Incorrect Options:** * **Von Hippel-Lindau (VHL):** Characterized by retinal and CNS hemangioblastomas (classically in the cerebellum), renal cell carcinoma, and pheochromocytoma. It does not typically present with gyriform calcifications. * **Tuberous Sclerosis:** Features **'ash-leaf spots'** clinically and **subependymal nodules** or **cortical tubers** on imaging. While it involves calcifications, they are typically nodular/periventricular (candle-guttering appearance), not 'tram track.' * **Neurofibromatosis:** NF-1 is associated with Lisch nodules, optic gliomas, and sphenoid wing dysplasia. NF-2 is associated with bilateral acoustic neuromas (MISME syndrome). Neither presents with this specific calcification pattern. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Triad of SWS:** Port-wine stain (Nevus Flammeus in the V1/V2 distribution), Leptomeningeal angioma, and Glaucoma. * **Imaging Gold Standard:** Contrast-enhanced **MRI** is the most sensitive modality to detect leptomeningeal enhancement (pial angioma) in early stages before calcification develops. * **Skull X-ray:** Can also demonstrate the 'tram track' sign in older children.

Question 42: Which of the following is the best radiological imaging modality to evaluate a posterior fossa tumor?

A. CT scan
B. MRI (Correct Answer)
C. Angiography
D. Myelography

Explanation: **Explanation:** **MRI (Magnetic Resonance Imaging)** is the gold standard and best radiological modality for evaluating posterior fossa tumors. The primary reason is its **superior soft-tissue contrast resolution**, which allows for precise anatomical localization and characterization of tumors (e.g., medulloblastoma, pilocytic astrocytoma, or ependymoma). Crucially, MRI is free from **beam-hardening artifacts** caused by the dense petrous and occipital bones, which often obscure details in the posterior fossa on a CT scan. Multiplanar imaging (axial, sagittal, and coronal) further helps in determining the tumor's relationship to the brainstem and fourth ventricle. **Why other options are incorrect:** * **CT Scan:** While useful for detecting acute hemorrhage or calcification, it is inferior for the posterior fossa due to "bone-streak artifacts" from the surrounding thick skull base. * **Angiography:** This is an invasive procedure used primarily to assess vascularity or for preoperative embolization; it does not provide the necessary parenchymal detail for primary diagnosis. * **Myelography:** This technique is used to visualize the spinal cord and subarachnoid space; it has been largely replaced by MRI and is not used for intracranial tumor evaluation. **High-Yield Clinical Pearls for NEET-PG:** * **Investigation of Choice (IOC)** for almost all intracranial tumors: **Contrast-enhanced MRI (CEMRI)**. * **Gadolinium** is the contrast agent used in MRI to check for blood-brain barrier disruption. * In children, the most common posterior fossa tumor is **Pilocytic Astrocytoma** (cystic with a mural nodule). * **Diffusion-Weighted Imaging (DWI)** is a specific MRI sequence helpful in differentiating tumors like medulloblastoma (which shows restricted diffusion) from other lesions.

Question 43: Which MRI sequence is known as Tractography?

A. DWI
B. SWI
C. DTI (Correct Answer)
D. FLAIR

Explanation: **Explanation:** **DTI (Diffusion Tensor Imaging)** is the correct answer. It is a specialized MRI technique that measures the **anisotropy** (directionality) of water molecule diffusion. In the brain, water diffuses more easily along the length of white matter axons rather than across them. By mapping these directional vectors, DTI can reconstruct 3D representations of white matter tracts, a process known as **Tractography**. This is clinically vital for preoperative planning to avoid damaging eloquent white matter pathways (e.g., the corticospinal tract). **Analysis of Incorrect Options:** * **DWI (Diffusion Weighted Imaging):** While DTI is an advanced form of DWI, standard DWI only measures the *magnitude* of water diffusion (Brownian motion). It is the gold standard for diagnosing **hyperacute ischemic stroke** (showing restricted diffusion) but does not provide directional tract mapping. * **SWI (Susceptibility Weighted Imaging):** This sequence is highly sensitive to substances that distort the magnetic field, such as **hemosiderin (blood)** and **calcium**. It is used to detect microhemorrhages, diffuse axonal injury (DAI), and venous malformations. * **FLAIR (Fluid Attenuated Inversion Recovery):** This is a T2-weighted sequence where the signal from free fluid (CSF) is suppressed (made black). This makes periventricular pathologies, like **Multiple Sclerosis plaques**, much easier to visualize. **High-Yield Clinical Pearls for NEET-PG:** * **DTI** is the best sequence to differentiate between displacement vs. infiltration of white matter tracts by a tumor. * **Fractional Anisotropy (FA)** is the primary quantitative parameter used in DTI; a decrease in FA usually indicates loss of white matter integrity. * For **Diffuse Axonal Injury (DAI)**, the most sensitive sequences are **SWI** or **GRE** (T2*).

Question 44: Which vessels are typically catheterized during carotid angiography?

A. Two external carotids and two vertebrals
B. Two internal carotids and two vertebrals
C. Two internal carotids and one vertebral (Correct Answer)
D. Two external carotids and one vertebral

Explanation: **Explanation:** The goal of diagnostic cerebral angiography (specifically a **four-vessel study**) is to visualize the entire intracranial circulation. This includes the anterior circulation (supplied by the internal carotid arteries) and the posterior circulation (supplied by the vertebral arteries). **Why Option C is Correct:** Standard carotid angiography focuses on the **Internal Carotid Arteries (ICA)** because they supply the majority of the cerebral hemispheres. To visualize the posterior circulation (brainstem, cerebellum, and occipital lobes), the **Vertebral Arteries** are catheterized. * In clinical practice, catheterizing **two ICAs and one vertebral artery** is often sufficient because the two vertebral arteries usually join to form a single **Basilar Artery**. Contrast injected into one dominant vertebral artery typically opacifies the entire vertebrobasilar system via retrograde flow into the contralateral vertebral artery, making the fourth vessel catheterization redundant in many diagnostic protocols. **Analysis of Incorrect Options:** * **Options A & D:** The **External Carotid Arteries (ECA)** supply the face, scalp, and meninges. While they are occasionally catheterized for specific pathologies (like meningiomas or epistaxis), they are not the primary vessels for standard cerebral angiography. * **Option B:** While a "four-vessel" study technically involves both ICAs and both vertebrals, the most common clinical convention for a diagnostic survey (and the standard answer for this classic board question) focuses on the three-vessel approach (2 ICA + 1 Vertebral) as the baseline requirement for adequate intracranial visualization. **NEET-PG High-Yield Pearls:** * **Gold Standard:** Digital Subtraction Angiography (DSA) remains the gold standard for diagnosing cerebral aneurysms and Arteriovenous Malformations (AVMs). * **Access Site:** The **Common Femoral Artery** is the most common access point (Seldinger technique), though the Radial Artery approach is increasing in popularity. * **Complication:** The most feared complication of carotid angiography is an embolic stroke (approx. 0.5–1% risk).

Question 45: What is the investigation of choice for acute stroke?

A. CT scan (Correct Answer)
B. MRI angiography
C. Functional MRI
D. Contrast CT

Explanation: **Explanation:** In the emergency management of acute stroke, the primary goal is to differentiate between **ischemic** and **hemorrhagic** stroke to determine if thrombolytic therapy (like tPA) can be safely administered. **1. Why CT Scan is the Correct Answer:** A **Non-Contrast Computed Tomography (NCCT) scan of the head** is the initial investigation of choice because of its high sensitivity in detecting **acute intracranial hemorrhage** (which appears hyperdense/white). It is fast, widely available, and cost-effective. In the hyperacute phase of an ischemic stroke (first 6 hours), the CT may appear normal, but its main utility is to "rule out" a bleed before starting anticoagulants or fibrinolytics. **2. Why the other options are incorrect:** * **MRI Angiography:** While excellent for visualizing vascular occlusions or aneurysms, it is time-consuming and not the first-line screening tool in an emergency setting. * **Functional MRI:** This is primarily used in research or pre-surgical mapping to study brain activity/metabolism; it has no role in the emergency diagnosis of acute stroke. * **Contrast CT:** Contrast is generally avoided in the initial screening because extravasated contrast can mimic the appearance of blood (hyperdensity), potentially leading to a misdiagnosis of hemorrhage. **Clinical Pearls for NEET-PG:** * **Earliest sign of Ischemic Stroke on CT:** "Hyperdense Middle Cerebral Artery (MCA) sign." * **Other early CT signs:** Insular ribbon sign, blurring of the gray-white matter interface, and sulcal effacement. * **Gold Standard for Ischemia:** **Diffusion-Weighted Imaging (DWI) MRI** is the most sensitive sequence for detecting early infarcts (within minutes), but NCCT remains the "investigation of choice" for initial triage. * **Door-to-CT time goal:** Should ideally be within 20–25 minutes of hospital arrival.

Question 46: What is an advantage of MRI?

A. Calcification is best seen
B. CSF is hypointense on T1 and hyperintense on T2
C. Vascular structures are best visualized (Correct Answer)
D. It is best to differentiate benign from malignant pulmonary nodules

Explanation: ### Explanation **Correct Option: C. Vascular structures are best visualized** MRI offers superior soft-tissue contrast and the unique ability to visualize blood flow without necessarily requiring exogenous contrast agents. Techniques like **Magnetic Resonance Angiography (MRA)** and **Magnetic Resonance Venography (MRV)** utilize "flow-void" phenomena or "Time-of-Flight" (TOF) sequences to create high-resolution images of the vasculature. This makes MRI the gold standard for evaluating intracranial aneurysms, vascular malformations, and dural venous sinus thrombosis. **Analysis of Incorrect Options:** * **A. Calcification is best seen:** This is incorrect. **Non-contrast CT (NCCT)** is the gold standard for detecting calcification. On MRI, calcification typically appears as a non-specific signal void (hypointense), making it difficult to distinguish from flowing blood or air. * **B. CSF is hypointense on T1 and hyperintense on T2:** While this statement is **physiologically true**, it is a *characteristic* of the sequences, not a comparative *advantage* of the modality itself. In the context of competitive exams, "advantage" refers to a diagnostic superiority over other modalities. * **D. Differentiating pulmonary nodules:** This is incorrect. **CT (High-Resolution CT)** is the modality of choice for lung parenchyma. MRI has limited utility in the lungs due to low proton density and motion artifacts from breathing and heartbeats. **High-Yield Clinical Pearls for NEET-PG:** * **Modality of Choice for Acute Stroke:** Diffusion-Weighted Imaging (DWI) MRI (detects changes within minutes). * **Modality of Choice for Acute Head Trauma/Hemorrhage:** NCCT (faster and highly sensitive to acute blood). * **T1 vs. T2 Mnemonic:** **W**ater is **W**hite on T**2** (CSF is hyperintense). * **Gadolinium:** The standard contrast agent used in MRI; it works by shortening T1 relaxation time, causing enhancement.

Question 47: A 25-year-old male presents to the emergency department following an accident with symptoms of headache and paralysis. A CT scan reveals subarachnoid hemorrhage. What is the next investigation of choice?

A. MRI
B. SPECT
C. 4-Vessel angiography (Correct Answer)
D. Doppler USG

Explanation: ### Explanation **Correct Option: C. 4-Vessel Angiography** In the context of a Subarachnoid Hemorrhage (SAH), the primary goal after confirming the bleed on a non-contrast CT (NCCT) is to identify the underlying vascular etiology (most commonly a ruptured berry aneurysm). **4-Vessel Angiography (Digital Subtraction Angiography - DSA)** remains the **gold standard** investigation. It allows for a high-resolution, 360-degree evaluation of the cerebral vasculature (both carotids and both vertebral arteries) and provides the necessary anatomical detail for surgical clipping or endovascular coiling. **Why other options are incorrect:** * **A. MRI:** While sensitive for chronic blood or associated parenchymal lesions, MRI is not the primary investigation for acute vascular mapping in SAH due to its time-consuming nature and lower sensitivity for small aneurysms compared to DSA. * **B. SPECT:** This is a functional imaging modality used to assess regional cerebral blood flow. It has no role in the acute diagnosis or anatomical localization of the cause of SAH. * **D. Doppler USG:** Transcranial Doppler is used bedside to monitor for **vasospasm** (a common complication occurring 3–14 days post-SAH) but cannot reliably identify the source of the hemorrhage. **Clinical Pearls for NEET-PG:** * **Initial Investigation of Choice (IOC):** Non-Contrast CT (NCCT) Head (shows hyperdensity in basal cisterns/Sylvian fissure). * **Gold Standard Investigation:** 4-Vessel Angiography (DSA). * **Most Common Cause (Spontaneous):** Ruptured Berry Aneurysm (most common site: Anterior Communicating Artery). * **Most Common Cause (Overall):** Trauma. * **Xanthochromia:** If CT is negative but clinical suspicion is high, a Lumbar Puncture showing yellowish CSF (bilirubin) confirms SAH.

Question 48: A 12-year-old boy presents with a 6-month history of progressive intellectual decline, behavioral changes, and myoclonic jerks. CT brain shows diffuse cortical atrophy with periventricular white matter hypodensity. Which of the following viral infections is the most likely underlying cause?

A. Measles (Correct Answer)
B. Varicella
C. Mumps
D. Rubella

Explanation: ***Measles*** - The clinical triad of **progressive intellectual decline**, **myoclonic jerks**, and **behavioral changes** in a 12-year-old is pathognomonic for **Subacute Sclerosing Panencephalitis (SSPE)**, a rare complication of measles virus. - CT findings of **diffuse cortical atrophy** with **periventricular white matter hypodensity** are characteristic imaging features of SSPE, reflecting chronic viral-induced neurodegeneration. *Varicella* - Varicella-associated encephalitis typically presents with **acute cerebellar symptoms** like ataxia and coordination problems, not progressive intellectual decline. - CT brain changes in varicella encephalitis predominantly show **cerebellar edema** and hemorrhage, not the cortical atrophy pattern seen here. *Mumps* - Mumps encephalitis presents as **acute viral encephalitis** with fever, headache, and altered consciousness, not chronic progressive deterioration. - CT findings are typically **non-specific acute changes** like cerebral edema, lacking the characteristic periventricular white matter hypodensity of SSPE. *Rubella* - **Congenital rubella syndrome** may cause neurological complications, but presents with **periventricular calcifications** on CT, not white matter hypodensity. - Acquired rubella infection rarely causes chronic progressive neurological deterioration; it typically presents as **acute encephalitis** with different imaging patterns.

Question 49: A male child presents with hyperintensities on T2-weighted MRI in the bilateral frontal lobes. What is the most probable diagnosis?

A. Canavan disease
B. Krabbe disease
C. X-linked adrenoleukodystrophy
D. Alexander disease (Correct Answer)

Explanation: ### **Explanation** The correct answer is **Alexander disease**. This diagnosis is primarily based on the characteristic neuroimaging pattern of **frontal lobe predominance** of white matter involvement. #### **1. Why Alexander Disease is Correct** Alexander disease is a rare leukodystrophy caused by mutations in the **GFAP gene**, leading to the accumulation of Rosenthal fibers in astrocytes. On MRI, it presents with symmetrical T2-weighted hyperintensities that classically begin in the **frontal lobes** and progress posteriorly. Other key imaging features include involvement of the caudate nuclei, thalamus, and contrast enhancement of affected white matter. #### **2. Analysis of Incorrect Options** * **Canavan Disease:** Characterized by **diffuse** white matter involvement with a hallmark involvement of the **subcortical U-fibers**. A key diagnostic feature is elevated **N-acetylaspartate (NAA)** on MR spectroscopy. * **Krabbe Disease:** Typically involves the **posterior** white matter (parieto-occipital) and is associated with hyperdensity of the thalami on CT and enlargement of the optic nerves. * **X-linked Adrenoleukodystrophy (X-ALD):** Classically shows a **posterior-to-anterior** progression, primarily affecting the **occipital and parietal lobes** and the splenium of the corpus callosum. #### **3. NEET-PG Clinical Pearls: Leukodystrophy Patterns** To quickly differentiate leukodystrophies on MRI, remember these "High-Yield Patterns": * **Frontal Predominance:** Alexander Disease. * **Posterior (Occipital) Predominance:** X-linked Adrenoleukodystrophy. * **Diffuse + Subcortical U-fibers + High NAA:** Canavan Disease. * **Diffuse + Subcortical U-fibers + Macrocephaly:** Alexander and Canavan (both have large heads). * **"Tigroid" Pattern:** Metachromatic Leukodystrophy (sparing of perivascular white matter).

Question 50: A mother presents with a one-and-a-half-year-old child who has a one-month history of increasing proptosis of the left eye. Examination reveals a left eye white reflex. A computed tomography scan of the orbit shows a left orbital mass with calcification, mainly centered within the globe. What is the most likely diagnosis?

A. Congenital cataract
B. Retinoblastoma (Correct Answer)
C. Endophthalmitis
D. Coats disease

Explanation: **Explanation:** The clinical presentation of a young child (typically under 2 years) with **leukocoria** (white pupillary reflex) and **proptosis**, combined with CT findings of an **intraocular mass containing calcification**, is pathognomonic for **Retinoblastoma**. **1. Why Retinoblastoma is correct:** Retinoblastoma is the most common primary intraocular malignancy of childhood. The "hallmark" imaging feature on CT is **intraocular calcification** (seen in over 90% of cases). Proptosis indicates extraocular extension of the tumor. The age of the patient (1.5 years) fits the typical peak incidence. **2. Why other options are incorrect:** * **Congenital Cataract:** While it causes leukocoria, it is a lens opacity and does not present as a calcified orbital mass or cause proptosis. * **Endophthalmitis:** This is an inflammation of the inner coats of the eye. While it can cause a hazy reflex, it is usually associated with pain, redness, and a history of trauma or surgery, rather than a calcified mass. * **Coats Disease:** An idiopathic vascular anomaly (telangiectasia). While it causes leukocoria (due to exudative retinal detachment), it rarely shows calcification on CT and typically affects slightly older children (6–8 years). **Clinical Pearls for NEET-PG:** * **Imaging Gold Standard:** **MRI** is the preferred modality to assess optic nerve involvement and intracranial extension (trilateral retinoblastoma), but **CT** is superior for detecting calcification. * **Genetics:** Associated with the **RB1 gene** on chromosome **13q14**. * **Flexner-Wintersteiner Rosettes:** The characteristic histopathological finding. * **Differential Diagnosis of Leukocoria:** Always consider Retinoblastoma, Coats disease, Persistent Hyperplastic Primary Vitreous (PHPV), and Toxocariasis.

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