Neuroradiology Practice Questions

Q: What is the characteristic 'thumb sign' on CT head indicative of?

Chordoma. **Explanation:** The **'Thumb sign'** (also known as the 'clivus thumb sign') is a classic radiological feature of a **Chordoma**. Chordomas are rare, slow-growing, but locally aggressive midline tumors arising from the remnants of the primitive **notochord**. When these tumors occur at the **clivus** (the most common intracranial site), they project posteriorly, indenting the pons. On a sagittal CT or MRI, this indentation creates a characteristic appearance where the tumor looks like a "thumb" pressing into the brainstem. **Why the other options are incorrect:** * **Metastasis:** While metastases can involve the clivus, they typically present as multifocal, osteolytic lesions without the specific midline "thumb-like" indentation of the pons. * **Glioblastoma Multiforme (GBM):** This is an intra-axial high-grade glioma. It typically presents as a ring-enhancing mass within the cerebral hemispheres, not as an extra-axial midline clival mass. * **Astrocytoma:** These are primary intraparenchymal tumors. While they can occur in the brainstem (pontine glioma), they cause expansion of the pons rather than external compression from the clivus. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** Chordomas most commonly occur at the **Sacrococcygeal** region (50%), followed by the **Clivus** (35%) and vertebral bodies (15%). * **Imaging:** On CT, they appear as midline, destructive bone lesions with irregular calcifications. On MRI, they are characteristically **T2 hyperintense**. * **Histopathology:** Look for **Physaliphorous cells** (large cells with vacuolated, bubbly cytoplasm). * **Immunohistochemistry:** Chordomas are positive for **Brachyury** (highly specific), S100, and Cytokeratin.

Q: Dawson's fingers on MRI are diagnostic of which condition?

Multiple sclerosis. **Explanation:** **Multiple Sclerosis (MS)** is the correct answer. **Dawson’s fingers** are a classic radiologic hallmark of MS seen on MRI (best visualized on T2-weighted or FLAIR sequences). They represent **perivenular demyelinating plaques** oriented perpendicular to the lateral ventricles. This specific orientation occurs because the inflammatory process follows the path of the medullary veins (periventricular veins) as they drain toward the ventricular surface. **Analysis of Incorrect Options:** * **Hyperparathyroidism:** Associated with skeletal changes like "Salt and Pepper" skull or subperiosteal bone resorption, but not specific brain parenchymal lesions. * **Psoriatic arthropathy:** An inflammatory arthritis characterized by "Pencil-in-cup" deformity on X-ray, involving joints rather than the central nervous system. * **Multiple exostosis (Diaphyseal Aclasis):** A genetic condition characterized by multiple benign cartilaginous tumors (osteochondromas) growing out of the metaphyses of long bones. **NEET-PG High-Yield Pearls:** * **Location:** Dawson’s fingers are found in the **callososeptal interface**. * **McDonald Criteria:** MRI is the gold standard for diagnosing MS by demonstrating "dissemination in space" and "dissemination in time." * **Other MRI signs in MS:** "Open-ring" enhancement (suggests active demyelination) and "Black holes" (T1 hypointensities indicating permanent axonal loss). * **CSF Finding:** Presence of **Oligoclonal bands** (IgG) on electrophoresis is a classic biochemical marker.

Q: Which of the following is the classic CT appearance of an acute subdural hematoma?

Crescent-shaped hyperdense lesion. ### Explanation **1. Why Option C is Correct:** An **Acute Subdural Hematoma (SDH)** occurs due to the rupture of **bridging veins** that drain from the cerebral cortex into the dural sinuses. On a non-contrast CT (NCCT), blood appears **hyperdense (bright white)** because of high hemoglobin concentration. The blood collects in the potential space between the dura mater and the arachnoid mater. Because it is not restricted by cranial sutures but is limited by dural reflections (like the falx), it spreads along the brain's surface, resulting in a characteristic **crescent-shaped (concavo-convex)** appearance. **2. Why Other Options are Incorrect:** * **Options A & D (Lentiform-shaped):** This "lemon-shaped" or biconvex appearance is characteristic of an **Epidural Hematoma (EDH)**. EDHs are usually arterial (middle meningeal artery) and are restricted by cranial sutures where the dura is firmly attached to the bone. * **Option B (Crescent-shaped hypodense):** While the shape is correct for an SDH, **hypodensity (darker than brain)** indicates a **Chronic Subdural Hematoma** (typically >3 weeks old), where the blood has liquefied and the hemoglobin has broken down. **3. High-Yield Clinical Pearls for NEET-PG:** * **Shape vs. Source:** SDH = Crescent (Bridging Veins); EDH = Lentiform (Middle Meningeal Artery). * **Suture Lines:** SDH **crosses** suture lines but does not cross dural attachments (falx/tentorium). EDH **does not cross** suture lines. * **Density Evolution:** * Acute ( 21 days): Hypodense (Black) * **Concave vs. Convex:** SDH has a **concave** inner margin (following the brain contour); EDH has a **convex** inner margin.

Q: A 20-year-old man presented with epistaxis. DSA showing the sphenopalatine branch of the maxillary artery is provided. The arrow most likely points to which pathology?

Arteriovenous Malformation (AVM). ***Arteriovenous Malformation (AVM)*** - **DSA** shows characteristic **nidus** with early venous filling and abnormal vascular tangle in the **sphenopalatine territory**, typical of **extracranial sinonasal AVM**. - On **multiphase DSA**, the lesion demonstrates a **nidus** (tangled vascular core) with **early draining veins** visible in the arterial phase, distinguishing it from angiofibroma which shows a homogeneous tumor blush without early venous drainage. - On **cross-sectional imaging (MRI/CT)**, an extracranial sinonasal AVM appears as a **serpiginous flow-void cluster** without an associated soft-tissue mass, in contrast to angiofibroma which presents as a **well-defined enhancing nasopharyngeal mass** centered at the sphenopalatine foramen. *Rhinosporidiosis* - An **infection caused by Rhinosporidium seeberi, an aquatic protistan organism** causing **nasal polyps** with characteristic **sporangia**, not vascular abnormalities on DSA. - Would show **soft tissue masses** on imaging, not the vascular nidus pattern seen in AVMs. *Angiofibroma* - **Juvenile nasopharyngeal angiofibroma** appears as a **hypervascular mass** with intense contrast enhancement but lacks the **nidus pattern**. - Typically arises from the **sphenopalatine foramen** as a solid tumor, not tangled vessels with early venous drainage. - On multiphase DSA, angiofibroma shows a **prolonged tumor blush** persisting into the venous phase without early draining veins, unlike the rapid arteriovenous shunting seen in AVM. - On MRI, angiofibroma demonstrates a **solid nasopharyngeal mass** with flow voids (salt-and-pepper pattern) and bony remodeling, absent in sinonasal AVM. *Pseudoaneurysm* - Shows a **saccular outpouching** with contrast pooling and delayed washout, not the tangled vessel pattern. - Usually results from **trauma** or **infection**, presenting as a focal arterial wall defect rather than a nidus.

Q: The 'swirl sign' is associated with which of the following conditions?

Epidural hematoma. **Explanation:** The **'Swirl Sign'** is a critical radiological finding on non-contrast CT (NCCT) scans of the head, specifically associated with an **Epidural Hematoma (EDH)**. It represents an area of low attenuation (hypodensity) within a high-attenuation (hyperdense) extra-axial clot. **1. Why Epidural Hematoma is correct:** The swirl sign indicates **hyperacute, active bleeding**. The hypodense "swirl" represents unclotted, liquid blood, while the surrounding hyperdense area represents blood that has already clotted. Its presence is a surgical emergency as it predicts rapid hematoma expansion and clinical deterioration. **2. Why other options are incorrect:** * **Subdural Hematoma (SDH):** While SDH can show mixed density (e.g., acute-on-chronic), the specific "swirl" morphology is classically described for EDH. SDH typically presents as a crescent-shaped collection. * **Subarachnoid Hemorrhage (SAH):** This presents as hyperdensity within the sulci, cisterns, and Sylvian fissures, not as a focal swirling mass. * **Acute Bleeding:** While the swirl sign *does* represent active bleeding, in the context of NEET-PG, it is a specific sign used to identify the nature of an **Epidural Hematoma**. **High-Yield Clinical Pearls for NEET-PG:** * **EDH Shape:** Biconvex/Lentiform (does not cross sutures). * **Source of Bleed:** Most commonly the **Middle Meningeal Artery**. * **Clinical Hallmark:** The **Lucid Interval** (temporary improvement before rapid decline). * **Management:** If the swirl sign is present, immediate neurosurgical evacuation is usually indicated regardless of the initial volume, due to the high risk of herniation.

Q: Abnormal signals in bilateral thalami on MRI brain are seen in which of the following conditions?

Japanese encephalitis. **Explanation:** The presence of **bilateral thalamic involvement** on MRI is a classic neuroimaging hallmark for several specific conditions, most notably **Japanese Encephalitis (JE)**. **1. Why Japanese Encephalitis is correct:** JE is a flavivirus infection with a unique predilection for the deep gray matter nuclei. MRI typically shows T2/FLAIR hyperintensities in the **thalami (most common)**, basal ganglia, substantia nigra, and brainstem. Thalamic lesions are often bilateral and may show hemorrhagic transformation, which is highly suggestive of JE in an endemic setting. **2. Analysis of Incorrect Options:** * **Wilson’s Disease:** While it involves the basal ganglia, the characteristic MRI finding is the **"Face of the Giant Panda"** sign (midbrain) and the "Miniature Panda" sign (pons). Thalamic involvement can occur but is usually secondary to prominent lentiform nucleus changes. * **Wernicke’s Encephalopathy:** This condition classically involves the **mammillary bodies**, periaqueductal gray matter, and the **dorsomedial thalami**. While it involves the thalami, JE is the more "classic" answer for generalized bilateral thalamic signals in a viral prodrome context. * **Rasmussen’s Encephalitis:** This is a chronic inflammatory disease characterized by **unilateral** hemispheric atrophy and progressive neurological deficit. It does not present with bilateral thalamic signals. **High-Yield Clinical Pearls for NEET-PG:** * **Differential Diagnosis for Bilateral Thalamic Lesions:** Japanese Encephalitis, Artery of Percheron infarct, Wernicke’s Encephalopathy, and Deep Venous Thrombosis (Internal Cerebral Veins). * **JE Key Feature:** Look for "Thalamic involvement with hemorrhage" in the clinical stem. * **Artery of Percheron:** A rare anatomical variant where a single arterial trunk supplies bilateral paramedian thalami; occlusion leads to sudden onset bilateral thalamic infarcts.

Q: The radiolucency shown by the following radiograph is due to:

Nasopalatine cyst. ***Nasopalatine cyst*** - Classic **midline anterior maxillary** radiolucency located in the **incisive canal/nasopalatine foramen** region, often with a characteristic **heart-shaped** or **inverted pear** appearance. - Most common **non-odontogenic cyst** of the maxilla, arising from embryonic remnants of the **nasopalatine duct**. *Solitary bone cyst* - Typically occurs in the **mandible** (especially posterior region) rather than the anterior maxilla, appearing as a **unilocular radiolucency**. - More common in **younger patients** and often **asymptomatic**, but location doesn't match the midline anterior maxillary presentation. *Ameloblastoma* - Predominantly affects the **posterior mandible** and presents as a **multilocular** ("soap bubble" or "honeycomb") radiolucency. - **Aggressive benign tumor** that causes significant **expansion** and **cortical thinning**, unlike the typical presentation of a midline maxillary radiolucency. *Nasolabial cyst* - **Soft tissue cyst** located in the **nasolabial fold** that is typically **not directly visible** on conventional radiographs, as it does not produce an intraosseous radiolucency. - May cause **pressure-related remodeling** of the adjacent maxilla in some cases, but does not present as a radiolucency within bone structure.

Q: Which sequence of MRI is used to detect microhemorrhages?

SWI. **Explanation:** The correct answer is **SWI (Susceptibility Weighted Imaging)**. **1. Why SWI is the Correct Answer:** SWI is a high-spatial-resolution 3D gradient-echo sequence that is extremely sensitive to substances that cause "magnetic susceptibility" effects, such as **hemosiderin** (from old blood) and **calcium**. * **Mechanism:** When microhemorrhages occur, hemoglobin breaks down into paramagnetic hemosiderin. This creates local magnetic field distortions, leading to a loss of signal. On SWI, these appear as small, dark "blooming" spots (the **Blooming Effect**). SWI is significantly more sensitive than conventional T2* Gradient Echo (GRE) for detecting tiny punctate hemorrhages. **2. Why Other Options are Incorrect:** * **T1WI (T1 Weighted Imaging):** Primarily used for anatomy. While acute/subacute blood can appear bright (hyperintense) on T1, it lacks the sensitivity to detect chronic microhemorrhages. * **T2WI (T2 Weighted Imaging):** Standard T2 sequences are poor at detecting microbleeds as they do not emphasize magnetic susceptibility. * **DWI (Diffusion Weighted Imaging):** This sequence measures the random motion of water molecules. It is the "Gold Standard" for detecting **Hyperacute Ischemic Stroke** (cytotoxic edema), not microhemorrhages. **3. High-Yield Clinical Pearls for NEET-PG:** * **Differential Diagnosis for Microhemorrhages:** 1. **Hypertensive Microbleeds:** Usually located in the basal ganglia, thalamus, and pons. 2. **Cerebral Amyloid Angiopathy (CAA):** Characteristically located in the **peripheral/lobar** cortical-subcortical junctions. 3. **Diffuse Axonal Injury (DAI):** Microhemorrhages at the grey-white matter junction, corpus callosum, or brainstem following trauma. * **Mnemonic:** "SWI for Blood and Bone (Calcium)." * **Comparison:** If both GRE and SWI are in options, **SWI** is the superior choice for microhemorrhage detection.

Question 1

What is the characteristic 'thumb sign' on CT head indicative of?

Accepted Answer

Chordoma

Answer

Metastasis

Answer

Glioblastoma multiforme

Answer

Astrocytoma

Question 2

Dawson's fingers on MRI are diagnostic of which condition?

Accepted Answer

Multiple sclerosis

Answer

Hyperparathyroidism

Answer

Psoriatic arthropathy

Answer

Multiple exostosis

Question 3

Since 15-20 days, a 40-year-old man is unable to look properly upwards. On CT scan study, a cystic lesion within the inferior oblique muscle with probable mural eccentric 'dot' is noted. What is the most-likely diagnosis?

Accepted Answer

Ocular cysticercosis

Answer

Ocular dermoid

Answer

Toxocara infection

Answer

Ocular lymphangioma

Question 4

Which of the following is the classic CT appearance of an acute subdural hematoma?

Accepted Answer

Crescent-shaped hyperdense lesion

Answer

Lentiform-shaped hyperdense lesion

Answer

Crescent-shaped hypodense lesion

Answer

Lentiform-shaped hypodense lesion

Question 5

A 20-year-old man presented with epistaxis. DSA showing the sphenopalatine branch of the maxillary artery is provided. The arrow most likely points to which pathology?

Accepted Answer

Arteriovenous Malformation (AVM)

Answer

Angiofibroma

Answer

Rhinosporidiosis

Answer

Pseudoaneurysm

Question 6

The 'swirl sign' is associated with which of the following conditions?

Accepted Answer

Epidural hematoma

Answer

Subdural hematoma

Answer

Subarachnoid hemorrhage

Answer

Acute bleeding

Question 7

Abnormal signals in bilateral thalami on MRI brain are seen in which of the following conditions?

Accepted Answer

Japanese encephalitis

Answer

Wilson's disease

Answer

Wernicke's encephalopathy

Answer

Rasmussen's encephalitis

Question 8

The radiolucency shown by the following radiograph is due to:

Accepted Answer

Nasopalatine cyst

Answer

Solitary bone cyst

Answer

Ameloblastoma

Answer

Nasolabial cyst

Question 9

A 57-year-old woman, a smoker of 1 pack/day for 40 years, presents with new-onset generalized seizures of approximately 1 minute duration, witnessed by her husband. She has experienced a 25 lb weight loss in the past 3 months. Examination reveals she is thin and nervous, with otherwise normal neurological findings. Chest radiographs show a 4-cm nodule in the right upper lung lobe. To exclude cerebral metastasis as a cause of her seizure, what should be the next diagnostic test?

Accepted Answer

MRI of the brain with intravenous contrast

Answer

Electroencephalogram (EEG)

Answer

CT scan of the brain with intravenous contrast

Answer

Spinal tap to measure opening pressure and obtain CSF for cytology

Question 10

Which sequence of MRI is used to detect microhemorrhages?

Accepted Answer

SWI

Answer

T1WI

Answer

T2WI

Answer

DWI

Neuroradiology — MCQs

Neuroradiology — MCQs

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