Neuroradiology Practice Questions

Q: On MRI, how can epidermoids be differentiated from arachnoid cysts?

Restricted diffusion. **Explanation:** The differentiation between an **epidermoid cyst** and an **arachnoid cyst** is a classic high-yield topic in neuroradiology, as both typically appear as extra-axial lesions that are isointense to CSF on T1 and T2-weighted imaging. **Why Restricted Diffusion is the Correct Answer:** The gold standard for differentiation is **Diffusion-Weighted Imaging (DWI)**. * **Epidermoid cysts** show **restricted diffusion** (appearing bright/hyperintense on DWI and dark on ADC maps) due to their solid content of desquamated keratin and cholesterol crystals. * **Arachnoid cysts** contain simple fluid (CSF) and show **facilitated diffusion** (appearing dark on DWI), similar to normal cerebrospinal fluid. **Analysis of Incorrect Options:** * **A. Contrast enhancement:** Neither epidermoid nor arachnoid cysts typically show internal enhancement. While the wall of an epidermoid might rarely show minimal enhancement, it is not a reliable differentiating feature. * **B. Smooth margins:** Both lesions generally exhibit smooth or scalloped margins, though epidermoids are more likely to "encase" vessels and nerves rather than displace them. * **D. CSF signal on FLAIR:** On FLAIR sequences, an arachnoid cyst will suppress completely (becoming dark like CSF). While epidermoids often fail to suppress fully (appearing "dirty" or heterogeneously bright), this finding is less definitive and reliable than the restricted diffusion seen on DWI. **High-Yield Pearls for NEET-PG:** * **Location:** Epidermoids are most commonly found in the **Cerebellopontine (CP) angle** (most common congenital lesion here). * **Morphology:** Epidermoids are known as "pearly tumors" and have a "cauliflower-like" growth pattern that creeps into subarachnoid spaces. * **Chemical Shift:** Epidermoids do not contain macroscopic fat; therefore, they do not show a chemical shift artifact (unlike dermoid cysts).

Q: A patient presents with loss of consciousness following a road traffic accident. CT scan shows multiple spotty hemorrhages and full basal cisterns. What is the most likely diagnosis?

Diffuse axonal injury. **Explanation:** **Diffuse Axonal Injury (DAI)** is the most likely diagnosis. It occurs due to high-velocity rotational acceleration-deceleration forces (e.g., road traffic accidents), leading to the shearing of axons. 1. **Why it is correct:** The classic CT presentation of DAI includes **multiple small, punctate (spotty) hemorrhages** typically located at the **gray-white matter junction**, corpus callosum, or brainstem. While CT is often normal in mild cases, "full basal cisterns" indicate significant cerebral edema and increased intracranial pressure, which are common in severe DAI. 2. **Why incorrect options are wrong:** * **Brain Contusion:** These are "bruises" of the brain, usually larger and localized to the cortical surface (often frontal or temporal lobes) due to direct impact (coup/contrecoup), rather than deep-seated spotty hemorrhages. * **Subdural Hematoma:** This presents as a crescentic, hyperdense collection that crosses suture lines, not as multiple parenchymal spots. * **Multiple Infarcts:** These typically follow vascular territories and are usually hypodense on CT; they are rarely the primary finding immediately following acute trauma. **Clinical Pearls for NEET-PG:** * **Imaging Gold Standard:** **MRI (Susceptibility Weighted Imaging - SWI)** is the most sensitive sequence for detecting the microhemorrhages of DAI. * **Clinical-Radiological Dissociation:** A hallmark of DAI is a patient with a very low GCS (comatose) despite a relatively "normal-looking" or minimally involved initial CT scan. * **Common Sites:** Gray-white matter junction (most common) > Corpus callosum (Splenium) > Brainstem (Dorsolateral aspect).

Q: Which MRI sequence is used to detect cytotoxic edema before vasogenic edema?

DWI. **Explanation:** **Diffusion-Weighted Imaging (DWI)** is the most sensitive MRI sequence for detecting early ischemic changes. The core concept lies in the movement of water molecules (Brownian motion). In **cytotoxic edema** (seen in early stroke), the failure of the Na+/K+ ATPase pump causes water to shift from the extracellular space into the intracellular space. This intracellular water is "restricted" in its movement. DWI detects this **restricted diffusion**, appearing as a **hyperintense (bright)** signal within minutes of an arterial occlusion (as early as 30 minutes). **Why other options are incorrect:** * **T1WI & T2WI:** These sequences rely on changes in total tissue water content (**vasogenic edema**). It takes several hours (usually >6 hours) for enough water to accumulate to be visible on T2/FLAIR (appearing bright) or T1 (appearing dark). Therefore, they are insensitive to hyperacute stroke. * **SWI (Susceptibility Weighted Imaging):** This sequence is highly sensitive to paramagnetic substances like blood (hemorrhage), iron, and calcium. It is used to rule out hemorrhage or detect "microbleeds," not to visualize early cytotoxic edema. **High-Yield Clinical Pearls for NEET-PG:** * **ADC (Apparent Diffusion Coefficient):** Always correlate DWI with ADC maps to rule out "T2 shine-through." True restricted diffusion (infarct) shows **High signal on DWI** and **Low signal on ADC**. * **Earliest Sign on CT:** Loss of insular ribbon sign or obscuration of the lentiform nucleus. * **DWI-FLAIR Mismatch:** If a lesion is bright on DWI but normal on FLAIR, the stroke is likely <4.5 hours old, making the patient a candidate for thrombolysis.

Q: Which type of hemorrhage classically presents as a lenticular shape on imaging?

Extradural hemorrhage. ### Explanation **1. Why Extradural Hemorrhage (EDH) is Correct:** An Extradural (Epidural) hemorrhage occurs when blood collects between the inner table of the skull and the dura mater, most commonly due to a rupture of the **middle meningeal artery** following a temporal bone fracture. The dura mater is firmly attached to the skull at the **cranial sutures**. Because the expanding hematoma cannot easily cross these suture lines, it is forced inward toward the brain, resulting in a characteristic **biconvex or lenticular (lens-like) shape** on a CT scan. **2. Why the Other Options are Incorrect:** * **Subdural Hemorrhage (SDH):** Occurs between the dura and arachnoid mater (usually due to tearing of bridging veins). Unlike EDH, it is not limited by sutures and spreads along the brain's convexity, appearing **crescent-shaped (concavo-convex)**. * **Subarachnoid Hemorrhage (SAH):** Bleeding into the subarachnoid space (often from a ruptured berry aneurysm). It presents as hyperdensity within the **sulci, fissures, and basal cisterns** (often described as a "star-like" pattern). * **Intracerebral Hemorrhage (ICH):** Bleeding within the brain parenchyma itself. It typically appears as a **hyperdense globoid mass** within the lobes or basal ganglia, often associated with surrounding edema. **3. Clinical Pearls for NEET-PG:** * **Lucid Interval:** Classically associated with EDH (the patient regains consciousness temporarily before deteriorating). * **Suture Rule:** EDH **does not** cross suture lines (but can cross the midline/dural reflections), whereas SDH **does** cross suture lines (but does not cross the midline). * **Source of Bleed:** EDH is usually arterial (Middle Meningeal Artery); SDH is usually venous (Bridging Veins). * **Imaging Choice:** Non-contrast CT (NCCT) Head is the gold standard for acute intracranial hemorrhage.

Q: What is the imaging modality of choice for diagnosing brain metastases?

MRI. **Explanation:** **MRI with Gadolinium contrast** is the gold standard and imaging modality of choice for diagnosing brain metastases. Its superiority lies in its high soft-tissue contrast and multiplanar imaging capabilities. MRI is significantly more sensitive than CT for detecting small lesions (especially those <5 mm), identifying lesions in the posterior fossa (where CT has bone-streak artifacts), and differentiating between solitary and multiple lesions—a distinction crucial for surgical planning. **Analysis of Options:** * **CECT (Contrast-Enhanced CT):** While often the first-line screening tool in emergency settings due to speed and availability, it lacks the sensitivity of MRI. It may miss small cortical or posterior fossa metastases. * **MRS (Magnetic Resonance Spectroscopy):** This is a functional imaging technique used to differentiate metastases from other lesions (like abscesses or primary gliomas) by analyzing metabolite peaks (e.g., high choline, low NAA). It is an adjunct, not the primary diagnostic modality. * **PET (Positron Emission Tomography):** While useful for systemic staging and finding the primary tumor, PET has limited utility for primary brain diagnosis due to the high baseline glucose metabolism of the normal brain (high background noise). **Clinical Pearls for NEET-PG:** * **Most common source:** Lung cancer (most common overall), followed by Breast cancer and Melanoma. * **Location:** Most metastases occur at the **gray-white matter junction** due to narrowing of blood vessels trapping tumor emboli. * **Distribution:** 80% occur in the cerebral hemispheres, following the distribution of blood flow. * **Imaging Hallmark:** "Ring-enhancing lesions" with significant perilesional vasogenic edema.

Q: In intervertebral disc prolapse, what does a Schmorl node on MRI imply?

Not significant. **Explanation:** A **Schmorl node** is defined as the herniation of the nucleus pulposus through the vertebral body endplate into the adjacent vertebral body. While it represents a form of disc displacement, it is considered an **incidental finding** in the majority of cases. **1. Why "Not significant" is correct:** In the context of intervertebral disc prolapse (IVDP), clinical symptoms like radiculopathy or myelopathy are caused by *posterior* or *posterolateral* herniation into the spinal canal or neural foramina. Schmorl nodes are *vertical* herniations. They are frequently seen in asymptomatic individuals (prevalence up to 75% in autopsy) and usually do not correlate with the patient's acute symptoms or the need for surgical intervention. Therefore, they are clinically "not significant" regarding the management of symptomatic disc disease. **2. Why other options are incorrect:** * **Significant:** Schmorl nodes do not cause nerve root compression or spinal stenosis, which are the hallmarks of "significant" IVDP. * **Good prognosis:** The presence of a Schmorl node does not predict a better recovery from a separate symptomatic disc herniation. * **Not prognostic:** While they don't predict outcomes, the term "not significant" better describes their status as a common, benign radiological variant in the context of a diagnostic workup. **High-Yield Clinical Pearls for NEET-PG:** * **Scheuermann’s Disease:** Multiple Schmorl nodes, along with anterior wedging of vertebrae and kyphosis, are diagnostic hallmarks of this condition in adolescents. * **Modic Changes:** Acute Schmorl nodes may show inflammatory changes (edema) on MRI, but chronic ones are asymptomatic. * **Common Site:** Most frequently found in the **thoracolumbar junction** (T8-L1). * **Differential Diagnosis:** Must be distinguished from "limbus vertebrae" (herniation beneath the ring apophysis).

Q: Focal bilateral thalamic, posterior internal capsule showing hyperdensity and calcification in CT scan and extensive involvement of deep white matter is characteristic of which condition?

Krabbe's disease. **Explanation:** **Krabbe’s Disease (Globoid Cell Leukodystrophy)** is an autosomal recessive lysosomal storage disorder caused by a deficiency of the enzyme **galactocerebrosidase**. This leads to the accumulation of psychosine, which is toxic to oligodendrocytes. **Why Krabbe’s Disease is correct:** The hallmark CT finding in the early infantile stage is **hyperdensity** (with or without frank calcification) involving the **thalami**, caudate nuclei, and **posterior limb of the internal capsule**. This is a highly specific "spotter" for Krabbe’s. MRI typically shows symmetric T2 hyperintensity in the deep white matter, often sparing the subcortical U-fibers initially, and may show "tigroid" patterns or enhancement of the cranial nerves (especially the optic nerve). **Why other options are incorrect:** * **Alexander’s Disease:** Characterized by a **frontal lobe predominance** of white matter involvement and macrocephaly. It does not typically present with thalamic hyperdensity. * **Metachromatic Leukodystrophy (MLD):** Shows a characteristic **"tigroid" or "leopard skin" pattern** of demyelination due to spared perivascular white matter. Thalamic hyperdensity is not a feature. * **Multiple Sclerosis:** A primary demyelinating disease of adults (usually) presenting with asymmetric, focal "Dawson’s fingers" (periventricular plaques) rather than diffuse deep white matter involvement with thalamic calcification. **High-Yield Clinical Pearls for NEET-PG:** 1. **Krabbe’s:** Look for "Thalamic Hyperdensity" on CT and "Optic nerve enlargement/enhancement" on MRI. 2. **Canavan Disease:** Associated with **elevated NAA peak** on MR Spectroscopy and macrocephaly. 3. **Adrenoleukodystrophy:** Characterized by **posterior (occipito-parietal) predominance** of white matter changes. 4. **Pelizaeus-Merzbacher:** Classic "tigroid" appearance with near-total lack of normal myelin.

Q: This classical "Ice-cream cone" appearance of an intensely enhancing lesion at the left CP angle recess suggests:

Acoustic schwannoma. ***Acoustic schwannoma*** - The classical **"ice-cream cone"** appearance consists of intense enhancement with the **cone portion extending into the internal auditory canal (IAC)** and the **ball portion in the CP angle cistern**. - **Acoustic schwannomas** characteristically show **homogeneous intense enhancement** and have a predilection for the **cerebellopontine angle** with IAC extension. *Epidermoid cyst* - Epidermoid cysts typically show **no enhancement** or minimal rim enhancement, unlike the intense enhancement described. - They appear **hyperintense on DWI** and follow **CSF signal** on T1 and T2, not showing the solid enhancing pattern. *Arachnoid cyst* - Arachnoid cysts show **no enhancement** and perfectly follow **CSF signal intensity** on all sequences. - They appear as **simple fluid collections** without the solid enhancing mass characteristic of the ice-cream cone sign. *High grade glioma* - High grade gliomas rarely occur at the **CP angle** and typically show **heterogeneous enhancement** with necrosis and surrounding edema. - They demonstrate **ring enhancement** or irregular enhancement patterns, not the homogeneous intense enhancement of acoustic schwannomas.

Q: A tumour showing dural enhancement with a tail is characteristic of which of the following entities?

Meningioma. ### Explanation **Meningioma** is the correct answer because the **"Dural Tail Sign"** is a classic radiological hallmark of this tumor. #### Why Meningioma is Correct: The dural tail sign refers to the thickening and enhancement of the dura mater immediately adjacent to a peripheral intracranial tumor. In meningiomas, this occurs due to **reactive vascularity and fibrovascular proliferation** of the dura, rather than direct tumor invasion. On contrast-enhanced MRI, this appears as a tapering linear enhancement extending away from the tumor mass along the dural surface. While not 100% pathognomonic, it is highly suggestive of meningioma (seen in ~60-72% of cases). #### Why Other Options are Incorrect: * **Medulloblastoma:** These are primitive neuroectodermal tumors (PNET) typically located in the posterior fossa (cerebellar vermis) of children. They show intense enhancement but do not typically exhibit a dural tail. * **Glioma:** These are intra-axial tumors (arising within the brain parenchyma). Since they are not primary dural-based tumors, they do not show a dural tail sign. * **Acoustic Neuroma (Vestibular Schwannoma):** While these are extra-axial tumors like meningiomas, they arise from the CN VIII sheath. They typically present with an "ice-cream cone" appearance in the internal auditory canal and rarely show a dural tail. #### NEET-PG High-Yield Pearls: * **Most common** primary intracranial tumor: Meningioma. * **Histology:** Look for **Psammoma bodies** (laminated calcifications) and whorled patterns. * **Imaging:** Meningiomas are typically **isointense** on T1/T2 and show **intense, homogenous enhancement** on contrast. * **Other causes of Dural Tail:** Glioblastoma (rarely), Sarcoidosis, and Metastases. However, in exams, always prioritize Meningioma.

Q: What condition is characterized by a "tram track" appearance on a CT scan of the head?

Sturge-Weber syndrome. **Explanation:** **Sturge-Weber Syndrome (SWS)**, also known as encephalotrigeminal angiomatosis, is the correct answer. The "tram track" appearance on a non-contrast CT scan refers to **gyriform cortical calcifications**. These occur due to chronic ischemia caused by an underlying leptomeningeal angioma (usually on the same side as a facial Port-wine stain). This leads to calcium deposition in the second and third layers of the cerebral cortex, tracing the outlines of the sulci and gyri, resembling parallel railroad tracks. **Analysis of Incorrect Options:** * **Von Hippel-Lindau (VHL):** Characterized by retinal and CNS **hemangioblastomas** (typically in the cerebellum or spine), renal cell carcinoma, and pheochromocytoma. It does not feature gyriform calcification. * **Tuberous Sclerosis (TS):** Features **subependymal nodules** (which can calcify) and cortical tubers. While calcification is common, it presents as discrete nodules or "candle guttering" along the ventricles, not a "tram track" pattern. * **Neurofibromatosis (NF):** NF1 is associated with optic gliomas, Lisch nodules, and sphenoid wing dysplasia. NF2 is associated with bilateral vestibular schwannomas. Neither typically presents with intracranial tram-track calcifications. **High-Yield Clinical Pearls for NEET-PG:** * **Triad of SWS:** Facial capillary malformation (Port-wine stain in the $V_1/V_2$ distribution), leptomeningeal angioma, and glaucoma. * **Imaging Gold Standard:** **Contrast-enhanced MRI** is the most sensitive modality to detect the leptomeningeal enhancement (pial angioma) early in life, before calcifications develop. * **Skull X-ray:** Can also demonstrate the "tram track" sign in older children. * **Associated finding:** Enlargement and enhancement of the ipsilateral choroid plexus.

Question 1

On MRI, how can epidermoids be differentiated from arachnoid cysts?

Accepted Answer

Restricted diffusion

Answer

Contrast enhancement

Answer

Smooth margins

Answer

CSF signal on FLAIR

Question 2

A patient presents with loss of consciousness following a road traffic accident. CT scan shows multiple spotty hemorrhages and full basal cisterns. What is the most likely diagnosis?

Accepted Answer

Diffuse axonal injury

Answer

Brain contusion

Answer

Subdural hematoma

Answer

Multiple infarcts

Question 3

Which MRI sequence is used to detect cytotoxic edema before vasogenic edema?

Accepted Answer

DWI

Answer

T1WI

Answer

T2WI

Answer

SWI

Question 4

Which type of hemorrhage classically presents as a lenticular shape on imaging?

Accepted Answer

Extradural hemorrhage

Answer

Subdural hemorrhage

Answer

Subarachnoid hemorrhage

Answer

Intracerebral hemorrhage

Question 5

What is the imaging modality of choice for diagnosing brain metastases?

Accepted Answer

MRI

Answer

CECT

Answer

MRS

Answer

PST

Question 6

In intervertebral disc prolapse, what does a Schmorl node on MRI imply?

Accepted Answer

Not significant

Answer

Significant

Answer

Good prognosis

Answer

Not prognostic

Question 7

Focal bilateral thalamic, posterior internal capsule showing hyperdensity and calcification in CT scan and extensive involvement of deep white matter is characteristic of which condition?

Accepted Answer

Krabbe's disease

Answer

Alexander's disease

Answer

Metachromatic leukodystrophy

Answer

Multiple sclerosis

Question 8

This classical "Ice-cream cone" appearance of an intensely enhancing lesion at the left CP angle recess suggests:

Accepted Answer

Acoustic schwannoma

Answer

Arachnoid cyst

Answer

High grade glioma

Answer

Epidermoid cyst

Question 9

A tumour showing dural enhancement with a tail is characteristic of which of the following entities?

Accepted Answer

Meningioma

Answer

Medulloblastoma

Answer

Glioma

Answer

Acoustic neuroma

Question 10

What condition is characterized by a "tram track" appearance on a CT scan of the head?

Accepted Answer

Sturge-Weber syndrome

Answer

Von Hippel-Lindau syndrome

Answer

Tuberous sclerosis

Answer

Neurofibromatosis

Neuroradiology — MCQs

Neuroradiology — MCQs

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