Neuroradiology Practice Questions

Q: What is the best imaging study for the earliest diagnosis of cerebral infarct?

Diffusion-weighted MRI. **Explanation:** **Diffusion-Weighted Imaging (DWI)** is the gold standard and most sensitive sequence for the earliest diagnosis of an ischemic stroke. **Why DWI is the correct answer:** The underlying mechanism is **cytotoxic edema**. Within minutes of an arterial occlusion, the sodium-potassium pump fails, causing water to shift from the extracellular space into the intracellular space. This restricts the random Brownian motion of water molecules. DWI is exquisitely sensitive to this "restricted diffusion," appearing as a **hyperintense (bright)** signal within **15–30 minutes** of onset, long before changes appear on conventional MRI or CT. **Why other options are incorrect:** * **Non-contrast CT (NCCT):** This is the first investigation performed in the ER, but its primary role is to **exclude hemorrhage**, not to diagnose early infarct. It often remains normal for the first 6–12 hours (the "hyperacute" phase). * **FLAIR MRI:** This sequence is excellent for identifying subacute infarcts and edema, but it typically takes **4–6 hours** for an infarct to become visible on FLAIR. * **CECT:** Contrast-enhanced CT has no significant role in the early diagnosis of acute ischemic stroke and may even obscure subtle early signs like the "hyperdense MCA sign." **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sign on NCCT:** 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 (within the thrombolysis window). * **ADC Map:** To confirm true restricted diffusion and rule out "T2 shine-through," the lesion must appear **dark** on the Apparent Diffusion Coefficient (ADC) map.

Q: MRI is unsuitable for imaging or examining which of the following?

All of the above. **Explanation:** The suitability of MRI is primarily limited by the presence of ferromagnetic materials and the potential for electromagnetic interference. 1. **Cardiac Pacemakers (Option A):** These are traditionally a major contraindication. The strong static magnetic field can cause displacement of the device, while the radiofrequency (RF) pulses can induce electrical currents in the leads, leading to thermal injury (pacing tip heating) or life-threatening arrhythmias. Additionally, the magnetic field can reset the device to "asynchronous mode" or cause total failure. *Note: Modern "MRI-conditional" pacemakers exist, but standard ones remain unsuitable.* 2. **Metallic Clips (Option B):** Ferromagnetic intracranial aneurysm clips or vascular clips can undergo **torque (twisting)** or displacement due to the magnetic field, potentially causing catastrophic hemorrhage. 3. **Woody Items (Option C):** Wood is a non-paramagnetic organic material. On MRI, wood has very low proton density and appears as a **signal void (black)**, making it nearly impossible to distinguish from air or dense cortical bone. For detecting foreign bodies like wood or glass, **Non-Contrast CT (NCCT)** or Ultrasound is superior. **Clinical Pearls for NEET-PG:** * **Gold Standard for Foreign Bodies:** CT is the investigation of choice for metallic, glass, or stone foreign bodies. Ultrasound is excellent for superficial organic matter (wood). * **Absolute Contraindications:** Cochlear implants, older pacemakers, ferromagnetic ocular foreign bodies, and Swan-Ganz catheters. * **MRI Safety:** Tantalum and Titanium clips are generally MRI-compatible (non-ferromagnetic). * **The "Projectile Effect":** Ferromagnetic objects (like oxygen cylinders) can become high-velocity missiles in the MRI room.

Q: Geographic lytic lesions in the vault of the skull with bevelled edges are seen with which condition?

Eosinophilic granuloma. ### Explanation **1. Why Eosinophilic Granuloma is Correct:** Eosinophilic Granuloma (EG) is the most common and localized form of **Langerhans Cell Histiocytosis (LCH)**. The classic radiographic appearance in the skull is a "punched-out," geographic lytic lesion. The characteristic **"bevelled edge"** (or "hole-within-a-hole" appearance) occurs because the destruction of the inner table of the skull is more extensive than the outer table, creating slanted or overlapping margins. When a central density is seen within the lucency, it is termed a "sequestrum." **2. Why the Other Options are Incorrect:** * **Multiple Myeloma:** Presents as multiple, small, uniform, "punched-out" lytic lesions. Unlike EG, these lesions typically lack sclerotic margins and do not exhibit the classic bevelled edge. * **Hyperparathyroidism:** Characterized by a **"Salt and Pepper" skull** (mottled appearance) due to multiple tiny lucencies caused by trabecular resorption, rather than large geographic lytic lesions. * **Reticular Cell Carcinoma (Primary Lymphoma of Bone):** Usually presents as "moth-eaten" or permeative bone destruction with an associated soft tissue mass, rather than well-defined geographic lesions with bevelled edges. **3. NEET-PG High-Yield Pearls:** * **LCH Triad (Hand-Schüller-Christian disease):** Exophthalmos, Diabetes Insipidus, and lytic bone lesions. * **Vertebra Plana:** EG is the most common cause of a completely collapsed vertebral body (pancake vertebra) in children. * **Birbeck Granules:** On electron microscopy, LCH cells show "tennis racket-shaped" cytoplasmic inclusions. * **Immunohistochemistry:** LCH cells are typically positive for **S-100 and CD1a**.

Q: Mount Fuji sign is a feature of which of the following conditions?

Tension pneumocephalus. **Explanation:** The **Mount Fuji sign** is a classic radiological hallmark of **Tension Pneumocephalus**. It is best visualized on a non-contrast CT scan of the head. 1. **Why Tension Pneumocephalus is correct:** This condition occurs when air enters the cranial cavity (usually post-trauma or surgery) but cannot escape, creating a "one-way valve" effect. The increasing pressure causes the air to compress the frontal lobes and separate them from the skull. Crucially, the air also separates the two frontal lobes at the midline, creating two peaked silhouettes that resemble the twin peaks of Mount Fuji. This indicates that the intracranial pressure is high enough to overcome the surface tension of the cerebrospinal fluid. 2. **Why the other options are incorrect:** * **Fahr’s Disease:** Characterized by bilateral, symmetrical **calcifications** of the basal ganglia and dentate nuclei, not air. * **Acute Bleed:** Appears as a **hyperdense** (white) area on CT (e.g., biconvex for extradural or crescentic for subdural hemorrhage). * **Chronic Bleed:** Typically appears **hypodense** (darker than brain tissue) as the blood liquefies over time, but it does not present with the specific "peaked" configuration of air. **High-Yield Pearls for NEET-PG:** * **Mount Fuji Sign vs. Air Bubble:** Simple pneumocephalus shows scattered air; the Mount Fuji sign specifically implies **tension** (a neurosurgical emergency). * **Pathophysiology:** Often described via the "Ball-valve mechanism." * **Treatment:** Requires urgent decompression (e.g., burr hole) to prevent brain herniation. * **Related Sign:** The **"Peaked Midline Sign"** is another term used to describe the compression of the frontal poles.

Q: Mesencephalo-oculo-facial-angiomatosis is seen in which of the following conditions?

Wyburn-Mason syndrome. **Explanation:** **Wyburn-Mason Syndrome**, also known as **Bonnet-Dechaume-Blanc syndrome**, is a rare phakomatosis characterized by non-hereditary congenital arteriovenous malformations (AVMs). The hallmark of this condition is the presence of **racemose angiomas** involving the midbrain (mesencephalon), the retina (oculo), and occasionally the facial skin. This triad explains why it is termed **mesencephalo-oculo-facial-angiomatosis**. These AVMs do not typically pulsate or have a bruit, unlike other vascular malformations. **Analysis of Incorrect Options:** * **Klippel-Trenaunay-Weber Syndrome:** Characterized by a triad of port-wine stains, varicose veins, and bony/soft tissue hypertrophy, usually involving a single limb. It does not involve midbrain AVMs. * **Neurofibromatosis (NF1 & NF2):** NF1 is associated with Lisch nodules, café-au-lait spots, and neurofibromas. NF2 is characterized by bilateral vestibular schwannomas. Neither is defined by mesencephalic angiomatosis. * **Sturge-Weber Syndrome (Encephalotrigeminal Angiomatosis):** While it involves facial port-wine stains and leptomeningeal angiomas, the intracranial involvement typically affects the **cerebral cortex** (parieto-occipital region) rather than the midbrain, and it presents with "tram-track" calcifications. **Clinical Pearls for NEET-PG:** * **Key Imaging Finding:** "Bag of worms" appearance on angiography or MRI representing the racemose hemangioma. * **Clinical Presentation:** Patients often present with sudden vision loss (retinal hemorrhage) or neurological deficits/intracranial hemorrhage due to the midbrain AVM. * **High-Yield Association:** Unlike Sturge-Weber, Wyburn-Mason syndrome **lacks** cutaneous port-wine stains in most cases; facial involvement is usually via vascular nevi or small angiomas.

Q: A patient presents with severe headache. A CT scan of the brain reveals hyperdense areas in the right basal region, marked as 'X'. Which of the following is the most likely diagnosis?

Subarachnoid hemorrhage. ***Subarachnoid hemorrhage*** - The non-contrast CT scan shows **hyperdensity** (appears white) within the basal cisterns and Sylvian fissures (indicated by 'X'), which is the classic appearance of acute blood in the subarachnoid space. - This condition classically presents with a sudden, severe "**thunderclap headache**" and is most commonly caused by a ruptured **berry aneurysm**. *Meningococcal meningitis* - A non-contrast CT in meningitis is often normal. Key findings like **meningeal enhancement** would only be visible on a post-contrast CT scan, which is not the pattern seen here. - The clinical presentation typically involves a triad of **fever**, **nuchal rigidity**, and altered mental status, which are classic signs of meningeal irritation. *Brain abscess* - A brain abscess on a non-contrast CT typically appears as a **hypodense** (dark) or isodense mass within the brain parenchyma, often with surrounding vasogenic edema. - On a contrast-enhanced CT, it characteristically shows a **ring-enhancing lesion**, which is not depicted in this image. *Pneumocephalus* - Pneumocephalus refers to air within the cranial cavity, which appears as profoundly **hypodense** (black) on a CT scan. - The primary finding in the image is **hyperdensity** (blood), not the extreme hypodensity characteristic of air.

Q: Which of the following is shown in the image below (circled)?

Osteomeatal complex. ***Osteomeatal complex*** - The circled area highlights the **osteomeatal complex (OMC)**, a functional unit of the lateral nasal wall located in the middle meatus. - The OMC is the final common drainage pathway for the **frontal**, **maxillary**, and **anterior ethmoid sinuses**, and its obstruction is a primary cause of chronic rhinosinusitis. *Columella* - The **columella** is the external, soft tissue structure that separates the nostrils at the base of the nose. - It is an external feature and is not an internal bony or mucosal structure visible in this coronal CT view of the paranasal sinuses. *Nasal valve* - The **nasal valve** is the narrowest segment of the nasal airway, located much more anteriorly in the nasal cavity, near the nostril opening. - It is a functional area defined by the junction of the nasal septum and the upper lateral cartilage, not the region shown in the middle meatus. *Crest of maxilla* - The **crest of the maxilla**, or nasal crest, is a bony ridge on the floor of the nasal cavity where the inferior edge of the nasal septum articulates. - The circled structure is located superiorly and laterally within the middle meatus, not on the inferior floor of the nasal cavity.

Question 1

What is the best imaging study for the earliest diagnosis of cerebral infarct?

Accepted Answer

Diffusion-weighted MRI

Answer

FLAIR MRI

Answer

Non-contrast CT

Answer

CECT

Question 2

MRI is unsuitable for imaging or examining which of the following?

Accepted Answer

All of the above

Answer

Cardiac pacemakers

Answer

Metallic clips

Answer

Woody items

Question 3

Echoencephalography is most useful in detecting which of the following?

Accepted Answer

Ventricular dilatation

Answer

Midline shift

Answer

Epilepsy

Answer

Vascular lesions

Question 4

Geographic lytic lesions in the vault of the skull with bevelled edges are seen with which condition?

Accepted Answer

Eosinophilic granuloma

Answer

Multiple myeloma

Answer

Hyperparathyroidism

Answer

Reticular cell carcinoma

Question 5

Mount Fuji sign is a feature of which of the following conditions?

Accepted Answer

Tension pneumocephalus

Answer

Fahr's disease

Answer

Acute bleed

Answer

Chronic bleed

Question 6

What is the imaging tool of choice for evaluating a lacunar infarct?

Accepted Answer

Diffusion-weighted imaging (DWI) MRI with apparent diffusion coefficient (ADC) maps

Answer

HMPAO SPECT

Answer

MR Spectroscopy

Answer

PET

Question 7

Mesencephalo-oculo-facial-angiomatosis is seen in which of the following conditions?

Accepted Answer

Wyburn-Mason syndrome

Answer

Klippel-Trenaunay-Weber syndrome

Answer

Neurofibromatosis type 1 & 2

Answer

Sturge-Weber syndrome

Question 8

What is the most sensitive investigation to detect intracranial bleeding in a patient with head injury?

Accepted Answer

CT-scan

Answer

MRI

Answer

X-ray

Answer

Ultrasound

Question 9

A patient presents with severe headache. A CT scan of the brain reveals hyperdense areas in the right basal region, marked as 'X'. Which of the following is the most likely diagnosis?

Accepted Answer

Subarachnoid hemorrhage

Answer

Brain abscess

Answer

Pneumocephalus

Answer

Meningococcal meningitis

Question 10

Which of the following is shown in the image below (circled)?

Accepted Answer

Osteomeatal complex

Answer

Nasal valve

Answer

Columella

Answer

Crest of maxilla

Neuroradiology — MCQs

Neuroradiology — MCQs

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