Neuroradiology — MCQs

Neuroradiology Indian Medical PG Practice Questions and MCQs

Question 321: What is the best imaging study for the earliest diagnosis of cerebral infarct?

A. FLAIR MRI
B. Non-contrast CT
C. CECT
D. Diffusion-weighted MRI (Correct Answer)

Explanation: **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.

Question 322: MRI is unsuitable for imaging or examining which of the following?

A. Cardiac pacemakers
B. Metallic clips
C. Woody items
D. All of the above (Correct Answer)

Explanation: **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.

Question 323: Echoencephalography is most useful in detecting which of the following?

A. Ventricular dilatation (Correct Answer)
B. Midline shift
C. Epilepsy
D. Vascular lesions

Explanation: **Explanation:** **Echoencephalography (EchoEG)** is a diagnostic technique that utilizes ultrasound waves to visualize intracranial structures. While largely superseded by CT and MRI in adults due to the skull’s high attenuation of ultrasound, it remains a vital bedside tool in neonatal care. **Why Ventricular Dilatation is Correct:** In neonates, the **anterior fontanelle** acts as an acoustic window, allowing high-frequency ultrasound to visualize the brain parenchyma and ventricular system. Echoencephalography is highly sensitive for detecting **ventricular dilatation** (hydrocephalus) and intracranial hemorrhages (specifically Germinal Matrix Hemorrhage). It allows for real-time monitoring of ventricular size and the "Evans ratio" without exposing the infant to radiation or sedation. **Analysis of Incorrect Options:** * **B. Midline Shift:** While EchoEG was historically used in adults to detect midline shifts (by measuring the distance to the pineal gland or third ventricle), it is far less accurate and reliable than modern CT scans, which are now the gold standard for acute shifts. * **C. Epilepsy:** Epilepsy is a functional/electrical disorder of the brain. The primary diagnostic modality is **EEG (Electroencephalogram)**, not ultrasound. * **D. Vascular Lesions:** While Doppler ultrasound can assess blood flow velocities (e.g., in the Middle Cerebral Artery), EchoEG is not the primary modality for detecting structural vascular lesions like aneurysms or AVMs; **CT Angiography (CTA) or MRA** are preferred. **High-Yield Clinical Pearls for NEET-PG:** * **Acoustic Window:** In infants, the **Anterior Fontanelle** is the most common window used. * **Best Use Case:** Screening for **Periventricular Leukomalacia (PVL)** and **Intraventricular Hemorrhage (IVH)** in premature neonates. * **Adult Limitation:** In adults, ultrasound can only be used intraoperatively (during craniotomy) or via the temporal bone (Transcranial Doppler) to assess flow, not for detailed structural imaging.

Question 324: Geographic lytic lesions in the vault of the skull with bevelled edges are seen with which condition?

A. Eosinophilic granuloma (Correct Answer)
B. Multiple myeloma
C. Hyperparathyroidism
D. Reticular cell carcinoma

Explanation: ### 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**.

Question 325: Mount Fuji sign is a feature of which of the following conditions?

A. Fahr's disease
B. Acute bleed
C. Chronic bleed
D. Tension pneumocephalus (Correct Answer)

Explanation: **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.

Question 326: What is the imaging tool of choice for evaluating a lacunar infarct?

A. Diffusion-weighted imaging (DWI) MRI with apparent diffusion coefficient (ADC) maps (Correct Answer)
B. HMPAO SPECT
C. MR Spectroscopy
D. PET

Explanation: **Explanation:** **Diffusion-weighted imaging (DWI)** is the gold standard and most sensitive imaging modality for diagnosing acute ischemic strokes, including **lacunar infarcts** (small vessel disease involving deep penetrating arteries). 1. **Why DWI/ADC is correct:** Lacunar infarcts are often too small (typically <15mm) to be detected by CT or conventional MRI sequences (T1/T2) in the hyperacute phase. DWI detects the **restriction of water diffusion** caused by cytotoxic edema (failure of Na+/K+ ATPase pumps). A true acute infarct shows **"hyperintensity" (bright) on DWI** and corresponding **"hypointensity" (dark) on ADC maps**, which helps differentiate acute ischemia from "T2 shine-through." 2. **Why other options are incorrect:** * **HMPAO SPECT:** Measures regional cerebral blood flow. While it can show hypoperfusion, it lacks the spatial resolution required to identify small lacunar strokes and is not used in acute settings. * **MR Spectroscopy:** Analyzes metabolites (like NAA, Lactate). It is useful for tumors or metabolic disorders but is not a primary tool for diagnosing acute ischemia. * **PET:** Measures metabolic activity (glucose uptake). While sensitive to ischemia, it is expensive, not widely available, and impractical for emergency stroke evaluation. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sign of infarct on MRI:** DWI changes (visible within 15–30 minutes). * **Earliest sign of infarct on CT:** Loss of insular ribbon sign or obscuration of the lentiform nucleus (usually takes 6+ hours). * **Lacunar Stroke Syndromes:** Most common is **Pure Motor Hemiparesis** (posterior limb of the internal capsule). * **ADC Reversal:** The ADC map stays dark for about 7–10 days; if a lesion is bright on DWI but *not* dark on ADC, it is likely a chronic lesion or T2 shine-through.

Question 327: Mesencephalo-oculo-facial-angiomatosis is seen in which of the following conditions?

A. Klippel-Trenaunay-Weber syndrome
B. Neurofibromatosis type 1 & 2
C. Sturge-Weber syndrome
D. Wyburn-Mason syndrome (Correct Answer)

Explanation: **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.

Question 328: What is the most sensitive investigation to detect intracranial bleeding in a patient with head injury?

A. MRI
B. X-ray
C. CT-scan (Correct Answer)
D. Ultrasound

Explanation: **Explanation:** The correct answer is **CT-scan**. In the acute setting of head injury, a Non-Contrast Computed Tomography (NCCT) of the head is the gold standard and the most sensitive investigation for detecting intracranial hemorrhage (ICH). **Why CT-scan is the correct answer:** * **Sensitivity to Acute Blood:** Acute blood appears **hyperdense** (bright white) on CT due to the high protein content (hemoglobin), making it easily distinguishable from brain parenchyma. * **Speed and Accessibility:** It is rapid (takes seconds), widely available, and allows for life-saving decisions regarding surgical decompression. * **Bone Detail:** It is superior for identifying associated skull fractures. * **Safety:** It is the safest modality for unstable patients who may require life-support equipment (ventilators/monitors) that are often MRI-incompatible. **Why other options are incorrect:** * **MRI:** While MRI (specifically Gradient Echo/SWI sequences) is highly sensitive for microhemorrhages and Diffuse Axonal Injury (DAI), it is **not** the initial investigation of choice due to long scan times, motion artifacts in agitated patients, and limited availability in emergencies. * **X-ray:** Plain radiographs can show fractures but cannot visualize intracranial soft tissues or bleeding. A "normal" X-ray does not rule out a life-threatening hematoma. * **Ultrasound:** It is only useful in neonates (via the open anterior fontanelle) and has no role in adult head trauma due to the inability of ultrasound waves to penetrate the adult skull. **High-Yield Clinical Pearls for NEET-PG:** * **Epidural Hematoma (EDH):** Biconvex/Lens-shaped, does not cross sutures. Usually involves the Middle Meningeal Artery. * **Subdural Hematoma (SDH):** Crescent-shaped, can cross sutures. Usually involves bridging veins. * **Subarachnoid Hemorrhage (SAH):** Blood in the cisterns and sulci; "Star of David" sign. * **Investigation of Choice for DAI:** MRI (specifically Susceptibility Weighted Imaging - SWI).

Question 329: 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?

A. Brain abscess
B. Subarachnoid hemorrhage (Correct Answer)
C. Pneumocephalus
D. Meningococcal meningitis

Explanation: ***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.

Question 330: Which of the following is shown in the image below (circled)?

A. Osteomeatal complex (Correct Answer)
B. Nasal valve
C. Columella
D. Crest of maxilla

Explanation: ***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.

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