Neuroradiology Practice Questions

Q: Intra-tumoral calcification in the brain is seen in all except?

Hemangioblastoma. **Explanation:** The correct answer is **Hemangioblastoma**. In neuroradiology, identifying the presence or absence of calcification is a high-yield diagnostic marker for intracranial tumors. **1. Why Hemangioblastoma is the correct answer:** Hemangioblastomas are highly vascular, WHO Grade 1 tumors typically located in the posterior fossa (cerebellum). Characteristically, they present as a **cystic lesion with a highly enhancing mural nodule**. Crucially, hemangioblastomas **do not calcify**. Their primary imaging features are related to vascularity (flow voids on MRI) and associated erythropoietin production, which may lead to polycythemia. **2. Why the other options are incorrect:** * **Oligodendroglioma:** This is the "classic" answer for calcified brain tumors. Calcification is seen in **70–90%** of cases, often described as chunky or ribbon-like. * **Craniopharyngioma:** In the pediatric population (adamantinomatous type), calcification is a hallmark, occurring in approximately **90%** of cases. It follows the "90% rule": 90% are cystic, 90% calcify, and 90% enhance. * **Meningioma:** These are extra-axial tumors that frequently show calcification (about **20–25%**). When the calcification is diffuse and gritty, they are histologically termed "Psammomatous meningiomas." **NEET-PG High-Yield Pearls:** * **Mnemonic for Calcified Brain Tumors (Old Men Are Posh):** **O**ligodendroglioma, **M**eningioma, **A**strocytoma, **P**ineal tumors/ **P**apilloma (Choroid plexus). * **Most common calcified tumor in children:** Craniopharyngioma. * **Most common calcified tumor in adults:** Oligodendroglioma. * **Hemangioblastoma Association:** Frequently associated with **Von Hippel-Lindau (VHL) syndrome**; look for retinal angiomas and renal cell carcinoma in clinical stems.

Q: Which of the following brain tumors is typically hyperdense on CT scan?

Medulloblastoma. **Explanation:** The density of a tumor on a non-contrast CT (NCCT) scan is primarily determined by its **cellularity** and the **nuclear-to-cytoplasmic (N:C) ratio**. **1. Why Medulloblastoma is correct:** Medulloblastoma is a "Small Round Blue Cell Tumor." These tumors are characterized by extremely high cellular density and very little cytoplasm. Because DNA and cellular proteins attenuate X-rays more than water or lipids, the high concentration of cells makes the tumor appear **hyperdense** relative to the normal brain parenchyma on NCCT. This is a classic radiological hallmark of medulloblastoma, typically seen in the midline (cerebellar vermis) of pediatric patients. **2. Analysis of Incorrect Options:** * **Ependymoma:** Usually appears isodense or heterogeneous on CT. While they often contain calcifications (which are hyperdense), the soft tissue component itself is not typically hyperdense. * **Oligodendroglioma:** These are known for having the highest incidence of **calcification** (up to 90%), which is hyperdense. However, the tumor mass itself is usually hypo-to-isodense. * **Astrocytoma:** Most low-grade astrocytomas are **hypodense** due to high water content and associated edema. High-grade gliomas (GBM) are usually heterogeneous due to necrosis and hemorrhage. **3. High-Yield Clinical Pearls for NEET-PG:** * **Hyperdense tumors on CT (Mnemonic: "M-L-G"):** **M**edulloblastoma, **L**ymphoma (Primary CNS), and **G**erm cell tumors/Meningioma. * **Medulloblastoma:** Most common malignant brain tumor in children; associated with "drop metastases" (seeding via CSF). * **Calcification Mnemonic:** "Old Elephants Can't Dance" (**O**ligodendroglioma, **E**pendymoma, **C**raniopharyngioma, **D**ysembryoplastic Neuroepithelial Tumor).

Q: What is the investigation of choice for entrapment neuropathy?

MRI scan. **Explanation:** **Why MRI is the Correct Answer:** MRI is the investigation of choice for entrapment neuropathy because of its superior **soft-tissue contrast resolution**. It allows for the direct visualization of the nerve itself (MR Neurography). In entrapment syndromes, MRI can detect both **morphological changes** (nerve thickening, flattening, or displacement) and **signal intensity changes** (increased T2/STIR signal indicating intraneural edema or inflammation). Furthermore, MRI is excellent at identifying the extrinsic cause of compression, such as ganglion cysts, tumors, or anatomical variants. **Analysis of Incorrect Options:** * **CT Scan:** While CT is excellent for bone pathology, it has poor soft-tissue resolution and cannot visualize the internal structure of nerves or subtle inflammatory changes. * **Clinical Examination:** While clinical assessment (history and physical exams like Tinel’s or Phalen’s sign) is the first step in diagnosis, it is a **clinical tool**, not an "investigation." It cannot definitively localize the site or cause of compression as accurately as imaging. * **SPECT Scan:** This is a functional nuclear medicine imaging technique used primarily for bone turnover or myocardial perfusion; it has no role in the routine evaluation of peripheral nerves. **High-Yield Facts for NEET-PG:** * **Gold Standard for Function:** While MRI is the investigation of choice for *imaging*, **Electromyography (EMG) and Nerve Conduction Studies (NCS)** remain the gold standard for assessing the *physiological severity* of the nerve injury. * **MR Neurography:** Uses dedicated sequences (like 3D T2-weighted STIR) to suppress fat and vessel signals, making the nerve appear "bright" against a dark background. * **Common Sites:** Carpal Tunnel Syndrome (Median nerve) is the most common entrapment neuropathy, followed by Cubital Tunnel Syndrome (Ulnar nerve).

Question 1

Intra-tumoral calcification in the brain is seen in all except?

Accepted Answer

Hemangioblastoma

Answer

Craniopharyngioma

Answer

Meningioma

Answer

Oligodendroglioma

Question 2

Which of the following brain tumors is typically hyperdense on CT scan?

Accepted Answer

Medulloblastoma

Answer

Ependymoma

Answer

Oligodendroglioma

Answer

Astrocytoma

Question 3

A 7-year-old child presents with a posterior fossa mass characterized by cyst formation. On CT, the mass appears hypodense, while on T2-weighted MRI, it is hyperintense. Post-gadolinium administration, a nodular enhancement is observed. What is the most likely diagnosis?

Accepted Answer

Astrocytoma

Answer

Medulloblastoma

Answer

Ependymoma

Answer

Cysticercosis

Question 4

What is the investigation of choice for entrapment neuropathy?

Accepted Answer

MRI scan

Answer

CT scan

Answer

Clinical examination

Answer

SPECT scan

Question 5

What is the most common tumor of the pineal region?

Accepted Answer

Germinoma

Answer

Pineocytoma

Answer

Pineoblastoma

Answer

Secondaries

Neuroradiology — MCQs

Neuroradiology — MCQs

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