Neuroradiology Practice Questions

Q: The dense middle cerebral artery (MCA) sign is seen in which of the following conditions?

Acute infarct. **Explanation:** The **Hyperdense MCA sign** is one of the earliest radiological markers of an **acute ischemic stroke** on a non-contrast CT (NCCT) scan. **1. Why Acute Infarct is correct:** The sign represents a **thrombus or embolus** lodged within the first segment (M1) of the Middle Cerebral Artery. Because a fresh blood clot has a higher protein concentration and lower water content than flowing blood, it appears hyperattenuating (whiter) compared to the surrounding brain tissue and the contralateral vessel. It is typically seen within the first **0–6 hours** of symptom onset, often before parenchymal changes like "loss of insular ribbon" or "sulcal effacement" become visible. **2. Why other options are incorrect:** * **Subacute Infarct:** By this stage (24 hours to 2 weeks), the clot has usually started to lyse or organize, and the primary CT findings are vasogenic edema and mass effect (hypodensity), not vascular hyperdensity. * **Subacute Hemorrhage:** While blood is dense, a subacute hemorrhage refers to intraparenchymal or extra-axial collections. The "Dense MCA sign" specifically refers to an intravascular phenomenon. * **Chronic Infarct:** Chronic strokes are characterized by encephalomalacia and gliosis, appearing as CSF-filled cystic spaces (hypodense/black) with associated ventricular dilatation (ex-vacuo). **Clinical Pearls for NEET-PG:** * **High Specificity:** The sign is 90–100% specific for MCA occlusion but has low sensitivity (approx. 30%). * **Dot Sign:** A variation seen when the clot is in the M2 or M3 branches within the sylvian fissure, appearing as a high-density "dot." * **False Positives:** High hematocrit (polycythemia) or calcification of the arterial wall (atherosclerosis) can mimic this sign. Always compare with the opposite side. * **Prognostic Value:** Its presence often indicates a large territory infarct and a poorer functional prognosis.

Q: Widened Bat wing sylvian fissures are associated with which of the following conditions?

Glutaric aciduria. **Explanation:** **Glutaric Aciduria Type 1 (GA-1)** is an autosomal recessive metabolic disorder caused by a deficiency of glutaryl-CoA dehydrogenase. The hallmark neuroimaging finding is the **"Bat-wing appearance"** of the Sylvian fissures. This occurs due to significant frontotemporal atrophy and hypoplasia, leading to failure of opercularization (the brain tissue fails to cover the Insula). This creates wide, open CSF spaces in the temporal regions, resembling the wings of a bat. Additionally, these patients often show signal abnormalities in the basal ganglia (especially the putamen) and are prone to subdural hematomas. **Analysis of Incorrect Options:** * **Maple Syrup Urine Disease (MSUD):** Characterized by "MSUD edema," which involves intramyelinic cytotoxic edema. On MRI, this presents as restricted diffusion in the myelinated tracts (brainstem, cerebellar peduncles, and internal capsule). * **Galactosemia:** Typically presents with non-specific white matter changes, cerebral atrophy, and sometimes neonatal brain edema, but does not feature the characteristic bat-wing fissures. * **Canavan Disease:** A leukodystrophy characterized by diffuse, symmetric white matter involvement (including subcortical U-fibers) and **macrocephaly**. The classic finding is an elevated **NAA peak** on MR Spectroscopy. **Clinical Pearls for NEET-PG:** * **Bat-wing appearance:** Pathognomonic for Glutaric Aciduria Type 1. * **Macrocephaly + High NAA:** Canavan Disease. * **Macrocephaly + Rosenthal Fibers:** Alexander Disease. * **Tiger-eye appearance:** Pantothenate Kinase-Associated Neurodegeneration (PKAN). * **Molar Tooth Sign:** Joubert Syndrome.

Q: What is the investigation of choice for the diagnosis of a posterior fossa tumor?

MRI. **Explanation:** **MRI (Magnetic Resonance Imaging)** is the investigation of choice for posterior fossa tumors due to its superior soft-tissue contrast and multiplanar imaging capabilities. The posterior fossa is a small, bony compartment containing the brainstem and cerebellum. MRI allows for precise localization, assessment of brainstem invasion, and detection of associated complications like hydrocephalus or tonsillar herniation. **Why MRI is superior:** * **No Bone Artifact:** Unlike CT, MRI does not suffer from "beam-hardening artifacts" caused by the dense petrous temporal bone and occipital bone, which often obscure details in the posterior fossa. * **Multiplanar Imaging:** Sagittal and coronal views are essential to visualize the relationship of the tumor to the foramen magnum and tentorium cerebelli. * **Contrast Enhancement:** Gadolinium-enhanced MRI helps differentiate between various tumor types (e.g., Medulloblastoma vs. Ependymoma). **Why other options are incorrect:** * **CT Scan:** While useful in emergencies to detect acute hydrocephalus or calcification, it provides poor visualization of the posterior fossa due to significant bony artifacts. * **Angiography:** Primarily used to assess vascularity or for preoperative embolization (e.g., in Hemangioblastoma), but not for primary diagnosis. * **Myelography:** Used for spinal canal pathology; it has no role in diagnosing intracranial posterior fossa masses. **High-Yield Clinical Pearls for NEET-PG:** * **Most common posterior fossa tumor in children:** Cerebellar Astrocytoma (overall), but Medulloblastoma is the most common *malignant* one. * **"Step-off" sign on MRI:** Characteristic of Ependymomas as they tend to squeeze through the foramina of Luschka and Magendie. * **Investigation of choice for most CNS pathologies:** MRI (except for acute intracranial hemorrhage, where NCCT is preferred).

Q: Subependymal Giant Cell Astrocytoma is commonly associated with which of the following conditions?

Tuberous sclerosis. **Explanation:** **Subependymal Giant Cell Astrocytoma (SEGA)** is a benign (WHO Grade 1), slow-growing tumor typically located near the Foramen of Monro. It is the most common CNS neoplasm associated with **Tuberous Sclerosis Complex (TSC)**, occurring in approximately 5–15% of patients. 1. **Why Tuberous Sclerosis is Correct:** SEGA is considered a major diagnostic criterion for TSC. It typically arises from the transformation of subependymal nodules (SENs). On imaging, SEGAs appear as well-circumscribed, enhancing masses near the Foramen of Monro, often causing obstructive hydrocephalus. The underlying pathophysiology involves mutations in the *TSC1* (hamartin) or *TSC2* (tuberin) genes, leading to overactivation of the mTOR pathway. 2. **Why Other Options are Incorrect:** * **Neurofibroma:** Associated with Neurofibromatosis Type 1 (NF1). While NF1 involves CNS tumors (like Optic Nerve Gliomas), SEGA is not a feature. * **Schwannoma:** Classically associated with Neurofibromatosis Type 2 (NF2), particularly bilateral vestibular schwannomas. * **Ependymoma:** These are distinct glial tumors arising from the ependymal lining of ventricles or the central canal of the spinal cord; they are not syndromically linked to TSC. **High-Yield Clinical Pearls for NEET-PG:** * **Imaging Hallmark:** A calcified or enhancing mass >1 cm at the Foramen of Monro in a pediatric patient is highly suggestive of SEGA. * **Vogt’s Triad (TSC):** Adenoma sebaceum (facial angiofibromas), seizures, and mental retardation. * **Other TSC CNS findings:** Cortical tubers (hamartomas) and Subependymal Nodules (SENs). * **Treatment:** Surgical resection or **Everolimus** (an mTOR inhibitor), which is specifically used to shrink SEGAs in TSC patients.

Q: What is the most common primary brain tumor in adults?

Metastases. **Explanation:** The correct answer is **Metastases**. In the context of all brain tumors in adults, **metastatic lesions** are the most common, occurring more frequently than all primary brain tumors combined. They typically originate from the lung (most common), breast, kidney, or melanoma and often present as multiple, well-circumscribed lesions at the grey-white matter junction with significant perilesional edema. **Analysis of Options:** * **A. Glioma:** This is a broad category of tumors arising from glial cells. While common, they are less frequent than metastases. * **C. Meningioma:** This is the most common **extra-axial** and most common **benign** primary brain tumor in adults. * **D. Astrocytoma:** This is a subtype of glioma. Specifically, Glioblastoma Multiforme (GBM/Grade IV Astrocytoma) is the most common **malignant primary** brain tumor in adults, but it is still less common than metastatic disease. **High-Yield Clinical Pearls for NEET-PG:** * **Most common brain tumor overall:** Metastases. * **Most common primary brain tumor:** Meningioma (if benign is included) or Glioblastoma (if focusing on malignancy). * **Most common source of brain mets:** Lung cancer (specifically Small Cell and Adenocarcinoma). * **Imaging Hallmark:** Metastases often show "ring enhancement" on contrast-enhanced MRI. * **Rule of Thumb:** If a question asks for the most common tumor without specifying "primary," the answer is always Metastases. If it specifies "primary," the answer is Meningioma.

Q: Which of the following is NOT a characteristic feature of meningioma?

Intra-axial tumor. ### Explanation **Meningiomas** are the most common primary intracranial tumors. The core concept to understand here is their anatomical origin: they arise from **arachnoid cap cells** of the leptomeninges, making them **extra-axial** tumors (located outside the brain parenchyma). **Why Option D is the Correct Answer:** Meningiomas are classic examples of **extra-axial** tumors. They compress the brain from the outside rather than infiltrating it from within. Characteristics of extra-axial lesions include the displacement of gray matter, widening of the subarachnoid space (CSF cleft sign), and a broad-based attachment to the dura. Therefore, labeling it an "intra-axial tumor" is factually incorrect. **Analysis of Incorrect Options:** * **A. Calcification:** This is a very common feature, seen in approximately 20–25% of cases. On histopathology, these often appear as **Psammoma bodies**. * **B. Dural tail sign:** This represents thickening and enhancement of the dura mater adjacent to the tumor. While not pathognomonic, it is highly suggestive of meningioma. * **C. Mother-in-law sign:** This is a classic radiological "nickname" referring to the tumor's vascularity on angiography. The tumor "comes early and stays late"—meaning the contrast blush appears early in the arterial phase and persists long into the venous phase. **High-Yield Clinical Pearls for NEET-PG:** * **Most common location:** Parasagittal/Convexity. * **Gender Predilection:** More common in females (due to progesterone receptors). * **Association:** Strongly associated with **Neurofibromatosis Type 2 (NF2)**, especially when multiple. * **MRI Appearance:** Usually isointense to gray matter on T1 and T2; shows **intense, homogenous enhancement** post-gadolinium. * **Bone changes:** Often causes **hyperostosis** (thickening) of the overlying bone.

Q: What is the most common posterior fossa brain tumor in children?

Pilocytic astrocytoma. **Explanation:** The correct answer is **Pilocytic Astrocytoma**. While many older textbooks previously cited medulloblastoma as the most common, current epidemiological data and recent editions of standard radiology and neurosurgery texts (like Bailey's and Nelson's) confirm that **Juvenile Pilocytic Astrocytoma (JPA)** is the most common pediatric posterior fossa tumor and the most common primary pediatric brain tumor overall. **Why Pilocytic Astrocytoma is correct:** It is a WHO Grade I tumor, typically arising in the cerebellum. On imaging, it classically presents as a **large cystic lesion with a brightly enhancing mural nodule**. It has a relatively benign course and a favorable prognosis compared to other brain tumors. **Analysis of Incorrect Options:** * **Medulloblastoma:** This is the most common **malignant** (WHO Grade IV) brain tumor in children. It typically arises from the roof of the 4th ventricle (vermis) and shows a "drop metastasis" pattern via CSF. * **Hemangioblastoma:** While this is a common primary intra-axial tumor of the posterior fossa in **adults**, it is rare in children unless associated with Von Hippel-Lindau (VHL) syndrome. * **Occipital fossa tumor:** This is a general anatomical description rather than a specific pathological diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common posterior fossa tumor:** Pilocytic Astrocytoma. * **Most common malignant CNS tumor in children:** Medulloblastoma. * **Most common supratentorial tumor in children:** Craniopharyngioma. * **Imaging Hallmark (JPA):** Cyst with an enhancing mural nodule. * **Imaging Hallmark (Medulloblastoma):** Hyperdense mass on CT (due to high cellularity) filling the 4th ventricle.

Question 1

The dense middle cerebral artery (MCA) sign is seen in which of the following conditions?

Accepted Answer

Acute infarct

Answer

Subacute infarct

Answer

Subacute hemorrhage

Answer

Chronic infarct

Question 2

Widened Bat wing sylvian fissures are associated with which of the following conditions?

Accepted Answer

Glutaric aciduria

Answer

Maple Syrup urine disease

Answer

Galactosemia

Answer

Canavan disease

Question 3

A child presents with raised ICT; on CT scan, a lesion is seen around the foramen of Monro and multiple periventricular calcific foci are noted. What is the most probable diagnosis?

Accepted Answer

Subependymal giant cell astrocytoma

Answer

Central neurocytoma

Answer

Ependymoma

Answer

Ganglioglioma

Question 4

What is the investigation of choice for the diagnosis of a posterior fossa tumor?

Accepted Answer

MRI

Answer

CT scan

Answer

Angiography

Answer

Myelography

Question 5

Subependymal Giant Cell Astrocytoma is commonly associated with which of the following conditions?

Accepted Answer

Tuberous sclerosis

Answer

Neurofibroma

Answer

Schwannoma

Answer

Ependymoma

Question 6

Which of the following conditions is most commonly associated with calcification of the basal ganglia?

Accepted Answer

Wilson's disease

Answer

Berry's aneurysm

Answer

Cysticercosis

Answer

Idiopathic hyperparathyroidism

Question 7

What is the most common primary brain tumor in adults?

Accepted Answer

Metastases

Answer

Glioma

Answer

Meningioma

Answer

Astrocytoma

Question 8

Punch drunk syndrome is associated with which of the following conditions?

Accepted Answer

Subdural hematoma

Answer

Extradural hematoma

Answer

Subarachnoid hematoma

Answer

Intraventricular bleed

Question 9

Which of the following is NOT a characteristic feature of meningioma?

Accepted Answer

Intra-axial tumor

Answer

Calcification

Answer

Dural tail sign

Answer

Mother in law sign

Question 10

What is the most common posterior fossa brain tumor in children?

Accepted Answer

Pilocytic astrocytoma

Answer

Medulloblastoma

Answer

Hemangioblastoma

Answer

Occipital fossa tumor

Neuroradiology — MCQs

Neuroradiology — MCQs

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