Neuroradiology Practice Questions

Q: Which imaging modality is most sensitive for detecting early ischemic stroke?

MRI with DWI. ***MRI with DWI*** - **Diffusion-weighted imaging (DWI)** within an MRI scan is highly sensitive in detecting **cytotoxic edema** within minutes of **ischemic stroke** onset. This makes it crucial for early diagnosis and treatment decisions. - DWI can identify areas of restricted water diffusion, which is a hallmark of acute cellular injury due to **ischemia**, even before changes are visible on conventional T1 or T2-weighted MRI sequences. *CT* - While frequently used in acute stroke settings, **non-contrast CT** is primarily used to **rule out hemorrhagic stroke** and may only show subtle or no signs of acute ischemia in the first few hours. - Early ischemic changes on CT, often referred to as the **"ischemic penumbra"**, may appear hours after stroke onset, making it less sensitive for very early detection compared to DWI. *Ultrasound* - **Transcranial Doppler (TCD) ultrasound** can evaluate blood flow velocities in intracranial arteries and detect stenoses or occlusions but is not a primary imaging modality for directly visualizing brain parenchymal ischemia. - Cervical ultrasound (e.g., **carotid duplex**) assesses extracranial vessels but cannot directly detect **ischemic changes** within the brain tissue itself. *PET scan* - **PET (Positron Emission Tomography)** can assess brain metabolism and blood flow but is typically not the preferred or most sensitive modality for **early detection of acute ischemic stroke** due to its complexity, cost, and limited availability in emergency settings. - PET is more commonly used in research or for assessing chronic conditions and **metabolic abnormalities**, rather than acute stroke diagnosis.

Q: Which of the following lesions is typically hypodense on a non-contrast CT scan?

Chronic subdural hematoma. ***Chronic subdural hematoma*** - A **chronic subdural hematoma** (> 3 weeks old) is typically **hypodense** (dark) on a non-contrast CT scan because the blood products have aged, broken down, and become diluted with CSF-like fluid. - Its appearance is usually **crescent-shaped**, conforming to the brain surface, and located between the dura and arachnoid mater. - This hypodense appearance distinguishes it from acute hemorrhages. *Epidural hematoma* - An **acute epidural hematoma** is typically **hyperdense** (bright) on a non-contrast CT scan due to freshly clotted blood with high protein content. - It has a characteristic **lenticular (lens-shaped)** appearance located between the skull and dura mater. - Epidural hematomas present acutely and are evacuated surgically, rarely progressing to chronic hypodense stages. *Subdural hematoma* - An **acute subdural hematoma** is typically **hyperdense** on CT with a **crescent-shaped** appearance. - As time progresses: acute (0-3 days) = hyperdense, subacute (3-21 days) = isodense, chronic (> 3 weeks) = hypodense. - Without the qualifier "chronic," this refers to acute subdural, which is hyperdense. *Subarachnoid hemorrhage* - A **subarachnoid hemorrhage** appears **hyperdense** within the subarachnoid spaces, filling sulci, cisterns, and fissures on non-contrast CT. - Blood in the subarachnoid space is typically acute and hyperdense at presentation. - SAH is a medical emergency requiring immediate intervention.

Q: Which imaging modality is considered the best for evaluating spinal cord compression and soft tissue abnormalities?

MRI. ***MRI (Correct Answer)*** - **Magnetic Resonance Imaging (MRI)** is superior for visualizing **soft tissues** such as the spinal cord, nerves, ligaments, and intervertebral discs. - It provides excellent contrast resolution, making it the **gold standard** for detecting and characterizing **spinal cord compression**, nerve root impingement, and other soft tissue abnormalities. - MRI is non-invasive and does not use ionizing radiation, making it safer for repeated imaging when needed. *CT scan (Incorrect)* - **Computed Tomography (CT) scans** excel at imaging **bone structures** and showing **bony impingement** but are less effective for direct visualization of the spinal cord itself. - While it can indirectly show compression through bone changes, its ability to depict actual cord and nerve tissue is limited compared to MRI. *X-ray (Incorrect)* - **X-rays** primarily show **bone structures** and are useful for detecting fractures, dislocations, or degenerative changes in the vertebrae. - They provide very limited information about **soft tissues** like the spinal cord or intervertebral discs and cannot directly visualize spinal cord compression. *Bone scan (Incorrect)* - A **bone scan** is a nuclear medicine test that detects **increased metabolic activity** in bones, often used to identify infections, tumors, or fractures that may not be visible on standard X-rays. - It does not directly visualize the **spinal cord** or soft tissue abnormalities and is not used for assessing spinal cord compression.

Q: A 6-year-old child presents with a severe headache and vomiting. An MRI shows a cystic lesion in the cerebellum with an enhancing mural nodule. What is the likely diagnosis?

Pilocytic astrocytoma. ***Pilocytic astrocytoma*** - This is the most common **cerebellar tumor in children** and classically presents as a **cystic lesion with an enhancing mural nodule** on imaging. - The symptoms of **headache and vomiting** are indicative of increased intracranial pressure, often caused by the tumor obstructing CSF flow in the posterior fossa. *Medulloblastoma* - While also a common pediatric cerebellar tumor, medulloblastoma typically presents as a **solid, enhancing mass** in the midline of the cerebellum, not typically cystic with a mural nodule. - It is known for its tendency to **disseminate via CSF pathways** to other parts of the brain and spine. *Glioblastoma* - This is a highly malignant primary brain tumor that is **rare in children** and typically found in the **cerebral hemispheres** in adults, not the cerebellum. - Imaging usually shows an **irregularly enhancing mass with central necrosis** and surrounding edema. *Ependymoma* - Ependymomas can occur in the posterior fossa in children but typically arise from the **floor of the fourth ventricle** and often show heterogeneous enhancement, sometimes with calcifications. - They are less commonly characterized by the classic **cystic lesion with an enhancing mural nodule** seen in pilocytic astrocytomas.

Q: In evaluating a patient with suspected multiple sclerosis, which of the following findings would typically be seen on MRI?

Multiple periventricular white matter lesions. ***Multiple periventricular white matter lesions*** - **Multiple sclerosis (MS)** is characterized by **demyelination** in the central nervous system, which appears as bright lesions in the **periventricular white matter** on T2-weighted MRI. - The presence of multiple lesions disseminated in space and time is a key diagnostic criterion for MS, reflecting distinct episodes of demyelination. *Bilateral acoustic neuromas* - **Bilateral acoustic neuromas** are a hallmark finding of **Neurofibromatosis type 2 (NF2)**, a genetic disorder, not multiple sclerosis. - These tumors arise from the vestibulocochlear nerves and typically cause hearing loss and balance issues. *Hypointensities in the basal ganglia* - **Hypointensities in the basal ganglia** are often associated with conditions involving **iron deposition** or calcification, such as **Parkinson's disease** at later stages or metabolic disorders. - This finding is not characteristic of demyelinating lesions seen in multiple sclerosis. *Single enhancing brainstem lesion* - A **single enhancing lesion** in the brainstem can be seen in various conditions, including tumors, infections, or inflammatory processes like **acute disseminated encephalomyelitis (ADEM)**. - While MS can cause brainstem lesions, the finding of only a single enhancing lesion would not be typical for confirmed MS, which usually presents with multiple lesions.

Q: A 45-year-old male patient presents with a sudden severe headache, nuchal rigidity, and loss of consciousness. A CT scan shows hyperdensity in the subarachnoid spaces. What is the next best investigation?

CT angiography. ***CT angiography*** - A CT scan showing **hyperdensity in the subarachnoid spaces** confirms a **subarachnoid hemorrhage (SAH)**. - **CT angiography** is the most appropriate next step to rapidly identify the source of bleeding, typically an **aneurysm**, crucial for guiding immediate management. *MRI* - While MRI can provide detailed images, it is generally **slower to perform** and less accessible in an emergency setting for initial diagnostic evaluation of acute SAH. - It is often reserved for cases where the CT is negative but clinical suspicion of SAH remains high, or for evaluating **SAH mimics**. *Lumbar puncture* - A lumbar puncture would confirm the presence of blood or xanthochromia in the **cerebrospinal fluid (CSF)**, but it is typically performed only if the initial CT scan is negative and clinical suspicion for SAH remains high. - Given the positive CT scan showing hyperdensity indicative of SAH, a lumbar puncture is **unnecessary and delays definitive diagnosis** of the bleeding source. *Digital subtraction angiography* - **Digital subtraction angiography (DSA)** is considered the **gold standard** for detecting intracranial aneurysms. - However, it is an **invasive procedure** and takes longer to perform than CT angiography, making it less suitable as the *immediate* next best investigation in an acute, unstable presentation where speed is critical.

Q: Which imaging modality is most appropriate for evaluating a suspected acoustic neuroma?

MRI. ***MRI*** - **Magnetic Resonance Imaging (MRI)** is the gold standard for diagnosing acoustic neuromas due to its superior soft tissue contrast and ability to visualize the **internal auditory canal** and **cerebellopontine angle**. - MRI with **gadolinium contrast** can detect even small acoustic neuromas, which appear as enhancing lesions. *CT scan* - While CT can show larger tumors indirectly by revealing **bone erosion** or **widening of the internal auditory canal**, it has poor soft tissue resolution for early detection of acoustic neuromas. - CT scans expose the patient to **ionizing radiation**, and its primary role is usually limited to evaluating bone structures or for patients who cannot undergo MRI. *X-ray* - **Plain X-rays** (e.g., skull films) are not effective for diagnosing acoustic neuromas as they only show bone and cannot visualize soft tissue tumors in this region. - They lack the necessary detail and sensitivity to detect such a tumor, especially in its early stages. *Ultrasound* - **Ultrasound** is not suitable for evaluating intracranial structures like acoustic neuromas because the **skull bone** obstructs the transmission of sound waves. - Its utility is primarily in visualizing superficial soft tissue structures or organs in the abdomen and neck.

Q: A 35-year-old female presents with a history of seizures and headaches. An MRI shows a well-defined cystic lesion with an enhancing mural nodule in the temporal lobe. What is the most likely diagnosis?

Low-grade astrocytoma. ***Low-grade astrocytoma*** - The **cyst with enhancing mural nodule** appearance in the temporal lobe of a young adult with seizures is highly characteristic of **pleomorphic xanthoastrocytoma (PXA)**, a subtype of low-grade astrocytoma (WHO Grade II). - PXA typically presents as a **superficial, cortically-based cystic mass** with a solid enhancing nodule, often with **dural involvement** ("dural tail" sign). - The patient's age (35-year-old female) and presenting symptoms of **seizures** and **headaches** are consistent with the slow-growing nature of these tumors, which often irritate cortical structures. - PXA has a **favorable prognosis** compared to other astrocytomas and commonly occurs in the **temporal lobe**. *Glioblastoma multiforme* - **Glioblastoma multiforme (GBM)** is a highly aggressive WHO Grade IV tumor that typically presents with **thick irregular ring enhancement**, **central necrosis**, and **extensive surrounding vasogenic edema**. - GBM shows rapid clinical progression and would not typically present as a well-defined cyst with mural nodule. - The imaging appearance described is more consistent with a low-grade tumor. *Meningioma* - **Meningiomas** are **extra-axial (dural-based) tumors** that demonstrate **uniform, homogeneous enhancement** with a characteristic **dural tail** sign. - They are typically **solid masses** (not cystic) that compress rather than infiltrate brain parenchyma. - The described cystic lesion with mural nodule is more consistent with an intra-axial tumor like PXA. *Oligodendroglioma* - **Oligodendrogliomas** characteristically show **calcifications** (present in 70-90% of cases) and are commonly located in the **frontal lobes**. - They typically appear as **heterogeneous, infiltrative masses** rather than well-defined cystic lesions with mural nodules. - While they can cause seizures, the imaging appearance described is not typical for oligodendroglioma.

Q: What condition is shown in the MR angiogram of the skull?

Vein of Galen malformation. ***Vein of Galen malformation*** - The image provided is an **MR angiogram (MRA)**, which clearly shows a **large, dilated vein of Galen**. This is the characteristic appearance of a Vein of Galen malformation. - This congenital vascular malformation involves a direct artery-to-vein shunt, leading to the characteristic aneurysmal dilatation of the vein. *Dandy-Walker malformation* - This is a congenital brain malformation characterized by **agenesis or hypoplasia of the cerebellar vermis** and cystic dilation of the fourth ventricle. - While it affects brain structures, it does not involve the type of vascular abnormality seen in the image. *Pneumocephalus* - **Pneumocephalus** refers to the presence of **air within the intracranial cavity**, often due to trauma or surgery. - It would appear as dark areas on imaging, representing air, not the bright, dilated vascular structures seen here. *Crouzon syndrome* - **Crouzon syndrome** is a genetic disorder characterized by **craniosynostosis**, which is the premature fusion of skull sutures. - This condition primarily affects bone growth and skull shape, with no direct involvement of the cerebral vasculature as depicted in the MRA.

Question 1

Which imaging modality is most sensitive for detecting early ischemic stroke?

Accepted Answer

MRI with DWI

Answer

Ultrasound

Answer

PET scan

Answer

CT

Question 2

Which of the following lesions is typically hypodense on a non-contrast CT scan?

Accepted Answer

Chronic subdural hematoma

Answer

Epidural hematoma

Answer

Subdural hematoma

Answer

Subarachnoid hemorrhage

Question 3

Which imaging modality is considered the best for evaluating spinal cord compression and soft tissue abnormalities?

Accepted Answer

MRI

Answer

CT scan

Answer

X-ray

Answer

Bone scan

Question 4

A 6-year-old child presents with a severe headache and vomiting. An MRI shows a cystic lesion in the cerebellum with an enhancing mural nodule. What is the likely diagnosis?

Accepted Answer

Pilocytic astrocytoma

Answer

Glioblastoma

Answer

Medulloblastoma

Answer

Ependymoma

Question 5

In evaluating a patient with suspected multiple sclerosis, which of the following findings would typically be seen on MRI?

Accepted Answer

Multiple periventricular white matter lesions

Answer

Bilateral acoustic neuromas

Answer

Hypointensities in the basal ganglia

Answer

Single enhancing brainstem lesion

Question 6

A 45-year-old male patient presents with a sudden severe headache, nuchal rigidity, and loss of consciousness. A CT scan shows hyperdensity in the subarachnoid spaces. What is the next best investigation?

Accepted Answer

CT angiography

Answer

MRI

Answer

Lumbar puncture

Answer

Digital subtraction angiography

Question 7

Which imaging modality is most appropriate for evaluating a suspected acoustic neuroma?

Accepted Answer

MRI

Answer

CT scan

Answer

X-ray

Answer

Ultrasound

Question 8

A 35-year-old female presents with a history of seizures and headaches. An MRI shows a well-defined cystic lesion with an enhancing mural nodule in the temporal lobe. What is the most likely diagnosis?

Accepted Answer

Low-grade astrocytoma

Answer

Meningioma

Answer

Oligodendroglioma

Answer

Glioblastoma multiforme

Question 9

How does cerebrospinal fluid (CSF) appear on T1 and T2 weighted MRI images?

Accepted Answer

Hypointense on T1 weighted image and hyperintense on T2 weighted image

Answer

Hyperintense on T1 weighted image and hypointense on T2 weighted image

Answer

Hyperintense on both T1 and T2 weighted images

Answer

Hypointense on both T1 and T2 weighted images

Question 10

What condition is shown in the MR angiogram of the skull?

Accepted Answer

Vein of Galen malformation

Answer

Dandy-Walker malformation

Answer

Pneumocephalus

Answer

Crouzon syndrome

Neuroradiology — MCQs

Neuroradiology — MCQs

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