Neuroradiology Practice Questions

Q: Empty thecal sac sign is seen in:

Arachnoiditis. ***Arachnoiditis*** - The **empty thecal sac** sign is a characteristic imaging finding in severe chronic arachnoiditis, where nerve roots clump together and adhere to the dura, leaving the center of the thecal sac empty of contrast or cerebrospinal fluid. - This condition involves **inflammation and fibrosis** of the arachnoid membrane, often leading to adhesion of nerve roots. *Discitis* - Discitis is an **inflammation of the intervertebral disc** space, typically presenting with back pain and fever, but does not cause an empty thecal sac sign. - Imaging usually shows **disc space narrowing** and endplate changes. *Vertebral osteomyelitis* - This is an **infection of the vertebral bone**, distinguished by progressive bone destruction and sometimes epidural abscess formation. - It does not lead to the **empty thecal sac** sign; instead, imaging reveals bony changes and potential soft tissue masses. *Tethered Cord syndrome* - Tethered cord syndrome involves the **spinal cord being anchored to the spinal canal**, restricting its movement and causing traction. - While it can manifest with neurological symptoms, it is characterized by a low-lying conus medullaris and a thickened filum terminale, not an **empty thecal sac**.

Q: What is the typical MRI finding in multiple sclerosis (MS)?

Periventricular lesions. ***Periventricular lesions*** - **Demyelinating plaques** in a periventricular distribution are a hallmark MRI finding in **multiple sclerosis**, often appearing as **Dawson's fingers**. - These lesions reflect areas of **demyelination** and inflammation characteristic of the disease. *Basal ganglia calcification* - This finding is more commonly associated with conditions like **Fahr's disease**, **hypoparathyroidism**, or certain infections, not primary to MS. - While calcifications can occur in rare cases of MS, they are not a typical or diagnostic feature. *Diffuse cortical atrophy* - **Cortical atrophy** can be present in later stages of MS, but it is a **non-specific** finding not unique to MS and not a primary diagnostic marker. - It is more commonly seen in neurodegenerative diseases like **Alzheimer's disease** or in the elderly, and less characteristic of early MS. *Subdural hematoma* - A **subdural hematoma** is a collection of blood between the dura mater and arachnoid mater, usually due to trauma. - This is an **acute neurological emergency** and entirely unrelated to the pathology and typical MRI features of multiple sclerosis.

Q: What is the most common cause of 'banana sign' in prenatal ultrasound?

Spina bifida. ***Spina bifida*** - The **"banana sign"** is a characteristic ultrasound finding where the **cerebellum is compressed and flattened**, resembling a banana due to the caudal displacement of the posterior fossa contents into the spinal canal. - This compression is typically caused by the **Chiari II malformation**, which is almost always present with **myelomeningocele**, the most severe form of spina bifida. *Anencephaly* - Anencephaly results in the **absence of most of the brain and skull**, which is a distinctly different finding from the "banana sign." - The characteristic ultrasound finding for anencephaly is the **absence of the cranial vault and cerebral hemispheres** above the orbits. *Dandy-Walker malformation* - This malformation involves an **enlarged posterior fossa** with cystic dilation of the fourth ventricle and **agenesis/hypoplasia of the cerebellar vermis**. - It does not cause the cerebellar compression that creates the "banana sign." *Hydrocephalus* - Hydrocephalus involves the **enlargement of the ventricles** due to excessive cerebrospinal fluid (CSF) accumulation, leading to increased intracranial pressure. - While it can be associated with spina bifida and Chiari II malformation, **hydrocephalus itself doesn't directly cause the "banana sign"** as a primary feature.

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: A 45-year-old female presents with the acute onset of a severe headache and vomiting. A non-contrast CT shows a crescent-shaped hyperdense area crossing suture lines. What is the most likely diagnosis?

Subdural hematoma. ***Subdural hematoma*** - A **crescent-shaped hyperdense area** on a non-contrast CT that **crosses suture lines** is the classic imaging finding for a subdural hematoma. - This typically results from the tearing of **bridging veins** and can present acutely or chronically. *Epidural hematoma* - This typically appears as a **lenticular (lens-shaped) hyperdense collection** on CT. - Epidural hematomas characteristically **do not cross suture lines** because the dura is tightly adherent to the skull at these points. *Subarachnoid hemorrhage* - Identified by the presence of blood within the **subarachnoid space**, appearing as **hyperdensity in the sulci and basal cisterns** on CT. - While it causes severe headache, its CT appearance is diffuse and does not form a contained crescent or lenticular shape. *Intracerebral hemorrhage* - Appears as a **focal, hyperdense collection of blood within the brain parenchyma** itself. - It does not conform to the shape of an extra-axial collection like a crescent or lenticular shape.

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.

Question 1

Empty thecal sac sign is seen in:

Accepted Answer

Arachnoiditis

Answer

Discitis

Answer

Vertebral osteomyelitis

Answer

Tethered Cord syndrome

Question 2

What is the typical MRI finding in multiple sclerosis (MS)?

Accepted Answer

Periventricular lesions

Answer

Basal ganglia calcification

Answer

Diffuse cortical atrophy

Answer

Subdural hematoma

Question 3

What is the most common cause of 'banana sign' in prenatal ultrasound?

Accepted Answer

Spina bifida

Answer

Anencephaly

Answer

Dandy-Walker malformation

Answer

Hydrocephalus

Question 4

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

Accepted Answer

MRI with DWI

Answer

Ultrasound

Answer

PET scan

Answer

CT

Question 5

A 45-year-old female presents with the acute onset of a severe headache and vomiting. A non-contrast CT shows a crescent-shaped hyperdense area crossing suture lines. What is the most likely diagnosis?

Accepted Answer

Subdural hematoma

Answer

Epidural hematoma

Answer

Subarachnoid hemorrhage

Answer

Intracerebral hemorrhage

Question 6

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 7

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 8

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 9

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 10

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

Neuroradiology — MCQs

Neuroradiology — MCQs

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