Functional Neuroimaging Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Functional Neuroimaging. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Functional Neuroimaging Indian Medical PG Question 1: Structure of brain involved in emotion: a) Neocortex b) Limbic system c) Thalamus d) Hippocampus
- A. Neocortex
- B. Thalamus
- C. Limbic system (Correct Answer)
- D. Hippocampus
Functional Neuroimaging Explanation: ***Limbic system***
- The **limbic system** is a complex set of brain structures located on top of the brainstem and underneath the cortex that is primarily associated with **emotion**, motivation, memory, and behavior.
- Key components include the **amygdala** (crucial for fear and emotional responses), **hippocampus** (memory formation with emotional context), **hypothalamus** (autonomic responses to emotion), and **cingulate gyrus** (emotional processing).
- This is the **primary neuroanatomical system** responsible for emotional processing and regulation.
*Neocortex*
- The **neocortex** is the outermost layer of the brain involved in higher-level functions such as **conscious thought**, sensory perception, motor commands, and language.
- While it modulates and interprets emotions, it is not the primary center for generating basic emotional responses.
*Thalamus*
- The **thalamus** acts as a **relay station** for sensory and motor signals to the cerebral cortex.
- While it processes emotional stimuli, it does not initiate or primarily control emotional responses itself.
*Hippocampus*
- The **hippocampus** is a crucial part of the limbic system primarily involved in **memory formation**, particularly the consolidation of short-term to long-term memory, and **spatial navigation**.
- While it plays a role in recalling emotionally charged memories, it is not the primary structure for the generation or direct experience of emotion itself.
Functional Neuroimaging Indian Medical PG Question 2: Cerebral blood flow is regulated by all of the following except:
- A. Calcium ions (Correct Answer)
- B. Blood pressure
- C. Arterial PCO2
- D. Potassium ions
Functional Neuroimaging Explanation: ***Calcium ions***
- While **calcium ions (Ca²⁺)** are mechanistically essential for vascular smooth muscle contraction and relaxation, they are **not considered a primary regulatory signal** for cerebral blood flow (CBF) in the same way as the other factors listed.
- Ca²⁺ acts as an **intracellular second messenger** that mediates the effects of other regulatory factors (like PCO2, K⁺, and vasoactive substances), rather than being a direct extracellular regulatory signal itself.
- The question refers to primary regulatory factors that directly modulate CBF, not the intracellular mechanisms by which vascular smooth muscle responds.
*Blood pressure*
- **Cerebral autoregulation** maintains relatively constant CBF despite changes in **mean arterial pressure (MAP)** between approximately 60-150 mmHg.
- Blood pressure is a **key regulatory factor** - when MAP falls below or exceeds this range, CBF becomes pressure-dependent.
- This protective mechanism prevents cerebral ischemia or hyperemia with systemic blood pressure fluctuations.
*Arterial PCO2*
- **Arterial partial pressure of carbon dioxide (PaCO2)** is one of the **most potent direct regulators** of CBF.
- **Hypercapnia** (increased PaCO2) causes cerebral vasodilation and increased CBF (approximately 1-2 mL/100g/min increase per 1 mmHg rise in PaCO2).
- **Hypocapnia** (decreased PaCO2) causes vasoconstriction and reduced CBF, utilized therapeutically in managing elevated intracranial pressure.
*Potassium ions*
- **Increased extracellular K⁺** in the perivascular space causes **direct vasodilation** of cerebral arterioles.
- This mechanism is crucial for **neurovascular coupling** (functional hyperemia) - when neurons are active, they release K⁺, which dilates nearby vessels to increase local blood flow.
- K⁺-mediated vasodilation helps match cerebral perfusion to metabolic demand during neuronal activity.
Functional Neuroimaging Indian Medical PG Question 3: EEG waves prominent in occipital lobe are
- A. Gamma
- B. Alpha (Correct Answer)
- C. Beta
- D. Theta
Functional Neuroimaging Explanation: ***Alpha***
- **Alpha waves** are typically most prominent in the **occipital and parietal lobes** when an individual is awake but in a relaxed state with their eyes closed.
- They are associated with a state of **relaxed awareness** and tend to disappear when the eyes open or during mental activity or sleep.
*Gamma*
- **Gamma waves** are the fastest brain waves and are associated with **higher-level cognitive functions**, such as learning, memory, and information processing across different brain regions.
- While present throughout the brain, they are not specifically prominent in the occipital lobe in isolation during baseline resting states.
*Beta*
- **Beta waves** are characteristic of an **alert, awake state** and are often recorded over the frontal and central regions of the brain.
- They are associated with active thinking, problem-solving, and concentration, and tend to be suppressed in the occipital region during rest.
*Theta*
- **Theta waves** are typically associated with **sleep stages 1 and 2**, as well as deep meditation and certain emotional states.
- While they can be observed in various brain regions during specific activities or sleep, they are not primarily prominent in the occipital lobe during awake, relaxed states.
Functional Neuroimaging Indian Medical PG Question 4: All the following are indications for brain imaging in epilepsy, except:
- A. EEG shows a focal seizure source
- B. Control of seizures is difficult
- C. Seizures have focal features clinically
- D. Epilepsy starts after the age of 5 years (Correct Answer)
Functional Neuroimaging Explanation: Address the indications for brain imaging in epilepsy based on clinical guidelines.
***Epilepsy starts after the age of 5 years***
- The recommendation for **brain imaging** is typically suggested for epilepsy onset after the age of **16 years** to rule out structural causes, rather than age 5 [2]. An onset at age 5 does not exclude the possibility of idiopathic epilepsy, which often does not require imaging [1].
- While it's a good practice to image any new onset epilepsy, age 5 by itself is not a specific indication that *demands* imaging beyond standard workup if no other red flags are present.
*EEG shows a focal seizure source*
- A **focal seizure source identified on EEG** strongly indicates a structural lesion in the brain that could be responsible for the seizures [2].
- **Brain imaging** (e.g., MRI) is essential to identify the underlying **structural abnormality**, such as a tumor, malformation, or scar tissue [2].
*Control of seizures is difficult*
- Poorly controlled or **refractory seizures** warrant further investigation with brain imaging to look for an **underlying structural cause** that might be amenable to surgical intervention or require alternative therapies [2].
- This suggests the possibility of a lesion that is not responding to standard anti-epileptic drugs, necessitating a search for the **etiology of intractability** [3].
*Seizures have focal features clinically*
- **Focal clinical features** (e.g., twitching of one limb, sensory disturbances on one side) strongly point to a specific area of the brain where the seizures originate [4].
- **Brain imaging** is crucial to identify any **structural lesion** (e.g., tumor, malformation, stroke) corresponding to the clinically localized area of seizure onset [2].
Functional Neuroimaging Indian Medical PG Question 5: Substance used for PET scan is
- A. Gadolinium
- B. Gastrografin
- C. Iodine
- D. 18F-FDG (Correct Answer)
Functional Neuroimaging Explanation: ***18F-FDG***
- **18F-FDG (Fluorodeoxyglucose)** is a glucose analog labeled with a **positron-emitting radioisotope**, fluorine-18 (18F).
- It is the most commonly used radiotracer in PET scans, as it accumulates in cells with high metabolic activity, particularly **cancer cells** and activated brain cells.
*Gadolinium*
- **Gadolinium** is a paramagnetic contrast agent primarily used in **MRI scans** to enhance the visualization of blood vessels and abnormal tissues.
- It does not emit positrons and is therefore not suitable for PET imaging.
*Gastrografin*
- **Gastrografin** is an oral, water-soluble contrast agent containing **iodine**, typically used in **X-rays** and **CT scans** of the gastrointestinal tract.
- It is not a radioactive tracer and has no application in PET imaging.
*Iodine*
- **Iodine** in various forms can be used as a contrast agent in **X-rays** and **CT scans**, or as a radioactive isotope (e.g., **I-131**) for **thyroid imaging** and treatment.
- While some isotopes of iodine are radioactive, they are not typically used for PET imaging, which relies on positron emission.
Functional Neuroimaging Indian Medical PG Question 6: Radiation-induced necrosis can be diagnosed by:
- A. MRI
- B. CT
- C. PET
- D. Biopsy (Correct Answer)
Functional Neuroimaging Explanation: ***Biopsy***
- A **biopsy** is the definitive diagnostic method for radiation-induced necrosis, allowing for histological examination of tissue to confirm necrosis and rule out residual or recurrent tumor. [1], [2]
- It provides a direct view of cellular changes, identifying **necrosis, atypical cells**, and ruling out **malignancy**.
*MRI*
- While **MRI** can show structural changes indicative of necrosis (e.g., mass effect, edema), it often cannot definitively differentiate between **radiation necrosis** and **tumor recurrence.** [2]
- It often shows **T1 hypointensity** and **T2 hyperintensity**, but these findings are not specific.
*CT*
- **CT scans** are useful for detecting gross changes like **mass effect** and **edema** but have limited sensitivity for distinguishing necrosis from tumor recurrence.
- It may show **low-density lesions** but lacks the resolution and specificity for precise diagnosis.
*PET*
- **PET scans** measure metabolic activity and can help distinguish between **tumor recurrence** (high uptake) and **radiation necrosis** (low uptake) in some cases.
- However, false positives can occur, as some inflammatory processes in necrosis can also show increased uptake, making it **less definitive** than a biopsy.
**References:**
[1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1307-1308.
[2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 340-341.
Functional Neuroimaging Indian Medical PG Question 7: Pine-tree bladder is a sign of.
- A. Pelvic abscess
- B. Bilharziasis (Correct Answer)
- C. Intraperitoneal bladder rupture
- D. Neurogenic bladder
Functional Neuroimaging Explanation: ***Bilharziasis***
- The "pine-tree bladder" appearance on a retrograde cystogram is characteristic of **chronic bilharzial cystitis**, also known as **schistosomiasis of the bladder**.
- This appearance results from **fibrosis**, **granulomas**, and **calcification** of the bladder wall leading to multiple irregular diverticula and trabeculations, which resemble pine-tree branches.
*Pelvic abscess*
- A pelvic abscess causes an **extrinsic compression** on the bladder, leading to mass effect or displacement, rather than intrinsic wall changes.
- It would typically present with symptoms of infection, such as fever and localized pain, and imaging would show a fluid collection.
*Intraperitoneal bladder rupture*
- An intraperitoneal bladder rupture would lead to extravasation of urine into the peritoneal cavity, which would be visible on imaging as **free fluid** around abdominal organs.
- The bladder itself would appear flaccid and potentially collapsed, without the characteristic "pine-tree" appearance.
*Neurogenic bladder*
- Neurogenic bladder is characterized by **detrusor-sphincter dyssynergia** or loss of bladder sensation, leading to features like **trabeculation**, cellules, and diverticula due to high intravesical pressure.
- While it can cause some bladder wall changes, the specific "pine-tree" pattern is not its hallmark, and it is usually associated with neurological deficits.
Functional Neuroimaging Indian Medical PG Question 8: Intra-tumoral calcification in the brain is seen in all except?
- A. Craniopharyngioma
- B. Meningioma
- C. Oligodendroglioma
- D. Hemangioblastoma (Correct Answer)
Functional Neuroimaging Explanation: **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.
Functional Neuroimaging Indian Medical PG Question 9: Which of the following techniques is the best for differentiating recurrence of a brain tumor from radiation therapy-induced necrosis?
- A. MRI
- B. Contrast-enhanced MRI
- C. PET scan (Correct Answer)
- D. CT scan
Functional Neuroimaging Explanation: **Explanation:**
The differentiation between **tumor recurrence** and **radiation necrosis** is a common diagnostic dilemma because both entities appear similar on conventional imaging (enhancing mass with surrounding edema).
**Why PET Scan is the Correct Answer:**
The distinction is based on **metabolic activity**.
* **Tumor Recurrence:** Malignant cells are hypermetabolic and demonstrate high glucose uptake. Therefore, they appear as **"Hot" lesions** on FDG-PET (Fluorodeoxyglucose) or Amino Acid PET (e.g., Methionine-PET).
* **Radiation Necrosis:** This represents dead tissue and inflammatory changes, which are metabolically inactive. These appear as **"Cold" lesions** (photopenic) on PET scans.
This functional assessment makes PET the gold standard for differentiation.
**Why Other Options are Incorrect:**
* **MRI & Contrast-enhanced MRI (CE-MRI):** While MRI is the investigation of choice for initial diagnosis, it cannot reliably distinguish recurrence from necrosis. Both conditions cause a breakdown of the blood-brain barrier, leading to similar contrast enhancement and T2/FLAIR signals.
* **CT Scan:** CT lacks the soft-tissue resolution required for neuro-oncology and provides no metabolic information, making it the least sensitive modality for this purpose.
**NEET-PG High-Yield Pearls:**
* **MR Spectroscopy (MRS):** If PET is not an option, MRS is the next best functional MRI technique. Recurrence shows **increased Choline** (cell turnover) and **decreased NAA** (neuronal loss), whereas necrosis shows a "dead" spectrum (low peaks across the board or a Lactate/Lipid peak).
* **Perfusion MRI (rCBV):** Tumor recurrence typically shows **increased** relative Cerebral Blood Volume (rCBV) due to neoangiogenesis, while necrosis shows **decreased** rCBV.
* **Gold Standard:** Histopathology remains the definitive gold standard, but PET is the best non-invasive imaging technique.
Functional Neuroimaging Indian Medical PG Question 10: Which of the following brain tumors is typically hyperdense on CT scan?
- A. Ependymoma
- B. Medulloblastoma (Correct Answer)
- C. Oligodendroglioma
- D. Astrocytoma
Functional Neuroimaging Explanation: **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).
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