A 35-year-old woman presents with headaches and seizures. MRI shows a well-circumscribed, calcified frontal lobe mass. Histology reveals oligodendroglioma with 1p/19q codeletion and IDH1 mutation. She undergoes gross total resection. Two years later, surveillance MRI shows a new enhancing nodule at the resection margin. Biopsy shows increased mitotic activity, microvascular proliferation, and retained 1p/19q codeletion but new CDKN2A/B homozygous deletion. What is the most critical factor in determining management strategy?
Q2
A 55-year-old man presents with progressive supranuclear gaze palsy, axial rigidity, and frequent falls. MRI shows midbrain atrophy with hummingbird sign. He dies 7 years later. Autopsy reveals globose neurofibrillary tangles in the basal ganglia and brainstem. Tau immunostaining shows 4-repeat tau predominance. His brother had similar symptoms. Genetic testing reveals a MAPT mutation. How does this change the pathogenic understanding and potential therapeutic approach?
Q3
A 70-year-old man with progressive dementia undergoes autopsy. Microscopy shows neuritic plaques and neurofibrillary tangles meeting criteria for Alzheimer disease (AD). However, sections also reveal Lewy bodies in the substantia nigra and cortex, moderate atherosclerosis with old lacunar infarcts, and TDP-43 positive inclusions in the hippocampus. He had no parkinsonian features clinically. What is the most appropriate neuropathologic interpretation?
Q4
A 42-year-old woman presents with behavioral changes, memory loss, and myoclonus. MRI shows cortical ribboning and T2 hyperintensity in the caudate and putamen. EEG shows periodic sharp wave complexes. CSF 14-3-3 is elevated, but real-time quaking-induced conversion (RT-QuIC) is negative. PRNP gene sequencing reveals E200K mutation. Her mother died of similar symptoms at age 45. What feature distinguishes this case from sporadic disease?
Q5
A 58-year-old man with HIV (CD4 count 45 cells/μL) presents with seizures and altered mental status. MRI shows multiple ring-enhancing lesions in the basal ganglia and cortex. Despite empiric treatment for toxoplasmosis for 2 weeks, lesions enlarge. Brain biopsy shows necrosis with surrounding large cells containing intranuclear inclusions and ground-glass nuclei. JC virus PCR is negative. What explains the unusual presentation and biopsy findings?
Q6
A 6-year-old boy presents with seizures and a calcified brain lesion on CT. Surgical resection shows a cystic tumor with a mural nodule. Histology reveals elongated bipolar cells with Rosenthal fibers and eosinophilic granular bodies. The tumor cells are GFAP-positive. Despite complete resection, which factor would most significantly impact long-term prognosis?
Q7
A 65-year-old man presents with progressive bradykinesia, resting tremor, and cogwheel rigidity. He later develops visual hallucinations and fluctuating cognition. He dies 8 years after symptom onset. Autopsy shows depigmentation of substantia nigra, and microscopy reveals eosinophilic cytoplasmic inclusions in neurons that are immunoreactive for alpha-synuclein. These inclusions are also found in the cortex. What is the most likely diagnosis?
Q8
A 28-year-old woman presents with vision loss in her right eye and numbness in her left leg that resolved spontaneously over 2 weeks. MRI shows multiple periventricular white matter lesions perpendicular to the lateral ventricles (Dawson fingers). Lumbar puncture reveals oligoclonal bands and elevated IgG index. Which pathologic finding would be expected on brain biopsy?
Q9
A 72-year-old man with a history of chronic hypertension presents with sudden onset right hemiparesis and aphasia. CT scan shows a hyperdense lesion in the left basal ganglia with surrounding edema and mass effect. He dies 48 hours later. Autopsy reveals a cavity filled with blood clot and hemosiderin-laden macrophages. Which vessels were most likely affected?
Q10
A 45-year-old woman presents with progressive weakness, ataxia, and dementia over 6 months. MRI shows diffuse cortical atrophy and T2 hyperintensities in the basal ganglia. EEG demonstrates periodic sharp wave complexes. CSF analysis shows elevated 14-3-3 protein and normal cell count. Brain biopsy reveals spongiform changes and no inflammation. What is the most likely underlying pathogenic mechanism?
Neuropathology US Medical PG Practice Questions and MCQs
Question 1: A 35-year-old woman presents with headaches and seizures. MRI shows a well-circumscribed, calcified frontal lobe mass. Histology reveals oligodendroglioma with 1p/19q codeletion and IDH1 mutation. She undergoes gross total resection. Two years later, surveillance MRI shows a new enhancing nodule at the resection margin. Biopsy shows increased mitotic activity, microvascular proliferation, and retained 1p/19q codeletion but new CDKN2A/B homozygous deletion. What is the most critical factor in determining management strategy?
A. The tumor has progressed to anaplastic oligodendroglioma requiring combined chemoradiation with temozolomide and RT
B. CDKN2A/B deletion indicates transformation to glioblastoma requiring maximal therapy
C. Retained 1p/19q codeletion predicts continued chemosensitivity to PCV regimen (Correct Answer)
D. Loss of IDH1 mutation suggests new primary tumor requiring re-resection only
E. Microvascular proliferation mandates anti-angiogenic therapy with bevacizumab
Explanation: ***Retained 1p/19q codeletion predicts continued chemosensitivity to PCV regimen***
- The preservation of **1p/19q codeletion** in a recurrent tumor is the strongest predictor of clinical response to alkylating chemotherapy, specifically the **PCV (Procarbazine, Lomustine, Vincristine)** regimen.
- While the tumor shows histological progression, the underlying molecular subtype remains an **oligodendroglioma**, which generally carries a better prognosis and higher chemosensitivity than non-codeleted gliomas.
*The tumor has progressed to anaplastic oligodendroglioma requiring combined chemoradiation with temozolomide and RT*
- While the histology suggests a higher grade, the standard of care for 1p/19q codeleted tumors frequently favors **PCV** over **Temozolomide** due to more robust long-term survival data from clinical trials like RTOG 9402.
- Grading alone does not dictate management as much as the **molecular profile** does in modern neuro-oncology guidelines.
*CDKN2A/B deletion indicates transformation to glioblastoma requiring maximal therapy*
- Under the current WHO classification, **glioblastoma** is defined as an **IDH-wildtype** tumor; since this tumor has an **IDH1 mutation**, it cannot be classified as a glioblastoma.
- **CDKN2A/B homozygous deletion** is a marker of high-grade malignancy (WHO Grade 4) in IDH-mutant astrocytomas, but its presence in an **oligodendroglioma** does not change the lineage-defining 1p/19q status.
*Loss of IDH1 mutation suggests new primary tumor requiring re-resection only*
- **IDH1 mutations** are early, trunk events in gliomagenesis and are almost never
Question 2: A 55-year-old man presents with progressive supranuclear gaze palsy, axial rigidity, and frequent falls. MRI shows midbrain atrophy with hummingbird sign. He dies 7 years later. Autopsy reveals globose neurofibrillary tangles in the basal ganglia and brainstem. Tau immunostaining shows 4-repeat tau predominance. His brother had similar symptoms. Genetic testing reveals a MAPT mutation. How does this change the pathogenic understanding and potential therapeutic approach?
A. It suggests prion-like propagation requiring anti-aggregation compounds
B. It demonstrates autoimmune etiology requiring immunosuppression
C. It reveals mitochondrial dysfunction requiring coenzyme Q10 supplementation
D. It confirms primary tauopathy amenable to tau-directed antisense oligonucleotide therapy (Correct Answer)
E. It indicates concurrent alpha-synuclein pathology requiring dual-target therapy
Explanation: ***It confirms primary tauopathy amenable to tau-directed antisense oligonucleotide therapy***
- The presence of **MAPT mutations** and **4-repeat (4R) tau** predominance confirms that tau dysfunction is the primary driver of the neurodegenerative process in this **Progressive Supranuclear Palsy (PSP)** phenotype.
- Targeting the underlying genetic cause with **antisense oligonucleotides (ASOs)** can reduce the expression of toxic tau protein, offering a disease-modifying approach rather than just symptomatic relief.
*It suggests prion-like propagation requiring anti-aggregation compounds*
- While **prion-like seeding** occurs in tauopathies, the discovery of a **MAPT mutation** specifically points to a genetic production error rather than isolated misfolding propagation.
- **Anti-aggregation compounds** are a general strategy, but they do not address the primary genetic driver identified by the mutation in this specific case.
*It demonstrates autoimmune etiology requiring immunosuppression*
- **PSP** and related **tauopathies** are degenerative proteinopathies, not autoimmune conditions, and show no response to **immunosuppressive therapy**.
- The **hummingbird sign** and **globose tangles** are classic markers of protein deposition, not inflammatory-mediated demyelination or vasculitis.
*It reveals mitochondrial dysfunction requiring coenzyme Q10 supplementation*
- Although some **mitochondrial deficit** is seen in neurodegeneration, it is a downstream effect and not the primary cause identified by a **MAPT mutation**.
- **Coenzyme Q10** has failed to show significant disease-modifying efficacy in clinical trials for primary tauopathies like **PSP**.
*It indicates concurrent alpha-synuclein pathology requiring dual-target therapy*
- The **MAPT mutation** and **4R tau** findings are specific to tauopathies; **alpha-synuclein** is the hallmark of synucleinopathies like **Parkinson’s disease** or **Multiple System Atrophy (MSA)**.
- Clinical features like the **hummingbird sign** (midbrain atrophy) and **axial rigidity** without resting tremors strongly favor a pure tau pathology over a dual-pathology state.
Question 3: A 70-year-old man with progressive dementia undergoes autopsy. Microscopy shows neuritic plaques and neurofibrillary tangles meeting criteria for Alzheimer disease (AD). However, sections also reveal Lewy bodies in the substantia nigra and cortex, moderate atherosclerosis with old lacunar infarcts, and TDP-43 positive inclusions in the hippocampus. He had no parkinsonian features clinically. What is the most appropriate neuropathologic interpretation?
A. Alzheimer disease with multiple contributing pathologies (mixed dementia) (Correct Answer)
B. Dementia with Lewy bodies with concurrent Alzheimer pathology
C. Vascular dementia with incidental Alzheimer changes
D. Frontotemporal dementia with secondary Alzheimer pathology
E. Primary age-related tauopathy with multiple comorbidities
Explanation: ***Alzheimer disease with multiple contributing pathologies (mixed dementia)***
- The presence of **neuritic plaques** and **neurofibrillary tangles** meeting AD criteria identifies Alzheimer's as the primary pathology, but the coexistence of **vascular**, **Lewy body**, and **TDP-43** changes defines mixed dementia.
- In the elderly, it is increasingly common to find multiple concurrent neurodegenerative processes, which collectively contribute to the clinical presentation of **progressive dementia**.
*Dementia with Lewy bodies with concurrent Alzheimer pathology*
- **Dementia with Lewy bodies (DLB)** requires clinical features such as **visual hallucinations** or **parkinsonism**, which were specifically noted as absent in this patient.
- While **Lewy bodies** were present, their occurrence alongside dominant AD pathology and other changes is better categorized under **mixed dementia** pathology.
*Vascular dementia with incidental Alzheimer changes*
- **Vascular dementia** is usually identified when ischemic changes are the primary drivers; here, the patient met full pathologic criteria for **Alzheimer Disease**.
- **Lacunar infarcts** and **atherosclerosis** in this context are considered contributing factors rather than the singular cause of the patient's decline.
*Frontotemporal dementia with secondary Alzheimer pathology*
- **Frontotemporal dementia (FTD)** typically presents with early changes in **personality**, **behavior**, or **language**, which did not match this patient's clinical history.
- While **TDP-43** inclusions are seen in variants of FTD, in an 70-year-old with AD, they are often a regional comorbid finding called **LATE** (Limbic-predominant Age-related TDP-43 Encephalopathy).
*Primary age-related tauopathy with multiple comorbidities*
- **Primary age-related tauopathy (PART)** is characterized by **neurofibrillary tangles** in the absence of significant **amyloid-beta (neuritic) plaques**.
- Since this patient met formal AD criteria (which includes neuritic plaques), **PART** is an incorrect diagnosis for the underlying tauopathy.
Question 4: A 42-year-old woman presents with behavioral changes, memory loss, and myoclonus. MRI shows cortical ribboning and T2 hyperintensity in the caudate and putamen. EEG shows periodic sharp wave complexes. CSF 14-3-3 is elevated, but real-time quaking-induced conversion (RT-QuIC) is negative. PRNP gene sequencing reveals E200K mutation. Her mother died of similar symptoms at age 45. What feature distinguishes this case from sporadic disease?
A. Longer disease duration with slower progression
B. Younger age of onset and positive family history with genetic mutation (Correct Answer)
C. Absence of spongiform changes on brain biopsy
D. Negative RT-QuIC despite elevated 14-3-3 protein
E. Presence of PrP amyloid plaques in cerebellum
Explanation: ***Younger age of onset and positive family history with genetic mutation***
- The presence of the **E200K mutation** in the **PRNP gene** and a mother affected by similar symptoms at age 45 confirms **familial Creutzfeldt-Jakob disease (fCJD)**.
- Inherited forms typically present at a **younger age** (early 40s to 50s) compared to sporadic CJD, which usually affects patients in their late 60s.
*Longer disease duration with slower progression*
- Both sporadic and **familial CJD** (especially the E200K variant) typically follow a **rapidly progressive** course leading to death within months.
- Only rare genetic prion diseases, like **Gerstmann-Sträussler-Scheinker (GSS)** syndrome, characteristically show a significantly longer disease duration.
*Absence of spongiform changes on brain biopsy*
- **Spongiform degeneration**, consisting of small vacuoles in the gray matter, is the hallmark pathologic feature of **all forms of CJD**, including familial types.
- The absence of these changes would argue against a diagnosis of **transmissible spongiform encephalopathy**.
*Negative RT-QuIC despite elevated 14-3-3 protein*
- While **RT-QuIC** is highly sensitive for sporadic CJD, its sensitivity can vary in **familial cases**; however, a negative result is an assay limitation, not a defining distinguishing feature of the etiology.
- Both **14-3-3 protein** and **RT-QuIC** are diagnostic markers used to support the diagnosis across different subtypes of prion disease.
*Presence of PrP amyloid plaques in cerebellum*
- **Amyloid plaques** containing prion protein are more commonly associated with **vCJD** or **GSS**, whereas E200K fCJD often lacks these plaques.
- The classic **E200K phenotype** closely mimics the sporadic form's pathology, focusing on **vacuolation** and **astrogliosis** rather than plaque formation.
Question 5: A 58-year-old man with HIV (CD4 count 45 cells/μL) presents with seizures and altered mental status. MRI shows multiple ring-enhancing lesions in the basal ganglia and cortex. Despite empiric treatment for toxoplasmosis for 2 weeks, lesions enlarge. Brain biopsy shows necrosis with surrounding large cells containing intranuclear inclusions and ground-glass nuclei. JC virus PCR is negative. What explains the unusual presentation and biopsy findings?
A. Disseminated toxoplasmosis with atypical morphology
B. CNS cryptococcosis with granulomatous inflammation
C. Primary CNS lymphoma with EBV-transformed B cells (Correct Answer)
D. Cytomegalovirus encephalitis with microglial nodules
E. Progressive multifocal leukoencephalopathy variant
Explanation: ***Primary CNS lymphoma with EBV-transformed B cells***
- **Primary CNS lymphoma (PCNSL)** is the second most common cause of **ring-enhancing lesions** in AIDS patients (CD4 <50) and typically fails to respond to **anti-toxoplasma therapy**.
- The biopsy findings of large, atypical cells with dense nuclei represent **EBV-infected B cells** that have undergone malignant transformation, often appearing in a characteristic **perivascular distribution**.
*Disseminated toxoplasmosis with atypical morphology*
- While **Toxoplasma gondii** is common, it should show clinical or radiological improvement after 2 weeks of **sulfadiazine and pyrimethamine**.
- Histology would reveal **tachyzoites** and **bradyzoite cysts** rather than large cells with malignant nuclear inclusions and ground-glass features.
*CNS cryptococcosis with granulomatous inflammation*
- **Cryptococcus neoformans** typically presents as **meningitis** or small gelatinous "soap bubble" lesions in the **basal ganglia**, rather than large ring-enhancing masses.
- Diagnosis is usually confirmed via **India ink stain** or **cryptococcal antigen** testing, showing encapsulated yeasts instead of cellular necrosis.
*Cytomegalovirus encephalitis with microglial nodules*
- **CMV encephalitis** in AIDS patients generally presents as **periventricular enhancement** or ventriculitis rather than focal ring-enhancing mass lesions.
- While CMV features large cells with **intranuclear inclusions (Owl's eye)**, these are usually found in the setting of microglial nodules and diffuse encephalitis.
*Progressive multifocal leukoencephalopathy variant*
- **PML** is caused by the **JC virus** and typically presents as **non-enhancing white matter lesions** without mass effect or ring enhancement.
- Although it involves oligodendrocytes with ground-glass inclusions, the **negative JC virus PCR** and MRI findings rule out this diagnosis.
Question 6: A 6-year-old boy presents with seizures and a calcified brain lesion on CT. Surgical resection shows a cystic tumor with a mural nodule. Histology reveals elongated bipolar cells with Rosenthal fibers and eosinophilic granular bodies. The tumor cells are GFAP-positive. Despite complete resection, which factor would most significantly impact long-term prognosis?
A. BRAF V600E mutation status (Correct Answer)
B. Presence of necrosis on histology
C. Extent of perilesional edema
D. Number of mitotic figures per high-power field
E. Patient age at diagnosis
Explanation: ***BRAF V600E mutation status***
- While **pilocytic astrocytoma** (WHO Grade 1) generally has an excellent prognosis, the **BRAF V600E mutation** is associated with a higher risk of recurrence and decreased response to standard therapy.
- This molecular marker is more clinically significant for long-term monitoring than traditional histopathologic features in this low-grade tumor.
*Presence of necrosis on histology*
- In **pilocytic astrocytoma**, necrosis is commonly present as an **infarct-like** phenomenon rather than a sign of malignancy.
- Unlike in high-grade gliomas, the presence of necrosis does not shift the tumor to a higher grade or worsen the prognosis.
*Extent of perilesional edema*
- **Perilesional edema** is a radiologic and clinical indicator of acute mass effect and intracranial pressure but does not determine biological tumor behavior.
- Long-term prognosis in pediatric low-grade gliomas is primarily driven by **molecular drivers** and surgical resectability.
*Number of mitotic figures per high-power field*
- **Pilocytic astrocytomas** are characterized by a very low **mitotic index**; occasional mitoses do not change the WHO Grade 1 status.
- Mitotic count is a poor predictor of outcome for this specific tumor type compared to **molecular alterations** like BRAF status.
*Patient age at diagnosis*
- Age is a significant factor in some pediatric brain tumors, but for **pilocytic astrocytoma**, the tumor remains **indolent** across the pediatric age range.
- Once **complete surgical resection** is achieved, the primary determinants of long-term outcome are genetic mutations rather than the patient's age.
Question 7: A 65-year-old man presents with progressive bradykinesia, resting tremor, and cogwheel rigidity. He later develops visual hallucinations and fluctuating cognition. He dies 8 years after symptom onset. Autopsy shows depigmentation of substantia nigra, and microscopy reveals eosinophilic cytoplasmic inclusions in neurons that are immunoreactive for alpha-synuclein. These inclusions are also found in the cortex. What is the most likely diagnosis?
A. Dementia with Lewy bodies (Correct Answer)
B. Parkinson disease with dementia
C. Progressive supranuclear palsy
D. Corticobasal degeneration
E. Multiple system atrophy
Explanation: ***Dementia with Lewy bodies***
- Characterized by the triad of **parkinsonism**, **fluctuating cognition**, and **visual hallucinations**, with cognitive decline occurring within one year of motor symptoms.
- Histopathology shows **alpha-synuclein** positive eosinophilic inclusions called **Lewy bodies** in both the **substantia nigra** and the **cerebral cortex**.
*Parkinson disease with dementia*
- Clinical diagnosis requires that **motor symptoms** (tremor, rigidity, bradykinesia) precede **dementia** by at least one year.
- While it also features **Lewy bodies**, they are initially localized to the **brainstem** and only reach the cortex in the very late stages of the disease.
*Progressive supranuclear palsy*
- Presents with **vertical gaze palsy**, postural instability, and frequent falls early in the disease course.
- Pathologically characterized by **tau protein** aggregates forming **globose neurofibrillary tangles**, rather than alpha-synuclein inclusions.
*Corticobasal degeneration*
- Features progressive **asymmetric parkinsonism**, limb apraxia, and the **alien limb phenomenon**.
- Histology reveals **tau-positive** neuronal and glial inclusions, specifically **astrocytic plaques** and thread-like lesions in the cortex and basal ganglia.
*Multiple system atrophy*
- Characterized by a combination of parkinsonism, **autonomic dysfunction** (orthostatic hypotension), and **cerebellar ataxia**.
- Histopathology shows **alpha-synuclein** inclusions, but these are uniquely found within **oligodendrocytes** as **glial cytoplasmic inclusions**.
Question 8: A 28-year-old woman presents with vision loss in her right eye and numbness in her left leg that resolved spontaneously over 2 weeks. MRI shows multiple periventricular white matter lesions perpendicular to the lateral ventricles (Dawson fingers). Lumbar puncture reveals oligoclonal bands and elevated IgG index. Which pathologic finding would be expected on brain biopsy?
A. Perivenular demyelination with relative axonal preservation (Correct Answer)
B. Concentric layers of demyelination and remyelination (onion bulbs)
C. Spongiform vacuolation of grey matter
D. Lewy bodies in substantia nigra neurons
E. Neurofibrillary tangles and neuritic plaques
Explanation: ***Perivenular demyelination with relative axonal preservation***
- This finding is the hallmark of **Multiple Sclerosis (MS)**, where autoimmune attacks target **oligodendrocytes**, causing plaques in the **white matter**.
- The preservation of **axons** (relative to the loss of myelin) is a key diagnostic feature, especially in the presence of **Dawson fingers** and **oligoclonal bands**.
*Concentric layers of demyelination and remyelination (onion bulbs)*
- This is characteristic of **Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)** or **Charcot-Marie-Tooth disease**, involving the **peripheral nervous system**.
- It represents repeated cycles of **segmental demyelination** and Schwann cell proliferation, rather than **CNS white matter** plaques.
*Spongiform vacuolation of grey matter*
- This finding is typical of **Prion diseases**, such as **Creutzfeldt-Jakob Disease (CJD)**, which present with rapidly progressive dementia.
- It involves the formation of **small vacuoles** within the neuropil and neurons, unlike the **inflammatory demyelination** seen in MS.
*Lewy bodies in substantia nigra neurons*
- These are **alpha-synuclein** inclusions pathognomonic for **Parkinson's disease**, leading to motor symptoms like **bradykinesia** and resting tremors.
- This pathology affects **deep grey matter** nuclei rather than the **periventricular white matter** lesions seen in this patient.
*Neurofibrillary tangles and neuritic plaques*
- These are the classic pathologic markers for **Alzheimer's Disease**, involving **hyperphosphorylated tau** and **amyloid-beta** deposition.
- They primarily affect the **cerebral cortex** and **hippocampus**, resulting in cognitive decline rather than **focal neurological deficits** like vision loss.
Question 9: A 72-year-old man with a history of chronic hypertension presents with sudden onset right hemiparesis and aphasia. CT scan shows a hyperdense lesion in the left basal ganglia with surrounding edema and mass effect. He dies 48 hours later. Autopsy reveals a cavity filled with blood clot and hemosiderin-laden macrophages. Which vessels were most likely affected?
A. Posterior cerebral artery perforating branches
B. Superior cerebellar artery branches
C. Anterior choroidal artery branches
D. Lenticulostriate branches of the middle cerebral artery (Correct Answer)
E. Anterior communicating artery branches
Explanation: ***Lenticulostriate branches of the middle cerebral artery***
- These small penetrating arteries are the most common site of **hypertensive intracerebral hemorrhage**, specifically involving the **basal ganglia** (putamen) and internal capsule.
- Chronic hypertension leads to **Charcot-Bouchard microaneurysms** and **lipohyalinosis**, making these vessels prone to rupture and subsequent hematoma formation.
*Posterior cerebral artery perforating branches*
- These branches typically supply the **thalamus** and midbrain; while a site for hypertensive bleeds, they do not primarily supply the **basal ganglia**.
- Rupture here usually results in **pure sensory loss** or thalamic syndromes rather than the motor hemiparesis and aphasia described.
*Superior cerebellar artery branches*
- These vessels supply the **cerebellum** and midbrain; an injury here would present with **ataxia**, vertigo, and nausea.
- They are not associated with **aphasia** or the specific CT finding of a left basal ganglia lesion.
*Anterior choroidal artery branches*
- This artery supplies the **optic tract**, choroid plexus, and parts of the internal capsule, but is a less frequent site for spontaneous hypertensive hemorrhage.
- Obstruction or rupture would typically cause a clinical triad of **hemiplegia**, hemianesthesia, and **homonymous hemianopia**.
*Anterior communicating artery branches*
- This is the most common site for **saccular (berry) aneurysms**, which typically cause **subarachnoid hemorrhage** rather than focal intraparenchymal bleeding.
- A bleed here usually presents with a sudden "**worst headache of life**" and blood localized within the cisterns on a CT scan.
Question 10: A 45-year-old woman presents with progressive weakness, ataxia, and dementia over 6 months. MRI shows diffuse cortical atrophy and T2 hyperintensities in the basal ganglia. EEG demonstrates periodic sharp wave complexes. CSF analysis shows elevated 14-3-3 protein and normal cell count. Brain biopsy reveals spongiform changes and no inflammation. What is the most likely underlying pathogenic mechanism?
A. Accumulation of misfolded prion protein (PrPSc) (Correct Answer)
B. Autoimmune antibodies against neuronal surface antigens
C. Progressive demyelination due to oligodendrocyte loss
D. Accumulation of hyperphosphorylated tau protein
E. Deposition of beta-amyloid plaques
Explanation: ***Accumulation of misfolded prion protein (PrPSc)***
- This patient presents with **Creutzfeldt-Jakob disease (CJD)**, characterized by rapid **progressive dementia**, ataxia, and **periodic sharp wave complexes** on EEG.
- The pathogenesis involves the conversion of normal **PrPC** into the abnormal **PrPSc** isoform, leading to **spongiform degeneration** and the presence of **14-3-3 protein** in CSF.
*Autoimmune antibodies against neuronal surface antigens*
- This describes **Autoimmune Encephalitis** (e.g., Anti-NMDA receptor encephalitis), which typically reveals a **pleocytosis** on CSF analysis unlike this case.
- While it causes rapid cognitive decline, it lacks the characteristic **spongiform changes** and specific EEG findings seen in CJD.
*Progressive demyelination due to oligodendrocyte loss*
- This mechanism is characteristic of **Progressive Multifocal Leukoencephalopathy (PML)**, usually associated with **JC virus** reactivation in immunocompromised patients.
- MRI in PML shows focal white matter lesions rather than the **diffuse cortical atrophy** and basal ganglia involvement seen here.
*Accumulation of hyperphosphorylated tau protein*
- Tau pathology is central to **Alzheimer's disease** (neurofibrillary tangles) and **Frontotemporal dementia**, which typically progress over years rather than months.
- These conditions do not present with **periodic sharp waves** on EEG or the specific CSF marker **14-3-3 protein**.
*Deposition of beta-amyloid plaques*
- Extracellular **amyloid-beta plaques** are the hallmark of chronic neurodegeneration in **Alzheimer's disease**.
- This mechanism does not explain the **spongiform vacuolation** of the neuropil or the acute clinical deterioration observed in this patient.
