MI6.1-3 | Central Nervous System Infections — Graded Quiz

A 3-week-old neonate is admitted with fever (38.8°C), high-pitched cry, and opisthotonus. LP shows turbid CSF with 4,200 WBC/mm³ (88% neutrophils). Gram stain of the CSF pellet reveals gram-positive rods with a tumbling motility pattern on wet mount. Which empiric antibiotic should be added to cefotaxime to cover the most likely organism?

A 68-year-old diabetic man on immunosuppressive therapy presents with fever, neck stiffness, and confusion. LP shows 1,200 WBC/mm³ (90% neutrophils), protein 380 mg/dL, glucose 12 mg/dL. Gram stain shows gram-positive lancet-shaped diplococci. Blood cultures are pending. Which host factor MOST directly predisposes this patient to this organism?

A 42-year-old HIV-positive man (CD4 count 38 cells/μL) presents with 3 weeks of progressive headache, blurred vision, and vomiting. LP opening pressure is 420 mm H₂O. CSF shows 15 WBC/mm³ (lymphocytes), protein 110 mg/dL, glucose 28 mg/dL. India ink is positive. Serum CrAg titre is 1:2048. Which CSF parameter MOST directly explains his raised intracranial pressure?

A 45-year-old woman presents with subacute headache (4 weeks), weight loss, and night sweats. She is non-HIV. LP: 240 WBC/mm³ (80% lymphocytes), protein 190 mg/dL, glucose 22 mg/dL (blood glucose 88 mg/dL). ZN stain is negative. GeneXpert Ultra (CBNAAT) on CSF returns: MTB DETECTED, rifampicin resistance NOT DETECTED. Adenosine deaminase (ADA) level is 18 IU/L. Which statement about CBNAAT in TBM is MOST accurate?

A 17-year-old student develops fever (39.5°C), severe headache, photophobia, and a rapidly spreading non-blanching petechial rash on the lower limbs. On examination: Kernig's sign positive, GCS 13/15. LP is performed after CT head (normal). CSF: 2,800 WBC/mm³ (95% neutrophils), glucose 8 mg/dL, protein 410 mg/dL. Gram stain shows gram-negative diplococci. Which additional systemic complication is MOST important to monitor for in this patient?

A 32-year-old software engineer is admitted with 6 days of fever, frontal headache, personality change (inappropriate laughing, hypersexual behaviour), and two witnessed generalised seizures. MRI T2/FLAIR shows hyperintense signal in the right temporal and inferior frontal lobes with mild haemorrhagic changes. CSF PCR for HSV-1 is ordered. While awaiting results, which management step is MOST critical?

During a monsoon-season outbreak of acute encephalitis in rural Uttar Pradesh, 12 children aged 5–12 years are admitted with high fever, acute-onset altered consciousness, and seizures. Serum IgM MAC-ELISA for JEV is positive in 9 of 12 cases. On MRI, lesions are noted in the thalamus and basal ganglia bilaterally. Which statement about the pathogenesis of thalamic involvement in JE is MOST accurate?

A microbiologist receives a CSF specimen and must perform a Gram stain for suspected bacterial meningitis. She centrifuges the CSF at 3,000 rpm for 10 minutes and uses the sediment for the smear. Why is centrifugation of CSF critical before preparing a Gram stain smear?

A 16-year-old boy swam in a warm stagnant pond in Odisha 4 days ago. He now presents with severe frontal headache, high fever (40°C), neck stiffness, photophobia, and confusion. He deteriorates rapidly over 24 hours. CSF is turbid and haemorrhagic; wet mount shows actively motile amoebic trophozoites. No bacteria are isolated on culture. Which organism is responsible and what is the prognosis?

A 2-month-old infant is admitted with fever, high-pitched cry, and a full fontanelle. The attending intern plans to start ceftriaxone alone. The attending paediatrician insists on adding ampicillin before LP results. The intern questions this decision, pointing out the CSF Gram stain shows gram-negative rods (likely E. coli). Why should ampicillin still be added at this age, even with gram-negative rods on stain?

A post-mortem brain biopsy from a 55-year-old farmer who died after a 12-day encephalitic illness shows intracytoplasmic eosinophilic inclusion bodies in the Purkinje cells of the cerebellum and pyramidal neurons of the hippocampus on H&E staining. He had been bitten by an unvaccinated dog 3 months previously but received only 2 of 5 scheduled post-exposure prophylaxis doses. These inclusion bodies are MOST specifically diagnostic of:

A 50-year-old man with known pulmonary tuberculosis (on RIPE therapy for 3 months) develops subacute worsening headache, vomiting, and diplopia (right VI nerve palsy). LP shows lymphocytic pleocytosis 220/mm³, protein 210 mg/dL, glucose 24 mg/dL. GeneXpert Ultra on CSF returns MTB DETECTED with RIFAMPICIN RESISTANCE DETECTED. Which therapeutic change is MOST appropriate?