Title : When pneumococcal meningoencephalitis masquerades as stroke: Recognizing the immune turning point
Abstract:
Background: In patients with pneumococcal meningoencephalitis, neurological worsening is often reflexively labeled as ischemic stroke or failure of antimicrobial therapy. However, apparent clinical recovery can be deceptive. A hidden immune-mediated phase may emerge after infection control, where vascular inflammation—not active infection—drives brain injury. Failure to recognize this biological switch represents a dangerous diagnostic trap.
Objective: To demonstrate immune-mediated cerebral vasculitis as a critical and under-recognized cause of delayed neurological deterioration in pneumococcal meningoencephalitis and to highlight the importance of identifying this therapeutic turning point.
Methods: We present two adults with microbiologically confirmed Streptococcus pneumoniae meningoencephalitis who initially improved on appropriate antimicrobial therapy. In the first patient, early MRI suggested uncomplicated meningitis, followed by evolution of micro-abscesses and vasculitic infarcts without immediate clinical decline. Steroids were tapered as per routine practice, after which abrupt neurological deterioration occurred. Repeat MRI revealed progression of inflammatory lesions, prompting escalation of corticosteroid therapy with dramatic clinical recovery. Applying this insight, steroid tapering was deliberately deferred in the second patient with similar clinical and radiological features.
Results: Both patients exhibited a biphasic disease course, with delayed neurological deterioration characterized by infarct-like lesions mimicking stroke despite microbiological control. Serial MRI supported an immune-mediated vasculitic process. Targeted continuation or escalation of corticosteroids resulted in marked neurological improvement and radiological resolution in both cases.
Conclusion: Not every infarct in pneumococcal meningoencephalitis is a stroke. Delayed deterioration may signal an immune-mediated turning point identifiable on evolving MRI. Recognizing this moment is crucial, as timely immunomodulation—rather than antibiotic escalation or antithrombotic therapy—can lead to neurological salvage.
