When a patient presents with sudden neurological changes accompanied by a fever, the diagnostic focus naturally shifts toward central nervous system pathology. Encephalitis, meningitis, or intracranial vascular events usually top the list of differential diagnoses. However, systemic viral illnesses can occasionally present with subtle neurological manifestations before classic systemic symptoms like jaundice become evident. Understanding these atypical presentations is essential for emergency physicians, neurologists, and general practitioners.
The Clinical Presentation
Consider a young, immunocompetent male who presented with a high-grade fever, generalized body aches, and malaise lasting two days. Shortly after experiencing multiple episodes of bilious vomiting, he experienced a brief period of altered mental status. For approximately six hours, he remained conscious but was entirely unable to communicate with those around him, accompanied by a transient vacant stare. Interestingly, he retained partial recall of the event, and the episode resolved spontaneously without leaving focal neurological deficits.
Initial laboratory evaluations revealed markedly elevated liver enzymes—SGOT and SGPT levels soared into the thousands—alongside mild thrombocytopenia and mild acute kidney injury. Surprisingly, initial physical examinations showed no jaundice. Standard cerebrospinal fluid (CSF) analysis and electroencephalogram (EEG) studies were within normal limits.
Radiological Breakthrough: MERS
The crucial diagnostic clue appeared on magnetic resonance imaging (MRI) of the brain. Diffusion-weighted imaging (DWI) demonstrated restricted diffusion strictly localized to the splenium of the corpus callosum. This neuroimaging finding, in the context of a resolving transient encephalopathy, points directly toward Mild Encephalopathy with Reversible Splenial Lesion (MERS).
Unlike classic, non-reversible lesions in the corpus callosum, MERS typically runs a benign, self-limiting course. Patients rarely exhibit severe hemispheric disconnection syndromes—such as alien hand syndrome, apraxia, alexia, or agraphia—commonly linked to anatomical disruptions in this central white matter tract.
Unraveling the Underlying Etiology
As the clinical picture unfolded, the patient eventually developed overt scleral icterus. Targeted viral serology confirmed acute Hepatitis A virus (HAV) infection, positive for anti-HAV IgM. While HAV typically presents as an acute enteric illness marked by jaundice, fatigue, and right upper quadrant discomfort, extrahepatic manifestations can occur. The transient neurological event in this setting was an immune-mediated secondary response rather than direct central nervous system invasion by the virus.
Key Takeaways for Clinicians
This case highlights two critical clinical lessons:
Atypical Initial Presentations: Systemic infectious agents like Hepatitis A can manifest with neurological symptoms before overt hepatic markers (such as jaundice) fully develop.
Recognizing MERS: Identifying splenial diffusion restriction on MRI in a patient with acute confusion should prompt a search for systemic infectious, metabolic, or post-ictal triggers. Recognizing MERS prevents unnecessary invasive testing and reassures clinicians and patients of a favorable prognosis.