Herpes simplex encephalitis presenting as stroke-like symptoms with atypical MRI findings and lacking cerebrospinal...

Area of Science:

• Neurology
• Infectious Diseases
• Neuroimaging

Background:

• Herpes simplex encephalitis (HSE) is a severe neurological infection often associated with characteristic temporal lobe involvement on MRI and cerebrospinal fluid (CSF) pleocytosis.
• Early diagnosis and treatment with antiviral agents like acyclovir are critical for improving outcomes in HSE.

Observation:

• A 73-year-old woman presented with stroke-like symptoms (hemiparesis) and left parietal lesions on diffusion-weighted MRI, initially diagnosed as cerebral infarction.
• The patient subsequently developed myoclonus, aphasia, altered consciousness, and fever, prompting transfer with suspected viral encephalitis.
• Brain MRI revealed lesion expansion to the cingulate gyrus, insula, and thalamus, notably sparing the temporal lobes throughout the clinical course.

Findings:

• Herpes simplex virus DNA was detected in the CSF, confirming HSE.
• Despite confirmed HSE, the patient exhibited an absence of CSF pleocytosis and atypical MRI findings without temporal lobe involvement.
• The clinical presentation was characterized by an initial stroke-like episode followed by progressive neurological deterioration.

Implications:

• This case highlights the importance of considering atypical presentations of HSE, which may not conform to classic diagnostic criteria.
• Physicians should maintain a high index of suspicion for HSE in patients with unexplained neurological deficits, even with non-specific CSF findings or unusual MRI patterns.
• Prompt initiation of empirical acyclovir treatment is essential in suspected HSE cases to prevent severe neurological sequelae, pending definitive diagnosis.