Objective:

To describe a rare case of neurosyphilis with mesiotemporal involvement on neuroimaging mimicking HSV encephalitis.

Background:

As the incidence of syphilis continues to rise worldwide, it remains crucial for clinicians to recognize the diverse clinical manifestations of neurosyphilis. Imaging patterns of neurosyphilis can have considerable variability, ranging from syphilitic myelitis to thalamic, hippocampal, or mesiotemporal lobe involvement. An early and accurate diagnosis of neurosyphilis is essential given the profound implications for treatment.

Design/Methods:

N/A

Results:

A 35-year-old male presented with seizures. T2-FLAIR MRI showed abnormal cortical hyperintensities with speckled enhancement in the left medial temporal lobe including hippocampus, left insular cortex, and left anteromedial frontal lobe. There were also subtle hyperintensities in the left medial thalamus and right caudate head as well. CSF sampling on two occasions showed lymphocytic pleocytosis but tested negative for HSV1/2 PCR. The patient’s sexual partner endorsed a history of treatment for syphilis so empiric antibiotic treatment for neurosyphilis was initiated. Serum RPR and CSF VDRL titers (1:8) returned positive. Subsequent confirmatory testing for Treponema pallidum antibodies also returned positive. The patient responded clinically to a 14-day course of intravenous penicillin G.

Conclusions:

Mesiotemporal involvement on MRI is a rare finding of neurosyphilis that can radiographically mimic HSV encephalitis. In patients presenting with altered mental status and seizures with said imaging findings, thorough history should be obtained for the consideration of neurosyphilis.