Neuroimaging of six neurosyphilis cases mimicking viral encephalitis.

BACKGROUND: Neurosyphilis is known as "the great imitator" due to its wide range of clinical symptoms and abnormalities upon magnetic resonance imaging (MRI). Typical findings of both neurosyphilis and viral encephalitis include unilateral or bilateral MR hyperintensities in mesiotemporal lobes upon T2-weighted imaging or fluid attenuation inversion recovery (FLAIR) imaging. Accordingly, patients with neurosyphilis are frequently misdiagnosed with viral encephalitis, which prevents them from receiving appropriate treatment and often results in greater neurologic damage.
METHODS: Clinical characteristics and MRI changes of 6 neurosyphilis patients admitted to our hospital between March 2012 and November 2012 were retrospectively reviewed.
RESULTS: All 6 cases were tested positive for assays measuring Treponema pallidum hemagglutination (TPHA), rapid plasma reagin (RPR), and antibodies against syphilis in the serum and cerebrospinal fluid (CSF). Likewise, all patients were negative for antibodies against viral pathogens. T2-weighted or FLAIR MRI of the brains in all cases revealed either unilateral or bilateral hyperintensities in the mesiotemporal lobes, including the hippocampi. Electroencephalography showed relevant, localized slow or spiked waves. Patient prognoses were good in the 4 cases that received early anti-syphilis treatment, but the 2 cases that received delayed treatment due to misdiagnoses did not see substantial symptomatic improvements.
CONCLUSIONS: Neurosyphilis should be considered when there is mesiotemporal involvement upon MRI. Early treatment for syphilis is critical for positive outcomes.