Case Presentation: A 41-year-old male with a history of intravenous drug use presented with status epilepticus. His seizures were preceded by episodic catatonia, hallucinations, and paranoia over the last two months. He was intubated and admitted to the ICU for evaluation of acute encephalopathy and seizures. Collateral history revealed absence of fevers or headache, and nuchal rigidity was not present. Labs were remarkable for positive herpes simplex IgG, and reactive RPR; drug screen, HIV and Lyme titers were negative. Continuous EEG revealed epileptiform activity. Computed tomography of the head was negative for acute processes, but MRI T2/FLAIR was remarkable for contrast enhancement symmetrically in bilateral temporal lobes, suspicious for HSV encephalitis. Acyclovir was initiated as well as broad spectrum coverage with vancomycin, ceftriaxone, and doxycycline, awaiting further studies. A lumbar puncture revealed lymphocytic pleocytosis and positive VDRL. Serum RPR was positive at 1:16. An autoimmune encephalitis panel and HSV PCR were negative. Acyclovir was discontinued at 2 days, and treatment was narrowed to penicillin. The patient improved clinically and repeat MRI head showed improvement of previous abnormalities.
Discussion: Classically, syphilis is subdivided into three stages: primary, secondary, and tertiary, with progressively worsening symptomatology. Central nervous system involvement can occur at any stage of disease and is classified as early or late neurosyphilis. Disease can be asymptomatic or present with variable clinical symptoms. Early symptoms include meningitis and meningovascular disease while late neurosyphilis involves the brain and spinal cord, presenting with memory deficits, dementia, and psychiatric symptomatology or general paresis, ocular findings and tabes dorsalis. Our patient was diagnosed with encephalitis with temporal lobe enhancement, a typical presentation for HSV or autoimmune encephalitis. However, HSV PCR and autoimmune evaluations were negative, and he improved despite discontinuation of acyclovir after 2 days. Syphilitic encephalitis is very rare but is reported, and mimics both autoimmune and HSV encephalitis. Temporal lobe abnormalities can be seen on imaging, and patients present with cognitive changes (71%), seizures (54%), and/or psychiatric symptoms (50%). Treatment with high dose penicillin is recommended. Ceftriaxone and doxycycline are alternative therapies for those with penicillin allergy.
Conclusions: This case reminds physicians of the variable presentations of neurosyphilis, including symptomatology and imaging features that mimic autoimmune and HSV encephalitis. Testing for syphilis must be included in patients presenting with presumed viral or autoimmune encephalitis to ensure appropriate treatment.
