Introduction: Herpes simplex virus type 1 encephalitis is the most common cause of sporadic fatal encephalitis worldwide. Typical presentation includes fever, altered mental status, focal cranial nerve deficits, and seizures. Diagnosis is confirmed by polymerase chain reaction of CSF with very high sensitivity of 98% and specificity of 94% .Atypical symptoms include urinary and fecal incontinence, aseptic meningitis, Guillan-Barre syndrome, amnesia, Kluver-Bucy syndrome, and hypomania. This case demonstrates syncope secondary to sinoatrial dysfunction as an atypical presenting symptom. Case Description: A 50 year old male with a past medical history of childhood traumatic brain injury and hepatitis B on Entecavir presented to the hospital after new onset syncopal episodes. On exam he was afebrile and tachycardic. WBC count was 14,000, , K+ 2.8, and lactate 3.7. Antibiotics were briefly initiated but not continued due to lack of source. Potassium was replaced and patient was preparing for discharge when another syncopal event occurred. Telemetry showed sinus pauses greater than 10 seconds. Electrophysiology was consulted and performed heart catheterization and pacemaker placement. The next day he developed fever of 39.2 C, altered mental status, and seizure. He was transferred to the ICU and started on broad spectrum antibiotics and acyclovir. Electroencephalography showed left frontotemporal epileptogenicity and CTA and CT head were noncontributory. Lumbar puncture had normal cytology, negative PCR for herpes and echoviruses, and negative antibodies for flaviviridae. Acyclovir was discontinued, antiepileptic medication started, and antibiotics were changed to rule out drug fever. Fevers up to 40 degrees continued despite thorough source investigation and advanced cooling efforts. A second lumbar puncture was competed which showed lymphocytic pleocytosis and a CT head with contrast showed a new enhancing focus of the mesial left temporal lobe. Despite negative culture data, our clinical suspicion remained very high for herpes encephalitis so acyclovir was then restarted. Several days later culture data from both spinal fluid samples became positive for herpes simplex 1. His fever broke, he showed clinical improvement on antiretroviral therapy, and he was discharged home several days later in stable condition.

Discussion: In this case, the patient presented with syncope and then developed typical findings of HSV1 encephalitis but the misleading negative HSV PCR led to disregarding the correct diagnosis. This resulted in a delay in care until unsurmountable evidence forced a clinical diagnosis which was then later reinforced by corrected objective data. Herpes Simplex Virus 1 has been known to precipitate encephalopathy and seizures but significant viral load causing sinoatrial conduction abnormalities is less described. It is thought that SA node dysfunction is secondary to autonomic dysfunction in the central nervous system rather than myocardial involvement evidenced by autopsy examination. Be aware of atypical presentations of HSV encephalitis as well as the potential for clinical and laboratory disparity in order to not miss this life-threatening illness.