Acyclovir is effective in treating the herpes virus infection, especially chickenpox and shingles. Hyponatremia caused by acyclovir has been rarely reported. We present a shingles patient with symptomatic hyponatremia that was presumably caused by acyclovir affecting the hypothalamus or posterior pituitary gland. This case demonstrates that the serum electrolyte levels should be checked regularly and careful observation of symptoms such as nausea, convulsions, or mentality change is necessary in patients treated with acyclovir.

A 59-year old man was admitted for drowsiness and stiff neck. CSF examination showed lymphocytic pleocytosis and PCR for herpes simplex virus (HSV)-1 was positive in CSF. Brain MRI revealed enhanced lesions in left temporal lobe. His symptom improved with acyclovir. Follow-up studies showed red blood cells in CSF and a hematoma in the left temporal lobe. There was no additional symptom related to the hematoma. He was discharged after conservative care. Although rare, hematoma can develop in HSV-1 meningoencephalitis.

Background
: Bell's palsy(BP) is defined as an idiopathic peripheral facial paralysis of sudden onset and account more than 50% of facial paralysis. It's etiology is unclear, but herpes simplex virus type-1 (HSV-1) has been the most suspicious causative agent of BP that over been studied. We evaluated the effect of add-on acyclovir in acute stages of BP. Methods : Subject consisted of 35 patients who developed acute within 10 days after onset of BP. Facial nerve function was assessed by the House-Brackman facial nerve grading scale and facial nerve conduction study including blink reflex. Follow-up evaluation were made 2 month after onset. Twenty of 35 patients were treated with combined therapy of acyclovir and prednisone. As a control group, 15 patients were treated with prednisone only. We compared the improvement of neurologic defects at recovery phase. Results : Compared with two groups, difference in grading scale at recovery phase is statistically significant(p<0.01). So, acyclovir-prednisone group showed a significant improvement in grading at recovery phase compared with prednisone group. Conclusion : We identified the benefit of add-on acyclovir in the acute stage of BP