A Case of Postinfectious Autoimmune Encephalitis Recovery Without Long-term Management

Abstract

Background: Postinfectious autoimmune encephalitis has been established as a disease mechanism after herpes simplex virus encephalitis (HSVE) and is generally associated with the presence of N-methyl-D-aspartate receptor (NMDAR) antibodies but is not necessarily limited to these.1,2,3 Presentation neuropsychiatric symptoms that develop 3-6 weeks following the initial infection and should prompt the search for underlying autoantibodies, though they are not always present. While symptom improvement has been seen and documented with corticosteroid, plasma separation, immunoglobulin, and rituximab treatment, there are no set guidelines on the length of treatment needed for symptom resolution and relapse prevention.1,2,3,4 Results: This is a 71-year-old woman who presented with altered mental status and seizure-like activity in the setting of fever. MRI brain showed FLAIR changes in bilateral medial frontal and L temporal/insula region. CSF analysis revealed WBC 58 and HSV1 PCR positive - consistent with HSV-1 encephalitis. Her Mayo autoimmune encephalitis panel was negative. She completed a 21-day course of acyclovir and after a 2-month long hospitalization she was eventually able to return home with only mild cognitive deficits. However, a month post discharge, she started having seizure-like activity with agitation and behavioral disturbances found to be profoundly bradycardic requiring urgent pacemaker placement. Extensive workup including LP and continuous EEG were negative for ongoing seizure activity or recurrence of HSV encephalitis. She was treated with a 5-day course of IV methylprednisolone followed by 2g/kg IVIG without significant improvement in her altered mental status. Mayo autoimmune encephalitis panel was again negative. Family declined further immunosuppressive treatment and 3 weeks post admission decided to pursue hospice. About 6 weeks post discharge to hospice, she had significant recovery in mentation and decline in episodes of agitation. She only received phenobarbital for seizure management during her hospice stay. She is currently one year post discharge from hospice without any new symptoms and is not on any long-term immunosuppressive agents. Repeat MRI is stable. Discussion: No specific standard guidelines currently exist for the management of postinfectious autoimmune encephalitis. Many patients are treated with various immunosuppressive agents for a varying time frame depending on clinical course and physician preference. Current practices for long-term treatment of autoimmune encephalitis as found by one study show that 38% of physicians used an oral prednisone taper while 46% used rituximab.5 However, as seen in this case presentation, the patient achieved remission without a long-term treatment, which warrants a further dive into understanding the efficacy of long-term treatment options and practices. Conclusions: Relapse of autoimmune encephalitis has been seen with and without long-term treatment, which warrants a further dive into understanding the efficacy and duration of long-term treatment options.