Unilateral cortical autoimmune encephalitis: A case series and comparison to late-onset Rasmussen's encephalitis

Abstract

Objective

To report a novel anatomical pattern of autoimmune encephalitis characterized by strictly unilateral cortical inflammation and a clinical picture overlapping with late-onset Rasmussen's encephalitis.

Methods

We retrospectively gathered data of patients identified at two tertiary referral academic centers who met inclusion criteria.

Results

We identified twelve cases (average age 65, +/− 19.8 years, 58% female). All patients had unilateral cortical inflammation manifesting with focal seizures, cognitive decline, hemicortical deficits, and unilateral MRI and/or EEG changes. Six cases were idiopathic, two paraneoplastic, two iatrogenic (in the setting of immune checkpoint inhibitors), and two post-COVID-19. Serologically, ten patients were seronegative, one had high titer anti-GAD65, and one had anti-NMDAR. Five patients met Rasmussen's encephalitis criteria, and six did not fully meet the criteria but had symptoms significantly overlapping with the condition. Most patients had significant improvement with immunotherapy.

Discussion

Unilateral cortical AE seems to be more prevalent in the elderly and more frequently idiopathic and seronegative. Patients with this anatomical variant of autoimmune encephalitis have overlapping features with late-onset Rasmussen's encephalitis but are more responsive to immunotherapy. In cases refractory to immunotherapy, interventions used in refractory Rasmussen's encephalitis may be considered, such as functional hemispherectomy.