Acute radiological features facilitate diagnosis and prognosis of anti-N-methyl-d-aspartate receptor (NMDAR) and anti-voltage-gated potassium channel (VGKC) encephalitis in adults

Background: Anti-N-methyl-d-aspartate receptor (NMDAR) and anti-voltage-gated potassium channel (VGKC) encephalitis are the commonest antibody-associated autoimmune encephalitides (AIE). Acute clinical features have been well-described, but data on the role of radiological findings in diagnosis and prognosis of AIE are limited.

Methods: Anti-NMDAR and anti-VGKC encephalitis patients from the National Neuroscience Institute were identified. We compared clinical and paraclinical features, at acute presentation and on follow-up between and within groups.

Results: Twenty-six anti-NMDAR and 11 anti-VGKC encephalitis patients were reviewed. At acute presentation, dysautonomia (57.7%) and impairment of consciousness (84.6%) occurred exclusively in anti-NMDAR encephalitis. Cerebrospinal fluid pleocytosis was more common in anti-NMDAR encephalitis (88.5% vs 20.0%, p = 0.003), while ictal electroencephalography abnormalities were more frequent in anti-VGKC encephalitis (11.5% vs 45.5%, p = 0.022). On acute imaging, leptomeningeal enhancement was seen only in anti-NMDAR encephalitis (37.5%), while hippocampal T2 hyperintensities supported the diagnosis of anti-VGKC encephalitis (63.6% vs 12.5%, p = 0.002). At follow-up (median 53.0 months, range 13.0-119.0), anti-NMDAR encephalitis patients had better modified Rankin scale scores (median 0.0 vs 3.0, p = 0.023). Relapses occurred equally in both groups. Anti-VGKC encephalitis patients with abnormal acute MRI were more likely to have poor outcomes compared to those with normal imaging (100% vs 25%, p = 0.008), whereas acute imaging features in anti-NMDAR encephalitis did not predict long-term outcomes.

Conclusions: Acute MRI findings can aid in early diagnosis and prognostication in suspected AIE. Leptomeningeal enhancement in anti-NMDAR encephalitis and hippocampal lesions in anti-VGKC encephalitis, together with typical clinical features, may allow distinction between these antibody subtypes, and specific abnormal imaging features in anti-VGKC encephalitis may be used as a prognostic marker.