MRI findings in autoimmune voltage-gated potassium channel complex encephalitis with seizures: one potential etiology for mesial temporal sclerosis

Abstract

Background and purpose: Autoimmune voltage-gated potassium channel complex encephalitis is a common form of autoimmune encephalitis. Patients with seizures due to this form of encephalitis commonly have medically intractable epilepsy and may require immunotherapy to control seizures. It is important that radiologists recognize imaging characteristics of this type of autoimmune encephalitis and suggest it in the differential diagnosis because this seizure etiology is likely under-recognized. Our purpose was to characterize MR imaging findings in this patient population.

Materials and methods: MR imaging in 42 retrospectively identified patients (22 males; median age, 56 years; age range, 8-79 years) with seizures and voltage-gated potassium channel complex autoantibody seropositivity was evaluated for mesial and extratemporal swelling and/or atrophy, T2 hyperintensity, restricted diffusion, and enhancement. Statistical analysis was performed.

Results: Thirty-three of 42 patients (78.6%) demonstrated enlargement and T2 hyperintensity of mesial temporal lobe structures at some time point. Mesial temporal sclerosis was commonly identified (16/33, 48.5%) at follow-up imaging. Six of 9 patients (66.7%, P = .11) initially demonstrating hippocampal enhancement and 8/13 (61.5%, P = .013) showing hippocampal restricted diffusion progressed to mesial temporal sclerosis. Conversely, in 6 of 33 patients, abnormal imaging findings resolved.

Conclusions: Autoimmune voltage-gated potassium channel complex encephalitis is frequently manifested as enlargement, T2 hyperintensity, enhancement, and restricted diffusion of the mesial temporal lobe structures in the acute phase. Recognition of these typical imaging findings may help prompt serologic diagnosis, preventing unnecessary invasive procedures and facilitating early institution of immunotherapy. Serial MR imaging may demonstrate resolution or progression of radiologic changes, including development of changes involving the contralateral side and frequent development of mesial temporal sclerosis.

Fig 1.

A 66-year-old man with autoimmune VGKC epilepsy. Coronal FLAIR at presentation (A), 7-month follow-up (B), and 46-month follow-up (C) demonstrate progression from unilateral increased signal intensity and enlargement of the left hippocampus (A) to left MTS (arrow, B) and finally progression to bilateral MTS (arrows, C).

Fig 2.

A 25-year-old man with autoimmune VGKC epilepsy. Imaging at presentation demonstrates enlargement and increased signal intensity in the bilateral hippocampi (A) and bilateral amygdalae (B) on coronal FLAIR, with faint ill-defined enhancement (arrowheads) of the hippocampi (C) on coronal contrast-enhanced T1. Follow-up coronal FLAIR imaging (D) at 4 years demonstrates progression to bilateral MTS (arrows).

Fig 3.

A 60-year-old man with autoimmune VGKC epilepsy. Initial imaging findings (not shown) were normal. At 1-month follow-up, axial diffusion-weighted imaging demonstrates restricted diffusion in the left hippocampus (A), left perisylvian cortex (arrowheads), and right caudate nucleus (arrow, B). Axial FLAIR (C) shows enlargement and increased signal intensity of the left hippocampus, and axial contrast-enhanced T1-weighted image (D) shows faint ill-defined enhancement (arrowheads) in the left hippocampus. Coronal FLAIR (E) 3 years after presentation shows progression to left MTS (arrow).

Fig 4.

Time to development of MTS from initial MR imaging abnormality.

Fig 5.

A 74-year-old man with autoimmune VGKC epilepsy. Coronal FSE T2 image (A) shows mild enlargement and increased signal in the right hippocampus. Follow-up coronal FSE T2 (B) at 1 year shows resolution of hyperintense signal and enlargement of the right hippocampus.