Autoimmune encephalitis as an increasingly recognised cause of non-convulsive status epilepticus: A retrospective, multicentre evaluation of patient characteristics and electroencephalography (EEG) results

Abstract

Status epilepticus (SE) is a severe condition of unrelenting seizures requiring urgent identification and treatment. SE may be unprovoked, occurring in someone with epilepsy, or may be provoked by acute intracranial disease or metabolic derangement. Increasingly encephalitis, particularly autoimmune types, is reported to cause refractory seizures. Whilst convulsive SE is readily identified, non-convulsive SE (NCSE) can be difficult to identify clinically, and electroencephalography (EEG) is required. Therefore, it is critical to identify the key clinical features associated with NCSE on EEG to inform future use of EEG. Methods: We conducted a multicentre, retrospective analysis of EEG requests from four general and one specialist neurology hospital in the Northwest of England (2015England ( -2018. Cases were identified from EEG requests for patients with suspected NCSE or other indications such as encephalopathy. We compared demographic and clinical characteristics between EEG-confirmed cases of NCSE and a randomly selected sample of negative controls. Results: 358 EEGs were reviewed, and 8 positive cases of NCSE were identified. Epilepsy was identified as the aetiology in 2 of these cases, and autoimmune encephalitis another 2 cases (one patient with N-methyl-D-aspartate receptor antibodies and another with voltage gated potassium channel antibodies). Previous alcohol excess (p = 0.005) and subtle motor signs (p = 0.047) on examination were observed more frequently in patients with NCSE compared to controls. Conclusion: Physicians should have a low threshold for urgent EEG in patients with suspected or previous encephalitis, especially if autoimmunity is suspected or subtle motor signs are present.

Acute seizure risk in patients with encephalitis: development and validation of clinical prediction models from two independent prospective multicentre cohorts

“…EEG abnormalities were strongly associated with clinical seizure activity and EEG also identified three cases of NCSE, which is increasingly recognised in encephalitis, particularly autoimmune aetiologies. 21 22 Status epilepticus in the context of encephalitis is frequently refractory and has a poor outcome. 23 24 Patients with seizures were less likely to have CSF pleocytosis or low CSF glucose.…”

“…Further questions remain regarding choice and duration of antiepileptic agents 6. Any intervention strategy would need to consider the high baseline risk of seizures in patients with encephalitis and the presence of subtle and subclinical seizures including NCSE 14 21 36…”

Encephalitis: diagnosis, management and recent advances in the field of encephalitides

“…Indeed, autoimmune may be an important cause of non-convulsive status epilepticus in high-income settings. 73 Certain characteristic patterns have been described in autoimmune encephalitis, in particular the pathognomic extreme delta brush appearance in NMDAR-antibody encephalitis. 74 The above investigations should be undertaken alongside more common investigations to rule out differentials.…”

“…Electroencephalogram can be useful in investigating encephalitis as it can provide evidence of encephalopathy, which would be unusual in primary psychiatric diagnoses, or subclinical seizures. Indeed, autoimmune encephalitis may be an important cause of non-convulsive status epilepticus in high-income settings 73. Certain characteristic patterns have been described in autoimmune encephalitis, in particular the pathognomic extreme delta brush appearance in NMDAR-antibody encephalitis 74…”