Objective:

This study aims to describe the incidence, characteristics, and risk factors for developing post-encephalitic epilepsy (PEE).

Background:

Encephalitis leads to significant morbidity and mortality, with an estimated global incidence of 0.07–12.6 cases per 100,000. It results mainly from infectious (IE) or autoimmune (AE) causes, with AE cases increasing over the past two decades. Patients with encephalitis face a high risk of acute symptomatic seizures, status epilepticus, and PEE, which occurs in 10 to 40% of cases. However, the contributing factors for developing PEE are poorly understood.

Design/Methods:

We conducted a retrospective chart review of patients treated for encephalitis at a tertiary academic center between 2006 and 2022 (n= 269), with follow-up 1 year post-discharge (n=139). Data on presenting characteristics, in-hospital outcomes, treatment, and PEE development were collected. PEE was defined as having seizures or being on at least one AED 1 year after discharge. Chi-Square and Mann-Whitney U tests were performed.

Results:

Of 139 patients, 45 had AE (32.4%), 35 had IE (25.2%), and 59 had unknown etiology (UE, 42.4%). Of these, 52 patients (47.9%) developed PEE (13 with AE, 16 with IE, and 23 with UE). Among these, 16 (30.7%) met the seizure component, and 45 (86.5%) met the AED component of the PEE definition. 32 (71.1%) were on 1 AED, while 13 (28.9%) were on 2 or more. Factors associated with PEE development were new onset fever (p=0.029), confusion (p=0.005), headaches (p=0.020), acute symptomatic seizures (p<0.001), and status epilepticus (p=0.004). The etiology and treatment modalities were not linked to PEE development.

Conclusions:

About half of the cohort developed PEE. Predictors were new onset fever, confusion, headaches, acute symptomatic seizures, and status epilepticus. Future studies will compare EEG findings between those who developed PEE and those who did not, aiding in identifying patients who might benefit from AEDs, thereby reducing post-discharge complications.