Abstracts

Rationale: Rasmussen encephalitis (RE) is a rare inflammatory neurological disorder affecting one hemisphere, causing progressive neurological deficits and intractable seizures. Most patients will present in childhood or young adulthood, with a median age of onset at 6 years. While immunomodulatory treatments have a role in slowing disease progression, surgery remains the only option of a cure for patients with RE. The existing literature is limited by small sample sizes or meta-analysis methodologies with restricted ability to evaluate the full clinical spectrum and possible predictors of outcome. We report long-term seizure outcomes, reoperations, and functional outcomes in RE patients who underwent hemispherectomy at our institution.

Methods: Retrospective review was performed for all RE patients who had surgery between 1998 and 2020 at the Cleveland Clinic. All surgeries were hemispherectomies (either functional or anatomic) and performed by a single surgeon. We collected seizure history, postoperative outcomes, and functional data. Seizure outcome at the time of last follow-up, defined by the Engel classification, was used as the primary outcome. Pre and postoperative magnetic resonance imaging (MRI) was independently reviewed in a blinded fashion by two neurosurgeons and a neuroradiologist.

Results: We analyzed 30 patients with RE who underwent 35 hemispherectomies (5 reoperations). Using Kaplan-Meier analysis, seizure-freedom rate was 81.5%, 63.6% and 55.6% at 1, 5, and 10 years after surgery, respectively. Patients with shorter duration of hemiparesis preoperatively were less likely to be seizure-free at follow up (p=0.011) and more likely to undergo reoperation (p=0.004). Shorter duration of epilepsy (p=0.026) and preoperative bilateral MRI abnormalities (p=0.011) were associated with increased risk of reoperation. Complete disconnection of diseased hemisphere on postoperative MRI after the first operation improved seizure-freedom (p=0.021) and resulted in fewer reoperations (p=0.034), and re-operation resulted in seizure-freedom in every case.

Conclusions: Obtaining complete disconnection is critical for favorable seizure outcomes from hemispherectomy and neurosurgeons should have a low threshold to reoperate in RE patients with recurrent seizures. Rapid progression of motor deficits and bilateral MRI abnormalities may indicate a subpopulation of RE patients with more explosive disease and increased risk of needing reoperation. Overall, we believe that hemispherectomy is a curative surgery for the majority of RE patients, with good long-term seizure outcomes.

Funding: Please list any funding that was received in support of this abstract.: Dr. Jehi is funded by NIH grant #R01 NS097719.