Long-term mood, quality of life, and seizure freedom in intracranial EEG epilepsy surgery

Highlights

• At last follow-up, 69.4% (43/62) of patients who underwent iEEG monitoring were completely free from seizures (Engel Class I).

• 34% of patients were depressed as measured by NDDI-E (score > 15).

• 74% had a good quality of life as measured by QOLIE-10 (score < 25).

• Seizure freedom was associated with good quality of life (p < 0.001), but there was no association with mood (p = 0.24).

Abstract

Objectives

To determine the long-term outcomes in patients undergoing intracranial EEG (iEEG) evaluation for epilepsy surgery in terms of seizure freedom, mood, and quality of life at St. Vincent’s Hospital, Melbourne.

Methods

Patients who underwent iEEG between 1999 and 2016 were identified. Patients were retrospectively assessed between 2014 and 2017 by specialist clinic record review and telephone survey with standardized validated questionnaires for: 1) seizure freedom using the Engel classification; 2) Mood using the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E); 3) Quality-of-life outcomes using the QOLIE-10 questionnaire. Summary statistics and univariate analysis were performed to investigate variables for significance.

Results

Seventy one patients underwent iEEG surgery: 49 Subdural, 14 Depths, 8 Combination with 62/68 (91.9%) of those still alive, available at last follow-up by telephone survey or medical record review (median of 8.2 years). The estimated epileptogenic zone was 62% temporal and 38% extra-temporal. At last follow-up, 69.4% (43/62) were Engel Class I and 30.6% (19/62) were Engel Class II-IV. Further, a depressive episode (NDDI-E > 15) was observed in 34% (16/47), while a ‘better quality of life’ (QOLIE-10 score < 25) was noted in 74% (31/42). Quality of life (p < 0.001) but not mood (p = 0.24) was associated with seizure freedom.

Significance

Long-term seizure freedom can be observed in patients undergoing complex epilepsy surgery with iEEG evaluation and is associated with good quality of life.

Introduction

At least one-third of patients with focal epilepsy become drug resistant and may be eligible for surgery [1]. Careful estimation of the epileptogenic zone (EZ) is critical in epilepsy surgery as it is associated with post-surgical seizure freedom, survival, and better quality of life [1]. However, for a proportion of patients it is difficult to localize seizures using conventional structural and functional imaging methods or have potential surgical solutions involving or in close proximity to eloquent cortex. Intracranial electroencephalography (iEEG) over the past few decades has been the gold-standard technique to guide resective surgery where the EZ is less well-delineated or eloquent cortex is potentially at risk, allowing for greater accuracy in resection planning, and preservation of healthy brain tissue [2]. More recently stereo-EEG (SEEG) is becoming increasingly used and more widely adopted in many tertiary epilepsy centers and may be more suitable compared to grid/strip electrodes in some cases in relation to seizure freedom and surgical morbidity [3]. Nonetheless, subdural electrodes with iEEG monitoring may be preferred in certain instances to allow further functional and language mapping.

While there are several studies assessing post-operative surgical outcomes in patients undergoing iEEG monitoring for epilepsy surgery, only a few studies have systematically assessed seizurefreedom in this cohort, with even fewer evaluating wider long-term outcomes [4]. Most follow-up studies assess seizurefreedom from one year up to 10 years, using the Engel Classification (I-IV), whereby Engel Class I is defined as complete freedom from disabling seizures [4], [5]. However, this common outcome measure is often used in isolation and does not adequately reflect how epilepsy affects day-to-day life. Patients undergoing iEEG monitoring present a more vulnerable subgroup of epilepsy surgery patients, with difficult to localize lesions, making the need to assess longer term outcomes even more important. To our knowledge, qualityoflife and mood have not been reported in an iEEG epilepsy surgery cohort previously. At St. Vincent’s Hospital, Melbourne, we are also now moving toward SEEG and elected to take this opportunity to assess our adult cohort undergoing iEEG epilepsy surgery from 1999 to 2016 and report on post-operative seizure freedom, mood, and quality of life for this cohort.