Review of new articles: Epilepsy surgery outcomes

Three recent papers describe the outcome of epilepsy surgery from different points of view:

Lowe AJ, Efraim D, Kilpatrick CJ, et al. Epilepsy surgery for pathologically proven hippocampal sclerosis provides long-term seizure control and improved quality of life. Epilepsia 2004; 45: 237-242.

Lowe and colleagues (1) reported on long-term seizure control and quality-of-life outcomes after surgery. The special feature of this report is that the investigators included a homogeneous cohort of 50 patients with hippocampal sclerosis (verified by pathology, MRI), evaluated at least 2 years post-surgery. The long-term self-report assessment revealed seizure-freedom for 82% of patients for 1 year, 76% for 2 years, and 63% for approximately 5 years, based on the Engel Classification Grade 1 (2). Thus, although the prognosis for complete seizure control was excellent for people with this well-defined temporal lobe syndrome, a risk of recurrence remained even after 2 years of seizure freedom. Notably, the 10 patients who discontinued all medications had rare seizures or none. The higher-than-usual rates for seizure control compared to other reports are likely related to inclusion of the homogeneous population limited to hippocampal sclerosis.

The QOLIE-89, an assessment of health-related quality of life (HRQOL), was completed by 84% of patients. As expected, successful control of seizures was associated with higher HRQOL. Highest QOLIE-89 scores were reported by patients with no seizures or rare seizures, followed by those with more frequent seizures. This confirms previous reports, but shows less difference in HRQOL between seizure-free and other groups. This difference probably occurred because of the limited number of patients and lack of baseline assessment, but could relate to the homogeneneity of patients with hippocampal sclerosis. We need to know more about which types of patients and which domains of HRQOL improve, as well as whether total seizure freedom is the only outcome that provides improved HRQOL. Reports of HRQOL change after epilepsy surgery should describe clinically meaningful change, as well as statistical significance. Larger cohorts of patients with carefully defined abnormalities and followed prospectively for long periods (5-10 years), are needed to answer these questions.

Stavem K, Bjornaes H, Langmoen IA. Predictors of seizure outcome after temporal lobectomy for intractable epilepsy. Acta Neurol Scand 2004; 109: 244-249.

Stavem and coworkers (3) described predictors of successful seizure elimination for 63 patients undergoing temporal lobectomy for intractable epilepsy. This cohort achieved only 44% seizure freedom after anterior temporal lobectomies, based on the Engel Classification Grade 1 (2). Using a variety of preoperative variables, they retrospectively determined that focal pathological abnormalities found by MRI and the extent of hippocampal resection were significant predictors of seizure freedom for 2 years. In contrast to the report by Lowe and colleagues (1), these authors used the heterogeneity of the patient population to define predictors of successful outcome. Nonetheless, the limitation of follow-up to 2 years does not tell patients about the likelihood of long-term success.

Spencer SS, Berg AT, Vickrey BG, Sperling MR, Bazil CW, Shinnar S, Langfitt JT, Walczak TS, Pacia SV, Ebrahimi N, Frobish D; Multicenter Study of Epilepsy Surgery. Initial outcomes in the Multicenter Study of Epilepsy Surgery. Neurology. 2003;61:1680-1685.

Spencer's group (4) described initial outcomes for 355 patients enrolled in a multicenter protocol, followed for a minimum of 1 year. Remission (1 year seizure-free) was achieved by 77% of patients with medial temporal resections and 56% of those with neocortical resections (p = 0.01). Similar to the other studies described above, relapse rates were higher in the medial temporal group (24%) than in the neocortical group (4%) (p=0.02).

Periodic QOLIE-89 assessments revealed that most of the gain was made in the first 3 months after surgery, with little change thereafter except in the epilepsy-related domain. All patients made gains, regardless of surgery outcome. Patients who were seizure-free at 12 and 24 months had significant gains in HRQOL, however, while those with continuing seizures experienced declines. The authors note that successful surgery has a "gradual but lasting effect on QOL."

Surely, HRQOL is impacted by concerns about the possibility of recurrence if the (often complex) drug regimen is reduced or eliminated. We need to know more about which types of patients and which domains of HRQOL improve, as well as whether total seizure freedom is the only outcome that provides improved HRQOL. Reports of changes in HRQOL after epilepsy surgery should describe clinically meaningful change, as well as statistical significance. Larger cohorts of patients with carefully defined abnormalities and followed prospectively for long periods (5-10 years), are needed to answer these questions.

[See more on the Multicenter Study of Epilepsy Surgery.]

All of these reports demonstrate that careful selection of candidates for surgery can lead to higher rates of successful seizure control. Prospective studies that follow large numbers of patients for longer periods are in progress. Those results will provide more much-needed information to guide patients and epileptologists as to the likelihood of successful surgery.

These papers include good lists of references to major reports of epilepsy surgery outcomes. My concern about the literature on surgical outcome is the use of the Engel Classification (2), which empirically combines:

• total seizure-freedom
• "auras" (technically, simple partial seizures)
• 2-year remission
• seizures only on drug withdrawal.

My view is that seizure-free means zero seizures. Inclusion of a time-frame of 2 years seems both arbitrary and a factor that should be encompassed in longitudinal analyses rather than in classification. I was pleased to see that Lowe and colleagues reported time to seizure recurrence by subtype, allowing the reader to determine how many patients remained totally free of seizures. Stavem's analysis was limited by the combination of total seizure-freedom with "auras." The inclusion of seizures after drug withdrawal also makes it difficult for patients to know what to expect. What are the predictors of success after surgery and drug withdrawal? Now that numerous reports have demonstrated the efficacy of epilepsy surgery, particularly for temporal lobectomy, is it time to revisit this classification to provide better information about long-term prognosis in well-defined subsets of patients?

References

1. Lowe AJ, Efraim D, Kilpatrick CJ, et al. Epilepsy surgery for pathologically proven hippocampal sclerosis provides long-term seizure control and improved quality of life. Epilepsia 2004; 45: 237-242.

2. Engel J, Van Ness PC, Rasmussen TB, et al. Outcome with respect to epileptic seizures. In: Engel J, ed. Surgical Treatment of the Epilepsies. New York: Raven Press, 1993: 609-621.

3. Stavem K, Bjornaes H, Langmoen IA. Predictors of seizure outcome after temporal lobectomy for intractable epilepsy. Acta Neurol Scand 2004; 109: 244-249.

4. Spencer SS, Berg AT, Vickrey BG, Sperling MR, Bazil CW, Shinnar S, Langfitt JT, Walczak TS, Pacia SV, Ebrahimi N, Frobish D; Multicenter Study of Epilepsy Surgery. Initial outcomes in the Multicenter Study of Epilepsy Surgery. Neurology. 2003;61:1680-1685.

Posted April 13, 2004