SEARCH

SEARCH BY CITATION

Keywords:

  • extratemporal lobe resection;
  • seizure outcome;
  • temporal lobe resection

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Abstract  We analyzed the seizure outcome of 357 patients who were followed for at least 2 years after resective surgeries; 282 underwent temporal lobe resection and 75 had extratemporal lobe resection. This study confirmed that resective surgery provides sustained, positive benefits with a high seizure-free rate of nearly 80% for most medically refractory patients. In patients with no MRI-detectable lesion who underwent extratemporal lobe resection, however, Engel's class I–II (seizure-free or rare seizures) was achieved in less than 50% of patients. High-resolution MRI should be performed at the early stage of disease in all patients with partial epilepsies. The findings would certainly urge clinicians to actively select surgical intervention.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

In 1983, surgical treatment of epilepsy was incorporated into the comprehensive care program at the National Epilepsy Center in Shizuoka, Japan. By the end of July 2001, we had performed resective surgeries in medically refractory cases: temporal lobe resection (TLR) in 368 patients and extratemporal lobe resection (ETLR) in 120 patients. The aim of this study was to analyze the seizure outcome of 357 patients who had been followed for at least 2 years after surgery, and to clarify whether a high seizure-free rate was indeed achieved in these refractory patients.

METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Patients with temporal lobe resection

A total of 282 patients underwent TLR. Their ages at surgery ranged from 2 to 55 years (mean, 25.5 years). The age of seizure onset ranged from birth to 45 years (mean, 10.9 years), with 126 patients having seizure onset before 10 years of age. The duration of illness was 1–40 years (mean, 15.7 years), including 15 patients with a duration of <5 years. Complex partial seizures occurred at least monthly in all except one patient who had several seizures a year.

Presurgical work-up for all patients included neurological and psychological examinations, CT, and long-term EEG/video monitoring. MRI was added to the presurgical evaluations from 1986, SPECT from 1987, and MEG from 1994. MRI or CT disclosed nonexpanding lesions in 87 patients. A total of 137 patients had long-term invasive monitoring, usually with combined subdural and depth electrodes.1 Surgical procedures were anterior temporal lobectomy in 215 patients, selective amygdalohippocampectomy by trans-T1 subpial approach in 49, tailored neocortical resection with or without the mesial temporal structures in 15, and total temporal lobectomy in three. Of 250 patients with data of speech dominance determined  by  the  Wada  test,  121  had  dominant-side  re-sections and 129 had non-dominant-side resections. Histological diagnoses were hippocampal sclerosis in 172 patients, dysembryoplastic neuroepithelial tumor (DNT) in 61, cortical dysplasia in 12, cavernoma in 11, arteriovenous malformation (AVM) in two, glioma in two, and non-specific in 22.

Patients with extratemporal lobe resection

A total of 75 patients underwent ETLR. Their ages at surgery ranged from 2 to 40 years (mean, 21.8 years). The age of seizure onset ranged from birth to 28 years (mean, 7.6 years), with 20 patients having seizure onset before 5 years of age. The duration of illness was 2–36 years (mean, 14.0 years), including five patients with a duration of <5 years. Disabling seizures occurred at least weekly in all patients, including 38 patients who had more than 10 seizures a day.

The presurgical work-up was similar to patients who underwent TLR. MRI disclosed nonexpanding lesions with various sizes and shapes in 64 patients. Forty-eight patients had invasive long-term monitoring, usually with subdural grid electrodes. The frontal lobe was resected in 47 patients, the occipital lobe in six and the parietal lobe in five. Seventeen patients underwent multilobar resection, including two patients with Rusmussen's functional hemispherectomy. Of 48 patients with data of speech dominance determined by the Wada test, 37 patients had dominant side resections, and 11 had non-dominant side resections. Histological diagnoses were cortical dysplasia in 35 patients, DNT in 10, encephalomalacia in 15, cortical atrophy in three, cephalocele in two, non-specific in seven, and cavernoma, thrombosed AVM, and Rusmussen's encephalitis in on patient each.

Outcome analysis

Two years after surgery, all patients were admitted for evaluation. After that, most patients continued to visit the outpatient clinic in our center but some returned to their previous doctors. The subjects in this study were followed at our center and their seizure events were abstracted from clinical charts. The follow-up period from surgery to the last visit ranged from 2.0 to 16.3 years (mean, 6.4 years) in 282 patients with TLR, and 2.0–12.8 years (mean, 4.7 years) in 75 patients with ETLR. The seizure outcome was classified according to Engel's classification.2 However, we defined ‘rare seizures’ in class II as one to three seizure days per year as proposed by ILAE Commission on Neurosurgery,3‘worthwhile improvement’ in class III as more than 50% reduction of baseline seizure days, and ‘significant seizure reduction’ in class IV as less than 50% reduction of baseline seizure days. Twenty-four per cent of patients with TLR had discontinued medication at the time of their last visit.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

Outcome of patients with temporal lobe resection

Overall seizure outcome

The overall seizure outcome in 282 patients who underwent TLR was class I in 221 patients (78%), class II in 34 (12%), class III in 17 (6%), and class IV in 10 (4%) (Table 1). Of 221 patients categorized as class I, 145 were completely seizure-free and 28 had auras only. Consequently, these 173 patients (61%) had experienced no disabling seizure after surgery.

Table 1. Seizure outcomes of 282 patients with temporal lobe resection and 75 patients with extratemporal resection
Engel's classificationTemporal (n = 282)Extratemporal (n = 75)
Class I: ‘Seizure free’221 (78%)48 (64%)
 Completely seizure free14532
 Aura only 28 8
 Some seizures after surgery, but seizure-free for at least 2 years 33 4
 Withdrawal seizures only 15 4
Class II: Rare seizures (3 days/year or less) 34 (12%) 8 (11%)
 Initially free, but rare seizures now 5 1
 Rare seizures since surgery 24 3
 More than rare after surgery, but rare seizures for at least 2 years 4 2
 Nocturnal seizure only 1 2
Class III: Worthwhile improvement (>50% seizure reduction) 17 (6%) 6 (8%)
 Worthwhile seizure reduction 15 6
 Prolonged seizure-free intervals 2 0
Class IV: No worthwhile improvement 10 (4%)13 (17%)
 Significant seizure reduction (<50%) 6 8
 No appreciable change 3 3
 Seizure worse 1 2

The remaining 109 patients (39%) had at least one disabling seizure. Seizures recurred within 6 months in 54 patients, 7–12 months in 19, 13–24 months in 17, and after 24 months in 19. Of the 73 patients with early seizure recurrence within 12 months, 25 (34%) belonged to class III–IV. However, 34 of 36 patients (94%) with late recurrence after 12 months were in class I–II, including 14 patients in class Id.

Long-term seizure outcome

Long-term seizure outcomes were investigated in the 159 patients who were followed for at least 6 years, including 50 patients with follow up for 12 years. The upper part in Fig. 1 demonstrates the chronological changes of outcome in individual patients. At the end of the second postoperative year, each patient was categorized under one of Engel's classes I–IV, and was re evaluated at the end of the 4th, 6th, 8th, 10th or 12th year. The lower part of Fig. 1 presents the percentage of class I–IV patients in this sample, indicating that the seizure outcome is stable as a whole for a long-term period after surgery.

image

Figure 1. Long-term seizure outcome in 159 patients with at least 6 years’ follow up after surgery.

Download figure to PowerPoint

Other outcome analyses

Seizure outcome was analyzed according to other parameters. In 172 patients with histologically proven hippocampal sclerosis, 138 patients (80%) were class I, 23 (13%) class II, eight (5%) class III, and three (2%) class IV. In 87 patients with MRI/CT-detected lesions, 71 patients (82%) were class I, nine (10%) class II, four (5%) class III, and three (3%) class IV.

Outcome of patients with extratemporal lobe resection

Overall seizure outcome

The overall seizure outcome of 75 patients with ETLR was class I in 48 patients (64%), class II in eight (11%), class III in six (8%), and class IV in 13 (17%) (Table 1). The proportion of class I (64%) cases in ETLR was low compared with 78% in TLR.

Outcome according to MRI finding

The seizure outcome was analyzed according to whether patients had a MRI-detected lesion. Patients with MRI lesions were divided further into two groups based on the greatest diameter of lesion: under 5 cm (discrete) or over 5 cm (widespread). The proportion of class I–II was 85% (35 of 41) in patients with discrete lesions, 70% (16 of 23) in patients with widespread lesions, and 45% (five of 11) in patients with no lesion. In four of five patients with no lesion on MRI who achieved class I–II seizure outcome after surgery, histological examination disclosed cortical dysplasia.

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES

This study confirmed that resective surgeries provided sustained, excellent benefit with a high seizure-free rate in most patients with medically intractable partial epilepsies. Among patients who underwent TLR, the postsurgical seizure-free rates were 80 and 82% in those with histologically verified hippocampal sclerosis and those with foreign tissue lesions on MRI, respectively. Even in patients who underwent ETLR, the proportion of Engel's class I–II reached 85% with MRI revealing discrete lesions less than 5 cm in diameter. Today, hippocampal sclerosis is easily identified as atrophy or high signal of the hippocampus on MRI. Furthermore, the recently developed high-resolution MRI permits the detection of cortical dysplasia regarded as intrinsically associated with epileptogenesis. In patients who underwent ETLR, cortical dysplasia accounted for nearly 50% of histological diagnoses in this series. This fact is extremely important because it indicates that cortical dysplasia is one of the principal causes of partial epilepsies, next to hippocampal sclerosis. High-resolution MRI should be performed at the early stage of disease in all patients with partial epilepsies. The findings would certainly prompt clinicians to actively select the option of surgical intervention.4

In contrast, of patients with no MRI-detectable lesion who underwent ETLR, less than 50% had a seizure outcome of Engel's class I–II. However, these patients should not be excluded as surgical candidates, because some patients had achieved freedom from disabling seizures. Under the present situation, surgical indication for patients with no detectable lesion on MRI might be restricted to those with other findings. These findings are localized hyperperfusion on ictal SPECT, clustering of MEG dipoles locating in the cortical surface, or elementary seizure manifestations.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. REFERENCES
  • 1
    Mihara T & Baba K. Combined use of subdural and depth electrodes. In: LüdersHO, ComairYG (eds). Epilepsy Surgery, 2nd edn. Lippincott Williams & Wilkins, Philadelphia, 2001; 613621.
  • 2
    Engel J Jr, , Van Ness P, Rasmussen TB, Ojemann L. Outcome with respect to epileptic seizures. In: EngelJJr (ed.). Surgical Treatment of the Epilepsies, 2nd edn. Raven Press, New York, 1993; 609621.
  • 3
    Wieser HG, Blume WT, Fish D et al. Proposal for a new classification of outcome with respect to epileptic seizures following epilepsy surgery. Epilepsia 2001; 42: 282286.
  • 4
    Mihara T, Inoue Y, Matsuda K et al. Recommendation of early surgery from the view of daily quality of life. Epilepsia 1996; 37 (Suppl.): 3336.