Ictal SPECT statistical parametric mapping in temporal lobe epilepsy surgery

OBJECTIVE

Although subtraction ictal SPECT coregistered to MRI (SISCOM) is clinically useful in epilepsy surgery evaluation, it does not determine whether the ictal-interictal subtraction difference is statistically different from the expected random variation between 2 SPECT studies. We developed a statistical parametric mapping and MRI voxel-based method of analyzing ictal-interictal SPECT difference data (statistical ictal SPECT coregistered to MRI [STATISCOM]) and compared it with SISCOM.

METHODS

Two serial SPECT studies were performed in 11 healthy volunteers without epilepsy (control subjects) to measure random variation between serial studies from individuals. STATISCOM and SISCOM images from 87 consecutive patients who had ictal SPECT studies and subsequent temporal lobectomy were assessed by reviewers blinded to clinical data and outcome.

RESULTS

Interobserver agreement between blinded reviewers was higher for STATISCOM images than for SISCOM images (kappa = 0.81 vs kappa = 0.36). STATISCOM identified a hyperperfusion focus in 84% of patients, SISCOM in 66% (p < 0.05). STATISCOM correctly localized the temporal lobe epilepsy (TLE) subtypes (mesial vs lateral neocortical) in 68% of patients compared with 24% by SISCOM (p = 0.02); subgroup analysis of patients without lesions (as determined by MRI) showed superiority of STATISCOM (80% vs 47%; p = 0.04). Moreover, the probability of seizure-free outcome was higher when STATISCOM correctly localized the TLE subtype than when it was indeterminate (81% vs 53%; p = 0.03).

CONCLUSION

Statistical ictal SPECT coregistered to MRI (STATISCOM) was superior to subtraction ictal SPECT coregistered to MRI for seizure localization before temporal lobe epilepsy (TLE) surgery. STATISCOM localization to the correct TLE subtype was prognostically important for postsurgical seizure freedom.

Epilepsy surgery outcomes in temporal lobe epilepsy with a normal MRI

PURPOSE

To determine the long-term efficacy of anterior temporal lobectomy for medically refractory temporal lobe epilepsy in patients with nonlesional magnetic resonance imaging (MRI).

METHODS

We identified a retrospective cohort of 44 patients with a nonlesional modern "seizure protocol" MRI who underwent anterior temporal lobectomy for treatment of medically refractory partial epilepsy. Postoperative seizure freedom was determined by Kaplan-Meyer survival analysis. Noninvasive preoperative diagnostic factors potentially associated with excellent surgical outcome were examined by univariate analysis in the 40 patients with follow-up of >1 year.

RESULTS

Engel class I outcomes (free of disabling seizures) were observed in 60% (24 of 40) patients. Preoperative factors associated with Engel class I outcome were: (1) absence of contralateral or extratemporal interictal epileptiform discharges, (2) subtraction ictal single photon emission computed tomography (SPECT) Coregistered to MRI (SISCOM) abnormality localized to the resection site, and (3) subtle nonspecific MRI findings in the mesial temporal lobe concordant to the resection.

DISCUSSION

In carefully selected patients with temporal lobe epilepsy and a nonlesional MRI, anterior temporal lobectomy can often render patients free of disabling seizures. This favorable rate of surgical success is likely due to the detection of concordant abnormalities that indicate unilateral temporal lobe epilepsy in patients with nonlesional MRI.

Assessing Central Nervous System Symptoms

The major value and primary application of clinical neurophysiology is in the assessment and characterization of neurologic disease. Selection of appropriate studies for the problem of an individual patient requires a careful clinical evaluation to determine possible causes of the patient’s symptoms. The nature of the symptoms and the conclusions of the clinical evaluation are the best guides to appropriate use of clinical neurophysiologic testing.

Cerebral Function Monitoring

Intraoperative electrophysiologic monitoring of cerebral function during cardiovascular surgery requires a thorough knowledge of the effect of anesthetic agents on electrophysiologic signals. Although there are variations among anesthetic agents and their effects on the EEG, most of the agents produce similar changes that can be recognized and distinguished from the effects of ischemia. Success of the monitoring also depends heavily on the technical aspects of recording, such as the timescale of the EEG display and adjustment of the anesthetic agent used.

What is known about the mechanisms underlying SUDEP?

This article highlights studies in three major domains of potential mechanisms of sudden unexplained death in epilepsy (SUDEP): cardiac, respiratory, and autonomic. Ictal cardiac arrest is a clinically rare but well-recognized potential mechanism of SUDEP. Studies have failed to identify preexisting cardiac electrophysiologic or structural abnormalities that distinguish SUDEP persons. Some degree of pulmonary congestion is a common autopsy finding, but severe pulmonary edema occurs very rarely with seizures. In contrast, periictal apnea and hypoxia occur commonly with generalized tonic-clonic seizures and, to a lesser degree, with complex partial seizures. There are several animal models of postictal respiratory arrest. Postictal respiratory arrest in audiogenic seizure mice can be induced by serotonin receptor inhibition or prevented by selective serotonin reuptake inhibitor (SSRI) drugs. Reduced heart rate variability occurs in patients with refractory epilepsy and can be induced in animal seizure models, but its precise role in predisposing persons to sudden death requires further investigation.

History and seizure semiology in distinguishing frontal lobe seizures and temporal lobe seizures

This study aimed to determine the reliability of clinical history and seizure semiology for distinguishing between frontal lobe seizures (FLS) and temporal lobe seizures (TLS). FLS patients (n=23) were consecutively identified through an epilepsy surgery database. TLS patients (n=27) were selected randomly from 238 patients who had undergone temporal lobe surgery for epilepsy. The criterion standard for seizure localization was the location of resective epilepsy surgery that controlled seizures for a minimum of 2 years. Blinded comparisons of 13 historical information items (HII) and 19 video-recorded semiologic features (VSF) were made. We identified 3 HII (sex, history of febrile convulsions, and history of generalized tonic-clonic seizures) and 2 VSF (fencing posturing and postictal confusion) that significantly distinguished between FLS and TLS. The multivariate analysis model correctly identified 87% of FLS patients and 74% of TLS patients. No single HII or VSF is sufficient for distinguishing between FLS and TLS. A model integrating multiple HII and VSF may assist in this differentiation, but some patients still may be misclassified.

Ictal scalp EEG recording during sleep and wakefulness: Diagnostic implications for seizure localization and lateralization

To determine the localizing value of electroencephalography (EEG) for seizures during sleep versus seizures during wakefulness, we compared scalp EEG for 58 seizures that occurred during sleep with 76 seizures during wake in 28 consecutive patients with temporal lobe epilepsy. Regression analysis showed that seizures during sleep are 2.5 times more likely to have focal EEG onset (p = 0.01) and 4 times more likely to correctly localize seizure onset (p = 0.04) than seizures during wake. EEG seizure onset preceded clinical onset by a longer duration in sleep seizures (mean, 4.69 s) than in wake seizures (mean, 1.23 s; p < 0.01). Sleep seizures showed fewer artifacts, but the difference was not significant (p = 0.07). For temporal lobectomy candidates undergoing video-EEG monitoring, the recording of seizures during sleep may be favored.

Temporal lobe seizure semiology during wakefulness and sleep

We used regression analysis to compare the semiologic features of temporal lobe seizures that occur during sleep (TLS-S) and wake (TLS-W) in the same patient. Most semiologic features correctly lateralized seizure activity during either sleep or wake. No significant differences were found between TLS-S and TLS-W in the 18 semiologic features analyzed. The diagnostic value of TLS-S semiology is similar to that of TLS-W semiology.

Demystifying Sudden Unexplained Death in Epilepsy?Are We Close?

The cause of sudden unexplained death in epilepsy (SUDEP) is still elusive, despite multiple studies over the past few decades. This review assesses recent progress in the understanding of risk factors (situations that predispose patients to SUDEP) and terminal events (events immediately associated with death) that potentially contribute to SUDEP. Recent studies strongly support a close relationship between seizure episodes (especially generalized convulsions) and SUDEP. The lethal nature of some seizure-induced cardiorespiratory events has been documented fortuitously in rare patient cases, and these events have been consistently reproduced in SUDEP animal models. Nonetheless, SUDEP likely does not have a single cause, and risk factors identified thus far may vary in importance among persons with epilepsy. In the absence of a complete understanding of the pathophysiologic mechanisms underlying SUDEP, potential preventive measures for high-risk patients are offered for consideration. Seizure control is most important for reducing SUDEP risk. Circumstantial data suggest that heightened supervision of patients with frequent seizures may be beneficial. Relatively simple interventions may be sufficient to interrupt potentially lethal events such as periictal suffocation or apnea. However, application of these preventive measures to all epilepsy patients has not been proven to substantially reduce the rate of SUDEP. Additional clinical and laboratory investigations are needed to identify and confirm pathogenic factors and preventive measures.

Value and Limitations of Seizure Semiology in Localizing Seizure Onset

Seizure semiology has been the foundation of clinical diagnosis of seizure disorders. This article discusses the value and the limitations of behavioral features of seizure episodes in localizing seizure onset. Studies have shown that some semiologic features of seizures are highly accurate in the hemispheric lateralization and lobar localization of seizures. There is good agreement between blinded reviewers in lateralizing video-recorded seizures in temporal lobe and extratemporal lobe epilepsies. However, seizure semiology alone should not be used to determine the site of seizure onset. Each semiologic feature may falsely localize seizure onset. Seizure semiology in some patients may signify the site of seizure propagation rather than origination. Moreover, seizure semiology may not be as reliable in multifocal epilepsies as it is in unifocal epilepsies. Many semiologic features of seizures of adults are often missing in seizures of children. Seizure semiology should be analyzed and integrated with EEG and neuroimaging data to localize the seizure focus. A sample of the recorded seizures should be shown to the patient's relatives or friends to verify that it is representative of habitual seizures.

Subtraction ictal single-photon emission computed tomography coregistered to magnetic resonance imaging in evaluating the need for repeated epilepsy surgery

Object

The aim of this study was to determine whether ictal single-photon emission computed tomography (SPECT) is useful in localizing the site of seizure onset in patients in whom surgery for intractable epilepsy failed and who are being considered for repeated surgery.

Methods

Subtraction ictal SPECT coregistered to magnetic resonance imaging (SISCOM) studies were retrospectively analyzed in 58 patients who were being evaluated for possible repeated resection for intractable partial epilepsy between January 1, 1996, and October 31, 1999. All patients had persistent seizures subsequent to an initial resection and underwent another excision. The SISCOM-demonstrated abnormalities were classified as concordant, discordant, or indeterminate, compared with the localization of the epileptogenic zone revealed on video electroencephalography monitoring. The ability of SISCOM to predict operative outcome was also determined in patients who had undergone repeated surgical procedures.

The SISCOM studies revealed a localized hyperperfused alteration in 46 (79%) of 58 patients. Forty-one (89%) of these 46 patients had a SISCOM-demonstrated alteration in the hemisphere of the previous epilepsy surgery. Imaging changes in 33 (72%) of the 46 patients were at the site of the previous focal cortical resection. Eight (17%) of the 46 had SISCOM-demonstrated abnormalities remote from the lobe in which surgery had been performed but in the ipsilateral hemisphere. The hyperperfusion focus was in the contralateral hemisphere in the remaining five patients (11%). The site of the epileptogenic zone was concordant with the SISCOM focus in 32 (70%) of 46 patients. Twenty-six patients underwent repeated resection and were followed up for a mean of 44 months thereafter; 11 of these patients (42%) had a significant reduction in seizure tendency. Only five patients (19%) were seizure free. Ten (50%) of 20 patients with a concordant SISCOM focus compared with none (0%) of three patients with a discordant focus had a favorable surgical outcome (p = 0.23).

Conclusions

The SISCOM method might be useful in the evaluation of, and the surgical planning for, patients with intractable partial epilepsy in whom previous resective treatment has failed and who are being considered for reoperation.

Coroner and medical examiner documentation of sudden unexplained deaths in epilepsy

BACKGROUND

Prevalence data for sudden unexplained death in epilepsy (SUDEP) are hampered by its underuse as a final diagnosis on death certificates in appropriate cases. Few data exist about how coroners (COs) and medical examiners (MEs) in the United States use the diagnosis of SUDEP.

METHODS

A survey instrument that addressed demographics, professional background, annual cases of epilepsy, seizure history, percentage of post-mortem examinations, cause of death, and use of SUDEP as a diagnosis was sent to all COs and MEs in the United States. Unadjusted comparisons between categorical variables used chi2 tests. A multiple regression model examined the odds of respondents considering SUDEP to be a valid diagnosis.

RESULTS

Of 2995 surveys, 80.7% went to COs and 19.3% to MEs. The response rate was 15.9% for COs and 21.8% for MEs. Acknowledgment of SUDEP as a valid entity was greatest among pathologists (83.5%) versus other physicians and non-physicians (P< .001) and correlated with higher autopsy rates and seeing more cases of epilepsy. In actual practice, SUDEP was not used routinely as a death certificate diagnosis in most cases with no cause of death found at autopsy by any group in the survey regardless of title, educational background, location, autopsy rate, or number of seizure cases seen annually.

CONCLUSIONS

SUDEP appears to be an underused final diagnosis by COs and MEs throughout the United States. There is a need to educate officials at all levels about this diagnosis in persons who have epilepsy with no other cause of death.

Injuries due to seizures in persons with epilepsy: a population-based study

BACKGROUND

Previous studies of injuries due to epileptic seizures predominantly involved patients with intractable epilepsy. These studies may have overestimated the risk of injuries in persons with epilepsy.

METHODS

Patients consisted of 247 Rochester, MN, residents who were diagnosed with epilepsy between 1975 and 1984. Seizure-related injuries were defined as any injury, other than orolingual trauma, resulting from a seizure, sufficient for the patient to seek medical attention or for injury occurrence to be determined during the course of medical care. To identify risk factors for injury, characteristics of patients with seizure-related injury were compared with those without injury.

RESULTS

During a total of 2,714 patient-years of follow-up, 62 seizure-related injuries were identified in 39 patients (16%, one injury in every 44 person-years). Most injuries involved cranial soft tissue contusions or lacerations (79%). The majority of seizure-related injuries (82%) occurred during generalized convulsive seizures. Univariate analyses identified five potential risk factors for seizure-related injury: greater number of antiepileptic drugs used, less independent living situation, higher Rankin score, history of generalized convulsive seizures or drop attacks, and higher seizure frequency score. Seizure frequency, however, was the only significant risk factor identified by multivariate analysis (p < 0.001; relative risk, 1.33).

CONCLUSIONS

This population-based study shows that seizure-related injuries are infrequent and generally of minor severity. In most epilepsy patients, excessive restriction of daily activities to avoid injury is unnecessary. Effective seizure control reliably reduces the risk of seizure-related injuries.

Resective reoperation for failed epilepsy surgery: Seizure outcome in 64 patients

OBJECTIVE

To determine the surgical outcome and factors of predictive value in patients undergoing reoperation for intractable partial epilepsy.

METHODS

The authors retrospectively studied the operative outcome in 64 consecutive patients who underwent reoperation for intractable partial epilepsy. Demographic data, results of comprehensive preoperative evaluations, and the seizure and neurologic outcome after reoperation were determined. All patients were followed a minimum of 1 year subsequent to their last operative procedure.

RESULTS

Fifty-three patients had two surgeries, and 11 patients had three or more operations. The first surgery involved a lesionectomy (n = 33), "nonlesional" temporal lobe resection (n = 28), and a "nonlesional" extratemporal resection (n = 3). The mean duration between the first and second procedure was 5.5 years. Fifty-five patients underwent an intralobar reoperation, whereas nine had a resection of a different lobe. After reoperation, 25 patients (39%) were free of seizure, 6 patients (9%) had rare seizures, 12 patients (19%) had a worthwhile improvement, and 21 patients (33%) failed to respond to surgery. Predictors of seizure-free outcome were age at seizure onset >15 years (p = 0.01), duration of epilepsy < or =5 years at the time of initial surgery (p = 0.03), and focal interictal discharges in scalp EEG (p = 0.03). Using a logistic regression model, two significant predictors emerged: duration of epilepsy < or =5 years (odds ratio, 3.18; p = 0.04) and preoperative focal interictal discharge (odds ratio, 4.45; p = 0.02). Complications of reoperation included visual field deficits (n = 9), wound infection (n = 2), subdural hematoma (n = 1), and hemiparesis (n = 1).

CONCLUSION

Reoperation may be an appropriate alternative form of treatment for selected patients with intractable partial epilepsy who fail to respond to initial surgery.

Peri-ictal SPECT and surgical treatment for intractable epilepsy related to schizencephaly

The authors evaluated four patients with schizencephaly who underwent subtraction ictal SPECT coregistered to MRI (SISCOM) prior to epilepsy surgery. Three patients had a SISCOM alteration that was concordant with the epileptic brain tissue. Two of these patients were rendered seizure-free and one individual experienced a significant reduction in seizures. The patient with an indeterminate SISCOM had an unfavorable outcome. SISCOM is useful in evaluating patients with schizencephaly for epilepsy surgery.

Ictal asomatognosia as a cause of epileptic falls: Simultaneous video, EMG, and invasive EEG

Intracranial EEG in a 33-year-old man with epilepsy with a history of falls and injuries showed seizure onset in the right posterior parietal region. Electrical stimulation of the region reproduced sudden estrangement of the left lower extremity. EMG and video recordings showed no alteration of extremity tone during the seizure, but his gait halted before he fell. Ictal asomatognosia may be a cause of falls in patients with epilepsy.

Digital video-electroencephalographic monitoring in the neurological-neurosurgical intensive care unit: clinical features and outcome

BACKGROUND

Prolonged electroencephalographic (EEG) recordings in the neurological-neurosurgical intensive care unit (NICU) may be performed in patients with status epilepticus, repetitive seizure activity, or an encephalopathy with or without seizures. The electroclinical correlation and neurological outcome of patients undergoing digital video-EEG monitoring (DVEEG) in the NICU has not been determined.

OBJECTIVES

To evaluate the clinical utility and prognostic importance of the DVEEG in the NICU.

METHODS

We retrospectively evaluated 105 patients who underwent DVEEG in the NICU at the Mayo Clinic, Rochester, Minn, between January 1, 1994, and July 31, 2001. All patients had a routine EEG recording performed prior to DVEEG.

RESULTS

The mean age of the patients at the time of the DVEEG was 54 years (age range, 16-88 years). The mean duration of the DVEEG was 2.9 days (range, 1-17 days). Forty-four patients (42%) had a severe encephalopathy (Glasgow Coma Scale score, <8) at the time of the DVEEG. Forty-five patients (42.8%) had generalized convulsive status epilepticus, 19 patients (18.1%) had nonconvulsive status epilepticus, and 7 patients (6.7%) had epilepsia partialis continua. The mean duration of follow-up was 7 months (range, 1-54 months). The outcome in 84 patients included death in 38 patients, severe neurological deficits, that is, bed bound and needs support for activities of daily living, in 6 patients, and a vegetative state in 3 patients. Fifteen individuals had no neurological impairment during follow-up. Refractory status epilepticus (P<.003), hypoxic-ischemic encephalopathy (P<.004), and multiple cerebral infarcts (P<.003) were the factors associated with increased mortality in univariate analysis. With multivariate logistic regression analysis only the presence of multiple strokes (P<.03; odds ratio, 5.62) was predictive of mortality.

CONCLUSIONS

Continuous EEG monitoring is essential in the diagnosis and treatment of refractory status epilepticus or an encephalopathy with seizures in the NICU. A minority of these patients, however, experienced a favorable neurological outcome.

The current place of single photon emission computed tomography in epilepsy evaluations

Single photon emission computed tomography is appropriate for peri-ictal imaging inpatients with focal epilepsy being considered for surgical treatment.

Ictal SPECT in Nonlesional Extratemporal Epilepsy

PURPOSE

Ictal single-photon emission computed tomography (SPECT) may be a reliable indicator of the ictal onset zone in patients with intractable partial epilepsy who are being considered for epilepsy surgery. The rationale for the illustrated case report is to evaluate the use of an innovation in SPECT imaging in a patient with nonlesional extratemporal epilepsy.

METHODS

We investigated the presurgical evaluation and operative outcome in a patient with intractable partial epilepsy. The ictal semiology indicated a "hypermotor" seizure with bipedal automatism. The electroclinical correlation and magnetic resonance imaging (MRI) did not suggest the appropriate localization of the epileptogenic zone. A subtraction periictal SPECT coregistered to MRI (SISCOM) was peformed.

RESULTS

SISCOM revealed a region of localized hyperperfusion in the right supplementary sensorimotor area. Chronic intracranial EEG monitoring confirmed the relationship between the localized SISCOM alteration and the ictal onset zone. The patient was rendered seizure free after surgical treatment.

CONCLUSIONS

SISCOM may be used to identify potential candidates for surgical treatment of nonlesional extratemporal epilepsy. Periictal imaging may also alter the strategy for intracranial EEG recordings and focal cortical resection.

Factors underlying scalp-EEG interictal epileptiform discharges in intractable frontal lobe epilepsy

AIMS

Scalp-EEG interictal epileptiform discharges (IEDs) may be less predictive of the outcome of frontal lobe epilepsy surgery than of temporal lobe epilepsy surgery. We identified factors associated with the location of scalp-EEG IEDs in intractable frontal lobe epilepsy.

METHODS

Ten factors were assessed in a retrospective review of 53 patients with either concordant (frontal lobe seizure focus) or discordant (generalized or outside frontal seizure focus) IED or both, who had excellent surgical outcomes. The Fisher exact test and the Wilcoxon rank sum test determined statistically significant associations.

RESULTS

Thirty-six patients (68%) had concordant IED, 24 (45%) discordant IED, and 17 (32%) both. Younger age at onset was significantly associated with discordant IED (mean, 7.5 years versus 17 years for patients without discordant IED; P < 0.01), whereas duration of epilepsy was not. Seizure foci at the frontal convexity were associated with concordant IED. About 72% of patients with a convexity seizure focus had concordant IED, compared with only 33% of patients with mesial frontal foci having concordant IED (P = 0.06).

CONCLUSIONS

Early seizure onset in intractable frontal lobe epilepsy is associated with IEDs discordant with seizure focus. Frontal convexity seizure foci are more likely than mesial frontal seizure foci to be associated with concordant discharges.

Advances in computer-assisted single-photon emission computed tomography (SPECT) for epilepsy surgery in children

Epilepsy surgery has emerged as an important option in the treatment of children with epilepsy that is refractory to antiepileptic drug management. The cornerstone of successful surgery is accurate localization of the brain region of seizure onset. Traditional techniques of seizure onset localization, e.g. surface electroencephalography (EEG) recording and magnetic resonance imaging (MRI), allow accurate localization in a significant number of patients. When the focus of seizure onset is not apparent from these non-invasive techniques, other methods of localization, e.g. intracranial EEG recording, may be needed before resection of the focus. Single-photon emission computed tomography (SPECT) is a nuclear medicine blood-flow technique that has been used to identify a region of epileptogenic brain associated with low blood flow in the resting state (interictal SPECT) or increased blood flow at the time of seizure activity (ictal SPECT). This report describes the validation and utility of a computer-assisted method of subtracting the interictal from the ictal SPECT scans and co-registering the difference image on the MRI. This method, called subtraction ictal SPECT co-registered on MRI (SISCOM), is used in guiding the location and the extent of intracranial electrode implantation, or in obviating the need for the implantation in some cases.

Subtraction SPECT Coregistered to MRI in Focal Malformations of Cortical Development: Localization of the Epileptogenic Zone in Epilepsy Surgery Candidates

PURPOSE

To determine the extent to which periictal subtraction single-photon emission computed tomography (SPECT) may improve detection and definition of the epileptogenic zone in patients with focal malformations of cortical development (MCDs).

METHODS

Subtraction SPECT coregistered to magnetic resonance (MR) images (SISCOM) were constructed for 22 consecutive patients with focal MCDs who underwent periictal SPECT injection (18 ictal and four postictal). In the 17 patients who had epilepsy surgery, concordance between the site of SISCOM localization and site of surgical resection was determined by coregistration of SISCOM images with postoperative MRIs.

RESULTS

SISCOM images were localizing in 19 (86%) patients, including eight of the 10 with nonlocalizing MRI. Concordance of SISCOM localization was 91% with MRI localization, 93% with scalp ictal EEG localization, and 100% with intracranial EEG localization. Eight patients whose SISCOM localization was concordant with the surgical resection site had lower postoperative seizure frequency scores (SFSs; p = 0.04) and greater postoperative improvement in SFSs (p = 0.05) than the nine patients whose SISCOM was either nonconcordant or nonlocalizing. On multiple regression analysis, a model combining SISCOM concordance with surgical resection site and extent of MRI lesion resection was predictive of postoperative SFS (R2 = 0.47; p = 0.03).

CONCLUSIONS

Periictal subtraction SPECT using the SISCOM technique provides useful information for seizure localization in patients with focal MCDs, even when MRI is nonlocalizing.

Acute postoperative seizures after frontal lobe cortical resection for intractable partial epilepsy

PURPOSE

To evaluate the incidence and prognostic importance of acute postoperative seizures (APOSs) occurring in the first week after a focal corticectomy in patients with partial epilepsy of frontal lobe origin.

METHODS

We retrospectively evaluated 65 patients who underwent a frontal lobe cortical resection for intractable partial epilepsy between April 1987 and December 2000. All patients were followed up for a minimum of 1 year after surgery.

RESULTS

APOSs occurred in 17 (26%) patients. None of the following factors was shown to be significantly associated with the occurrence of APOSs: gender, duration of epilepsy, etiology for seizure disorder, use of subdural or depth electrodes, surgical pathology, or postoperative risk factor for seizures. Patients with APOSs were older at seizure onset and at the time of surgery (p = 0.003 and p = 0.05, respectively). At last follow-up, patients who had APOSs had a seizure-free outcome similar to that of individuals without APOSs (47.1% vs. 50.0%; p = 0.77). Patients with APOSs appeared less likely to have a favorable outcome [i.e., fewer than three seizures per year and >95% decrease in seizure activity (58.8 vs. 70.8%; p = 0.35)]. This result may not have reached statistical significance because of the sample size. No evidence suggested that precipitating factors or the timing of APOSs was an important prognostic factor.

CONCLUSIONS

The presence of APOSs after frontal lobe surgery for intractable epilepsy does not preclude a significant reduction in seizure tendency. These findings may be useful in counseling patients who undergo surgical treatment for frontal lobe epilepsy.