Elsevier

World Neurosurgery

Volume 102, June 2017, Pages 434-441
World Neurosurgery

Original Article
Epileptic Zone Resection for Magnetic Resonance Imaging–Negative Refractory Epilepsy Originating from the Primary Motor Cortex

https://doi.org/10.1016/j.wneu.2017.02.090Get rights and content

Objective

Because of the balance between achieving complete seizure freedom and minimizing the postoperative neurologic deficits, surgery for refractory epilepsy originating from the primary motor cortex is difficult. Here, we report the outcomes of surgery for magnetic resonance imaging–negative refractory epilepsy originating from the primary motor cortex in a case series.

Methods

Nine patients with refractory epilepsy originating from the primary motor cortex underwent intracranial electrodes implantation after preoperative evaluation. Subdural grid electrodes and depth electrodes were implanted through craniotomy assisted by stereotactic technique. We delineated the epileptic zone and executed tailored resection according to results of intracranial electroencephalography and mapping. The patients were followed up for at least 1 year. Muscle strength was evaluated at different postoperative times (day 1, 2 weeks, and 1 year).

Results

Regarding seizure outcome at the last follow-up, Engel class I outcome was achieved in 5 patients, class II was achieved in 3 patients, and class III was achieved in 1 patient. All cases had postoperative hemiparesis of different degree on the first day after operation. Three patients experienced distal muscle strength of single limb with grade 3 or lower and had obvious dysfunction at 1 year after operation. Six patients experienced distal muscle strength of grade 4 or 5 (Medical Research Council 6-point scale) and had no obvious dysfunction at that time.

Conclusions

Most patients of refractory epilepsy originating from the primary motor cortex were seizure free and had no obvious neurologic deficits at follow-up. Epileptogenic zone resection may not always be contraindicated for patients with nonlesional refractory epilepsy originating from the primary motor cortex.

Introduction

Resection of the epileptic zone in the primary motor cortex is generally regarded as high-risk surgery because of the neurologic deficits after surgery. Therefore, the treatment of magnetic resonance imaging (MRI)–negative refractory epilepsy originating from the primary motor cortex is full of challenges. Previously, there have been reports about epileptic zone resection for intractable partial epilepsy in functional areas of the brain.1, 2 However, in these articles, the pathology was mixed and included malformations of cortical development, tumors, perinatal lesions, vascular lesions, and so forth. These case series also included both MRI-negative and MRI-positive refractory epilepsy patients. There are few articles focused on MRI-negative refractory epilepsy originating from the primary motor cortex. It is thought that resection of the sensory motor cortex will inevitably lead to neurologic deficits.1, 3, 4, 5, 6, 7, 8 Epileptic zone resection of the primary motor area usually results in postoperative hemiplegia. However, it has been demonstrated that gross total resection of the seizure focused in the eloquent cortex is an important factor in achieving postoperative seizure freedom. The patient could not be seizure free without the complete resection of the epileptic zone.1, 9, 10, 11 Therefore, a balance is needed between achieving the ultimate goal of complete seizure freedom, while minimizing postoperative neurologic deficits. Multiple subpial transection was once used for patients who were not candidates for resective surgery.12, 13 However, the seizure-free rates of multiple subpial transections were relatively low.14, 15, 16 Cui et al.17 and Zhai et al.18 reported that cortex coagulation was effective in parts of nonlesional refractory epilepsy involving the functional areas. However, only 45% of the patients were seizure free, and 12.5% of the patients developed mild hemiparesis after bipolar electrocoagulation on functional cortex.18 In recent years, some researchers reported the outcome of radiofrequency thermocoagulation in the treatment of drug-resistant epilepsy. This may be an alternative treatment options for patients with drug-resistant rolandic epilepsy with a low chance of side effects. However, as previously reported, seizure freedom was achieved only in 7%–25% of patients.19, 20 Recently, it has been reported that patients with seizures arising from the rolandic and perirolandic cortex experienced good seizure outcome and low rate of neurological deficits after completely resection of the seizure focus.1 Here, we report the seizure outcome of epileptic zone resection for MRI-negative refractory epilepsy originating from the primary motor cortex in 9 cases.

Section snippets

Patients

Nine patients with refractory epilepsy involving the primary motor cortex who underwent resective surgery were included in this study. The resections were restricted to portions of the primary motor cortex. This case series includes 5 men and 4 women. The age range was from 12 to 44 years, with a mean age of 20.8 years. Every patient took at least 2 antiepileptic drugs in adequate dosage for more than 2 years. Detailed patient information is described in Table 1. For the purpose of this study,

Results

A total of 9 patients (5 men) with MRI-negative epileptogenic focus localized in the primary motor cortex underwent resective surgery and were evaluated in this study. Detailed information of each patient's characteristics is summarized in Table 1. The duration of epilepsy ranged from 3 to 36 years (mean, 9.1 years). All patients failed to have seizure relief after taking at least 2 different medications at maximally tolerated doses. Each patient had normal motor function before surgery. Six

Discussion

Surgical treatment of drug-resistant epilepsy arising from the rolandic cortex remains a challenge for both physicians and patients. In our patients with epilepsy originating from the primary motor cortex, we found that most patients achieved being seizure free and did not have motor deficits after surgery. This findings may help stratify the risk of future surgery and influence the decision-making process.

Epilepsy originating from the primary motor cortex has special semiology features.

Conclusions

Indeed, the ultimate goal of resection is to simultaneously achieve seizure freedom with functional preservation. Our data revealed that combination of grid electrode and depth electrode made it possible to exactly locate the epileptogenic focus in the primary motor cortex. A limited resection of the sensorimotor cortex was performed with excellent seizure outcome and without any motor deficits in many patients in our study. Therefore, the resective surgery may be an alternative to multiple

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    Conflict of interest statement: This project was supported by the National Natural Science Foundation of China (51472068).

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