Seizure Outcome After Surgery In Patients With Normal Preoperative MRI And Intractable Epilepsy

[Objective]:In this article we discuss whether the patients with normal brain MRI are worth pursuing surgery for intractable epilepsy. And we also discuss the surgical methods, seizure outcome after surgical treatment, and pathological changes in the resected brain tissue which determined the surgical strategy, in order to improve these patients surgery treatment efficacy.[Methods]:a retrospective study from January 2008 to December 2009 in 363 hospital neurosurgery department.73 patients with intractable epilepsy had surgical treatment during this time, and we collect their medical records include the the clinical history of seizure characteristics, preoperative brain MRI imaging scan results,24-hours video electroencephalogram monitoring results(24-VEEG), the preoperative clinical data of 20-contacts subdural grids which was inserted embracing both temporal lobe, the result of intraoperative cortical electrode monitoring and surgical methods, postoperative pathological examination of the brain tissues. All the patients had brain MRI scan, in accordance with the results of the MRI scans, the patients were divided into two groups. The group 1:all patients who are without any abnormal brain MRI imagings are defined as the patients with normal brain MRI and refractory epilepsy (40 patients, including 29 males,11 females, aged 8-42 years, mean age 20.5 years, the duration of epilepsy is from 6 months to 23 years, the mean duration of epilepsy is 9.4 years). The group 2:all the patients had abnormal brain MRI imagings (33 patients, 29 males,4 females, aged 9-60 years, mean age 22.5 years, the duration of epilepsy is 10 days -24 years, the mean duration of epilepsy is 7.9 years), the MRI imaging diagnosis include:malacia, arachnoid cyst, meningioma, brain atrophy, hippocampal sclerosis, vascular malformations, schizencephaly, and absence of septum pellucidum, glioma. All the patients underwent preoperative 24-hours video EEG (24h-VEEG) monitoring, and we get the informations of the ictal and interictal EEG discharges, and also get the position of epileptogenic focus. If the patients had more than 90% of the interictal discharges over one lobe and and all seizures clearly originating from the same lobe which was defined by video-EEG recording, so the patients are the best candidates for the surgical treatment. During the surgery we used intraoperative monitoring of the cortical electrodes to identify the epileptogenic zone in order to decide the scope of surgical resection. If we used the non-invasive of the EEG (non-invasive EEG) which could not clearly identified the epileptic focus in patients, we had to use cortical electrodes to be buried in the subdural space in order to localize epileptogenic focus. After surgery all specimens were send for pathological examination. All the patients had routine EEG examined before discharging. All the patients have been keeping in touch by telephone consultation, writing and other ways of communicating at least a year, at the most recent follow up, we evaluate the efficacy of seizure control according to Engel classification. [Results]:Group 1:40 patients with normal brain MRI, mean follow-up 1.8 years, of whom 16 (40%) get epilepsy completely control, classified as Engel I; 19 (47.5%) patients have a rare seizure, about 1 or 2 times per year, or only nocturnal seizures, classified as Engelâ…¡; 3 (7.5%) patients who were compared with preoperative seizures, the seizures reduced by 90%,which are classified as Engelâ…¢; 2 (5%) patients with no significant improvement in seizure control after surgery which are classified as Engel IV. The group 2:the 33 patients with brain MRI abnormalities and refractory epilepsy, mean follow-up 1.8 years, of whom 18 (54.5%) patients get epilepsy completely control, which are classified as Engel I; 7 (21%) patients have rare epileptic seizures, about 1 or 2 times per year or only have nocturnal seizures, which are classified as Engel II,4 (12%) patients who are compared with preoperative seizures the seizures reduced by 90%, which are classified as Engelâ…¢; four patients (12%) with no significant improvement in seizure control after surgery, which are classified as Engel IV. There is no statistically significant difference between two groups in efficacy of postoperative seizure control (P>0.05). The group 1:there are 29 patients have the frontal lobe, anterior temporal resection and amygdalo-hippocampectomy. The brain lesions can be found including:significant softening, vacuolar degeneration of brain cells and some swelling of brain cells, spotting, thin-walled blood vessels to dilate, glial cell proliferation and other non-specific changes. The remaining 11 patients had no pathological abnormalities. The group 2:the 33 patients with brain MRI abnormalities, the pathological changes include:diffuse astrocytoma, meningioma gravel, hippocampal sclerosis, arachnoid cyst, vascular malformations and and other non-specific pathological changes (local focal brain tissue softening, brain vacuolar degeneration and cloudy swelling, spotting, reactive inflammation, mild hyperplasia of glial cells). [Conclusion]:This study shows that 87.5% of the patients with normal cranial MRI have good seizure control (Engel I+ Engel II) after surgery, which is a efficacy therapy compared with a variety of antiepileptic drugs (AEDS) therapy; and the pathologies confirmed 70%(28/40) of the normal brain MRI patients have pathological changes. So if these patients have a rigorous assessment preoperation and identify the location of epileptogenic focus, they should have surgical therapy in time.