Epileptogenic Lesions Requiring Additional MRI Studies

Utility of Magnetic Resonance Imaging Brain Epilepsy Protocol in New-Onset Seizures: How is it Different in Developing Countries?

Introduction

Magnetic resonance imaging (MRI) is the current imaging tool of choice in the investigation of patients with seizures. The advent of high-resolution MRI with a dedicated seizure protocol has significantly increased the chances of identifying a cause, resulting in a positive clinical impact on the management of these patients.

Aims

The aims of this study were to evaluate the diagnostic efficacy of standard MRI, identify whether there is an increase in the diagnostic yield with the addition of dedicated seizure protocol, and compare the diagnostic yields of MRI and electroencephalogram (EEG) individually and in combination.

Subjects and Methods

This is a prospective study of 129 consecutive patients who presented with new-onset seizures over an 18-month period. The MRI scans performed on 1.5T were reviewed for their diagnostic yield and their association with abnormal electrical activity on EEG. Chi-square test of significance (P < 0.05) was used to test for the difference in proportion. The correlation between MRI brain and EEG was studied using McNemer test.

Results

MRI detected potentially epileptogenic lesions in 59 patients (47%). The frequency of epileptogenic lesions was highest in patients who had focal-onset seizures (81%). The most common lesion type was infection and inflammation (28%), with neurocysticercosis being the most common, followed by mesial temporal sclerosis, ischemia, and tumor. About 37% of epileptogenic lesions were missed by standard protocol, which were detected on a dedicated seizure protocol MRI. The diagnostic yield of EEG was 31%. Abnormal MRI and EEG were concordant in 18% of patients, with EEG being normal in 37% of patients with epileptogenic lesions.

Conclusions

MRI detects epileptogenic lesions in almost one half who presented with new-onset seizures and of these, more than third of them were detected using a "dedicated seizure protocol." While almost 50% with seizures will have a cause identified on MRI, the sensitivity can be substantially improved by utilizing a dedicated seizure protocol.

Clinical characteristics and surgical outcome of patients with temporal lobe tumors and epilepsy

This is a retrospective study of 21 surgically treated patients with temporal lobe tumors and epilepsy. Evaluation included clinical data, EEG findings, structural scans, pathological diagnosis and post-surgical follow-up. There were 9 cases of ganglioglioma, 5 pilocytic astrocytoma, 3 ganglioneuroma, 2 dysembryoplastic neuroepithelial tumor, 1 pleomorphic xantoastrocytoma, and 1 meningioangiomatosis. Mean follow-up time was 22 months and outcome was evaluated according to Engel's classification; 76.2% were classified in class I and 23.8% in II and III. All patients classes II and III had been submitted to mesial and neocortical resections. There were no differences related to clinical characteristics, pathological diagnosis or duration of follow-up in patients seizure-free or not. All patients had abnormal MRI and ten of these had normal CT; the MRI characteristics were compared to pathological diagnosis and specific histological characteristics of the tumors were not discernible by MRI. We concluded that MRI was essential for the diagnosis and precise location of TL tumors. Ganglioglioma was the most frequent tumor and lesionectomy associated to mesial resection doesn't guarantee a better prognosis.