Authors :
Presenting Author: Tomasz Mieszczanek, MD, PhD – The Danish Epilepsy Centre
Elene Gardella, MD, PhD – Department of Clinical Neurophysiology, Danish Epilepsy Centre “Filadelfia” Dianalund, Denmark & Institute for Regional Health Services, University of Southern Denmark, Odense, Denmark; Bo Jespersen, MD – Department of Neurosurgery, Copenhagen University Hospital Rigshospitalet, Denmark; Karen Larsen, MD, PhD – Department of Pathology, Copenhagen University Hospital Rigshospitalet, Denmark; camila Madsen, MD – Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Amager and Hvidovre, Denmark
Rationale:
Magnetic Resonance Imaging (MRI) is an essential part of the diagnostic evaluation in patients with focal epilepsy. MRI negative cases are most challenging for epilepsy surgery. Detection of concordant lesions on MRI in the epileptogenic region facilitates presurgical decision making and significantly increases the post-surgical outcome. EEG-telemetry did not modify decision making in the vast majority of resective surgery candidates with localized MRI lesion. There is increasing evidence that 3T MRI has better sensitivity and specificity than 1.5T especially in the detection of cortical malformations.
Methods:
We reviewed a single-center retrospective series of 18 epilepsy surgery patients with suspicion of low grade tumor or focal cortical dysplasia (FCD) in 3T MRI. Patients at the age between five and eighteen years old were referred to our Danish Epilepsy Center “Filadelfia” because of drug resistant epilepsy. 1.5T MRI were performed at local hospitals. Focal epilepsy onset in ictal EEG concordant with focal seizures symptomatology was confirmed in all patients and 3T MRI was performed at the Danish Research Centre for Magnetic Resonance Copenhagen University Hospital Amager and Hvidovre. Resective surgery was performed at the Department of Neurosurgery Copenhagen University Hospital Rigshospitalet in Denmark between 2018 and 2022. Information was gathered from digital patient records. Engel Class Scale was used to determine post-surgical outcomes.
Results:
All 18 patients were divided into 3 groups depending on the histopathological results.
Group A: Seven patients with FCD type 1 or type 2. In 3T MRI, FCD was described in all seven cases. In 1.5T MRI, dysplasia was not found in 6 patients and in 1 case low grade tumor was named. Post-surgical outcomes: three patients Engel 1A, 2 Engel 1B, 1 Engel 1D and 1 Engel 2A.
Group B: Five patients with normal histopathology and suspicion for FCD on 3T MRI. In the case of 1.5T MRI, FCD was named in two cases and polymicrogyria in one case. Of this group, four patients are seizure free after resection (Engel 1A) and one is seizure free over six months after resection. One patient had only occasional seizures in the first week after resection in six months follow.
Group C: Six patients with tumors (4 ganglioglioma WHO-1, 1 DNET WHO-1, pleomorphic xanthoastrocytoma grade II). In 3T MRI tumors were described in four cases, and in two cases differentiation between neoplasia and cortical dysplasia were named. No lesions were described in two cases of 1.5T MRI. Six patients were seizure free after resection - Engel 1A. One patient has only non-disabling simple partial seizures since surgery in the following six months.
Conclusions:
3T MRI has better sensitivity and specificity than 1.5T especially in the detection of FCD.
Evaluation by an experienced neuroradiologist, dedicated in epilepsy is mandatory for detection of most FCDs, together with 3T MRI.
Funding: No founding