title: Magnetoencephalography interictal spike clustering in relation with surgical outcome of cortical dysplasia.
abstract: OBJECTIVE
  The aim of this study was to devise an objective clustering method for magnetoencephalography (MEG) interictal spike sources, and to identify the prognostic value of the new clustering method in adult epilepsy patients with cortical dysplasia (CD).
  
  
  METHODS
  We retrospectively analyzed 25 adult patients with histologically proven CD, who underwent MEG examination and surgical resection for intractable epilepsy. The mean postoperative follow-up period was 3.1 years. A hierarchical clustering method was adopted for MEG interictal spike source clustering. Clustered sources were then tested for their prognostic value toward surgical outcome.
  
  
  RESULTS
  Postoperative seizure outcome was Engel class I in 6 (24%), class II in 3 (12%), class III in 12 (48%), and class IV in 4 (16%) patients. With respect to MEG spike clustering, 12 of 25 (48%) patients showed 1 cluster, 2 (8%) showed 2 or more clusters within the same lobe, 10 (40%) showed 2 or more clusters in a different lobe, and 1 (4%) patient had only scattered spikes with no clustering. Patients who showed focal clustering achieved better surgical outcome than distributed cases (p=0.017).
  
  
  CONCLUSIONS
  This is the first study that introduces an objective method to classify the distribution of MEG interictal spike sources. By using a hierarchical clustering method, we found that the presence of focal clustered spikes predicts a better postoperative outcome in epilepsy patients with CD.
authors: MEG Center, Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea.
authors: Woorim
authors: W
authors: Jeong
authors: Chun Kee
authors: CK
authors: Chung
authors: June Sic
authors: JS
authors: Kim
keywords: Cortical dysplasia; Epilepsy; Hierarchical clustering; Magnetoencephalography; Surgical outcome