[Clinicopathologic characteristics and causes of difficulty in locating the "difficult to locate" intractable...

Objective: To summarize the clinicopathological characteristics of "difficult to locate" intractable epilepsy patients, and investigate the causes of difficulty in their location. Method: Retrospective analysis was performed on the clinical data of 58 patients who underwent resection of the epileptogenic zones after intracranial electroencephalography (iEEG) detection at the Department of Neurosurgery of the First Affiliated Hospital of Fujian Medical University from January 2010 to December 2018. Clinicopathological characteristics and lesion lobes of "difficult to locate" intractable epilepsy were summarized. The prognosis of patients was assessed according to Engel grading.Univariate and multivariate logistic regression analysis were used to investigate the relevant factors affecting the prognosis of patients with "difficult to locate" intractable epilepsy related to malformation of cortical development(MCD). Results: Among the 58 patients, there were 47 cases of MCD (12 cases with mild malformation of cortical development (mMCD), 35 cases with focal cortical dysplasia (FCD)), and 11 cases of other types. Among the 47 MCD cases, univariate analysis showed that patients with preoperative magnetic resonance imaging(MRI) positive and completed resection of the epileptogenic zones had better prognosis (P<0.05). Multivariate analysis indicated that completed resection of epileptogenic zones was an independent factor affecting the postoperative efficacy of MCD (P=0.013,Wald χ(2)=6.149, 95%CI: 0.07-0.56). And among the 47 MCD cases, 18 cases were with mono-lobar lesions and 29 cases were with multi-lobar lesions, however, there was no significant difference of the efficacy between the two groups (P=0.511). Conclusions: MCD, especially FCD, is the main pathological types of patients with "difficult to locate" intractable epilepsy. Multi-lobar pathological changes, especially multi-lobar MCD, are the main reasons of being difficult to locate, however, accurate locating of epileptogenic zones and functional areas via effective use of iEEG can achieve satisfactory efficacy in these patients after resection of the epileptogenic zones.