Clinical and neuropsychological studies of patients before and after insular glioma resection

Abstract

The study was aimed to investigate the insula function based on analysis and comparison of epileptic seizures (irritation symptoms) and cognitive impairment (memory loss) in patients with insular gliomas. Epileptic seizures and cognitive impairment were analyzed in 51 patients with insular gliomas before and after surgery. The tumor was located on the left in 21 patients and on the right - in 30. Patients were aged 9 to 67 years; most patients were diagnosed with grade II and grade III gliomas. Patients were examined before surgery and 4-6 days after tumor resection. Neuropsychological examination was carried out according to the A.R. Luria method, which enabled establishing a correlation between detected impairments and the topography of injury to different brain areas. To identify the seizure features, the study presents data from two additional groups of patients: with temporal and frontal lobe tumors, 50 patients each. Epileptic seizures were detected in 45 (88.2%) of 51 patients in the main group and were similar to paroxysms associated with medial temporal lobe tumors, but quantitatively differed from them. Seizures in patients with frontal lobe tumors significantly differed from those with insular and temporal lobe tumors. Compared to temporal lobe epilepsy, symptomatic epilepsy in the setting of insular tumors was characterized by significantly less frequent losses of consciousness (84% versus 35.2%) but more frequent olfactory and taste hallucinations (16% versus 51%). Fear and anxiety attacks associated with these tumor localizations occurred at the same rate (in 17.6% of patients with insular tumors and in 14% patients with temporal tumors). The vegetative component of seizures did not differ in tumors of both localizations and different lateralization. Olfactory and taste hallucinations were qualitatively similar in tumors of the insula and temporal lobe: smell and taste were always unpleasant or corresponded to danger. Pleasant taste or smell was not developed in any case. Cognitive impairment before and after surgery directly depended on the tumor spread to the adjacent temporal or frontal lobes. Memory impairments were most frequent, and speech disorders were most frequent in the case left-sided lesions. Eight patients with total removal of the insula and without postoperative complications had no deterioration in speech and memory. Epileptic seizures associated with insular tumors are characterized by both similarities and differences with medial-temporal seizures, which is due to the close relationships between the insula and the limbic system. The nature of taste and olfactory hallucinations associated with insular tumors reflects a significant role of the insula in the formation of 'protective behavior'. The absence of clear cognitive impairment in focal lesions of the insula restricts extended interpretation of the insula role in implementation of cognitive functions. This issue needs further investigation.