ABSTRACT
Currently, visual field defects are considered as an inevitable consequence of occipital lobe surgery. However, recent advances in neuroimaging techniques, such as diffusion tensor tractography allowing better visualization of optic radiation and its relationship with occipital lobe tumors, as well as intraoperative monitoring of cortical visual evoked potentials (cVEPs) can contribute to correct planning of surgery and minimizing the risk of visual field defects after surgery. OBJECTIVE: To evaluate the effectiveness of intraoperative monitoring of cVEP in patients with occipital lobe tumors. MATERIAL AND METHODS: Ten patients with occipital lobe tumors have undergone surgery with neurophysiological monitoring since 2020. Mean age of patients was 57 years. There were 6 women and 4 men. In 7 patients, neoplasms were located in the right hemisphere, in 3 patients - in the left hemisphere. According to preoperative automatic perimetry data, 7 patients had various visual field defects, and other ones had intact visual fields. All patients underwent pre- and postoperative MRI for visualization of optic radiation, its relationship with tumor and control of resection quality. Intraoperative monitoring of cVEPs was performed in all patients. RESULTS: Biopsy verified glioblastoma in 5 cases, metastasis of adenocarcinoma - 2 cases, diffuse glioma - 1 case, ganglioglioma - 1 case, CNS lymphoma - 1 case. Postoperative MRI confirmed total or subtotal resection of tumor in all cases. Enlargement of visual fields occurred in 3 patients after surgery. Two ones had deterioration and/or new homonymous defect. No changes of visual fields was observed in other cases. Analysis of visual field defects after surgery found no correlation with functional state of visual tract according to fractional anisotropy before and after surgery. CONCLUSION: MR tractography of optic radiation and intraoperative monitoring of cVEP allow choosing the safest approach for resection of occipital tumor and minimizing the risk of damage to visual cortex and optic radiation fibers. In most cases, postoperative visual functions do not worsen after intraoperative mapping of visual cortex and determining the safest trajectory for resection of occipital lobe tumors. Moreover, improvement is observed in some cases.
Subject(s)
Evoked Potentials, Visual , Glioblastoma , Male , Humans , Female , Middle Aged , Monitoring, Intraoperative , Biopsy , Visual FieldsABSTRACT
OBJECTIVE: To search for correlations between intraoperative electrocorticographic data and seizure control after the multiple hippocampal transections (MHT) in patients with symptomatic pharmacoresistant medial temporal lobe epilepsy. MATERIAL AND METHODS: Six patients underwent MHT nearby the hippocampus. The left dominant hemisphere was affected in all cases. Patients had normal memory function. Follow up was 18 to 24 months. Scalp electroencephalogram (EEG) and electrocorticography (ECoG) were intaoperatively recorded. Transections of the hippocampus were performed until ECoG epileptiform discharges stopped. RESULTS: Seizure control was achieved in five patients. Synchronous epileptiform activity disappeared in the hippocampus in all patients after MHT. Complete disappearance of epileptiform activity in the hippocampus and basal cortex was demonstrated in 2 cases. The epileptiform activity remained in the basal cortex in 3 patients. CONCLUSIONS: Using the method of hippocampal transections it was possible to achieve the disappearance of synchronous epileptic activity in the hippocampus in all patients. It is correlated with good outcome in 5 out of 6 cases. Preservation and even arising of spiking in the basal temporal cortex are not a risk factor for maintaining seizures after complete resection of the epileptogenic substrate in the temporal lobe and hippocampal transections. A decrease in the background epileptiform activity on the scalp EEG was observed in 4 of 5 cases after the resection of the pathological substrate, uncus and amygdala.
