Corticobulbar motor evoked potentials in surgical treatment of tumors of the IV ventricle and brainstem

BACKGROUND: Intraoperative neurophysiological monitoring is an obligatory tool during fossa posterior surgery. Corticobulbar motor evoked potentials is the modality of intraoperative neurophysiological monitoring, which can be used during such neurosurgery interventions. It is used to determine the functional state of the caudal cranial nerves during surgery. However, there are technical features of this modality, therefore, corticobulbar motor evoked potentials are not used routine in neurosurgery now. AIM: To establish the predictive value of corticobulbar motor evoked potentials for development of dysphagia after removal of tumors of brainstem and fourth ventricle. MATERIALS AND METHODS: We analyzed 80 patients aged from 11 months to 67 years. In 49 cases tumor located in forth ventricle (34 adults and 15 children). In 31 cases tumor located in upper brainstem and craniospinal region (16 adults and 15 children). All patients underwent neurosurgery removal of tumor with intraoperative neurophysiological monitoring. We analyzed otoneurological symptoms before and after operation, MR-images, the volume of removed tumor was estimated. We analyzed data of intraoperative neurophysiological monitoring; the main modality of intraoperative neurophysiological monitoring was corticobulbar motor evoked potentials. RESULTS: Progress in neurological symptoms from caudal nerves was observed in 35% cases. Amplitude of corticobulbar motor evoked potentials statistically depends on neurological symptoms from caudal nerves in early postoperative period. When the amplitude of the corticobulbar motor evoked potentials decreases by more than 34% from the initial level, there is a high probability of appearance or increase of symptoms from the caudal group of cranial nerves after surgery. The sensitivity and specificity of the corticobulbar motor evoked potentails are 94.4 and 89.2%, respectively. CONCLUSIONS: It is necessary to use the corticobulbar motor evoked potentials to determine the functional state of the caudal group of cranial nerves during brainstem and forth ventricle surgery and to predict the development of dysphagia and dysarthria after surgery. The modality has a high prognostic value both in children and in adults.