Acute effect of transcranial direct current stimulation on photoparoxysmal response.

INTRODUCTION: Transcranial direct current stimulation (tDCS) is a non-invasive technique, used to modify the excitability of the central nervous system. The main mechanism of tDCS is to change the excitability by subthreshold modulation by affecting neuronal membrane potentials in the direction of depolarization or repolarization. tDCS was previously investigated as an alternative adjunctive therapy in patients with epilepsy. We aimed here to investigate the acute effect of tDCS on the photoparoxysmal response (PPR) in EEG. METHODS: We enrolled 11 consecutive patients diagnosed with idiopathic generalized epilepsy who had PPR on at least 2 EEGs. Three different procedures, including sham, anodal, and cathodal tDCS were applied to the patients at intervals of one week by placing the active electrode over Oz, for 2 mA, 20 minutes. Spike-wave indices (SWI) were counted by two researchers independently and were compared during intermittent photic stimulation (IPS) on EEGs both before and after the application. RESULTS: After cathodal tDCS, SWI increased compared to baseline EEG and sham EEG in 3 patients, and after anodal tDCS, SWI increased in 2 patients. Although the SWI values did not change significantly, 8 patients reported subjectively that the applications were beneficial for them and that they experienced less discomfort during photic stimulation after the sessions. There were no side effects except transient skin rash in one patient, only. CONCLUSIONS: In our sham controlled tDCS study with both cathodal and anodal stimulation, our data showed that there was no significant change in SWI during IPS, despite subjective well-being. tDCS' modulatory effect does not seem to act in the acute phase on EEG parameters after photic stimulation.

Intraoperative recording of laryngeal adductor reflex and cortical motor evoked potentials during jugular foramen schwannoma surgery: a case report and literature review.

PURPOSE: Schwannoma, a tumor originating from the peripheral nervous system, may arise from the vagus nerve, although it is not very often. Injury of the vagus nerve by surgical attempts may have consequences that will seriously affect the patient's quality of life. In recent years, continuous monitoring of the laryngeal adductor reflex (LAR) has become a promising methodology for evaluating vagus nerve function intraoperatively. We refer to our experience changing our surgical strategy due to concurrent deterioration in LAR and CoMEPs intraoperatively. We also provide a literature review and summarize the current knowledge of this technique. METHODS: The LAR was elicited and recorded by an electromyographic endotracheal tube in a 36-year-old man diagnosed with vagal nerve schwannoma. Subdermal needle electrodes were placed in both cricothyroid (CTHY) muscles for corticobulbar motor evoked potentials (CoMEPs) recording. RESULTS: Recordings of ipsilateral LAR and CTHY CoMEPs were obtained despite preoperative ipsilateral cord vocalis weakness. The surgical strategy was altered after the simultaneous decrease of CTHY CoMEPs and LAR amplitudes, and the surgery was completed with subtotal resection. No additional neurological deficit was observed in the patient except dysphonia, which resolved within a few weeks after the surgery. CONCLUSIONS: We conclude that LAR with vagal nerve CoMEPs are two complementary methods and provide reliable information about the functional status of the vagus nerve during surgery.