Intraoperative risk of seizures associated with transient direct cortical stimulation in patients with symptomatic epilepsy.

Direct cortical stimulation--either with the 60-Hz stimulation or the train-of-five technique--is commonly agreed on being the gold standard for intraoperative mapping of the motor cortex and the motor pathways but may result in an intraoperative seizure. The occurrence of intraoperative stimulation associated seizures with respect to symptomatic epilepsy was evaluated in a group of 129 patients undergoing tumor resection within the central region. Data were reviewed with respect to the frequency of seizures with both stimulation techniques and symptomatic epilepsy. Direct stimulation of the motor cortex was performed with a train of five consecutive pulses, an interstimulus interval of 4 ms, an individual pulse width of 0.5 ms, and 40 mA stimulation intensity at maximum. In 1 of 63 patients (1.6%) presenting with symptomatic epilepsy, a stimulation-associated seizure occurred, and 1 of the other 66 patients (1.5%) had a seizure (n.s., not significant). In the literature, stimulation associated seizures are reported in 1.2% with the train-of-five technique and significantly more frequently in 9.5% with the 60-Hz technique (P < 0.001). In summary, there is no increased risk of the occurrence of stimulation-associated seizures during surgery for patients with symptomatic epilepsy compared with those patients without.

Iatrogenic Peripheral Nerve Injuries-Surgical Treatment and Outcome: 10 Years' Experience.

BACKGROUND: Iatrogenic nerve injuries are nerve injuries caused by medical interventions or inflicted accidentally by a treating physician. METHODS: We describe and analyze iatrogenic nerve injuries in a total of 122 consecutive patients who received surgical treatment at our Institution during a period of 10 years, from January 1, 2003, to December 31, 2013. The final outcome evaluation was performed 2 years after surgical treatment. RESULTS: The most common causes of iatrogenic nerve injuries among patients in the study were the operations of bone fractures (23.9%), lymph node biopsy (19.7%), and carpal tunnel release (18%). The most affected nerves were median nerve (21.3%), accessory nerve (18%), radial nerve (15.6%), and peroneal nerve (11.5%). In 74 (60.7%) patients, surgery was performed 6 months after the injury, and in 48 (39.3%) surgery was performed within 6 months after the injury. In 80 (65.6%) patients, we found lesion in discontinuity, and in 42 (34.4%) patients lesion in continuity. The distribution of surgical procedures performed was as follows: autotransplantation (51.6%), neurolysis (23.8%), nerve transfer (13.9%), direct suture (8.2%), and resection of neuroma (2.5%). In total, we achieved satisfactory recovery in 91 (74.6%), whereas the result was dissatisfactory in 31 (25.4%) patients. CONCLUSIONS: Patients with iatrogenic nerve injuries should be examined as soon as possible by experts with experience in traumatic nerve injuries, so that the correct diagnosis can be reached and the appropriate therapy planned. The timing of reconstructive surgery and the technique used are the crucial factors for functional recovery.

Transcranial electric stimulation for intraoperative motor evoked potential monitoring: dependence of required stimulation current on interstimulus interval value.

STUDY OBJECTIVE: To evaluate the relationship between stimulus intensity by constant current transcranial electric stimulation and interstimulus interval (ISI) for eliciting muscle motor evoked potentials (MEPs) in three different hand muscles and the tibialis anterior muscles. PATIENTS/MATERIAL AND METHODS: We tested intraoperatively different monophasic constant current pulses and ISIs in 22 patients with clinically normal motor function. Motor thresholds of contralateral muscle MEPs were determined at 0.5 milliseconds (ms) pulse duration and ISIs of 1, 2, 3, 4, 5, and 10 ms using a train of 2, 3, and 5 monophasic constant current pulses of 62 to 104 mA before craniotomy and after closure of the dura mater. RESULTS: The lowest stimulation threshold to elicit MEPs in the examined muscles was achieved with a train of 5 pulses (ISI: 3 ms) before craniotomy, which was statistically significant compared with 2 pulses (ISI: 3 ms) as well as 3 pulses (ISIs: 3 and 10 ms). An ISI of 3 ms gave the lowest motor thresholds with statistical significance compared with the ISIs of 4 ms (2 pulses) and of 1 ms (3 pulses). All current intensity (mA) and ISI (ms) relationship graphs had a trend of the exponential function as y = a + bx + c ρ (x), where y is intensity (mA) and x is ISI (ms). The minimum of the function was determined for each patient and each muscle. The difference was statistically significant between 3 and 5 pulses before craniotomy and between 3 and 5 pulses and 2 and 5 pulses after closure of the dura mater. CONCLUSION: In adult neurosurgical patients with a normal motor status, a train of 5 pulses and an ISI of 3 ms provide the lowest motor thresholds. We provided evidence of the dependence of required stimulation current on ISI.