Sadahiro Nomura

13. Development of a functional mapping method using focal cortical cooling in awake craniotomy

The aim of this study is to determine the usefulness of abnormal muscle response (AMR) and facial motor evoked potential (FMEP) monitoring in predicting outcomes in patients with hemifacial spasm (HFS) who undergo microvascular decompression (MVD). AMRs were recorded from the mentalis and orbicularis oculi muscles. FMEPs were recorded from the orbicularis oculi muscle by transcranial stimulation via corkscrew electrodes placed at positions C3 or C4 and Cz. In 40 95%) of 42 patients, in whom either the amplitude of AMRs decreased <50% or the FMEP amplitude ratios (post/pre MVD) were <100%, the HFS resolved postoperatively. The remaining two patients had recurrences of their spasm 3 months after surgery. In 14 (70%) of 20 of the patients with persistent AMR after MVD, HFS gradually decreased over a mean of 6 weeks and disappeared. On the other hand, in 19 (95%) of the 20 patients with resolved MR, HFS disappeared immediately after MVD. Thus, the AMR findings significantly correlated with postoperative courses (p < 0.001). Our results suggest that both AMR monitoring and FMEP monitoring predict outcomes after MVD in HFS patients. The AMR findings also predict whether the HFS disappears immediately or gradually after surgery.

P31-14 Intraoperative monitoring of motor evoked potential during cerebral aneurysm surgery

surveillance, namely mapping of the posterior columns (SEP) and continuous monitoring of the motor pathways by means of motor evoked potentials (MEP). Technique of transcranial electrical stimulation with single pulse and train stimuli was employed. D-wave was recorded from epi or subdural electrodes placed above and beneath the tumour whereas motor potentials from the limbs. The excision was abandoned should the amplitude of D-wave be lesser than 50% of the base value. Results: Readable D-wave was recorded in 31 patients and MEPs from 124 limbs. Absence of changes in the recording signified that there would be no postoperative deficit. Similarly favourite prognosis was associated with persistent decrease of MEP amplitude providing the recording remained readable and with transient disappearance of MEPs providing D-wave was unchanged. Permanent loss of MEPs with unchanged D-wave heralded transient, a-few-days-lasting neurological deficit. 2 patients in whom the amplitude of D-wave suddenly decreased by 60% whereas the MEPs were lost, had permanent monoparesis. Conclusions: Decrease of the amplitude of D-wave greater than 50% is associated with a permanent neurological deficit. Persistent loss of MEPs with unchanged D-wave foretells a transient neurological deficit.

P31-9 Intraoperative monitoring of the motor evoked potential elicited by direct cortical stimulation of the lower extremities

distance. CST course shift on intraop MRI comparing pres MRI was shown in 6 cases (31.5%), that means 19 stimulation points (32.7%). Radical resection was performed in 14 (87.5%), subtotal in 2 patients (12.5%). After surgery developed 2 temporary hemiparesis and 1 speech disorders that resolved in 3 days and 3 months respectively. Permanent left side hemianopsia developed in one patient. Conclusion: Subcortical CST mapping is superior to extraoperative CST imaging on MRI DTI. Intraoperative MRI improves reliability of CST dermination.

P31-10 Intraoperative monitoring of the lower extremity motor evoked potential (LE-MEP) elicited by direct cortical stimulation

distance. CST course shift on intraop MRI comparing pres MRI was shown in 6 cases (31.5%), that means 19 stimulation points (32.7%). Radical resection was performed in 14 (87.5%), subtotal in 2 patients (12.5%). After surgery developed 2 temporary hemiparesis and 1 speech disorders that resolved in 3 days and 3 months respectively. Permanent left side hemianopsia developed in one patient. Conclusion: Subcortical CST mapping is superior to extraoperative CST imaging on MRI DTI. Intraoperative MRI improves reliability of CST dermination.

P9-16 An implantable, focal brain cooling device for epilepsy therapy: An animal and clinical investigation

Objective: Aim of this study is to investigate the prevalence and clinical correlates of obstructive sleep apnea (OSA) in acute stroke patients. Background: Recent literature demonstrates that OSA is an independent risk factor for acute stroke, yet stroke may also lead to OSA. Moreover, several studies suggest that OSA in acute stroke is associated with a worse clinical outcome by compromising hemodynamics and oxygenation in a phase of critically affected but viable brain tissue (penumbra). Continuous Positive Airways Pressure (CPAP) therapy in acute stroke patients has been proposed as a means of reducing secondary damage to the penumbra, yet the procedure seems hampered by feasibility issues in the acute stroke setting. This study aimed to (1) evaluate the prevalence of OSA in the setting of acute stroke, and (2) investigate which clinical characteristics distinguish acute stroke patients with from those without OSA. Methods: A prospective study was carried out in consecutive patients admitted to the stroke unit with an acute ischemic stroke. In all patients, clinical characteristics and a sleep history was performed and a polygraphic examination was conducted with an Embletta polygraph (Embla, USA) within 48 hours of stroke onset. Results: 20 patients consented to study inclusion (mean age 68 years, mean BMI 29). Stroke severity was mild to moderate (mean National Institute of Health Scale Score 7). OSA, defined as an apnea hypopnea index (AHI) 5, was seen in 55% and AHI 20 in 15% of the stroke patients. There were no clinical stroke characteristics that distinguished patients with from patients without OSA. Conclusions: OSA in acute ischemic stroke patients is a common phenomenon. In order to protect the penumbra, OSA screening and treatment might be considered as part of standard stroke unit care.