Resumen

Introduction: Posterior fossa surgery has rare perioperative complications which are not directly related to surgical excision of tumors such as duramater defects that can be covered with autologous grafting of adipose tissue to prevent cerebrospinal fluid leakage. Due to the mechanical effect of fat graft prolapsed into the cerebellopontine angle, micro-embolic fat dissemination, headaches, meningitis, and brainstem compression are reported as post-operative complications related to its placement. Brainstem compression due to fat graft prolapse is associated with significant morbidity and even death in the first postoperative days on patients who undergo cerebellopontine angle surgery. For this study, we have reported on two patients: one with changes in corticobulbar motor evoked potentials (CoMEP) and the other with changes in blink reflex (BR) after fat graft placement, with recovery of neurophysiologic signal after its removal during the operation. Methods: Corticobulbar MEP (CoMEP). Stimulation: Transcranial electrical stimulation (TES) was used for Corticobulbar MEP. We used montages C3 vs. Cz for left hemispheric stimulation and C4 vs. Cz for right hemispheric stimulation. The stimulation parameters were short trains consisting of 3 to 5 stimuli with 0.5 ms duration each. These stimuli were separated by 2 ms interstimulus interval, with a train repetition rate of 2 Hz and an intensity of up to 120 mA. We then delivered a single stimulus over the same stimulating montage ninety milliseconds after the train. When eliciting suprathreshold CoMEPs the TES intensity was in most cases 10–20 mA higher than the intensity required to elicit suprathreshold MEPs in the contralateral abductor pollicis brevis. Recording: In order to record CoMEPs from the facial muscles we used a pair of hook wire electrodes; each consisted of a Teflon coated wire 76 ìm in diameter that passed through 27 gauge needles (hook wire electrode, specially modified, Viasys Healthcare WI, MA). The recording wires have a stripped Teflon isolation of 2 mm at the tip and are curved to form the hook to anchor them after the needle is withdrawn from the facial muscles. The impedance of electrodes was below 20 KOhm. After inserting the wire electrodes in the facial muscles, each pair of wires were twisted and needles were withdrawn and covered in order to protect the patient from a possible accidental injury.

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2012-10-09   |   622 visitas   |   Evalua este artículo 0 valoraciones

Vol. 19 Núm.2. Abril-Junio 2012 Pags. 161-165 Neurocien Colom 2012; 19(2)