Posterior fossa intraoperative monitoring.

Monitoring of brainstem structures is requested of the neurophysiologist for both intra-axial and extra-axial surgeries of the posterior fossa. A variety of techniques to include upper extremities somatosensory evoked potentials, short latency auditory evoked potentials, spontaneous and evoked electromyographic activity, and recordings from the cochlea and the eighth nerve are available. The indication, implementation, and interpretation of each of these modalities are delineated. The efficacy and utility of these techniques are also discussed.