Loss of lower limb motor evoked potentials and spinal cord injury during the initial exposure in scoliosis surgery.

Purpose: To report a case of motor evoked potential changes and spinal cord injury during the initial dissection in scoliosis surgery.

Methods: Motor evoked potentials to transcranial electrical stimulation were recorded from multiple muscles. Somatosensory evoked potentials to limb nerve stimulation were recorded from the scalp.

Median nerve somatosensory evoked potential monitoring during carotid endarterectomy: does reference choice matter?

Median nerve somatosensory evoked potential monitoring is commonly used during carotid endarterectomy to permit selective shunting in only those patients who are determined to have inadequate collateral flow after carotid cross-clamping. The N20 component is recorded from the CPc (contralateral centroparietal) electrode; either CPi (ipsilateral centroparietal) or Fpz (forehead) can be used as the reference. Because of the distribution of the subcortically generated N18 component, the CPc-Fpz derivation might record both the N20 and the N18 components and might therefore inadequately detect hemispheric ischemia after carotid cross-clamping.

The utility of a forehead-to-inion derivation in recording the subcortical far-field potential (P14) during median nerve somatosensory-evoked potential testing.

American Clinical Neurophysiology Society (ACNS) guidelines recommend recording P14 between an ipsilateral centroparietal electrode (CPi) and a noncephalic reference, typically the contralateral Erb's point (EPc) (American Clinical Neurophysiology Society. Guideline 9D: guidelines on short-latency somatosensory evoked potentials. J Clin Neurophysiol.