when you stimulate the dorsal column tract

The cortical SSEP responses, however, are greatly affected by inhalational agents whichever recorded anesthetic management is very much required. Therefore any SSEP responses recorded below the level of medullary nuclei are affected only minimally by general anesthesia. Synapses are the sites of action for inhalational anesthetic agents. There is no synapses between the peripheral stimulation sites and the medullary nuclei. From there they cross and ascend in the medial lemniscal pathways to thalamic nuclei, which in turn project up to the somatosenory cortex. They arrive at the medulla and make synaptic connection at the medullary nuclei (nucleus cuneatus and nucleus gracilis).

Multiple dorsal or posterior column spinal pathways such as the gracile fasciculus (legs and trunk) and the cuneate fasciculus (arms and trunk) mediate the SSEP responses. The ascending sensory volley enters the spinal cord through dorsal nerve roots. Since then SSEP has become one of the earliest and primary tools for intraoperative neurophysiological monitoring.ĭistal peripheral nerves are stimulated for SSEP recordings typically the median or ulnar nerve at the wrist for upper extremity SSEPs, or posterior tibial nerve at the ankle for lower extremity SSEPs. It was utilized as a supplement to the wake-up test during correctional spinal surgeries for spinal deformities such as scoliosis to provide warning of compromised spinal cord function to the spine surgeons, as reported by McCallum et al and Nash et al in the 1970s. Early in the 1960s Larson et al introduced the use of somatosensory evoked potentials to monitor neural structure during neurosurgical procedures. They are time-locked responses, representing the function of the ascending sensory pathways. Somatosensory Evoked Potentials (SSEPs) are electric signals recorded from the scalp or spine following stimulation to the peripheral nerves.

When you stimulate the dorsal column tract