The somato-sensory evoked potentials (PESS) represent the electrical potentials obtained by stimulating a peripheral nerve and recorded in the peripheral nerves, spinal cord and cerebral cortex. In practice, stimulation of the median nerve and tibial nerve is used.
Through this examination, the path of deep, proprioceptive sensitivity is explored functionally. PESS abnormalities can indicate somato-sensory pathway damage at any level.
Therefore, PESS are useful in highlighting and evaluating peripheral nervous system disorders such as hereditary neuropathies (Charcot-Marie-Tooth disease, Friedrich's ataxia), diabetic neuropathy, inflammatory polyradiculoneuropathies (Guillain-Barré disease), demyelinating neuropathies, infectious or toxic cause neuropathy, plexopathies and radiculopathies.
In spinal cord disorders, when the posterior cords are affected, PESS allow the localization of the pathological process as well as the differentiation of the demyelinating processes from the axonal ones.
PESS are also used in the evaluation of lesions in the brainstem and/or the hemispheres (strokes, multiple sclerosis or other demyelinating diseases, cranial-cerebral trauma).
PESS allow intraoperative monitoring in spinal cord surgery, intra- and extra-cranial vascular surgery.
The advantages of PESS are:
- The ability to detect infra-clinical or silent lesions of the sensory pathways
- Ability to provide data on demyelinating disease or can also establish lesion topography through multi-segmental stimulation and/or multilocular recording