[The use of somatosensory evoked potentials for cortical localization during surgical operations].
BACKGROUND
Identification of the cortical areas of Roland, by means of anatomical references seen on craniotomy, with a view to their conservation during surgical operations, is found to be associated with a high rate of error which may reach 50% with experienced surgeons.


METHODS
Somatosensory evoked potentials (PESS) following stimulation of the median nerve may easily be recorded using electrodes situated directly over the cerebral cortex of patients under general anaesthesia. To obtain this recording, a bipolar set-up of a series of between 6 and 10 electrodes in line one centimetre apart allows identification, by means of phase opposition, of the cortical zones, usually the parietal zone adjacent to the sulcus of Roland, where these potentials are generated. Identification of motor sites (area 4) can be obtained by electrical stimulation of the cerebral cortex, although we have rejected this type of exploration because of its technical difficulty and possible undesirable effects.


CONCLUSIONS
We consider that, when at surgical operation the cortical area corresponding to the median nerve is identified, and care taken not to damage the cortex 2 cm rostrally, excellent results may be obtained, reducing the sequelae which may occur with this type of surgery.
Recuero
E
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Servicio de Neurofisiología Clínica, Hospital Virgen de la Arrixaca, Murcia, España.
D002540:Cerebral Cortex / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D006801:Humans; D016343:Monitoring, Intraoperative / Q000379:methods*; D019635:Neurosurgical Procedures / Q000379:methods*