Anterior neck recording of intraoperative somatosensory-evoked potentials in children
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S L Helmers1, L Carmant, D Flanigin
1Department of Neurology, Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Study Design:
The authors have developed technique of using anterior neck derivations to record posterior tibial nerve N28 during operative somatosensory-evoked potential monitoring.
Objective:
This prospective study of 10 patients compared the ease of application of electrodes and stability of waveforms with "traditional" posterior neck recordings.
Summary Of Background Data:
Somatosensory-evoked potential monitoring has been used in children since the 1980s. A number of important factors, patient related and technical, are unique to this age group, which can cause difficulty with execution and interpretation. A major patient-related problem is unreliability of the cortical response in somatosensory-evoked potential monitoring because of the effect of inhalation anesthesia. This has been described as occurring more often in the pediatric group, perhaps because of the continuing maturation of the complex somatosensory system. Thus, the authors have relied heavily on the cervical potential to monitor spinal cord integrity. Recording the cervical response using the traditional "posterior" montage may be technically impossible if the electrodes lie within the operative field.
Methods:
Posterior tibial somatosensory-evoked potentials were performed according to the guidelines of the American Electroencephalographic Society. Additional recordings were obtained from two anterior neck sites. Multiple reference electrodes were used to evaluate which montage rendered the most reliable waveform.
Results:
Optimal montage for recording an anterior neck potential was cricoid cartilage-Cz'. There were no significant differences in the onset latency or peak amplitudes between the anterior and posterior cervical recordings.
Conclusions:
The anterior neck derivation was found to be an acceptable adjunct to posterior montages, being stable, of comparable latency, and of stable amplitude. Electrodes are easier to apply, less invasive than nasopharyngeal or esophageal electrodes. This technique allows one to examine patients who previously could not be monitored.