Somatosensible evozierte Potentiale in der Diagnostik von Armplexusläsionen

Summary

Simultaneous recording of SEP from the contralateral scalp, the lower neck (C 7) and Erb's point following median or ulnar nerve stimulation may be helpful in the localisation of lesions of the brachial plexus and associated spinal roots. In lesions proximal to the dorsal root ganglia, the potential recorded from Erb's point (EP), as well as the first component of the necl-SEP („NSEP 1”, „N 9”) are normal, whereas the following components of the cervical response („NSEP 2 + 3”, „N 11 + N 13”) are reduced or absent, depending on the severity of the functional impairment (Fig. 1). In lesions distal to the ganglia the EP-potential shows a significant reduction in amplitude as compared to the normal side. The neck- and scalp-SEP are less attenuated or even normal in this condition, because of the phenomenon of synaptic amplification (Fig. 2). Combined lesions of the brachial plexus and cervical roots, which especially occur in traumatic injuries are characterized by an attenuation of the EP-potential and a relatively larger attenuation or an absence of the neck-SEP (N 13) (Fig. 3). SEP examination may therefore be valuable in estimating the degree of involvement distal and proximal to the dorsal root ganglia.

Zusammenfassung

Die Untersuchung der somatosensiblen evozierten Potentiale (SEP) bei Armplexuslähmungen erlaubt bei simultaner Aufzeichnung der Reizantworten vom Nacken (C 7) und vom Erbschen Punkt (EP) eine Differenzierung in supraganglionäre, infraganglionäre und kombinierte Schädigungstypen. Diese diagnostische Möglichkeit ist besonders bei den häufigen traumatischen Formen von prognostischer Bedeutung und stellt bei geplanter operativer Therapie eine Hilfe bei der Wahl des angemessenen Operationsverfahrens dar.

Key Words:

Somatosensory evoked potentials - Brachial plexus lesions