Transkranielle Magnetstimulation bei Querschnittverletzten mit Einzel- und Doppelreiztechnik

Summary

Motor evoked potentials (MEP's) are frequently used to assess spinal cord injuries. We performed MEP's in a healthy control group and in paraparetic patients with paired stimuli and two types of magnetic coils in order to compare the different coils and to study facilitation phenomena. The patient group I consisted of fourteen persons with a spinal cord injury, the patient group II included patients with a cauda equina syndrome. For stimulation a circular coil and a double cone coil were used. Interstimulus intervals varied between 10 and 60 ms. Recordings were taken from the tibialis anterior muscle.

In the healthy control group higher amplitudes were achieved when using the double cone coil; latencies were equal for both coils. In patient group I central motor conduction time was prolonged and MEP amplitudes were decreased (tab. 1 and 2). With the double cone coil a MEP could be elicited in 64 %, with the circular coil in 39 % (tab. 4). With paired stimuli an increase of amplitudes (120 %) was seen in the control group (fig. 1) whereas in patient group I increases of more than 600 % were registered (tab. 3). Paired stimuli evoked motor potentials in three of seven paralysed extremities (tab. 6). The best interstimulus interval was found to be between 30 and 40 ms (tab. 7). In patient group II no significant difference was seen between circular coil and double cone coil. This group did not show relevant facilitation effects with paired stimuli (tab. 5).

We conclude that the double cone coil is superior to the circular coil for the assessment of motor tracts to the legs. Facilitation phenomena are much more pronounced in patients with spinal cord injuries than in healthy controls or in patients with cauda equina syndrome. Using paired stimuli is an effective method to study the function of motor pathways to the legs, especially in patients with spinal cord disorders.

Zusammenfassung

Die motorischen Bahnen zu den unteren Extremitäten wurden mittels transkranieller Magnetstimulation bei Gesunden, Rückenmarkverletzten und Konus-Kauda-Patienten untersucht. Die Stimulationen erfolgten mit Rund- und Haubenspule in Einzel- und Doppelreiztechnik.

Die Haubenspule erbrachte höhere Amplituden als die Rundspule. Rückenmarkvcrlotzte zeigten wesentlich stärkere Fazilitierungsphänomene durch die Doppelstimulation im Vergleich zu Gesunden; in dieser Patientengruppe konnte die funktionelle Intaktheit der motorischen Bahn mit der Doppelreizung signifikant häufiger als mit Einzelstimulation nachgewiesen werden. Die optimalen Interstimulusintervalle lagen zwischen 30 und 40 ms. Konus-Kauda-Verletzte zeigten keine relevanten Fazilitierungen; Potentiale konnten jedoch häufiger mit der transkraniellen Magnetstimulation als mit der peripher-elektrischen Reizung evoziert werden.

Key words

Transcranial magnetic Stimulation - Spinal cord injury - Paired stimuli - Facilitation