Eine neue Methode zur Frührehabilitation zentralbedingter Lähmungen von Arm und Hand mittels Magnetstimulation

Summary

Recent functional and morphological investigations have shown, that the sensorimotor cortex has a remarkable capability to modulate his excitability when the sensory inflow is diminished. In central paresis, as a consequence of the loss of movement, the proprioceptive afferent inflow is diminished and the corresponding body frame is disturbed. For rehabilitation of central paresis the lack of proprioceptive inflow should be compensated. So far, such a compensation can be only achieved by externally applied passive movements in physical therapy. When the lost movements are induced by stimulating the centrally paralyzed muscles, the associated proprioceptive inflow is much higher and corresponds closer to the voluntary action patterns.

Our goal was to restore reaching and grasping in spastic paresis of finger and hand muscles. To induce smooth movements, controlled repetitive stimulation is necessary. To avoid pain - p.e. as in transcutaneous electrical stimulation - we apply repetitive peripheral magnetic stimulation (RPMS), which activates predominantly myelinated nerve fibres lying in well conducting tissue. For this purpose we developed a high power magnetic stimulator, which can be computer-controlled in instananeous intensity (max. 1500 J) and rate (max. 40 s^-1). By placing the center of a figure-of-8 coil over the innervation zone, we can generate movements even of single fingers.

So far we investigated 6 stroke patients with no remarkable somatosensory deficits suffering from distal hemiplegia with spastic paresis of arm and hand (Ashworth 4-5).

Following two series of 30-50 cycles each of induced extension and also flexion movements of hand and fingers the patients could extend the paretic fingers with larger displacement amplitude at diminished amounts of spastic flexor activity (mean EMC). Concomittantly, also the voluntary (extensor) activity was rather lower, although the movement was larger and faster.

The patients reported a long lasting effect (some days) with improvement of grasping and finger extension movements. The long duration of the effect following RPMS, reported in all patients, suggests process of neuroplasticity.

RPMS applied to the innervation zone elicits proprioceptive inflow to the CNS adequately via induced muscle contractions as well as directly via stimulation of afferent fibres. Besides orthodromic activity also an antidromic inflow is elicited by RPMS in the alpha motoneurones.

The decrease of spasticity may be caused on spinal and supraspinal level; an inhibitory lb interneuronal population could be disinhibited either by increased Colgi-feedback or by increased descending drive, p.e. via spino-cerebellar pathways influencing brainstem systems. In addition, the Renshaw inhibition may be effective due to antidromic stimulation of alpha motoneurones. The increased inhibition of the spastic activity of the alpha motoneurones may lead to a higher excitability of the alpha moto-neurone pool for cortico-spinal drive.

Besides the inhibitory mechanisms also facilitatory mechanisms may contribute to the improved motor performance. Via lemniscal-thalamic pathways projecting to the parietal and sensory motor cortex the increased propioceptive drive elicited by RPMS could modulate the corticospinal motor command.

We assume that also other forms of spastic paresis can be treated successfully, or, in early stages of central paresis, the development of spasticity could even be prevented by immediate application of RPMS.

Zusammenfassung

Ausgehend von der Überlegung, durch Erzeugen propriozeptiver Zuströme zum Zentralnervensystem - entsprechend aktiven Bewegungsmustern - die modulatorischen und plastischen Prozesse des Zentralnervensystem anzuregen, wurden bei Patienten mit spastischer Parese von Arm und Hand Bewegungen von Hand und Finger mittels repetitiver peripherer magnetischer Stimulation induziert. Hierdurch konnten Hand und Finger schneller und weiter gestreckt werden (bei geringerer Willküraktivität), wodurch auch Greifbewegungen erleichtert oder überhaupt erst ermöglicht wurden. Dieser Konditionierungseffekt hielt regelmäßig 1 -2 Tage an.

Die Verringerung der Spastizität wird auf eine erhöhte Besetzbarkeit der a-Motoneurone für Willkürantriebe durch vermehrte Aktivierung zentraler Hemmechanismen zurückgeführt. Zur Verbesserung der Parese könnten auch zusätzliche, zentrale Bahnungsvorgänge beitragen.

Das lange Anhalten des Konditionierungseffekts läßt sich nicht mit einer akuten Neurotransmitterwirkung erklären; vielmehr müssen hierfür Vorgänge der Neuroplastizität angenommen werden.

Key words:

Spasticity - Spastic hemiplegia - Treatment - Rehabilitation - Repetitive magnetic stimulation