H-reflex recovery curve in syringomyelia.

H-reflex recovery curves were obtained from 13 patients with cervical syringomyelia to assess motor neurone excitability, and results were compared with control subjects and patients with spasticity due to stroke. The median nerve was stimulated at the elbow and the H-reflex was recorded from the flexor carpi radialis muscle. Double pulses with interstimulus intervals ranging from 75 to 900 ms were delivered. The H-reflex was unobtainable from either limb in two patients with advanced disease and loss of all sensory modalities. H-reflex recovery curves from syrinx patients showed marked facilitation with interstimulus intervals ranging from 150 to 300 ms. Facilitation was higher than in patients with spasticity due to stroke. Results are indicative of an increased motor neurone excitability in patients with cervical syringomyelia.

Involuntary movements and abnormal spontaneous EMG activity in syringomyelia and syringobulbia.

OBJECTIVE: To describe different types of involuntary movements and abnormal spontaneous electromyographic (EMG) activity in patients with syringomyelia. BACKGROUND: A comprehensive study on involuntary movements in patients with syringomyelia has not yet been undertaken, to these authors' knowledge. METHODS: One hundred adult patients with syringomyelia were examined over the last 15 years. Involuntary movements were videotaped and evaluated by two independent observers. Electromyographic recordings were made using bipolar surface electrodes. The H-reflex recovery curve was obtained after stimulation of the median nerve at the elbow and recording from the flexor carpi radialis. RESULTS: Involuntary movements or abnormal postures were observed in 22 patients. Three patients showed segmental spinal myoclonus, nine minipolymyoclonus, and four propriospinal myoclonus. Five patients had unilateral or bilateral hand postural tremor (8-10 Hz). Focal or segmental dystonia was observed in three patients. Electromyography showed spontaneous bursts of grouped action potentials synchronous in muscles innervated by the same spinal segment, synchronous firing of neurogenic motor unit potentials, or continuous motor unit activity. Increased H-reflex responses to conditioning stimuli were found in patients with spinal myoclonus. Long latency responses were obtained during peripheral nerve stimulation in four patients. Four patients had rigidity and abnormal upper limb posture. Respiratory synkinesis was observed in three patients. One patient developed inverse masticatory muscle activity. CONCLUSIONS: Patients with syringomyelia showed a wide spectrum of involuntary movements. An increased excitability of spinal motor neurons was probably the basic underlying mechanism.