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.

Cardiovascular reflexes and pudendal evoked responses in chronic haemodialysis patients.

The bulbocavernous reflex (BCR), cortical pudendal evoked responses (CPERs), non-invasive cardiovascular tests and nerve conduction studies were performed in 16 patients on chronic haemodialysis and in a group of normal subjects. BCR and CPERs were more severely affected in patients with impotence. There was a significant correlation between the Valsalva ratio and P1 latency of the CPERs. The BCR and CPERs are alternative techniques for the assessment of impotence in uremic patients.

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.

[Single fiber electromyogram in myasthenia gravis and other neuromuscular diseases]. / Electromiograma de fibra única en miastenia gravis y otras enfermedades neuromusculares.

Single fibre electromyography (SFEMG) has been used to study neuromuscular transmission and the degree of reinnervation in patients with myasthenia gravis (MG) (n = 70); Lambert-Eaton syndrome (n = 3); myopathies (n = 8); motor neuron disease (n = 4) and peripheral neuropathies (n = 3) (Table 1). An automatic method was used to calculate neuromuscular jitter by means of a PC computer, a TECA TD 20 electromyograph and a jittermeter. Twenty pairs of potentials were selected from the extensor digitorum communis muscle for analysis using a trigger unit and a delay line. Mean jitter and percentage of pairs with normal and abnormal jitter were calculated (Figs. 1 and 2). MG patients showed pairs with normal (Fig. 3) and other with abnormal jitter and intermittent blocking (Fig. 4). Abnormalities were found in 72% of patients with ocular MG, in 95% with mild generalized MG, in 93% with moderate generalized MG and in 100% of severe MG cases (Table 2), (Fig. 5). There was a significant correlation between patient disability and jitter values (Fig. 6). The method was useful for the follow-up during immunosuppressant treatment (Fig. 7). Patients with other myopathies showed normal or mildly increased jitter and increased fibre density. The most common abnormality in patients with neurogenic conditions was increased fibre density, which ranged from 2.1 to 4.3 (Figs. 8 and 9). The method used showed high sensitivity for the detection of neuromuscular transmission defects. In some cases an abnormal jitter was found even before the appearance of transmission block and therefore it was possible to find abnormalities in clinically normal muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrodiagnostic findings in syringomyelia.

Electrodiagnostic abnormalities are well known to occur in syringomyelia although the findings are nonspecific. The objective of this work was to describe different types of spontaneous electromyographic (EMG) activity and reflex responses, which may be useful and more specific than conventional findings for the electrodiagnosis of syringomyelia. We studied 43 patients with syringomyelia by four-channel surface EMG and by recording the long-latency responses to distal stimulation of the median and tibial nerves. Continuous motor unit activity (CMUA) was found in 18 patients, synchronous motor unit potentials (SMUP) in 10, respiratory synkinesis (RS) in 5, and myokymic discharges in 4. Long-latency responses (LLR) with latencies ranging from 55 to 150 ms were found in 14 patients. Patients with syringomyelia thus show a wide variation of spontaneous EMG activity. An increase in excitability of spinal motor neurons is probably the basic underlying mechanism.

Automatic analysis of heart rate variation: I. Method and reference values in healthy controls.

Many patients referred to an electrophysiological laboratory may have autonomic dysfunction. Some parasympathetic tests are based on the assessment of heart rate variation induced by breathing, Valsalva maneuver, and standing. We have developed fast and practical computer-based methods to analyze heart rate variation using standard EMG equipment and a personal computer. For quantitative description we have evaluated different algorithms, both earlier described and new ones. Findings in patients with diabetes have been compared with those obtained from healthy subjects in order to determine the diagnostic utility of the various algorithms. The optimal algorithm has been chosen by this and other criteria, and a reference database from healthy subjects has been developed.

Automatic analysis of heart rate variation: II. Findings in patients attending an EMG laboratory.

An automatic method was used to measure the heart rate variation with breathing in patients with different neuromuscular conditions attending a laboratory of electromyography (EMG). The objective was to determine the frequency of abnormalities in various conditions and the relationship between R-R variation and different nerve conduction parameters. The percentages of reduced R-R variation were 73% in diabetics, 35% in Guillain-Barré syndrome, 22% in amyotrophic lateral sclerosis, and 50% in amyloidosis. R-R variation in diabetics was significantly correlated to most parameters of nerve conduction. In Guillain-Barré syndrome it correlated significantly with the ulnar and median M-response amplitudes. Most patients with myopathies showed normal R-R variation.

Risk of sudden death during sleep in syringomyelia and syringobulbia.

Clinical, respiratory, and polysomnographic findings in three patients with syringomyelia and syringobulbia who developed severe respiratory complications are described. Neurological examination showed evidence of IXth and Xth cranial nerve involvement with dysphagia and dysphonia, but there were no complaints of serious sleep difficulties. Two patients died during sleep and the other was resuscitated during a nap. All patients showed moderate restrictive ventilatory defects with reduced maximal buccal pressures and one also showed a low ventilatory response to CO2 rebreathing. Protracted central, obstructive, and mixed apnoeas and hypopnoeas were commonly observed during sleep. There were no changes in heart rate during these events. A combination of respiratory and cardiovascular mechanisms might have been responsible for the severe complications described.

Dystonia and reflex sympathetic dystrophy induced by ergotamine.

A 59-year-old man developed dystonia and reflex sympathetic dystrophy after receiving high doses of ergotamine for migraine treatment. Ischemia is suggested as the precipitating factor.

Cardiovascular reflexes in syringomyelia.

Cardiovascular reflexes were assessed by simple noninvasive tests in 18 patients with syringomyelia restricted to the spinal cord (syringomyelia) and 22 patients with syringomyelia and brainstem signs (syringobulbia), and the results compared with a control group. Postural hypotension occurred more frequently in patients with bilateral brainstem signs, palatal weakness or vocal cord palsy. Vagal cardiovascular reflexes were disturbed in patients with clinical evidence of involvement of the Xth cranial nerve, and also in those with other brainstem signs. The integrity of the efferent limb of the reflex arc was demonstrated in three patients by testing the heart rate response to intravenous atropine. It was observed that cardiovascular reflexes may be impaired in patients free of symptoms of autonomic dysfunction. These findings may be relevant to the occurrence of sudden death in such patients and to the possible anatomical localization of the defect.

Polyneuropathy in occult hypothyroidism.

A patient who developed symptoms and signs of a polyneuropathy was found to have hypothyroidism, though this diagnosis was not clinically suspected. Treatment with thyroxine resulted in resolution of his symptoms and restored his nerve conduction studies to normal.

Subarachnoid and intramedullary cysts secondary to epidural anesthesia for gynecological surgery.

Three women who received epidural anesthesia for gynecological surgery developed spinal arachnoiditis leading to subarachnoid cysts and cord cavitation. MRI was useful to show the subarachnoid and intramedullary cysts, as well as to monitor lesion extent and progress. Associated MRI findings were a Chiari anomaly in 1 case and a tethered cord in another. Two cases underwent surgery: 1 improved, but the other suffered progressive neurological deterioration. Although the 3rd patient had no treatment, there was spontaneous reduction in cavity size and clinical improvement. Careful handling of this procedure is urged to avoid such severe complications in young mothers.

SEPs and CNS magnetic stimulation in syringomyelia.

Somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) to transcranial and spinal stimulation from upper and lower limb muscles were elicited in 13 patients with syringomyelia. Seven had an associated Chiari type I anomaly. Diagnosis was confirmed by MRI. In 5 cases, SEPs and MEPs were performed before and after surgical treatment. Prolonged central motor conduction times or absent motor responses in upper or lower limbs were found in most patients. The greatest number of abnormalities was disclosed by measurement of CMCT followed by SEPs after tibial nerve stimulation. Two of 5 cases undergoing surgery improved clinically and showed reduction in CMCT after surgical treatment. Our study shows that MEPs were useful in the evaluation of neurophysiological status in syringomyelia patients, helping to estimate anterolateral spinal cord function.

Cardiovascular and respiratory consequences of bilateral involvement of the medullary intermediate reticular formation in syringobulbia.

We studied five patients with clinical and radiological evidence of syringobulbia (SB) to determine whether the distribution of lesions in relationship to the cardiorespiratory control networks in the medullary intermediate reticular zone (IRt) correlates with the presence of abnormalities in autonomic cardiovascular and respiratory control in these patients. All patients underwent high resolution MRI to characterize the size, volume and distribution of the SB lesions, cardiovascular autonomic function testing and polysomnography. One patient with bilateral IRt involvement at both the rostral and caudal medulla had orthostatic hypotension (OH), absent HR(DB), abnormal Valsalva ratio, exaggerated fall of BP during phase II and absent phase IV during VM, and a dramatic fall of BP during head up tilt; this patient also had severe obstructive sleep apnea (OSA) and exhibited BP drops during each respiratory effort. A second patient, with bilateral IRt involvement restricted to the caudal medulla, had less severe cardiovascular autonomic dysfunction but also exhibited severe OSA. The other three patients had small SB cavities sparing the IRt and had sleep apnea but no autonomic dysfunction. Autonomic dysfunction could not be related to the size of the syrinx or the degree of atrophy in the cervical spinal cord in any of the five patients. Bilateral involvement of the IRt by SB produces cardiovascular autonomic failure and sleep apnea. In patients with more restricted lesions, autonomic and respiratory dysfunction may be dissociated. Clinico-radiological correlations using high resolution MRI assessment of medullary lesions can provide insight into the central organization of cardiovascular and respiratory control in humans.