Propriospinal myoclonus: a neurophysiologic analysis

Electrophysiology in Functional Movement Disorders: An Update

Background

Functional movement disorders (FMD) are a diagnostic and therapeutic challenge, both to the neurologist and psychiatrists. The phenomenology is varied and can present as tremors, dystonia, jerks/myoclonus, gait disorder, other abnormal movements or a combination. There has been an increase in the use of electrophysiological studies that are an important tool in the evaluation of FMDs.

Methods

We searched the database platforms of MEDLINE, Google scholar, Web of Sciences, Scopus using the Medical Subject Heading terms (MeSH) for all the articles from 1st January 1970 till November 2022. A total of 658 articles were obtained by the search mechanism. A total of 79 relevant articles were reviewed thoroughly, of which 26 articles that had electrophysiological data were included in the present review.

Results

Variability, distractibility and entertainability can be demonstrated in functional tremors by using multichannel surface electromyography. Voluntary ballistic movements tend to decrease the tremor, while loading the tremulous limb with weight causes the tremor amplitude to increase in functional tremor. Presence of Bereitschaftspotential demonstrates the functional nature of palatal tremor and myoclonus. Co-contraction testing may be helpful in differentiating functional from organic dystonia. The R2 blink reflex recovery cycle has been found to be abnormally enhanced in organic blepharospasm, whereas it is normal in presumed functional blepharospasm. Plasticity is found to be abnormally high in organic dystonia and normal in functional dystonia, in addition to enhanced facilitation in patients with organic dystonia.

Conclusions

Electrophysiological tests supplement clinical examination and helps in differentiating FMD from organic movement disorders.

Periodic Limb Movements during Sleep in Acute Stroke: Prevalence, Severity and Impact on Post-Stroke Recovery

BACKGROUND

Periodic Limb Movements during Sleep (PLMS) have been described to be frequently present in stroke patients. We aimed to evaluate the prevalence and severity of PLMS in acute stroke patients and clarify the association between PLMS and coexisting Sleep Disordered Breathing (SDB). Additionally, we focused on identifying variables that could independently predict the presence of PLMS in patients with acute stroke. The potential impact of PLMS on stroke outcome at three months was investigated as well.

METHODS

In this study, we performed overnight polysomnography on consecutive stroke patients within 72 h from symptom onset. Data regarding clinical and imaging characteristics were prospectively collected. National Institute of Health Stroke Scale (NIHSS), modified Rankin Scale (mRS) and Epworth-Sleepiness Scale (ESS) were used to evaluate stroke severity on admission, stroke outcome at three months and history of daytime sleepiness, respectively. We documented PLMS and SDB using standard polysomnography criteria.

RESULTS

We prospectively assessed 126 patients with acute stroke [109 with ischemic and 17 with hemorrhagic stroke, mean age 60 ± 11 years, 68% men, median NIHSS score on admission: 3 (IQR: 2-7)]. The overall rate of PLMS in our cohort was 76%, and the rate of SDB among patients with PLMS was 83%. PLMS detection rates differed significantly (p-value: <0.001) according to SDB, with PLMS prevalence increasing with greater SDB severity. SDB could independently (OR:4.869, 95% CI: 1.884-12.784, p-value: 0.001) predict the presence of PLMS in the acute stroke phase in multivariable analyses adjusting for potential confounders. Moreover, baseline stroke severity (NIHSS-score increase in per-1 point: OR: 0.819, 95% CI: 0.737-0.895, p-value < 0.001) and PLMS (OR:0.099, 95% CI: 0.009-0.482, p-value = 0.015) were significantly associated with the likelihood of excellent functional outcome (mRS-scores: 0-1) at 3 months.

CONCLUSION

The common presence of mostly severe PLMS in patients with acute stroke and their negative effect on stroke outcomes point out the necessity for early PLMS detection and treatment.

[A case of idiopathic propriospinal myoclonus accompanied by giant somatosensory evoked potential]

A 41-year-old man visited our clinic because of headache with fever, suggestive of aseptic meningitis. His headache improved in a few days. His neurological examination showed positive jolt accentuation and myoclonus of the thoracoabdominal muscles extending to extremities upon patellar tapping. His myoclonus had been occurring spontaneously from early adolescence, especially in relaxed states such as drowsiness. The myoclonus was not triggered by tactile, auditory, or visual stimulation. Polymyography revealed that the myoclonus originated around the T4 spinal level and slowly propagated both upward and downward. These findings were indicative of spontaneous and reflex propriospinal myoclonus (PSM). No abnormalities were seen on brain and spinal MRI. Furthermore, the amplitude of the cortical component of the somatosensory evoked potential (SEP) after electrical stimulation of the tibial nerve was enlarged bilaterally. It was speculated that the ascending signals from the myoclonus generator at T4 to S1 may have modulated the excitability and inhibitory function of S1 in this patient. This report may be the first case of idiopathic PSM accompanied by giant SEP.

Repetitive sleep starts: An important differential diagnosis of infantile spasms

OBJECTIVE

Repetitive sleep starts (RSS) are clusters of nonepileptic, spasm-like movements occurring during sleep onset. However, their characteristics have yet to be defined. We conducted a clinicoelectroencephalographic study of children with RSS to clarify their detailed characteristics.

METHODS

To differentiate starts from epileptic spasms, we recruited children with brief "crescendo-decrescendo" muscle contractions that simultaneously involved the limbs and trunk without electroencephalogram changes, and that fulfilled the following criteria: (1) repeated occurrence (five or more) and (2) manifestation during sleep stage N1-N2. A total of nine children met these criteria. Their clinical information and video-electroencephalogram data were analyzed retrospectively.

RESULTS

The background conditions observed at onset of RSS were perinatal hypoxic-ischemic encephalopathy (n = 4), West syndrome of unknown etiology (n = 1), and traumatic brain injury (n = 1). The age at onset of RSS, the number of starts in a given RSS cluster, the interval between starts, and the duration of surface electromyogram activity were between 3 and 46 months, 5 and 547, <1 and 60 s, and 0.3 and 5.4 s, respectively. None of the median value of these parameters differed between children with and without corticospinal tract injury. During the median follow-up period of 33 months, RSS disappeared spontaneously in five.

CONCLUSION

This is the largest case series of RSS clarifying their clinicoelectroencephalographic characteristics reported to date. To avoid unnecessary antiepileptic therapies, clinicians should be aware of RSS and distinguish it from other disorders involving involuntary movements or seizures, especially epileptic spasms.

Propriospinal Myoclonus

Propriospinal myoclonus (PSM) consists of paroxysmal and sudden jerks involving axial flexion trunk and hip muscles, conditioning sudden myoclonias of the trunk and arms/limbs, both spontaneous and triggered by sensory stimulations, emerging in relaxed wakefulness typically during the transition between wake and sleep. Generally, PSM originates from a thoracic myelomere and spreads caudally and rostrally, provoking flexion and/or extension movements, leading to jumps or trunk jerks. They appear triggered by the lying-down position and disappear when the subject stands up. The main consequences are the difficulties in sleep start and the reappearance during the period of wakefulness after sleep onset.

Spinal myoclonus: a rare presentation of cervical myelopathy

Myoclonus describes a movement disorder characterised by brief, abrupt and involuntary contractions of muscles or groups of muscles, usually associated with intracranial lesions, with limited evidence linking it to spinal pathologies. The pathophysiology of spinal myoclonus is extensive and multifactorial. Infection, intramedullary and extramedullary space-occupying lesions, trauma, vascular abnormalities, degenerative processes and cervical spondylosis have been implicated with the disease, the latter been associated with cervical stenosis with no reported cases linking it to an underlying cervical disc herniation. Although medical therapy with clonazepam, levetiracetam, valproate, tetrabenazine hydrochloride and spinal block injections has been equivocal, spinal myoclonus secondary to disc herniation requires surgical intervention. This report describes a case of segmental spinal myoclonus, secondary to a herniated cervical intervertebral disc. After corpectomy and a cage-augmented fusion technique, the myoclonic symptoms resolved. To our knowledge, this was the first report to describe the successful management of discogenic spinal myoclonus with spinal surgery.

Electrophysiological Investigations in Orthostatic Myoclonus: Preliminary Findings

We report the clinical and electrophysiological findings in seven patients with orthostatic myoclonus (OM) associated with gait initiation failure and falls. OM is one of the causes of unsteadiness of stance and gait, and it may develop as a symptom of neurodegenerative disorders. Both positive myoclonic bursts and negative myoclonus may be seen in electrophysiological recordings, and electrophysiological analysis suggests a subcortical origin for OM.

And yet it moves: Recovery of volitional control after spinal cord injury

Preclinical and clinical neurophysiological and neurorehabilitation research has generated rather surprising levels of recovery of volitional sensory-motor function in persons with chronic motor paralysis following a spinal cord injury. The key factor in this recovery is largely activity-dependent plasticity of spinal and supraspinal networks. This key factor can be triggered by neuromodulation of these networks with electrical and pharmacological interventions. This review addresses some of the systems-level physiological mechanisms that might explain the effects of electrical modulation and how repetitive training facilitates the recovery of volitional motor control. In particular, we substantiate the hypotheses that: (1) in the majority of spinal lesions, a critical number and type of neurons in the region of the injury survive, but cannot conduct action potentials, and thus are electrically non-responsive; (2) these neuronal networks within the lesioned area can be neuromodulated to a transformed state of electrical competency; (3) these two factors enable the potential for extensive activity-dependent reorganization of neuronal networks in the spinal cord and brain, and (4) propriospinal networks play a critical role in driving this activity-dependent reorganization after injury. Real-time proprioceptive input to spinal networks provides the template for reorganization of spinal networks that play a leading role in the level of coordination of motor pools required to perform a given functional task. Repetitive exposure of multi-segmental sensory-motor networks to the dynamics of task-specific sensory input as occurs with repetitive training can functionally reshape spinal and supraspinal connectivity thus re-enabling one to perform complex motor tasks, even years post injury.

Bulbar and Limb Myorhythmia with "Smooch Sign": A Distinctive Movement Disorder in an Adult Patient with Reversible Anti-NMDA Receptor Encephalitis Associated with an Ovarian Teratoma

Anti-N-Methyl-D-Aspartate receptor encephalitis is a recently described entity (Dalmau et al. 2007, 2008) that may present with a variety of complex movements in addition to other features (Kleinig et al. 2008). The purpose of our presentation of such a patient is twofold: (1) to characterize these complex oculo-oro-linguo-masticatory and limb movements with "smooch sign" as myorhythmia, based on a combined clinical and electrophysiological analysis (Masucci et al. 1984); and (2) to document possibly characteristic EEG evolution in the course of observation in our institution for three weeks from diffuse slowing to evolving rhythmic delta activity, which may represent a pattern of electrographic seizure activity.

Functional jerks, tics, and paroxysmal movement disorders

Functional jerks are among the most common functional movement disorders. The diagnosis of functional jerks is mainly based on neurologic examination revealing specific positive clinical signs. Differentiation from other jerky movements, such as tics, organic myoclonus, and primary paroxysmal dyskinesias, can be difficult. In support of a functional jerk are: acute onset in adulthood, precipitation by a physical event, variable, complex, and inconsistent phenomenology, suggestibility, distractibility, entrainment and a Bereitschaftspotential preceding the movement. Although functional jerks and tics share many similarities, characteristics differentiating tics from functional jerks are: urge preceding the tic, childhood onset, rostrocaudal development of the symptoms, a positive family history of tics, attention-deficit hyperactivity disorder or obsessive-compulsive symptoms, and response to dopamine antagonist medication. To differentiate functional jerks from organic myoclonus, localization of the movements can give direction. Further features in support of organic myoclonus include: insidious onset, simple and consistent phenomenology, and response to benzodiazepines or antiepileptic medication. Primary paroxysmal dyskinesias and functional jerks share a paroxysmal nature. Leading in the differentiation between the two are: a positive family history, in combination with video recordings revealing a consistent symptom pattern in primary paroxysmal dyskinesias. In this chapter functional jerks and their differential diagnoses will be discussed in terms of epidemiology, symptom characteristics, disease course, psychopathology, and supportive neurophysiologic tests.

A restless abdomen and propriospinal myoclonus like at sleep onset: an unusual overlap syndrome

We report for the first time the association between restless abdomen, a phenotypic variant of restless legs syndrome in which symptoms are limited to the abdomen, and propriospinal myoclonus at sleep onset causing severe insomnia. The treatment with a low-dosage of dopaminergic drug (pramipexole) induced the immediate disappearance of both symptoms, which was documented by video-polysomnography.

Propriospinal myoclonus: The spectrum of clinical and neurophysiological phenotypes

Propriospinal myoclonus (PSM) is a rare type of spinal myoclonus characterized by muscle jerks that usually start in the midthoracic segments and then slowly propagate up and down into the spinal cord, resulting in repetitive and irregular jerky flexion, or extension of the trunk, neck, knees and hips. PSM can be symptomatic, but up to 80% of reported cases appear idiopathic. PSM tends to occur especially while the subject is lying down. PSM at sleep onset was first described by experts in sleep medicine. The original electrophysiological features included fixed pattern of muscle activations, slow spinal cord conduction (5-15 m/s), electromyographic burst duration less than 1000 ms, synchronous activation of agonist and antagonist muscles and no involvement of facial muscles. PSM has been reported to be a functional (psychogenic) movement disorder in a number of cohorts. The differential diagnosis between idiopathic PSM and the functional forms is not always straightforward. A consistent polymyographically documented muscle activation pattern may be supportive but by no means sufficient and additional neurophysiological investigations are required. PSM should be differentiated from other movement disorders involving the abdomen and trunk, or occurring at sleep-wake transition. This article offers a comprehensive overview of the spectrum of PSM phenotypes.

Propriospinal myoclonus: clinical reappraisal and review of literature

OBJECTIVE

Propriospinal myoclonus (PSM) is a rare disorder with repetitive, usually flexor arrhythmic brief jerks of the trunk, hips, and knees in a fixed pattern. It has a presumed generation in the spinal cord and diagnosis depends on characteristic features at polymyography. Recently, a historical paradigm shift took place as PSM has been reported to be a functional (or psychogenic) movement disorder (FMD) in most patients. This review aims to characterize the clinical features, etiology, electrophysiologic features, and treatment outcomes of PSM.

METHODS

Re-evaluation of all published PSM cases and systematic scoring of clinical and electrophysiologic characteristics in all published cases since 1991.

RESULTS

Of the 179 identified patients with PSM (55% male), the mean age at onset was 43 years (range 6-88 years). FMD was diagnosed in 104 (58%) cases. In 12 cases (26% of reported secondary cases, 7% of total cases), a structural spinal cord lesion was found. Clonazepam and botulinum toxin may be effective in reducing jerks.

CONCLUSIONS

FMD is more frequent than previously assumed. Structural lesions reported to underlie PSM are scarce. Based on our clinical experience and the reviewed literature, we recommend polymyography to assess recruitment variability combined with a Bereitschaftspotential recording in all cases.

Clinical diagnosis of propriospinal myoclonus is unreliable: an electrophysiologic study

Propriospinal myoclonus is a rare movement disorder that is hypothesized to arise from a spinal generator that transmits activity up and down the spinal cord via long propriospinal pathways. Polymyography is mandatory for the diagnosis, but the typical electrophysiological pattern described for propriospinal myoclonus has been also found in patients with psychogenic axial jerks, supported by the presence of a Bereitschaftspotential (BP; from German, "readiness potential," also called the premotor potential). We evaluated polymyographic findings in 65 patients referred to us with a clinical diagnosis of propriospinal myoclonus and also looked for the presence of the BP, as detected by jerk-locked back-averaging. At clinical reassessment by a movement disorder specialist, nearly one-half of the patients had clinical clues suggestive of a psychogenic cause of the jerks. Electrophysiological studies were carried out on all 65 patients. Polymyography findings revealed an incongruent electromyographic pattern for propriospinal myoclonus in 84.6% of patients and the presence of the BP in 86.1% of the entire cohort. When taking into account either the presence of BP and/or incongruence of polymyographic features, all patients, including the approximately 50% clinically diagnosed as organic propriospinal myoclonus by a movement disorder expert, had strong neurophysiological evidence for a psychogenic origin of their jerks. The clinical distinction of propriospinal myoclonus from psychogenic axial jerks is unreliable. This is the largest cohort of patients with axial jerks reported so far and we suggest that most of the patients with a clinical picture that clinically resembles propriospinal myoclonus are likely to be psychogenic.

Periodic leg movements in sleep in patients with supratentorial cerebral infarction

The pathophysiology of periodic leg movements in sleep (PLMS) is complex, and still lacks a consensus. Consecutive 35 patients with the diagnosis of acute supratentorial ischemic stroke and 35 age- and sex-matched control subjects were prospectively investigated. Clinical and sociodemographic evaluation and a whole-night polysomnographic recording were performed. In patients with supratentorial ischemic stroke, 27 patients (77.2%) had PLMS-index more than 5/h, and 19 out of 35 patients (54.3%) had PLMS-index more than 15/h; while only 10 participants (28.5%) in control group had PLMS-index more than 5/h, and 6 participants (17.1%) had PLMS-index more than 15/h (p < 0.05). None of the demographic variables showed statistically significant relationship with PLMS, such as gender (p = 0.952) and age (p = 0.435). Territorial localization of ischemic lesions showed no relation with the presence of PLMS (p = 0.867), PLMS-index (p = 0.432), or restless legs syndrome (p = 0.833). All patients demonstrated PLMS contralateral to ischemic lesion except eight patients with bilateral PLMS; these were also more prominent contralaterally. Our study supports the hypothesis that destructive lesions causing the loss of cortical or subcortical inhibition exerting on the reticular formation on spinal pathways could lead to the development of PLMS.

Reversible propriospinal myoclonus due to thoracic disc herniation: long-term follow-up

PSM is a rare form of myoclonus of spinal origin. The thoracic level is considered as the myoclonic generator in most cases; however, structural abnormality in conventional magnetic resonance imaging (MRI) related to PSM is more rare. We report the case of a 23-year-old man with PSM with ventral thoracic disc herniation confirmed by conventional MRI, which completely resolved after thoracic discectomy. This case indicates that decompressive surgery might be a valid treatment option.

Propriospinal myoclonus in a child

A 6-year-old girl was experiencing repetitive involuntary and massive jerks immediately involving limbs and trunk. The first motor events appeared approximately at 1 year old and only 5 months after a back trauma. Myoclonus became progressively more frequent and more violent, causing episodes of falls. Neurological examination showed jerks characterized by upper limb abduction, lower limb abduction, and head-body hyperextension. Apart from these motor events, the neurological examination was normal. The results of vitamin B(12) and folate, antinuclear antibody, anti-DNA, anti-Tiroglobulin, anti-thyroid peroxidase antibody, lupus anticoagulant, anti-cardiolipin antibody, rheumatoid factor, and C3 and C4 were unexceptional. Electroencephalography and brain and spinal magnetic resonance imaging were unremarkable. Electromyographic records with surface electrodes showed that duration of myoclonic jerks was ranging from 100 to 300 ms. We thought she had propriospinal myoclonus because of presence of the spreading through the shoulder, upper limbs, and lower limbs in addition to thoracolumbar paraspinal muscles.

Axial jerks: a clinical spectrum ranging from propriospinal to psychogenic myoclonus

Propriospinal myoclonus (PSM) is a rare disorder with repetitive flexor, arrhythmic jerks of the trunk, hips and knees. Its generation is presumed to relay in the spinal cord. We report a case series of 35 consecutive patients with jerks of the trunk referred as possible PSM to a tertiary referral center for movement disorders. We review classical PSM features as well as psychogenic and tic characteristics. In our case series, secondary PSM was diagnosed in one patient only. 34 patients showed features suggestive of a psychogenic origin of axial jerks. Diagnosis of psychogenic axial jerks was based on clinical clues without additional investigations (n = 8), inconsistent findings at polymyography (n = 15), regular eye blinking preceding jerks (n = 2), or the presence of a Bereitschaftspotential (BP) (n = 9). In addition, several tic characteristics were noted. Almost all patients referred with possible PSM in our tertiary referral clinic had characteristics suggesting a psychogenic origin even in the presence of a classic polymyography pattern or in the absence of a BP. Clinical overlap with adult-onset tics seems to exist.

Poststroke restless legs syndrome and lesion location: anatomical considerations

Several case studies have reported on restless legs syndrome (RLS) associated with stroke. In this study, we investigated the prevalence and the lesion topography of poststroke RLS. There were 137 patients with ischemic stroke included in this study. The diagnosis of RLS was made 1 month after the index stroke using the criteria established by the International RLS Study Group. All patients enrolled underwent magnetic resonance imaging within 7 days of the onset of the stroke. The prevalence of stroke-related RLS was calculated, and the topography of the associated ischemic lesions was analyzed. Among 137 patients, 17 patients (12.4%) were diagnosed with RLS after a stroke. Stroke-related RLS was found in 10 out of 33 patients with a basal ganglia/corona radiata infarct (30.3%), 1 out of 8 patients with an internal capsular infarct (12.5%), and 1 out of 7 patients with a thalamic infarct (14.3%). In addition, one out of 54 with a cortical lesion with/without subcortical involvement (1.9%), and 4 out of 18 patients with a pontine lesion (22.2%) had RLS. The analysis of the lesions in the cortical and subcortical group showed only 1 patient in the cortical group had stroke-related RLS, whereas 16 in the subcortical group had stroke-related RLS. The results of this study suggest that lesions of the subcortical brain areas such as the pyramidal tract and the basal ganglia-brainstem axis, which are involved in motor functions and sleep-wake cycles, may lead to RLS symptoms in patients after an ischemic stroke.

Propriospinal myoclonus: Utility of magnetic resonance diffusion tensor imaging and fiber tracking

Propriospinal myoclonus (PSM) is a rare movement disorder characterized by involuntary spinal-generated muscular jerks that spread rostrally and caudally to other spinally innervated muscles. Most patients have no clear etiology, and conventional MRI of the spinal cord is generally normal. Here we report the use of magnetic resonance diffusion tensor imaging (DTI) and fiber tracking to detect tract-specific abnormalities in a patient with propriospinal myoclonus. As the patient had the fragile-X premutation and antithyroid antibodies, spinal cord DTI abnormalities may be related to these conditions. Tract-specific analysis may provide new insights into the pathophysiology of propriospinal myoclonus.

Electromyography patterns of propriospinal myoclonus can be mimicked voluntarily

In order to investigate the clinical impact of polymyographic evaluation on the diagnosis of propriospinal myoclonus (PSM), we performed electromyography recordings of various truncal muscles in eight healthy volunteers while they mimicked PSM symptoms. Before the experiment, each volunteer learned how to mimic PSM by watching a videotape that showed typical PSM characteristics, i.e., brief symmetric flexion of the trunk. The recorded polymyographic patterns of all volunteers were quite compatible with those found in the previous reports. The present study demonstrates that previously known polymyographic patterns of PSM can be voluntarily mimicked. Additional studies, such as jerk-locked cortical potential, are required to confirm the diagnosis of true PSM.

Spinal myoclonus after spinal cord injury

BACKGROUND/OBJECTIVE

In the course of examining spinal motor function in many hundreds of people with traumatic spinal cord injury, we encountered 6 individuals who developed involuntary and rhythmic contractions in muscles of their legs. Although there are many reports of unusual muscle activation patterns associated with different forms of myoclonus, we believe that certain aspects of the patterns seen with these 6 subjects have not been previously reported. These patterns share many features with those associated with a spinal central pattern generator for walking.

METHODS

Subjects in this case series had a history of chronic injury to the cervical spinal cord, resulting in either complete (ASIA A; n = 4) or incomplete (ASIA D; n = 2) quadriplegia. We used multi-channel electromyography recordings of trunk and leg muscles of each subject to document muscle activation patterns associated with different postures and as influenced by a variety of sensory stimuli.

RESULTS

Involuntary contractions spanned multiple leg muscles bilaterally, sometimes including weak abdominal contractions. Contractions were smooth and graded and were highly reproducible in rate for a given subject (contraction rates were 0.3-0.5 Hz). These movements did not resemble the brief rapid contractions (ie, "jerks") ascribed to some forms of spinal myoclonus. For all subjects, the onset of involuntary muscle contraction was dependent upon hip angle; contractions did not occur unless the hips (and knees) were extended (ie, subjects were supine). In the 4 ASIA A subjects, contractions occurred simultaneously in all muscles (agonists and antagonists) bilaterally. In sharp contrast, contractions in the 2 ASIA D subjects were reciprocal between agonists and antagonists within a limb and alternated between limbs, such that movements in these 2 subjects looked just like repetitive stepping. Finally, each of the 6 subjects had a distinct pathology of their spinal cord, nerve roots, distal trunk, or thigh; in 4 of these subjects, treatment of the pathology eliminated the involuntary movements.

CONCLUSION

The timing, distribution, and reliance upon hip angle suggest that these movement patterns reflect some elements of a central pattern generator for stepping. Emergence of these movements in persons with chronic spinal cord injury is extremely rare and appears to depend upon a combination of the more rostrally placed injury and a pathologic process leading to a further enhancement of excitability in the caudal spinal cord.

Case of symptomatic propriospinal myoclonus evolving toward acute “myoclonic status”

Propriospinal myoclonus is a rare motor disorder consisting of involuntary spinal-generated muscular jerks. Here, we report a severe and uncommon case of propriospinal myoclonus that appeared after a vertebral fracture of T11. In this patient, the polysomnographic investigation showed continuing focal myoclonic activity in axial muscles during stable sleep and an acute progression into a myoclonic "status" associated with respiratory failure and loss of consciousness. It is necessary to consider this severe progression and support it with prompt emergency maneuvers and adequate pharmacotherapy.

Propriospinal myoclonus due to cervical disc herniation. Case report

Propriospinal myoclonus is a rare form of spinal myoclonus. In most cases the cause has remained unclear. Secondary propriospinal myoclonus has been described secondary to various disorders including trauma, tumor, and infection. Thus far, propriospinal myoclonus caused by cervical disc herniation has not been reported. In the present report, the authors describe the case of a 53-year-old man who presented with radicular symptoms of the right C-6 nerve root and myoclonic twitches predominantly affecting the abdominal muscles but spreading to adjacent muscles. The spread was triggered and enforced by certain movements. Magnetic resonance imaging studies revealed a C-6 nerve root compression at the C5-6 level on the right side but no cervical myelopathy. Electromyography studies confirmed the diagnosis of propriospinal myoclonus. After discectomy and cage-augmented fusion via an anterior approach, the myoclonic movement disorder gradually subsided. To the authors' knowledge, this is the first report on successful treatment of propriospinal myoclonus by spinal disc surgery.

Electrophysiological studies of myoclonus

As myoclonus is often associated with abnormally increased excitability of cortical structures, electrophysiological studies provide useful information for its diagnosis and classification, and about its generator mechanisms. The electroencephalogram-electromyogram polygraph reveals the most important information about the myoclonus of interest. Jerk-locked back-averaging and evoked potential studies combined with recording of the long-latency, long-loop reflexes are useful to investigate the pathophysiology of myoclonus further, especially that of cortical myoclonus. Recent advances in magnetoencephalography and transcranial magnetic stimulation have contributed significantly to the understanding of some of the cortical mechanisms underlying myoclonus. Elucidation of physiological mechanisms underlying myoclonus in individual patients is important for selecting the most appropriate treatment.

Epilepsia partialis continua of the abdominal muscles: a detailed electrophysiological study of a case

We describe the clinical and electrophysiological features of an elderly woman presenting with persistent clonic twitching of the abdominal muscles that were considered to represent a rare manifestation of epilepsia partialis continua due to a metastatic cortical lesion.

Propriospinal myoclonus after treatment with ciprofloxacin

The clinical and electrophysiological features of a truncal myoclonus in a 55-year-old man are described. The electromyographic characteristics point toward propriospinal myoclonus. It is suggested that a myoclonic generator was released after use of ciprofloxacin, by antagonising the gamma-aminobutyric acid metabolism.

Periodic limb movement during sleep developed after pontine lesion

We describe 2 patients who suffered a pontine infarction and subsequently developed periodic leg movement (PLM). The temporal relationship between a stroke and subsequent PLM, as well as the absence of sleep-related disorders in patients' histories, favors the argument of a cause-and-effect relationship, with the observed association providing evidence for an anatomic substrate for PLM.

Unique form of propriospinal myoclonus as a possible complication of an enteropathogenic toxin

Propriospinal myoclonus is an uncommon form of spinal myoclonus propagated, presumably, by slowly conducting polysynaptic intraspinal pathways. Although most patients demonstrate no clear etiology, a variety of disorders have been linked to this abnormal movement, including trauma, multiple sclerosis, tumors, and infectious disorders such as herpes zoster, human immunodeficiency virus, and Lyme disease. We describe 2 young male patients from the same town in Northern Ontario, Canada, exposed to an outbreak of Escherichia coli O157:H7 from contaminated municipal water, who developed identical clinical and electrophysiological features suggestive of a rhythmic form of propriospinal myoclonus with activity alternating between abdominal and paraspinal muscles. A toxin-mediated microvascular thrombosis is proposed as a possible pathogenic mechanism underlying this novel association.

Motor pattern of periodic limb movements in sleep in idiopathic RLS patients

OBJECTIVE

Periodic limb movements in sleep (PLMS) are recurrent sleep-related movements that often occur in association with restless legs syndrome (RLS). The purpose of the present study was to examine the pathophysiology of PLMS in patients with idiopathic RLS.

METHODS

Ten patients with idiopathic RLS who were medication-free or who had withdrawn from medication at least 2 weeks prior to the study underwent an extensive neurophysiological investigation that included nocturnal video-polysomnographic recording (VPSG), EMG recording, and the Multiple Sleep Latency Test (MSLT). Sleep efficiency and PLMS index were calculated during VPSG.

RESULTS

All patients had an increased PLMS index, decreased sleep efficiency, and a pathological MSLT score. Leg muscles were the first to be activated, often with alternation of side, and no constant recruitment pattern could be found from one episode of PLMS to another, even in the same patient. No ordinate caudal or rostral spread of the EMG activity was observed.

CONCLUSIONS

The results suggest that there are different, independent, and unsynchronized generators for PLMS. The direct participation of the cerebral cortex in the origin of PLMS is unlikely, suggesting that abnormal spinal cord hyperexcitability may act as the primary cause of PLMS, triggered by unidentified sleep-related factors.

Segmental myoclonus as the sole manifestation of a choroid plexus papilloma in the posterior fossa. Case report

The authors describe the case of a 22-year-old woman with involuntary contractions of the sternocleidomastoid and trapezius muscles that resulted in turning movements of the head. The jerks displayed the clinical and neurophysiological characteristics of segmental myoclonus (SM) restricted to muscles supplied bilaterally by the first four cervical segments. Magnetic resonance imaging disclosed a tumor in the midline above the cisterna magna that was later histologically proven to be a choroid plexus papilloma. The patient's involuntary movements did not extend to other muscle groups or, in particular, to the palate, as one might have expected in the case of brainstem lesions. Myoclonus was the sole clinical manifestation of the tumor in this patient; other signs and symptoms invariably reported in other cases of posterior fossa papilloma, such as increased intracranial pressure or cranial nerve palsies, were absent. Release from suprasegmental control is suggested as a possible pathophysiological mechanism in this case of SM.

Focal myoclonus and propriospinal propagation

OBJECTIVE

To investigate the relationship between axial segmental myoclonus and propriospinal myoclonus.

METHODS

A patient with a 3-year history of axial jerks evoked by physical effort and unexpected somesthetic and auditory stimulations was investigated. Polygraphy with multiple-channel axial and limb EMG recording was performed with off-line analysis.

RESULTS

Spontaneous, somesthetic and acoustic evoked jerks always began in the left rectus abdominis muscle with a single or repetitive EMG burst that could spread to other rostral and caudal muscles without engagement of cranial nerve innervated muscles, consistent with propriospinal propagation. Spontaneous and evoked jerks could however also appear focally in abdominal muscles and remain localized without any diffusion to other muscle segments.

CONCLUSION

Focal axial myoclonus and propriospinal myoclonus may coexist. Conceivably the same spinal generator responsible for a monomeric segmental myoclonus may, under conditions of heightened excitability, cause a multimeric propriospinally propagated muscular activation.

Myoclonus

The diagnosis and treatment of myoclonus pose a particular challenge to the neurologist. Few well-controlled double-blind studies of antimyoclonic agents have been performed, and clinical rating of the effectiveness of treatment has been primarily descriptive. As a result, therapy is often empiric. This article reviews the author's approach to treating patients with myoclonus. Three principles guide treatment. First, the cause and physiology of the myoclonic jerks must be ascertained before choosing the appropriate therapy. Second, multiple drugs often must be used in combination to achieve functional improvement. Third, given the paucity of adequately controlled trials, the treating physician must rely on well-documented case series of patients with myoclonic syndromes who obtained benefit from a drug.

Electrophysiological studies of myoclonus

As myoclonus is often associated with abnormally increased excitability of cortical structures, electrophysiological studies provide useful information for its diagnosis and classification and about its generator mechanisms. The EEG-EMG polygraph provides the most essential information about the myoclonus of interest. Jerk-locked back averaging and evoked potential studies combined with recording of the long latency, long loop reflexes are useful to further investigate the pathophysiology of myoclonus, especially that of cortical myoclonus. A recent advance in magnetoencephalographic techniques has contributed significantly to the elucidation of some of the cortical mechanisms underlying myoclonus. Elucidation of physiological mechanisms underlying myoclonus in each individual patient is important for selecting the most appropriate treatment of choice.

Periodic limb movements in syringomyelia and syringobulbia

Twenty-six patients with syringomyelia were studied with polysomnography to determine the frequency of periodic limb movements (PLM) and its relationship to the presence of a Chiari anomaly, the severity of corticospinal tract involvement, and localization of the syrinx. Sixteen patients showed PLM in stages I and II of non-REM sleep and three PLM also while awake. There were no statistically significant differences in overall disability, corticospinal signs, presence of an associated Chiari anomaly, and disease duration between patients with and without PLM, although there was a trend for patients with PLM to have more severe disease. There was preservation of the lumbosacral enlargement of the spinal cord by the syrinx in all patients with PLM. The latency delay between lower and upper limb muscles was suggestive of conduction along propriospinal pathways. Syringomyelia may lead to an abnormal state of spinal hyperexcitability favoring the appearance of PLM. Detailed magnetic resonance image studies of patients with different localizations of the syrinx cavities may help to determine which tracts are involved in the production of PLM.

Secondary periodic limb movement disorder and restless legs syndrome

Periodic limb movement disorder (PLMD) and restless legs syndrome (RLS) are well-known entities from a clinical and polysomnographic point of view. PLMD and RLS are seen mostly as primary or hereditary diseases, but may occur in conjunction to other diseases such as uremia, polyneuropathy, Parkinson's disease, and deficiencies of iron and magnesium. This review will discuss the prevalence, etiology and pathophysiology of secondary PLMD and RLS.

Neurophysiology of positive and negative myoclonus

Myoclonus is defined as a sudden, brief, jerky, shock-like, involuntary movement, arising from the central nervous system that can be caused by a muscular contraction, i.e. positive myoclonus, or by an interruption of muscular activity, i.e. negative myoclonus. Myoclonus can characterize a variety of neurological disorders, and often both positive and negative myoclonus can coexist. In this paper, we outline some relevant clinical aspects and neurophysiological features of the different types of myoclonus, with particular emphasis on the physiological findings. Indeed, since most myoclonus depend on enhancement of neuronal activities which are inherently present in normal subjects, electrophysiological studies are useful for elucidating the underlying pathophysiological mechanisms and for establishing the correct diagnosis [corrected].

Parasomnias including the restless legs syndrome

The three states of mammalian being, W, REM sleep, and NREM sleep, are not mutually exclusive, and may occur simultaneously, oscillate rapidly, or appear in dissociated or incomplete form to produce primary sleep parasomnias. In addition, dysfunctions of a wide variety of organ systems may take adwide variety of organ systems may take advantage of the sleeping state to declare themselves, resulting in secondary sleep parasomnias. Contrary to popular opinion, the majority of the often bizarre and frightening experiences are not the manifestation of underlying psychological or psychiatric conditions. There is an interesting interaction between sleep-disordered breathing and parasominas. Formal study in an experienced sleep disorders center will usually reveal a diagnosable and treatable condition that explains the spells. Continued study of unusual sleep-related events undoubtedly will reveal more fascinating conditions, expanding our knowledge of sleep physiology, and strengthening the bonds between clinicians and basic-science sleep researchers.

Cerebral generators involved in the pathogenesis of the restless legs syndrome

The pathophysiology of periodic limb movements and sensory leg discomfort in the restless legs syndrome is unknown. With high-resolution functional magnetic resonance imaging, we localized for the first time cerebral generators associated with sensory leg discomfort and periodic limb movements in 19 patients with restless legs syndrome. During sensory leg discomfort there was mainly bilateral activation of the cerebellum and contralateral activation of the thalamus. During the combined periodic limb movement and sensory leg discomfort conditions, patients also showed activity in the cerebellum and thalamus. In contrast to the sensory leg discomfort condition alone, the combined condition was associated with additional activation in the red nuclei and brainstem close to the reticular formation. Voluntary imitation of periodic limb movements by patients and control subjects was not associated with brainstem activity, but with additional activation in the globus pallidus and motor cortex. These findings indicate that cerebellar and thalamic activation may occur because of sensory leg discomfort and that the red nucleus and brainstem are involved in the generation of periodic limb movements in patients with restless legs syndrome.

Propriospinal myoclonus upon relaxation and drowsiness: a cause of severe insomnia

Three patients, aged 71, 50, and 41 years, presented with myoclonic activity arising in the relaxation period preceding sleep onset and causing severe insomnia. Polygraphic studies showed that the myoclonic activity began in spinally innervated muscles, propagating at low speed to rostral and caudal muscular segments. Myoclonus arose whenever patients relaxed mentally and showed diffuse electroencephalographic alpha activity and was independent of posture. The jerks disappeared during sleep. Clonazepam afforded symptomatic improvement. Propriospinal myoclonus arising from a spinal generator may be facilitated by changes in supraspinal control related to vigilance levels. When arising during relaxation and drowsiness, it may cause severe insomnia.

Reflex studies and MRI in the restless legs syndrome

Brainstem and spinal pathways of untreated patients with idiopathic restless legs syndrome (RLS) were examined using magnetic resonance imaging (MRI), blink reflex, first and second exteroceptive suppression (ES1, ES2) of temporalis muscle, and H reflex. MRI of 25 patients elicited no structural lesions beyond age-related atrophy or white matter lesions on proton density- and T2-weighted coronal and axial images. All patients showed a normal latency of the soleus H reflex (mean +/- SD latency = 31.22 +/- 2.81 ms) and the H/M ratio was 48 +/- 17%. The duration and onset latency of the direct and indirect blink reflex responses were normal in all patients compared with those of controls (p > 0.5). There was no significant difference in ES1 and ES2 latencies or duration between patients and controls (p > 0.5). These results suggest that the etiology of RLS symptoms does not involve structural lesions.

Electrophysiological pattern of involuntary limb movements in the restless legs syndrome

Patients with restless legs syndrome (RLS) suffer from involuntary limb movements during the day. We studied these leg movements in 18 idiopathic (n = 8) and uremic (n = 10) patients at rest. Electromyographically measured muscle contractions were preceded by sensory discomfort in all patients. The mean duration of the contractions ranged between 0.67 and 5.71 s with a mean frequency of 244 epochs of muscle activity per hour. Seven of 18 patients showed a constant order of recruitment with propagation of muscle activity up or down spinal segments (L3 to S1 and vice versa). No difference in electrophysiologically recorded patterns was observed between patients with idiopathic and uremic RLS. We suggest a brainstem disinhibition phenomenon as the pathological mechanism that activates a spinal generator. The spinal origin of the involuntary limb movements in patients with RLS is confirmed by the long duration of jerks, the recruitment characteristics, and the periodicity of the jerks. No jerk could be elicited by sensory reflexes.

Propriospinal myoclonus in tetraplegic patients: clinical, electrophysiological and therapeutic aspects

Propriospinal myoclonus is a rare and relatively little studied complication of spinal cord injury. We report two patients with an extension-producing myoclonus presenting with tetraplegia caused by cervical trauma. Rhythmic extension jerks of the trunk and lower limbs appeared several weeks after their injury in a context of severe spasticity. The characteristics of these jerks were determined by polymyography of 12 muscles. They lasted between 306 and 1127 ms with a frequency of 0.3 to 0.5 Hz. By comparing latencies their origin was found to be in the lumbar cord from which there was a slow (2 m s-1) upward and downward spread. Oral treatment with baclofen and sodium valproate was partially successful in one patient, but ineffective in the other. Intrathecal 75 or 100 micrograms baclofen produced a striking, complete disappearance of myoclonus prompting the implantation and successful use of a baclofen pump in one patient. These two new cases suggest the existence of a lumbar generator in which myoclonic extension jerks originate, and demonstrate a new therapeutic alternative in intrathecal baclofen for patients resistant to oral medication.