Muscle relaxation is impaired in dystonia: a reaction time study.

A simple visual reaction time (RT) paradigm was used to investigate whether the velocity of relaxation is impaired in dystonia. In 16 subjects with a clinical diagnosis of adult-onset focal, segmental or multifocal dystonia and in 15 age-matched normal controls, the relaxation reaction time (R-RT) and the contraction reaction time (C-RT) were compared across different tasks involving the flexor carpi radialis (FCR), biceps brachii (BB) and triceps brachii (TR) arm muscles. In normal controls, the latency of EMG termination (R-RT) was significantly shorter than the latency of electromyographic (EMG) onset (C-RT) in the BB and TR muscles, but not in the FCR muscle. In dystonic patients, the latency of EMG termination (R-RT) was significantly longer than the latency of EMG onset (C-RT) in the FCR and BB muscles. No significant difference of the C-RT was observed between patients and controls whereas the R-RT was prolonged significantly in the BB and TR muscles of patients with dystonia and almost significantly in the FCR muscle. This study indicates that muscle relaxation is abnormal in patients with focal (multifocal or segmental) dystonia. The impaired muscle relaxation may contribute to the longer overlap of agonist-antagonist activities (co-contraction) typically observed in dystonia and to the slowness of voluntary movement sequencing.     

Electromyographic evaluation of cervical dystonia for planning of botulinum toxin therapy

The success of botulinum toxin (BT) injections for treatment of cervical dystonia depends on precise identification of dystonic muscles and on quantification of their dystonic involvement. Conventionally, this is attempted by clinical examination analysing the dystonic head position. In this presentation, a more systematic approach is sought by using an electromyography (EMG)-based evaluation procedure. In 10 consecutive patients with cervical dystonia not previously exposed to BT clinical examination, analysing the dystonic head position was performed to classify patients into four groups with similar dystonic head positions. Additionally, a 2-channel concentric needle EMG was used to measure the amplitudes of dystonic and maximal voluntary activities in sternocleidomastoid (SCM), splenius capitis (SC) and trapezius/semispinalis capitis (T/SS) muscles bilaterally. The ratio between both amplitudes, the dystonia ratio, was used to quantify dystonic muscle involvement. In all patients dystonia ratios could be calculated. In patients with similar head positions, EMG evaluation revealed different qualitative and quantitative dystonic involvement patterns. In six patients, there were discrepancies in identification of dystonic muscles between clinical examination and EMG evaluation. EMG evaluation excluded dystonic involvement in five patients. All excluded muscles were SCM. In one of these patients, additional T/SS involvement was detected by EMG evaluation. In one patient, SC involvement was revealed by EMG evaluation. All dystonic muscle involvement detected by EMG evaluation represented genuine dystonic muscle coactivation rather than compensatory muscle activity. The EMG evaluation presented allows quantitative and qualitative identification of dystonic muscle involvement which cannot be achieved by clinical examination. Both pieces of information may be helpful for optimization of BT therapy.     

Spastic dystonia in stroke subjects: prevalence and features of the neglected phenomenon of the upper motor neuron syndrome

ObjectiveSpastic dystonia is one of the positive phenomena of the upper motor neuron syndrome (UMNS). It is characterised by the inability to relax a muscle leading to a spontaneous, although stretch-sensitive, tonic contraction. Although spastic dystonia is a recognized cause of muscle hypertonia, its prevalence among hypertonic muscles of stroke subjects has never been investigated. Differently from spasticity, which is an exaggerated stretch reflex, spastic dystonia is viewed as an efferent phenomenon, due to an abnormal central drive to motoneurons.MethodsIn 23 hemiparetic stroke subjects showing increased muscle tone of wrist flexors, surface EMG was used to investigate the presence of spontaneous, stretch-sensitive EMG activity in flexor carpi radialis.ResultsSpontaneous, stretch-sensitive EMG activity was found in 17 subjects. In the remaining 6 subjects, no spontaneous EMG activity was found.ConclusionsThe majority of stroke subjects is affected by spastic dystonia in their hypertonic wrist flexor muscles. Only a minority of subjects is affected by spasticity.SignificanceTo stop spastic dystonia from being the neglected aspect of UMNS, it is essential to link its definition to increased muscle tone, as occurred for spasticity. Recognizing the real phenomena underling muscle hypertonia could improve its management.     

Shortened cortical silent period in facial muscles of patients with cranial dystonia

OBJECTIVE: To study the cortical silent period (SP) in the orbicularis oculi and perioral muscles in 23 patients with cranial dystonia and 10 age-matched control subjects. METHODS: High-intensity magnetic stimuli were delivered with a round coil centered at the vertex during a maximal muscle contraction. Electromyographic (EMG) responses were recorded from surface electrodes placed over the orbicularis oculi and perioral muscles. RESULTS: SPs elicited in upper and lower facial muscles had a similar duration. Facial muscle SPs were significantly shorter in patients than in control subjects. Patients with blepharospasm plus oromandibular dystonia had shorter SPs than patients with blepharospasm alone. Although patients' recordings showed reduced voluntary and evoked EMG activity, neither activities correlated with the duration of the SP. CONCLUSIONS: Silent period (SP) shortening depends neither on the level of electromyographic activity nor on segmentary mechanisms. The shortened SP in facial muscles reflects hypoexcitability of cortical inhibitory neurons in cranial dystonia.     

Laryngeal dystonia--personal experience with botulin toxin treatment

Laryngeal dystonia is a focal dystonia occurring more often than it is diagnosed. Adductor type dystonia was described in 5 patients. In 3 cases it manifested itself as blepharospasm, which later developed into Meige's syndrome. The patients were treated with botulinum toxin A injections under EMG control administering 10 i.m. into laryngeal muscles on both sides with good and very good results. There were no serious side effects.     

Fluoroscopic, EMG-guided injection of botulinum toxin into the longus colli for the treatment of anterocollis

BackgroundAnterocollis is a form of cervical dystonia characterized by forward neck flexion. While botulinum toxin is the treatment of choice for cervical dystonia, patients with anterocollis, who receive injections into the sternocleidomastoid and anterior scalene muscles, represent a disproportionate number of treatment failures. Deep cervical muscles such as the longus colli likely play an important role in neck flexion but are not routinely injected.ObjectiveTo describe a technique for longus colli injection in cases of anterocollis and to report the clinical outcomes of 10 such injections of botulinum toxin.MethodsThree patients were referred for evaluation and treatment of anterocollis. All had previous treatment failures with sternocleidomastoid/anterior scalene injections or no activity noted on needle EMG investigation of these muscles. All patients received injections of botulinum toxin into the longus colli under fluoroscopic and EMG guidance.ResultsAll patients experienced symptomatic improvement (eight of 10 injections). Two patients reported mild dysphagia without serious complications after dose increases in botulinum toxin.ConclusionsIncomplete muscle selection may be one cause of treatment failures in anterocollis. Deep cervical flexors such as the longus colli represent an under-recognized potential target for symptomatic treatment of anterocollis.     

Treatment of cervical dystonia hand spasms and laryngeal dystonia with botulinum toxin

Summary One hundred and twenty-six patients with different forms of focal dystonia (89 with cervical dystonia, 12 with hand cramps and 25 with laryngeal dystonia) were treated with localised injections of botulinum toxin. Mean doses per muscle were 200 mouse units (m.u.) for treating cervical dystonia, 40–120 m.u. for forearm muscles in writers' cramp and 3.7 m. u. for the thyroarytenoid muscle in laryngeal dystonia. Responder rates have been above 80% in all patient groups and beneficial effects could be reproduced over follow-up periods of up to 4 years. The commonest side-effects were dysphagia after treatment of spasmodic torticollis, weakness of neighbouring muscles after injections for hand cramps and breathiness and hypophonia following laryngeal injections. All these were transient and generally well tolerated. It is concluded that botulinum toxin injections are a safe and effective treatment in all three types of focal dystonia.     

Utility of an EMG mapping study in treating cervical dystonia

Intramuscular injections of botulinum toxin are the cornerstone of treatment for cervical dystonia. Controversy exists regarding the necessity for EMG-guided injections. We compared the clinical examination of four movement disorder specialists to an electromyographic (EMG) mapping study. Clinical predictions of individual muscle involvement were only 59% sensitive and 75% specific. Muscle hypertrophy, shoulder elevation, and dominant head vector did not bolster clinical accuracy. An EMG mapping study facilitates identification of dystonic muscles in cervical dystonia, which may enhance botulinum toxin therapy.     

Polymyography combined with time-locked video recording (video EMG) for presurgical assessment of patients with cervical dystonia

We assessed 26 patients with cervical dystonia, in whom botulinum toxin (BT) injections had failed, before selective peripheral denervation. We decided to base the decision which muscle should be denervated on both clinical information and EMG data and focussed on the following features: activity at onset or during 'dystonic spasms' (according to the concept of the 'leading' dystonic muscle), paradoxical activity during voluntary head movements causing restriction of head movements opposite the side of head turn or tilt and activity when symptoms deteriorated during walking. To identify these muscles we developed a new recording system that integrates simultaneous video-taping and polymyography (video EMG) by means of a digital counter, driven by the recording software (resolution 0.1 s), that was fixed in view of the video camera. This system time-locked clinical signs with relevant EMG activity thus allowing demonstration of the above features. These were found in 68% of dystonic muscles with each of them being present in approximately 40%. Video EMG allows an integrated approach to identify overactive neck muscles in patients with cervical dystonia taking into account both relevant clinical findings and EMG data.     

Not paralysis, but dystonia causes stridor in multiple system atrophy

Electromyography (EMG) was performed in 10 patients with multiple system atrophy, laryngeal or pharyngeal symptoms, or both. In patients with stridor, EMG during quiet breathing revealed persistent tonic activity in both abductor and adductor vocal cord muscles. In patients with dysphagia, the cricopharyngeal muscle showed persistent EMG activity throughout all phases of swallowing. Botulinum toxin injection into the adductor muscle determined subjective improvement and reduced tonic EMG activity. Therefore, the cause of stridor in multiple system atrophy is dystonia of the vocal cords.     

Descending control of muscles in patients with cervical dystonia.

It was reported recently that specific features in the frequency analysis of electromyographic (EMG) activity in the sternocleidomastoid (SCM) and splenius (SPL) muscles were able to distinguish between rotational idiopathic cervical dystonia (CD) and voluntary torticollis in individual subjects. Those with CD showed an abnormal drive to muscles at 5 to 7 Hz and an absence of the normal 10 to 12 Hz peak in the autospectrum of SPL. We sought to determine whether the same abnormalities in the frequency domain are found in complex CD, in which the head is displaced in more than two planes. EMG activity was recorded in the SCM, SPL, trapezius, and levator scapulae muscles bilaterally in 10 patients with complex CD. Frequency analysis of EMG was compared with conventional clinical and polymyographic assessment. The autospectrum of SPL during free dystonic contraction showed an absence of a significant peak at 10 to 12 Hz in 8 of the 10 patients. The presence of a 5 to 7 Hz frequency drive showed a significant association with muscle pairs determined as dystonic by means of polymyography (P < 0.005). The neck posture predicted blindly, based on the low-frequency drive, correlated significantly with the clinical assessment of posture (P < 0.01). Conventional assessment and the results of frequency analysis correlated, suggesting that a low-frequency drive to neck muscle may be a general feature of simple rotational and more complex cervical dystonia. The pattern of coherence between the EMG in different neck muscles may provide a means of identifying leading dystonic muscles, especially in patients with complex cervical dystonia.     

Coronoidotomy as treatment for trismus due to jaw-closing oromandibular dystonia.

Oromandibular dystonia is a focal dystonia involving the masticatory and/or tongue muscles. This report describes 2 female patients with jaw-closing dystonia treated by surgical resection of the coronoid process. The patients could not open their mouths due to involuntary jaw-closing muscle contraction. We first treated them by injecting lidocaine and alcohol (muscle afferent block) into the masseter and temporal muscles and then botulinum toxin. However, the trismus improved mildly and transitorily. Therefore, coronoidotomy was done under general anesthesia. The jaw opening increased to 50 mm. Coronoidotomy is useful for patients with jaw-closing dystonia in whom other therapies are ineffective.     

Primary writing tremor and myoclonic writer's cramp

Four patients with primary writing tremor had a focal, task-specific tremor that responded to anticholinergic drugs. Physiologic features included EMG activity alternating in antagonist muscles, 5- to 20-microV cerebral potentials evoked by stretch of pronator teres, and no C-reflexes. Another patient had myoclonic jerks of the forearm on attempts to write ("myoclonic writer's cramp") that also responded to anticholinergic drugs; EMG activity appeared synchronously or alternating in antagonist muscles. These disorders have features of dystonia and enlarge the spectrum of writer's cramp.     

Involvement of the medial pallidum in focal myoclonic dystonia: A clinical and neurophysiological case study.

We successfully treated a patient with familial myoclonic dystonia (FMD), which primarily affected his neck muscles, with bilateral deep brain stimulation (DBS) to the medial pallidum, and investigated the role of the medial pallidum in FMD. A patient with FMD underwent bilateral implantation of DBS electrodes during which field potentials (FPs) in the medial pallidum and electromyograms (EMGs) from the affected neck muscles were recorded. The effects of high-frequency DBS to the medial pallidum on the FMD were also assessed by recording EMGs during and immediately after implantation, as well as 6 days and 8 weeks postoperatively. During spontaneous myoclonic episodes, increased FPs oscillating at 4 and 8 Hz were recorded from the medial pallidum; these correlated strongly with phasic EMG activity at the same frequencies in the contralateral affected muscles. The EMG activity was suppressed by stimulating the contralateral medial pallidum at 100 Hz during the operation and continuous bilateral DBS from an implanted stimulator abolished myoclonic activity even more effectively postoperatively. The phasic pallidal activity correlated with and led the myoclonic muscle activity, and the myoclonus was suppressed by bilateral pallidal DBS, suggesting that the medial pallidum was involved in the generation of the myoclonic activity. High-frequency DBS may suppress the myoclonus by desynchronising abnormal pallidal oscillations. This case study has significant clinical implications, because at present, there is no effective treatment for focal myoclonic dystonia.     

Accurate targeting of botulinum toxin injections: how to and why

Botulinum toxin (BTX), the exotoxin of the obligate anaerobe, Clostridium botulinum, is used to ameliorate pain and treat conditions associated with glandular, smooth and skeletal muscle overactivity. The benefits derived from the injection of BTX may be negated by unintended weakness of uninjected muscles. Performance of BTX injections may be facile, requiring only surface marking or clinical-localisation techniques but may be more technically demanding, necessitating the use of equipment, such as electromyography (EMG) or ultrasonography (U/S). Less often, endoscopic, fluoroscopic or computed tomographic (CT) guidance may be required. Despite evidence to support the efficacy of BTX injections in treating many conditions, there is no evidence to support the superiority of any one injection technique over needle localisation using surface anatomy. This is possibly due to the lack of well-designed controlled studies, that is, current studies are hampered by small patient numbers, lack of consistency of injection technique and the application of different rating scales. Intuitively, certain injection techniques are more suited to injection of specific muscles or conditions, for example, U/S or passive-monitoring EMG should be used to treat cervical dystonia, active-monitoring EMG applied for strabismus injections, whereas either active-monitoring EMG or endoscopy is indicated when giving BTX for spasmodic dysphonia. Finally, electrical-stimulation EMG or U/S (or a combination of both) would be most suitable when injecting the forearm muscles for spasticity or writer's cramps.     

Different mechanisms may generate sustained hypertonic and rhythmic bursting muscle activity in idiopathic dystonia

Despite that deep brain stimulation (DBS) of the globus pallidus internus (GPi) is emerging as the favored intervention for patients with medically intractable dystonia, the pathophysiological mechanisms of dystonia are largely unclear. In eight patients with primary dystonia who were treated with bilateral chronic pallidal stimulation, we correlated symptom-related electromyogram (EMG) activity of the most affected muscles with the local field potentials (LFPs) recorded from the globus pallidus electrodes. In 5 dystonic patients with mobile involuntary movements, rhythmic EMG bursts in the contralateral muscles were coherent with the oscillations in the pallidal LFPs at the burst frequency. In contrast, no significant coherence was seen between EMG and LFPs either for the sustained activity separated out from the compound EMGs in those 5 cases, or in the EMGs in 3 other cases without mobile involuntary movements and rhythmic EMG bursts. In comparison with the resting condition, in both active and passive movements, significant modulation in the GPi LFPs was seen in the range of 8-16 Hz. The finding of significant coherence between GPi oscillations and rhythmic EMG bursts but not sustained tonic EMG activity suggests that the synchronized pallidal activity may be directly related to the rhythmic involuntary movements. In contrast, the sustained hypertonic muscle activity may be represented by less synchronized activity in the pallidum. Thus, the pallidum may play different roles in generating different components of the dystonic symptom complex.     

Current status and prospects of medical therapy for dystonia]

The goal of medical therapy for primary dystonia is conservative. While botulinum toxin (BTX) therapy is a first choice for blepharospasm and cervical dystonia, medical therapy is selected as such for other types of dystonia. As oral medications, trihexyphenidyl and benzodiazepines are most frequently used. Muscle relaxants are also commonly used, but dopamine antagonists are not recommended because of the risk of inducing tardive dyskinesia. For childhood-onset generalized dystonia, levodopa should be considered to rule out levodopa-responsive dystonia. Mexiletine is reported to be effective not only for bleharospasm and cervical dystonia but for focal limb dystonia. To improve the therapeutic performance of BTX therapy for blepharospasm, it is recommended that corrugator supercilii and procerus muscles, as well as orbicularis oculi muscle, be added as target muscles. To improve the therapeutic performance of BTX therapy for cervical dystonia, it is recommended that this therapy be started as early as possible, especially within one year of illness, and that levator scapulae muscle be added as target if necessary. To improve usefulness of medical therapy for dystonia, its strategy must be standardized, and more useful therapies must be positively adopted. Algorithm for treatment of dystonia must also be established and generalized.     

Long-term botulinum toxin treatment of cervical dystonia--EMG changes in injected and noninjected muscles.

OBJECTIVE: To evaluate changes in quantitative EMG of injected and noninjected sternocleidomastoid muscles following long-term unilateral botulinum toxin treatment of cervical dystonia. METHODS: We investigated 27 patients with cervical dystonia, who received repeated unilateral botulinum toxin injections of the sternocleidomastoid muscle, with quantitative EMG at rest and at maximal voluntary contraction. The patients had on the average 7.1 botulinum toxin treatments and the follow-up period was on the average 31 months (SD 16). RESULTS: After the first treatment, the injected sternocleidomastoid muscles showed a significant decrease in turns/s (mean 45%) and amplitude (mean 52%) at rest, and in amplitude at maximal flexion (mean 24%) and rotation (mean 39%). Except for a reduction in turns/s at rotation (mean 19%) no further reductions in EMG parameters were seen after long-term treatment. The contralateral noninjected sternocleidomastoid muscles showed no significant change in EMG activity after the first BT treatment, but after long-term treatment a significant reduction in turns/s and amplitude at both maximal flexion (turns: mean 28%; amplitude: mean 25%) and rotation (turns/s: mean 32%; amplitude: mean 25%) were seen as compared to pretreatment values. CONCLUSION: The results indicate that there seems to be no cumulative chemodenervation by repeated botulinum toxin injections of sternocleidomastoid muscles measured by quantitative EMG. Contralateral noninjected sternocleidomastoid muscles however, seem to be affected following long-term treatment. The mechanism behind this finding is unknown.     

Cervical echomyography in cervical dystonia and its application to the monitoring for muscle afferent block (MAB)]

Muscle afferent block (MAB) is an intramuscular injection of 0.5% lidocaine and pure ethanol with a volume ratio of 10:1, introduced as an alternative to botulinum toxin injection for focal dystonia and spasticity. As in the case of botulinum toxin injection, the precise localization of target muscles is crucial to obtain the maximal effect from MAB. For this purpose, we performed ultrasonography of cervical muscles (echomyography) in 20 patients with cervical dystonia (11 men, 9 women; mean age 46.1), with ultrasonograph SSD-5500 (Aloca Co. Ltd., Japan) and a 7.5 MHz linear probe. In untreated subjects, the boundaries of muscles could be easily identified, while they tended to become ambiguous after repeated MAB sessions. At rest, there were involuntary worm-like movements of a specific muscle group observed in all patients. Contrary to our expectation, in all but one patient abnormal contraction was limited only in a part of synergists responsible for the abnormal posture. In normal subjects there was no abnormal contraction at rest, and all the synergists were simultaneously activated by the voluntary neck deviation. Normal subjects could not mimick the pattern of muscle activity in dystonic patients. The echo-guided MAB was performed in 16 patients. We could easily observe the diffusion of lidocaine and ethanol into the targeted muscle, and injected portions of the muscle stopped their activities just after MAB. The effect persisted for 3-4 days in at least 5 out of 10 patients who had follow-up examination. On the other hand, the movement stopped only temporarily after the injection of saline or lidocaine only. In 3 out of 16 patients, some of the uninjected synergists were activated as if to substitute for the treated muscle just after the injection. We conclude that cervical echomyography is useful to investigate the pattern of muscle activity in cervical dystonia and to accurately localize the contracting muscles during MAB.     

肌张力障碍的肌电图表现

目的:采用定量和定性相结合的肌电图方法对肌张力障碍(dystonia)病人进行测定,观察肌电活动情况,评价肌电图在捡出异常肌肉中的价值。方法:观察肌张力障碍患者48例,正常健康人群12例分别在静息时、小收缩时和大收缩时的肌电活动。结果:肌张力障碍患者在静息时有不规则的群化电位出现,或活动后运动单位持续存在,是肌肉痉挛的特异性改变;大收缩时募集相不完全其转折数明显降低。结论:所有肌电图的表现提示上运动神经元-脊髓、脑干或大脑皮层的异常放电,对病人进行肌电图检查有助于提高受损肌肉的检出率。