Focal dystonia: the role of botulinum toxin

Botulinum toxin (BTX) has been found to be effective in a wide range of focal dystonias. Debate surrounds the selection of injection sites. In general, localization is satisfactory by clinical examination, but poor response, requiring localization of deep muscles, may necessitate use of electromyography for localization. Delineation of optimal doses of BTX is a work in progress; as studies have tended to show efficacy at lower doses than used in the past, the trend is to use lower doses. This is important, because development of antibodies to BTX, the main reason for secondary resistance to this treatment, is more frequent with larger doses and shorter inter-injection intervals. Although the mechanism of denervation of the neuromuscular injunction by BTX is relatively well understood, secondary changes at the level of the basal ganglia, thalamus, and cortex, and their role in response to BTX, need further exploration.

Response to levodopa treatment in dopa-responsive dystonia

BACKGROUND

Dopa-responsive dystonia (DRD) is similar to Parkinson disease in that both disorders have impaired dopamine synthesis and respond to levodopa treatment. Dopa-responsive dystonia differs in that dopamine storage is intact in contrast to Parkinson disease in which it is markedly reduced.

OBJECTIVE

To examine the short- and long-duration responses to levodopa dosing in subjects with DRD.

METHODS

The response to brief infusions of levodopa was examined in 4 subjects with DRD and the effects of withdrawal of levodopa for 3 to 7 days studied in the 3 subjects receiving long-term levodopa therapy. Motor function was measured with tapping speed, Unified Parkinson's Disease Rating Scale motor score, and global dystonia score.

RESULTS

The short-duration response to levodopa dosing seems to develop more slowly and persists longer in subjects with DRD than in subjects with Parkinson disease. Withdrawal of levodopa leads to a gradual decline in tapping speed and reemergence of dystonia over several days, similar to the rate of decay of motor function in Parkinson disease. The short- and long-duration responses were not clearly differentiated in DRD.

CONCLUSIONS

This pilot study suggests that retained dopamine storage in DRD may prolong the short-duration response and blur the distinction of the short- and long-duration responses. The decline in motor function in DRD on withdrawal of long-term levodopa therapy resembles that in Parkinson disease, suggesting that a long-duration response, if it exists in DRD, is unrelated to dopamine storage.

[Camptocormia--segmental dystonia. Proposal of a new definition for an old disease]

Camptocormia is defined as a forced posture with a forward-bent trunk which appears during standing and sitting. It was first described in 1818 by Brodie. In the last 100 years, numerous cases were observed. A psychogenic origin was presumed in most cases. We describe four patients with typical symptoms of camptocormia who present with the clinical and electromyographical criteria of a segmental dystonia. A new classification of camptocormia is proposed including (1) the primary form, a segmental dystonia of the abdominal wall muscles and (2) secondary forms. Among other conditions (psychogenic disorder, neurosis, myopathy, myositis, Parkinson's disease, multiple-system atrophy, thoracolumbar kyphosis, paraneoplastic syndrome), camptocormia is to be considered in essential tremor. A combination of dystonia of the abdominal wall muscles and essential tremor seems possible.

[Botulinum toxin A for the treatment of headache disorders and pericranial pain syndromes]

For 20 years botulinum toxin A has been used for the treatment of a variety of disorders characterised by pathologically increased muscle contraction. Recently, treatment of tension headache, migraine, cluster headache, and myofascial pain syndromes of neck, shoulder girdle, and back with botulinum toxin A has become a rapidly expanding new field of research. Several modes of action are discussed for these indications. The blockade of cholinergic innervation reduces muscular hyperactivity for 3 to 6 months. Degenerative changes in the musculoskeletal system of the head and neck are prevented. Nociceptive afferences and blood vessels of the pericranial muscles are decompressed and muscular trigger points and tender points are resolved. The normalisation of muscle spindle activity leads to a normalisation of muscle tone and central control mechanisms of muscle activity. Oromandibular dysfunction is eliminated and muscular stress removed. However, the effect of botulinum toxin A cannot be explained by muscular actions only. Its retrograde uptake into the central nervous system modulates the expression of substance P and enkephalins in the spinal cord and nucleus raphe. Recent findings suggest an inhibition of sterile inflammation which may lead to a blockade of the neurogenic inflammation believed to be the pathophysiological substrate of primary headache disorders. The efficacy of botulinum toxin A in the treatment of pain disorders is being investigated in several studies at the moment. The results and experiences obtained so far present new alternatives in the treatment of chronic pain disorders. The practical use of botulinum toxin A is demonstrated.

[Reduction of pain and muscle spasms by botulinum toxin A]

Botulinum toxin A (BoNT-A) develops its muscle-relaxing effect by the inhibition of acetylcholine (ACh) release. This toxin is also known to relieve muscular pain in different disorders. Conspicuously, pain in some patients responds earlier and sometimes even better than muscle tension, indicating that the effect of BoNT-A on pain is not only due to inhibition of ACh release. A questionnaire was distributed to 88 patients suffering from cervical dystonia (CD). Thirty-five completed questionnaires could be used for data analysis. After intramuscular injections of BoNT-A, patients with CD experience significant reductions in pain which sometimes occur significantly earlier than the improvements in head posture. In the iris sphincter muscle of the rabbit and in dorsal root ganglion cells (DRG) of the rat, inhibition of the release of substance P by BoNT-A has been shown experimentally, and BoNT-C has been proven to develop endopeptidase activity toward substance P (SP) in vitro. Findings in the current literature and our observations allow the conclusion that alleviation of muscle pain by BoNT-A may also be due to an effect on the release of nociceptive neuropeptides, among which SP seems to have a key function.

Remote F-wave changes after local botulinum toxin application

OBJECTIVE

Although the therapeutic effects of botulinum toxin A can be explained by its action at the neuromuscular junction, central or more proximal effects have also been discussed.

METHODS

Eleven patients with torticollis spasmodicus and 3 patients with writer's cramp were studied before and 1 and 5 weeks after the first treatment with botulinum toxin. We measured compound muscle action potentials (CMAPs), motor conduction velocities (MCVs), the shortest (SFL) and the mean F-wave latencies (MFL) and F-wave persistence (30 trials) of untreated muscles for each side (ulnar nerve-abductor digiti minimi muscle, peroneal nerve-tibialis anterior muscle).

RESULTS

CMAPs and MCVs showed no significant changes. For both nerves, however, SFL and MFL were prolonged slightly 1 week after treatment and returned to about baseline after 5 weeks (t test). The F-wave persistence was reduced 1 week after treatment for the right ulnar and both peroneal nerves (t test).

CONCLUSIONS

These results are not likely due to an impairment of neuromuscular transmission. Instead, we propose a decreased excitability of alpha-motoneurons supplying non-treated muscles. A reduction of muscle spindle activity or changes of the recurrent inhibition are discussed as possible causes.

Clinical application of botulinum toxin in otolaryngology, head and neck practice (brief review)

Botulinum toxin (Botox) is useful in controlling the symptoms of patients with movement disorders. Application of Botox serves to (1) inhibit hypertonicity, (2) enhance the action of the antagonistic muscles, and (3) avoid an impingement in order to reestablish "the balance of forces". In accordance with the principles mentioned above, Botox can be used to treat dystonias of the larynx (adductor laryngeal spasmodic dysphonia, abductor laryngeal spasmodic dysphonia), laryngeal granulomas, laryngeal joint dislocation, cricopharyngeal spasm, and posterior glottic synechiae. In addition, extra-laryngeal disorders such as blepharospasm, hemifacial spasm, oromandibular dystonia, and spasmodic torticollis respond well to Botox. The effects of Botox are reversible and have specific localized activity. Hence, Botox has served as a powerful diagnostic method in exploring the underlying mechanism of various types of dystonias and provides some therapeutic benefits before pursuing surgical options. Here we review the literature and describe our experiences with Botox, including such topics as preparing and storing Botox, identifying the target muscles under EMG-guidance, choosing an appropriate dose, and outlining the applications of Botox in Otolaryngology, Head and Neck Surgery practice.

[Treatment of focal dystonia with botulinum toxin A]

Local injections with Botulinum toxin A (BtxA) are safe and effective in the treatment of focal dystonia. In cervical dystonia and blepharospasm, BtxA injections have become the treatment of choice. However, good results have also been reported with oromandibular dystonia, spasmodic dysphonia and writer's cramp. In cervical dystonia, muscles for injection are selected by clinical presentation or in complex forms with EMG guidance. Several studies have shown that 500 units Dysport are safe and effective in the treatment of cervical dystonia. In blepharospasm, injections are performed in the periorbital part of the orbicularis oculi muscle with good results for 12-14 weeks. The most frequently employed starting dose is 120 units Dysport per eye, divided in three periorbital injection sites. In case of levator inhibition, the pretarsal part of the orbicularis oculi muscle should be injected in a lower dose. EMG guidance is not necessary. By contrast, BtxA treatment of spasmodic dysphonia and writer's cramp require EMG-guided injections in order to avoid side-effects. Dose recommendations for the various types of dystonia are given in the text. In up to 5% of patients with dystonia, the development of neutralising antibodies is reported following repetitive injections with BtxA. Patients with antibodies had a shorter interval between injections, more "boosters", a higher dose per 3-month interval, and a higher total dose injected. In case of neutralizing antibodies against the A toxin, the treatment with Botulinum toxin B (Neurobloc) is a possible alternative.

Thalamic hand dystonia: an MRI anatomoclinical study

Focal dystonia has been attributed to lesions involving the basal ganglia and/or thalamus. Hand dystonia was studied in a patient with a unilateral thalamic infarction documented by MRI. A 18-year-old girl presented with severe isolated dystonia of the right hand as a sequel of perinatal infarction. MRI scan revealed infarction affecting part of the dorsomedian, lateral posterior, ventral lateral, ventral posterior lateral nuclei, and centromedian-parafascicular nucleus of the contralateral thalamus. The unique MRI anatomoclinical presentation of this case, taken together with the literature data, could provide evidence that a lesion affecting one or several thalamic nuclei, including the centromedian nucleus, can induce hand dystonia.

[Botulinum toxin treatment of patients with oromandibular dystonia]

INTRODUCTION

Oromandibular dystonia (OMD) is a frequently disabling focal dystonia, which may be treated with injections of botulinum toxin in the affected muscles. The aim of the present study was to evaluate the population, effect and side-effects of patients treated in Denmark during a nine year period.

METHODS

We evaluated all 45 consecutive patients treated with quantitative EMG guided injections of botulinum toxin for OMD.

RESULTS

The OMD symptoms varied but were most often mixed symptoms (n = 13), jaw closing (n = 11) and jaw opening (n = 7). Thirty-two patients (71%) had other focal or generalised dystonia, and in 24 the additional dystonia were also treated with botulinum toxin. The 45 patients had a total of 277 treatments (mean 6.2 treatments pr. patient), each including one to six muscles. Marked effect was observed or experienced after 193 (70%) treatments, and 33 patients (73%) experienced at least one effective treatment. Side-effects occurred after 35 treatments (13%) experienced by a total of 16 patients (35.6%), most frequently as transient mild dysphagia.

DISCUSSION

The study shows that botulinum toxin treatment of OMD, guided by quantitative EMG, is safe and effective.

[Familial myoclonus-dystonia syndrome associated with panic attacks]

We report a case of autosomal dominantly inherited dystonia and panic attacks to discuss successful treatment of a common serotonergic pathology with medication. The objective analysis of the movement disorder was done by Optotrak. First we demonstrate a reduction of the myoclonus by L-5-hydroxytryptophan, which inhibits after 11 months. After changing the medication to Nefadozone, the myoclonus and the frequency of panic attacks were reduced.

Comparison of Botox with a Chinese type A botulinum toxin

OBJECTIVE

To confirm and compare the therapeutic efficacies and remote effects of a Chinese type A botulinum toxin (CBTX-A, Lanzhou Biological Products Institute, China) and Botox (Allergan Inc., USA) for focal dystonia and muscle spasm.

METHODS

Prospective open study was conducted over 4 years for focal dystonia and muscle spasm. We enrolled 785 patients: 192 were injected with Botox and 593 with CBTX-A. They were followed for 3 to 48 months. Meanwhile single fiber electromyography (SFEMG) was performed in a subset of 40 patients before, 2-3 weeks, 5-8 weeks and 4-5 months after injection of Botox or CBTX-A.

RESULTS

There were no significant differences in clinical effects from two preparations, including the latency of response, maximal benefit and duration of improvement. The dose of the Chinese preparation which produced effects similar to Botox was higher. A significant increase in jitter was demonstrated 2-3 weeks after injection in both groups and fiber density values increased at the same time or later and remained 4-5 months after injections.

CONCLUSION

Both preparation are safe and effective treatments for patients with focal dystonia and muscle spasm. They both have subclinical effects on neuromuscular transmission of remote uninjected muscles. The Chinese preparation is a little less powerful but much cheaper than Botox.

Hereditary progressive dystonia with marked diurnal fluctuation

Hereditary progressive dystonia with marked diurnal fluctuation or the strictly defined dopa-responsive dystonia (HPD/DRD) is an autosomally dominantly inherited dystonia caused by abnormalities of the gene of the GTP cyclohydrolase I (GCH 1) located on the 14q22. 1-q22.2. The heterozygotic gene abnormality induces partial decrement of tetrahydrobiopterin (BH4) and affects synthesis of tyrosine hydroxylase (TH) rather selectively. The reduction of TH exists at the terminals of the nigrostriatal (NS) dopamine (DA) neuron, predominantly in the ventral area of the striatum and disfacilitates the D1 receptor-striatal direct pathway. This consequently disinhibit the inhibitory efferent pathways and develops postural dystonia via the particular descending pathways to the reticulospinal tract and postural tremor via the ascending pathways to the ventralis lateralis (VL) nucleus of the thalamus. This also inhibits the efferents to the superior colliculus, and affects voluntary saccade but spares that to the pedunculo-pontine nucleus (PPN) preserving locomotive movement clinically. The DA-D2 receptors, the striatal indirect pathways or the efferent connecting to these pathways are not involved in the pathophysiology of HPD/DRD. So parkinsonian plastic rigidity, parkinsonian resting tremor, cogwheel rigidity or levodopa induced dyskinesia are not observed. In some patients, particularly in compound hetereozygotes, there are symptoms suggesting the involvement of serotonergic neurons or those thought to be caused by exaggeration of DA-D2 receptors. Neuropathologically there is no degenerative changes. Clinical laboratory examinations suggest that levels of TH and DA activities are around 20% of the normal values throughout the course of illness. Therefore, the age-dependent clinical course, marked progression in the first one and one half decades, its subsiding in the third decade and almost stationary course from the fourth decade are just the reflection of age-related decremental variation of the TH activities at the terminal of the normal NS-DA neuron. The diurnal fluctuation is also the reflection of circadian oscillation of the TH activities at the terminal. Functional maturation of the striatal indirect pathways in the first one and one half decades and developmental decremental variation of the DA-D2 receptor in the first three decades also reflect in the age-dependent variation of symptoms by modulating the background tone of muscle. The later functional development of the ascending efferents of the basal ganglia to the thalamus, may cause the postural tremor which appears in the second decade and becomes predominant in the fourth decade. Early decrease of TH due to deficiency of BH4 in HPD/DRD also affects the DA-D4 receptor of the tuberoinfundibular DA neuron and cause stagnation of increase of body length in childhood. With normal preservation of the fundamental function of the NS-DA neuron, levodopa, by replacing the DA content at the terminal, alleviates the motor symptoms completely and the effects sustain without any side effects. Levodopa also improves the short body length, if it is administrated before puberty. Up to now 60 mutations have been detected in the GCH 1 gene. The locus of mutation differs among families except for two pare of families with different ethnic background which showed identical mutations. Experimentally, one abnormal heterozygotic gene decreased the production of the enzyme to less than 50%, e.g. some below 20% and others around 30-40%, which clinically as symptomatic patients and asymptomatic carriers, respectively. Other experiments show dominant negative effects which differ among families or the loci of mutation. These might be the background for developing the intra-familial variation, that is, in some there is anticipation, and in the other the symptoms and clinical course are identical or vary in a family without any relation to the generation. (ABSTRACT TRUNCATED)

Gene mutation in hereditary progressive dystonia with marked diurnal fluctuation (HPD), strictly defined dopa-responsive dystonia

Mutations of the guanosine triphosphate (GTP)-cyclohydrolase I (GCH-I) gene, which catalyzes the first step in the tetrahydrobiopterin (the natural cofactor for tyrosine hydroxylase) biosynthesis, are demonstrated to cause HPD, i.e. strictly defined dopa-responsive dystonia. We analyzed the GCH-I gene of patients who fulfilled clinical criteria for typical hereditary progressive dystonia (HPD) to finalize the diagnosis. Two novel point mutations in two independent families and one novel de novo point mutation in one sporadic patient were identified. In a Japanese family, a T-to-C transition was found at exon 2, which resulted in a substitution of Cys 141 to Arg. In another Japanese family, a C-to-T mutation in exon 4 caused a nonsense codon Gln180Stop. In a clinically sporadic Japanese patient, T-to-G transition in exon 1 brought Met 102 Arg missense mutation, which was not observed in its biological parents. These three mutations were not observed in previously reported 57 pedigrees/patients and no polymorphisms in the coding region of the GCH-I gene were identified. None of the mutations of GCH-I gene in HPD reported to date or in this study have been detected more than once in any ethnicity suggesting a relatively high spontaneous mutation rate in this gene.

Botulinum toxin antibody testing: comparison between the mouse protection assay and the mouse lethality assay

Conventionally, the standard test for detection of antibodies against botulinum toxin (BT-A) has been the mouse lethality assay (MLA). Because this test has a number of disadvantages, a novel mouse protection assay (MPA) was recently introduced. We sought to compare the results of both tests. Forty-three samples from 38 patients with cervical dystonia and complete or partial subjective BT-A therapy failure underwent simultaneous MPA and MLA testing. Twenty-seven samples showed concordant results in both tests. Eleven of them were MPA- and MLA-positive and 16 MPA- and MLA-negative, resulting in a significant association of the dichotomous test results (Fisher exact test, p <0.01). Sixteen samples showed discordant results. All of those were MPA-positive and MLA-negative. This excess of MPA-positive results was also significant (Wilcoxon signed-rank test, p <0.001). Of the patients with MPA-positive samples, 62% had complete and 38% had partial therapy failure. Of the patients with MLA-positive samples, 90% had complete and 10% had partial therapy failure. MPA and MLA results show significant association. Statistical analysis and predominance of partial therapy failure in MPA-positive patients demonstrate higher sensitivity of MPA. With its methodologic advantages, its test parameter being more relevant to BT-A therapy, and its higher sensitivity, the MPA appears to be superior to the MLA.

Focal shoulder-elevation dystonia

We describe 13 cases of isolated focal dystonia of the shoulder with dystonic elevation but without clinically obvious cervical dystonia. All had significant trapezius muscle hypertrophy and limitation of shoulder movement causing substantial morbidity. In nine, this developed in the immediate aftermath of shoulder region trauma, most often a motor vehicle accident; clinically significant head trauma was not a factor. In two other cases this developed in the context of chronic heavy labor (suggesting possible overuse) and in one other it developed concurrent with the symptoms of discogenic cervical (C6-7) radiculopathy. In the one remaining case, no precipitating factors were identified. Preexisting risk factors for dystonia, such as dopamine antagonist drug use, family history of dystonia, or prior brain injury, were not identified in these patients. Administration of medications used to treat dystonia was unsuccessful but botulinum toxin therapy was beneficial in all six treated cases.

Dystonia, botulinum neurotoxin, and the aviator

Dystonia is both a symptom and the name for group of illnesses called the dystonias. The physical manifestation consists of sustained, involuntary contractions of the muscles in one or more parts of the body, resulting in twisting or distortion of that part of the body. For focal dystonias including torticollis, blepharospasm and spasmodic dysphonia, botulinum toxin injections have become the treatment of choice because of the ability of this toxin to sufficiently weaken the muscle to reduce the spasm but not so much as to cause paralysis. This paper involves the fate of four airmen all afflicted with a form of dystonia who had been reviewed in the Aeromedical Certification Division of the FAA Civil Aeromedical Institute.