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β0ToxinA® – An Alternative to Pharmacotherapy in Cervical Dystonia

Cervical dystonia, also known as spasmodic torticollis, or idiopathic torsion dystonia, is a chronic condition occurring more commonly in people over the age of 40 (although it can appear at any age), characterized by neck muscles contracting involuntarily, causing abnormal posture of the head and neck if contractions are sustained, and jerky head movements in case spasms are periodic. Spasms can be in any direction: forward (anterocollis), backwards (retrocollis), and sideways (torticollis or laterocollis), and may result in pain and discomfort varying in intensity from mild to severe.

In some cases, the condition may gradually become more severe for about five years and then stabilize. In others, it hardly progresses at all. Occasionally, it may remit for a period, and return later. Because every case of cervical dystonia is different, prognosis is difficult to predict.

Apart from the discomfort, this disease is quite stressful, as it affects every aspect of a person's life. Everyday activities are impaired, the 'body language' is affected, and other people may misinterpret it, emotional reactions are common, just like embarrassment and a loss of confidence.

Despite incomplete understanding of the neurological mechanisms underlying cervical dystonia, and research still being undertaken to learn more about it, this condition is believed to be due to the abnormal functioning of the basal ganglia, deep brain structures involved in the control of movement. An imbalance of dopamine, a neurotransmitter in the basal ganglia, may underlie several forms of dystonia. There may also be a connection with head or neck trauma, or a genetic predisposition and other possible causes such as toxins (such as manganese), certain medications (such as haloperidol), or diseases (such as Parkinson's).

There is currently no known cure for dystonia, and treatment is symptomatic, attempting to lessen the symptoms of spasms, pain, and disturbed postures and functions. Many drugs have been used - anticholinergics, dopaminergics, GABAergics - but while some help a number of sufferers, none is universally effective.

Physical therapy may help to increase range of motion, flexibility, and balance, improve posture and coordination. Support groups help to cope with this problem. Surgery - undertaken to interrupt, at various levels of the nervous system, the pathways responsible for the abnormal neck movements - may be considered when patients are no longer receptive to other treatments.

Injections of botulinum toxin type A have been used in the management of dystonia since the late 1980s, although the United States Food and Drug Administration (FDA) approved its use in the management of cervical dystonias only at the end of December of 2000.

Botulinum toxin injections can be used either alone or in combination with oral medications. There is some controversy as to whether Botulinum or pharmacotherapy should be offered as primary therapy. The benefits of Botulinum toxin depend on the location of the dystonic muscles and severity of the condition. In general, it cannot be used alone to treat widespread or extremely severe generalized dystonia, as the drug dose required would be too high. In these patients, Botulinum toxin injections may be used to target specific dystonic muscles, thereby improving particular aspects of care and function or relieving discomfort or pain.

Its benefits, instead, outweigh those of pharmacotherapy in the treatment of some specific kinds of focal dystonia, such as rotational cervical dystonia. In these cases, as well as where there is inadequate response with pharmacotherapy, or adverse side effects, the use of botulinum toxin has dramatically improved the quality of life of patients, decreasing the severity of abnormal head positioning and postures as well as neck pain and the migraine and chronic tension-type headache sometimes associated with craniocervical dystonia.

Its efficacy, reported in many randomized, multi-centre, double blind, placebocontrolled studies, is further testified by the fact that in some countries treatment of cervical dystonia with Botulinum Toxin Type A is covered by health insurance or other reimbursement programs.

Injection of the drug, by inhibiting release of acetylcholine (ACH), a neurotransmitter responsible for activation of muscle contraction, temporarily weakens the targeted dystonic muscle, thus relaxing the spasm and allowing for a more normal posture and function. The goal of botulinum treatment is a delicate balance: weakening the dystonic muscle enough to reduce spasms without interfering with its function.

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Complete neck-muscle tables. According to the spasm location, a muscle or another will be injected.

A crucial element to successful botulinum toxin injections is that the appropriate muscles are injected. And this is especially vital in this case as the muscular structure of the neck is very complicated. The practitioner must therefore be particularly experienced in the anatomy of the neck and its variations. The target muscles will be identified by listening to the patient, observing his head position, the pattern of shift, tilt and rotation of the neck, and palpating the muscles. Electromyographic (EMG) guidance is generally advised to locate deeper muscles. A solution of botulinum toxin is then injected directly into several sites (from 1 to 4, depending on the size) in the overactive, dystonic muscle. These sites are near the nerve terminals or that part of the nerve cell that actually stimulates the muscle to contract.

To avoid immunity, it is best to use the lowest possible dose, which should be assessed depending on the muscle size. Approximately 10-70 U are needed for each neck muscle. A typical, fairly low dose for treatment of cervical dystonia is 150 U. Up to 250 U have been used in many studies, yet, doses that exceed 200 U seem to increase the risk of developing a resistance to the toxin. One important benefit is that the dose may be adjusted on following treatments to provide the precise degree of weakness needed to overcome dystonia; however, some strength for normal function is preserved. Some nerve terminals remain unaffected; therefore, the injected muscle may still contract but with less force.

Maximum effects of treatment with botulinum toxin injections are usually reported for a two- to six-week period following injection. In most patients, effects gradually fade approximately three to six months after injection administration. Then, new injections may be given. In particular a long term follow-up study on 100 patients, carried out by Prof. Andres O. Ceballos-Baumann, leading neurologist at the Neurological Clinic in Munich, proved that approximately 70% of patients continuing with this treatment over more than 10 years still gained meaningful benefits.

In order to decrease the possibility of antibody formation, reinjections should not be administered before three months after the last injection.

The most common side effects include excessive muscle weakness, reduced head control and especially dysphagia, with reports in the medical literature of rare cases severe enough to require the insertion of a gastric feeding tube, and extremely rare cases where subsequent to the finding of dysphagia a patient developed aspiration pneumonia and died. As injections into the sternocleidomastoid and scalenes have a higher risk of dysphagia, it is advisable to avoid bilateral sternocleidomastoid injections, targeting its insertion and ensuring that the muscle bulk is not penetrated.

References:

  • Adler CH, Kumar R. Pharmacological and surgical options for the treatment of cervical dystonia. Neurology. 2000;55(12 Suppl 5):S9-14.
  • Albani G, Bulgheroni MV, Mancini F, Mauro A, Fundaro C, Pacchetti C, Sandrini G, Nappi G. The position of the head in space: a kinematic analysis in patients with cervical dystonia treated with botulinum toxin. Funct Neurol. 2001 Apr-Jun;16(2):135-41.
  • Borgmann R. Treatment of spasmodic torticollis with botulinum toxin A. A 5-year experience. Tidsskr Nor Laegeforen. 1997 May 20;117(13):1889-91.
  • Brans JW, Aramideh M, Koelman JH, Lindeboom R, Speelman JD, Ongerboer de Visser BW. Electromyography in cervical dystonia: changes after botulinum and trihexyphenidyl. Neurology. 1998 Sep;51(3):815-9.
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  • Brin MF, Comella C, Jankovic J, eds. Dystonia: Etiology, Clinical Features, and Treatment. Lippincott Williams & Wilkins, Philadelphia, PA, 2004:1-262.
  • Ceballos-Baumann AO. Evidence-based medicine in botulinum toxin therapy for cervical dystonia. J Neurol. 2001 Apr;248 Suppl 1:14-20. Review.
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  • Gonçalves Maria Rubia R., Barbosa Egberto R., Zambon Antonio A., Marchiori Paulo E. Treatment of cervical dystonia with Botulinum toxin A in a patient with myasthenia gravis. Arq. Neuro-Psiquiatr. vol.57 n.3A São Paulo Sept. 1999.
  • Hsiung GY, Das SK, Ranawaya R, Lafontaine AL, Suchowersky O. Long-term efficacy of botulinum toxin A in treatment of various movement disorders over a 10-year period. Mov Disord. 2002 Nov;17(6):1288-93. 12465070.
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  • Kwan MC, Ko KF, Chan TP, Chan YW. Treatment of dystonia with botulinum A toxin: a retrospective study of 170 patients. HKMJ 1998;4:279-82.
  • Molloy, Fiona M. (2002). Botulinum toxin (Botox): Dystonia treatment. eMedicine, accessed at http://www.emedicine.com/neuro/topic585.htm.
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  • Ondo WG, Gollomp S, Galvez-Jimenez N. A pilot study of botulinum toxin A for headache in cervical dystonia, Headache. 2005 Sep;45(8):1073-7.
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To learn more about this condition, you can visit the websites of the Dystonia
Society http://www.dystonia.org.uk/about-dystonia-page7537.html
and the Dystonia Medical Research Foundation http://www.dystoniafoundation.org/defined/cervical.asp

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