Cervical Dystonia

• Originally known as spasmodic torticollis and first described by Foltz in 1959, is a neurological syndrome characterized by abnormal head and neck posture due to tonic involuntary contractions in a set of cervical muscles

• Myoclonic or tremulous movements are often superimposed in CD, producing a “tremor like” appearance – especially early in the disease state

• Classified into 4 types based on the principal direction of head posture:

1.Torticollis (abnormal rotation of the head to the right or to the left in the transverse plane)

2.Laterocollis (the head tilts toward the right or left shoulder)

3.Anterocollis (the head pulls forward with neck flexion)

4.Retrocollis (the head pulls back with the neck hyperextended)

• M:F 1:1.2

• Onset is usually insidious, although in some patients the onset has been reported as sudden

• Cervical dystonia may develop in patients of all age groups, but the peak age of onset is 41 years

• Idiopathic CD usually progresses in severity over the first five years until it reaches a plateau, during which time the CD remains fairly constant and becomes a lifelong condition

• Although remission can occur, it is rare and the dystonia usually returns after a period of time

• Transient relief from symptoms with a sensory trick or “geste antagoniste.”

• A common form of a sensory trick in CD is placing the hand lightly on the cheek. This allows the head to return to a more normal posture

• Resting the head against the headrest while driving or against a pillow while watching TV are examples of sensory tricks

• May obtain temporary relief from symptoms of CD in the morning hours following sleep

• Stress can exacerbate symptoms of CD

• Neck pain is common in CD and has been reported in 70–80%

• Pain does not appear to be correlated with the degree of severity of CD, and is thought to involve central mechanisms in addition to pain arising from muscle spasms

• Degenerative disc disease seems to be accelerated in CD, which can aggravate the pain associated with this disorder

• Depression, anxiety, and social phobia are also common associated conditions

• Brain MRI is usually normal

• Cervical MRI may show cervical muscle hypertrophy and cervical disc disease

• Most often, the cause of CD is unknown

• Cases of hereditable forms of CD, such as DYT7, autosomal dominant transmission and incomplete penetrance

• Affected family members may present with different signs/symptoms in different body regions

• A component of various secondary dystonias that manifest in a number of neurodegenerative diseases

• Secondary causes of CD include neuroleptic medication exposure or trauma

• May occur following a relatively mild trauma

• Usually begins within days of an incident, lacks the sensory trick response and tends to be more resistant to treatment with botulinum toxin

• 54 muscles affecting action on head and neck posture

• Dystonic muscles can show a dominant tonic activity, myoclonic or tremulous activity often in complex mixtures

• Intramuscular injections of BoNT are considered the first line of treatment in CD

• Both botulinum toxin serotype A (BoNT-A) (Botox, Dysport, Xeomin) and serotype B (BoNT-B) (NeuroBloc/Myobloc) have been used

• Anticholinergic trihexyphenidyl and benztropine have some beneficial effects and can be used in more severe cases alongside BoNT injections

• Benzodiazepines, such as diazepam or lorazepam, and tricyclic antidepressants, such as amitriptyline and nortriptyline

• Surgical treatment with selective peripheral denervation has been reported in open studies to be helpful in some severe cases that do not respond to either oral medications or chemodenervation

• Surgical myectomy has also been used; however, the dystonia tends to involve other muscles or continues to involve remnants of the resected muscles

• Deep brain stimulation

BTX in Cervical Dystonia• The most effective treatment for CD

• Treatment with BoNT should be initiated as early as possible, since secondary changes to the muscles involved (contractures) and of connective tissues, bony tissues, and cervical discs may occur with longstanding CD

• Worsening of CD while being treated with BoNT could be due to resistance of BoNT or the result of an actual increase in severity – often, wrong muscles have been injected

• Botulinum toxin treatment results in the improvement of neck posture, muscle hypertrophy, and pain

• Effect of BoNT begins 3–12 days after an injection and is sustained for approximately 3 months

• Injections at 3-month intervals (or longer) are thought to reduce the risk of antibodies to the BoNT

• number of injection sites within a muscle ranges from one site in smaller muscles to eight sites in larger muscles

• The following questions must be answered before BoNT therapy of CD is considered:

1. Is the abnormal posture of the head and of the shoulder induced by dystonia or by another abnormality that only imitates CD?

2. Is the CD the primary cause of disability?

3. Does the patient have myasthenia gravis or other neuromuscular junction disorders?

4. Are there already secondary changes of muscles or connective and bony tissues?

• Patients must be requested to release any compensatory voluntary muscle activities in non-dystonic muscles, avoid the use of sensory tricks (geste antagoniste), and report accurately on pain severity

• They should be asked to perform slow head movements in all common directions: evaluation of head posture is performed with the patient standing, walking slowly, and lying down

• In cases of bilateral injections in the sternocleidomastoid, the dose per muscle is half of the regular dose; Swallowing problems happen more frequently in cases of bilateral injections to the SCM

• In cases of bilateral injection into the splenius capitis and semispinalis capitis muscles, the individual dose per muscle should be reduced to 60% of the regular dose to prevent neck weakness; Neck muscle weakness, which may cause problems with holding the head upright, is more frequent if injecting splenius capitis and semispinalis capitis muscles bilaterally

• Lower dose is used initially in the newly diagnosed CD patient

• Side effects of BoNT include hypersensitivity reactions, injection site infections, injection site bleeding or bruising, dry mouth, dysphagia, upper respiratory infection, neck pain, and headache

• To reduce the risk of developing resistance, a 3-month interval between injections is recommended