Spasmodic dysphonia is a focal dystonia characterized by task-specific, action-induced spasm of the vocal cords.

There are three types of spasmodic dysphonia: Adductor spasmodic dysphonia (ADSD) is characterized by a strained-strangled voice quality and intermittent voice stoppage or breaks, resulting in a staccato-like voice, caused by overadduction of the vocal folds.

Abductor spasmodic dysphonia (ABSD) is characterized by intermittent breathy breaks and associated with prolonged abduction folds during voiceless consonants in speech.

Mixed-type spasmodic dysphonia has features of both.

The efficacy of botulinum neurotoxin (BoNT) injection in the treatment of spasmodic dysphonia has been proven. This chapter enumerates the muscles involved in each type of spasmodic dysphonia, diagrams and describes different approaches for injection, along with the use of guidance techniques such as laryngoscopy and electromyography, and tabulates dose ranges of the different types of BoNT for each muscle.

In cervical dystonia (CD), outcome of treatment with botulinum neurotoxin (BoNt), is highly dependent on the correct identificationof the muscles involved. There are “simple” (in one plane) and “complex” (in two or more levels) forms of CD. The difficulty lies in the treatment of complex CD, requiring a more extensive analysis. For such analysis, different diagnostic methods are used. These include: ultrasound, CT neck soft tissue imaging (particularly the deep muscles of the neck), electromyography (EMG) of neck muscles, and standardized photographs of patients with measurements of angles (head, neck, thorax).

Cervical dystonia may occur in principle in three axes (rotation, lateral flexion and sagittal flexion). The head or the neck can be affected alone in each of these planes of movements. Therefore, eight clinical forms can be distinguished: torticollis, laterocollis, antecollis, retrocollis, torticaput, laterocaput, antecaput and retrocaput. In this chapter, involved muscles, their origins and insertions are presented in a table for each of these clinical forms. Injection under CT guidance is described.

Oromandibular dystonia (OMD) is a form of focal dystonia that involves the masticatory, lower facial, labial and lingual musculature affected by the trigeminal, facial and hypoglossal cranial nerves. OMD can be classified into various subtypes, which include jaw-opening, jaw-closing, jaw-deviating, lingual, perioral and/or pharyngeal dystonia. Dystonic spasms may result in clenching, or trismus; grinding of the teeth, or bruxism; tongue thrusting; lip pursing; and other movements.

Evidence-based reviews and clinical experience strongly regard botulinum neurotoxin (BoNT) injection as the first-line treatment for OMD. Patients with OMD require careful examination to determine the particular muscles involved and their pattern of contraction to enable proper selection and targeting for BoNT injection. This chapter enumerates the particular muscles involved in each subtype of OMD, discusses localization and approach for injection and use of guidance techniques where applicable, and tabulates typical dose ranges for different formulations of BoNT. Typical adverse events and techniques to avoid them are discussed.

Botulinum neurotoxins (BoNTs) are protins derived from the bacterium Clostridium botulinum. Nine serotypes are known; seroptypes A and B have been formulated for clinical use. BoNTs cleave one of the three soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) proteins: vesicle-associated membrane protein (VAMP), synaptosomal-associated protein 25 (SNAP-25), or syntaxin. Upon entry into the synaptic terminal, BoNT inhibits the exocytosis of neurotransmitter containing synaptic vesicles. Cliical effects begin developing within a week after injection into skeletal muscle, then wear off after 2–4 months, requiring repeat injection. Neutralizing antibodies may develop, reducing clinical effects. Newer toxin preparations under development are listed in a table.

In 1980, Alan B Scott published the use of botulinum neurotoxin type A by injection into extraocular muscles for treatment of strabismus. Use in blepharospasm was published in 1985, and cervical dystonia in 1986, followed by hemifacial spasm and other dystonias, including spasmodic dysphonia, hand dystonia, and conditions such as limb spasticity.

Formulations of neurotoxin type A worldwide include: Botox/onabotulinumtoxinA, Dysport/abobotulinumtoxinA, Xeomin/incobotulinumtoxinA, and a Chinese product marketed under various brand names in Asia. Botulinum neurotoxin type B is marketed as Neurobloc/Myobloc, or rimabotulinumtoxinB. PrabotulinumtoxinA and daxibotuinumtoxinA-Ianm are type A toxins under development.

Focal hand dystonia (FHD) is characterized by dystonic hand contractions that are often aggravated by purposeful actions and may be specific to a particular task. The term “occupational dystonia” is used when dystonia affecting performance of the job arises in individuals with a particular occupation, usually an occupation requiring repetitive and excessive fine motor activity.

One task-specific FHD, writer’s cramp, causes disabling spasms of the hands when attempting to write, and is particularly likely in people whose profession involves excessive writing. Musician’s dystonia (cramp) is applied to a focal dystonia localized to hand muscles controlling fine movements of the digits or the embouchure muscles involved in playing instruments.

Injection of botulinum neurotoxin (BoNT) is effective in writer’s cramp and other occupational dystonias. This chapter discusses the different common patterns of dystonic movement of the hand and arm, identifies the particular muscles active in each dystonia pattern to aid in target selectio, and illustrates the muscular anatomy and injection approach using anatomical diagrams. Guidance of injections with EMG is discussed. Dosing recommendations for three different BoNT formulations are tabulated.

Cervical dystonia (CD) is an idiopathic focal dystonia characterized by abnormal head and neck posture caused by tonic involuntary contractions in a set of cervical muscles. Four subtypes, based on the principal direction of posture, consist of:

• - Torticollis: Rotation of the head left or right in the transverse plane.

• - Lateralcollis: Head tilt toward left or right shoulder, in the coronal plane.

• - Anterocollis: Head tilt forward, with neck flexion in the sagittal plane.

• - Retrocollis: Head tilt backward, with neck extension, in the sagittal plane.

The clinical spectrum of CD is extremely variable: the 54 muscles involved in head and neck posture may show complex mixtures of involvement, unilateral or bilateral, with contractions of tonic, tremulous or myoclonic character. Currently, the most effective, and now first-line treatment of CD, has become intramuscular injection of botulinum toxin.

This chapter enumerates the different muscles involved in major subtypes of CD, grouped by anatomical location, and their principal direction of action. Sets of muscles involved in different head postures are presented in tabular format for easy selection and targeting. Dose ranges for individual muscles are tabulated for each of the four commonly used botulinum neurotoxin preparations.

Introduction

Oromandibular dystonia (OMD) is a form of focal dystonia that involves the masticatory, lower facial, labial and lingual musculature. The term “cranial dystonia” is used when oromandibular dystonia occurs in association with blepharospasm. This particular combination is often referred to as Meige’s syndrome (reviewed by Bhidayasiri et al., 2006).

Epidemiology, clinical features and etiology

Oromandibular dystonia frequently affects women more than men and the prevalence was estimated to be around 68.9 cases per 1 million in the USA (Bhidayasiri et al., 2006). The mean age at onset is between 50 and 60 years. The involvement of masticatory muscles in OMD may cause jaw closing or jaw opening, lateral deviation, protrusion, retraction, or a combination of these. These movements often result in involuntary biting of the tongue, cheek or lips and difficulty with speaking and chewing. Its appearance is often socially embarrassing and disfiguring. In patients with jaw-closing OMD, dystonic spasms of the temporalis and masseter muscles may result in clenching or trismus and grinding of the teeth or bruxism. Jaw-opening OMD commonly involves the lateral pterygoids, anterior belly of the digastric muscle and other submental muscles; contractions of these muscles may lead to some degree of anterocollis. The effects of OMD may be alleviated by different proprioceptive sensory inputs (“sensory tricks”). These include touching the lips or chin, chewing gum or biting on a toothpick. Coexistence with dystonia in other regions and presences of sensory tricks is more common in jaw-opening than jaw-closing OMD. The contraction of mouth and pharynx muscles may cause involuntary vocalizations, occasionally confounded with vocal tics. In addition to the dystonic symptoms, many patients with OMD complain of tension-type headache, dental wear, temporomandibular joint syndrome and, more rarely, temperomandibular joint dislocation, resulting in upper airway collapse.

Introduction

Spasmodic dysphonia is a focal dystonia characterized by task-specific, action-induced spasm of the vocal cords. It adversely affects a patient’s ability to communicate. It can occur independently, as part of cranial dystonia (Meige’s syndrome), or in other disorders such as in tardive dyskinesia.

Clinical features

There are three types of spasmodic dysphonia: the adductor type, the abductor type and the mixed type:

• adductor spasmodic dysphonia (ADSD) is characterized by a strained-strangled voice quality and intermittent voice stoppage or breaks, resulting in a staccato-like voice, caused by overadduction of the vocal folds

• abductor spasmodic dysphonia (ABSD) is characterized by intermittent breathy breaks and associated with prolonged abduction folds during voiceless consonants in speech

• patients with the mixed type have presentations of both.

Symptoms of spasmodic dysphonia begin gradually over several months to years. The condition typically affects patients in their mid-forties and is more common in women (Adler et al., 1997; Schweinfurth et al., 2002).