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Article Excerpt
This study investigated the effect of botulinum toxin type A (BtA) on the speech intelligibility of an individual with lingual dystonia. Perceptual measures of intelligibility were obtained for single words, carrier phrases, and sentences. Acoustic analyses were performed on prolonged phonemes and selected single words. A second objective of this study was to explore the relationship between BtA use and the subject's perception of activity and participation restrictions contributing to her quality of life. A subjective evaluation of quality of life was obtained using the Voice Activity and Participation Profile (VAPP) measure. Results of this preliminary study suggest that BtA injected bilaterally into the intrinsic muscles of the tongue can improve speech intelligibility and speech acoustics in lingual dystonia. In addition, a substantial subjective benefit was derived on all domains of this patient's activity and participation scores, and ultimately, her quality of life following treatment with BtA. Results of this case study provide preliminary support for the use of BtA in the treatment of focal lingual dystonia.
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Dystonia is a slow hyperkinetic movement disorder characterized by sustained or tonic muscle contractions. These tonic muscle contractions frequently are associated with abnormal and sometimes painful posturing and positioning, twisting and repetitive movements (Duffy, 1995; Fahn, Marsden & Calne, 1987; Zraick, LaPointe, Case, & Duane, 1993). In a recent European study, Muller et al. (2002) reported the prevalence rate of primary dystonia to be 732 per 100,000 in the general population aged 50 and over. However, the exact prevalence of dystonia is unknown. Since dystonia is a heterogeneous disorder it has been classified according to age of onset, distribution, and etiology. Classification by age of onset includes childhood onset (0-12 years), adolescent onset (13-20 years), and adult onset (>20 years) (Fahn et al., 1987). Classification by distribution of bodily symptoms include focal, segmental, generalized, multifocal, and hemidystonia. Focal dystonia affects only one muscle or body part such as the tongue (i.e., lingual dystonia), larynx (i.e., spasmodic dysphonia), or arm (i.e., writer's cramp). Segmental dystonias involve contiguous muscle groups as in axial (i.e., neck and trunk are affected) or cranial dystonia (i.e., two or more parts of cranial and neck muscles are affected). In generalized dystonia symptoms typically begin in the arms or legs and advance to other parts of the body including the trunk. Multifocal dystonia involves several noncontiguous muscles or muscle groups in more than one part of the body, and hemidystonia affects only one side of the body such as ipsilateral arm and leg involvement (Fahn et al., 1987). Finally, etiology can be classified according to whether or not the dystonia is primary (i.e., when dystonia is the only or primary symptom), or secondary, implying that the dystonia is one of several symptoms resulting from another condition. These conditions include, but are not limited to, tumors, focal cerebral vascular accidents (CVA) of the basal ganglia, traumatic brain injury, or carbon monoxide poisoning (Freed, 2000). Classifying dystonias according to the above parameters can assist with accurate diagnosis, appropriate approaches to management/therapy, and prognostic factors.
LINGUAL DYSTONIA
Of the various dystonia classifications, the remaining discussion will focus specifically on a case of adult-onset, primary focal lingual dystonia. Lingual dystonia is characterized by sometimes painful muscle contractions and/or abnormal postures of the intrinsic and/or extrinsic muscles of the tongue. As a result, dysphagia and dysarthria are often present (Blitzer, Brin, & Fahn, 1991). Due to the waxing and waning of the tongue musculature at rest and/or during speech, the effects of lingual dystonia can result in devastating effects on speech intelligibility. In 1969, Darley, Aronson, and Brown studied 30 patients with hyperkinetic dysarthria associated with dystonia. These researchers established the most deviant speech dimensions of dystonia from most to least severe to be imprecise consonant articulation, vowel distortion, harsh voice, irregular articulatory breakdown, strained-strangled voice quality, monopitch, and monoloudness. Additionally, speech rate in dystonia was found to generally be slow, with abnormal direction and rhythm of movement. It should be noted, however, that Darley et al.'s 30 subjects with dystonia included individuals with oromandibular dystonia (OMD) and individuals with laryngeal dystonia (spasmodic dysphonia). The underlying site(s) of lesion(s) in lingual dystonia and other focal dystonias are thought to involve lesions of the basal ganglia control circuit. This appears to involve a neurochemical imbalance in dopaminergic and cholinergic activity (Duffy, 1995; Dworkin, 1996).
The social, emotional, and vocational consequences of lingual dystonia can be profoundly disabling in those affected. Decreased speech intelligibility, difficulty managing oral intake of food and liquids, dysphagia, and altered orofacial esthetics are likely sequelae of a diagnosis of lingual dystonia. Since treatment is not curative, but to manage symptomatology, many individuals with lingual dystonia feel a sense of helplessness over their condition and can become depressed and socially isolated (Charles, Davis, Shannon, Hook, & Warner, 1997).
THERAPEUTICS
Therapeutically, there is no cure for lingual dystonia or any dystonia. The principal goals of therapy focus on reducing lingual spasms or abnormal postures of the tongue, improving orofacial esthetics, and ultimately restoring functional speech, masticatory, and swallowing capabilities. The current literature reviewing therapeutic options for individuals with primary focal lingual dystonia appear limited; however, lingual dystonia as the primary symptom of OMD has been treated with various success rates via pharmacotherapy, dental appliances (i.e., bite-block therapy), and chemodenervation. The traditional treatment of OMD (with or without lingual dystonia) has included a variety of systemic pharmacologic agents including anticholinergics (trihexyphenidyl, benztropine), benzodiazepines (clonazepam, lorazepam, diazepam), baclofen, and drugs that deplete dopamine (tetrabenazine) (Klein & Ozelius, 2002; Tan, 2004; Tinter & Jankovic, 2002). Frequent side effects and poor to modest therapeutic improvement has suggested that pharmacotherapy with these agents is largely unsatisfactory for patients with OMD with or without lingual dystonia (Charles et al., 1997; Dworkin, 1996; Tinter & Jankovich, 2002).
Bite-block therapy was demonstrated to improve the speech intelligibility and orofacial postural control in two patients with Meige's syndrome (Dworkin, 1996). Results of this study revealed that when a bite-block was placed between the teeth of each of the two patients with dystonia, there was improvement in facial appearance, articulatory precision, and hyperactive oromandibular movements (Dworkin, 1996). The dramatic improvement in articulatory precision evidenced when the bite block was in place was suggested to be primarily related to stabilization of the jaw (Dworkin, 1996). It is unclear, however, whether bite-block therapy is clinically effective in individuals presenting with primary...
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