Dystonia

INDEX

 

Spasmodic dysphonia affects the laryngeal muscles causing involuntary and sustained muscle contraction. The condition can involve the larynx alone, or it can be associated with a spectrum of head and neck dystonias such as blepharospasm, torticollis, hemifacial spasm, cervical dystonia, and Meige syndrome (blepharospasm and oromandibular dystonia).

As with many forms of focal dystonia, isolated voice tremor is most suggestive of laryngeal dystonia (known as spasmodic dysphonia).
Patients with isolated spasmodic dysphonia have an approximate 7% risk that dystonia may spread to another body part.  Patients with spasmodic dysphonia are more likely to have associated tremor.

Spasmodic dysphonia can encompass a variety of clinical manifestations, sometimes including a tremor component involving the voice.
 
The presentation may be that of an adductor-type or an abductor-type dystonia.

Video 1. Patients with adductor type dysphonia, and response to botulinum toxin treatment.

 

(vv)Dysphonia.mp4(tt)

From; Brin MF, Blitzer A, Fahn S, Gould W, Lovelace RE. Adductor laryngeal dystonia (spastic dysphonia): treatment with local injections of botulinum toxin (Botox). Mov Disord. 1989;4(4):287-96. 

Examination

Adductor dysphonia:
The spasms are best elicited when the vocal folds are approximating, for example, with vowels and voiced consonants such as /b/, /d/, /g/, and /m/.

Vocal tasks:

Abductor dysphonia

The involuntary opening of the vocal folds causes excessive airflow to escape and loss of vocalization. Patients have difficulty with /h/, /s/, /f/, /P/, /t/, and /k/. The breathy interruptions in speech commonly occur when going from unvoiced consonant to a voiced phoneme or vowel. For the tasks below, listeners would hear “Puheeter will kuheep at the puheek” when patients read, “Peter will keep at the peak,” or “sahixty” when saying “sixty.

Vocal Tasks:

 

Voice tremor

Voice tremor is a feature of a number of neurological conditions, including PD, ET, ataxia, and spasmodic dystonia, and specifically in dystonia, may be observed in DYT-THAP1 and DYT-ANO3 mutation carriers.  Tremor of the voice due to essential tremor (ET) is more common in women and appears most frequently in the seventh decade. 

Comparing dystonia and tremor, spasmodic dysphonia is provoked by phrases containing many voiced onsets (eg, counting from 80 to 90), whereas the voice of patients with essential voice tremor is affected across all voice tasks without regard to phonetic composition.

Laryngeal tremor is present in about 25% of patients with any type of essential tremor and in 50% of patients with head tremor.

Patients may also have isolated laryngeal tremor, although this is most suggestive of spasmodic dysphonia. The voice may exhibit a shaky or quavering quality, and tremor may be mistaken for spasmodic dysphonia because muscular tremors can mimic glottic stops.

Examination

Sustained phonation: tremor may be present with sustained phonation due to ET, which is not present with spasmodic dystonia.

Patients with dystonic vocal tremors cannot change pitch during vocalization, and performing this manoeuvre can aid in the bedside diagnosis (see Dystonic Tremor).  The patient is requested to make a sustained sound (“ahh” or “eee”) for 7 seconds, while listening for breaks in the voice.
A sustained phonatory vowel task carried out with fibreoptic examination of pharyngeal and laryngeal musculature, supplemented by acoustic measures can help to characterize and confirm the nature of the tremor1.

Laryngoscopy of essential tremor patients with vocal tremor shows an entrained, oscillatory motion of several anatomic structures during sustained phonation. Many patients have oscillatory movements during quiet respiration. Tremor can involve muscles of the palate, pharynx, tongue, and other articulatory muscles in addition to the larynx. This distribution does not distinguish vocal tremor of essential tremor from spasmodic dysphonia. Dystonic patients were more likely to have reduction of tremor in the palate, pharynx, and larynx  when using a higher “falsetto” pitch3.

Laryngeal Anatomy

Muscle tension dysphonia (MTD)

MTD describes voice disorders caused by poorly regulated or abnormal laryngeal movements during phonation.
 Other frequently used terms include muscle misuse, hyperfunctional dysphonia, and tension-fatigue syndrome. There is hypercontraction or excessive tension in the intrinsic and/or extrinsic musculature. Individuals with MTD have a more evenly produced strained or breathy voice that is consistently present throughout all vocal tasks. They frequently lack the predictable breaks in targeted phonemes, and symptoms can wax and wane.
MTD may also be a compensatory mechanism for spasmodic dysphonia as the patient strains to produce desired phonemes. Similarly to spasmodic dysphonia, patients may still be able to sing, cough, and cry without difficulty.

Treatment predominately rests with voice therapy, and some patients may benefit from psychiatric evaluation to address emotional stressors that often contribute to MTD.
A trial of voice therapy can be helpful to unload any vocal strain when trying to differentiate MTD from spasmodic dysphonia.
Functional dysphonia can be considered a subtype of MTD. The term relates to a psychogenic voice disorder in absence of an organic cause of vocal framework pathology. Patients may mimic strained or aphonic voice issues such as those present in spasmodic dysphonia. Treatment resides in voice therapy and psychiatric intervention.

 

 

 

 

References