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الأربعاء، 13 أكتوبر، 2010

Laryngeal dystonia

Laryngeal dystonia (spasmodic dysphonia)Laryngeal dystonia/spasmodic dysphonia, a focal dystonia, involves involuntary contractions of the vocal cords causing interruptions of speech and affecting the voice quality. One of the most characteristic features of spasmodic dysphonia is the patterned, repeated “breaks” in speech. Symptoms of spasmodic dysphonia come in several varieties. Symptoms can be broadly divided into two forms: adductor and abductor. The more common adductor type causes a tight, “strangled-sounding” voice quality, often with abrupt starting and stopping of the voice. The abductor type causes a breathy, whispering voice. Most cases of spasmodic dysphonia/laryngeal dystonia are primary and develop in adults

Terms used to describe laryngeal dystonia include: spasmodic dysphonia (SD); adult-onset focal dystonia

Symptoms
Symptoms of spasmodic dysphonia come in several varieties. One of the most characteristic features of spasmodic dysphonia is the patterned, repeated “breaks” in speech. Spasmodic dysphonia can be broadly divided into two varieties: adductor and abductor. In the more common adductor type, speaking causes abnormal involuntary excessive contraction of the muscles that bring the vocal cords together. This causes a tight, “strangled-sounding” voice quality, often with abrupt starting and stopping of the voice resulting in a broken speech pattern and short breaks in speech

In the abductor type, there is an overcontraction of the muscles that separate the vocal cords. The vocal cords are held apart, resulting in a breathy, whispering voice

Other sub-types of spasmodic dysphonia have been identified by clinicians. One is a combination of adductor and abductor symptoms in which an individual may demonstrate both types of spasms as he/she speaks. In a second subtype, symptoms are accompanied by a voice tremor. A third subtype involves a primary voice tremor that is so severe the patient experiences adductor voice breaks during the tremor

Symptoms may improve or disappear when whispering, laughing, or singing. Many of the symptoms vary during the day, become aggravated by certain speaking—especially talking on the phone—or increase during stressful situations

Although it can start any time during adult life (and very rarely in adolescence), spasmodic dysphonia seems to begin frequently in people between 40-50 years old

Cause
Most cases of spasmodic dysphonia are primary, meaning that it is the only apparent neurological disorder, with or without a family history. In most individuals, the cause of spasmodic dysphonia is unknown. The general medical consensus is that spasmodic dysphonia is a central nervous system disorder and a focal form of dystonia. Researchers are investigating possible mechanisms involved in the triggering of spasmodic dysphonia including genetic factors, inflammation, and/or injury that may lead to changes in the central nervous system that impact motor control of the vocal cords

Spasmodic dysphonia may occur with other dystonias such as blepharospasm, oromandibular dystonia, or cervical dystonia

Diagnosis
Spasmodic dysphonia is reported to be one of the most frequently misdiagnosed conditions in speech-language pathology. Because there is no definitive test for the spasmodic dysphonia, the diagnosis rests on a physician’s ability to identify the symptoms and signs in the absence of other conditions that may mimic spasmodic dysphonia

It is important that an interdisciplinary team of professionals evaluate and provide accurate diagnosis. This team usually includes a speech-language pathologist who evaluates voice production and voice quality; a neurologist who carefully searches for other signs of dystonia or other neurological conditions; and an otolaryngologist who examines the vocal cords and their movements

The excessive strain and misuse of muscle tension dysphonia, the harsh strained voice of certain neurological conditions, the weakened voice symptoms of Parkinson's disease, certain psychogenic voice problems, and voice tremors are often confused with spasmodic dysphonia

Treatment
The treatment of choice for most cases of spasmodic dysphonia is regular injections of botulinum toxin into the vocal cord muscles. Voice therapy is often incorporated into the treatment plan, especially before and after the injections

Oral medications may also be tried but typically provide little relief in the symptoms of spasmodic dysphonia

A form of surgery called selective laryngeal adduction denervation and reinnervation (SLAD/R) may be an option for some individuals with adductor spasmodic dysphonia/laryngeal dystonia. Botulinum toxin injections may or may not be needed following the surgery

Speech/voice therapy can help minimize spasms and the effects of the spasms. Fatigue is often a significant component of spasmodic dysphonia/laryngeal dystonia because it may take a great effort to speak. Voice therapy techniques that focus on controlling the breath and using the breath to make the most of the voice may be surprisingly helpful