Laryngeal Dystonia

1. What is the disease?

Laryngeal dystonia is an uncommon movement disorder affecting one or more of the paired laryngeal muscles. During speech production exhaled air is modified by the coming together and separation of the vocal cords, which also vibrate resulting in sound production. Precise, accurate controlled approximation of the vocal cords involves activation of the muscles which move the vocal cords together (adductor muscles), counterbalanced by initial controlled tension followed by progressive relaxation of the muscles which pull the vocal cords apart (abductor muscles). Laryngeal dystonia is a neurological disorder of central motor processing causing impaired co-ordination of this finely controlled laryngeal cycle of vocal cord tension and relaxation. Typically, this results in an inappropriate increased tension in the abductor or abductor laryngeal muscles, relative to its opposing (antagonistic) muscle group and causes muscle spasms. There is an underlying genetic susceptibility to muscle dystonia’s, but trigger factors such as a viral neuritis or local trauma are frequent precursors. The condition may occur at any age and spontaneous recovery is rare.

2. What are the symptoms?

The patients’ symptoms are dictated by the primary muscle groups involved. About 90% of patients suffer from Adductor Laryngeal Dystonia (also called Spasmodic Dysphonia). Marked relative overactivity of the adductor muscles results in vocal cord spasms causing a severely strained, staccato, hoarse voice with variable pitch breaks. With mild adductor dystonia the voice quality may just be slightly strained and ‘creaky’, but equally disabling. In Abductor Laryngeal Dystonia there is relative overactivity of the abductor muscles, causing a weak, breathy voice often with a sudden reduction or total loss of speech volume with the spasms. Cricothyroid Laryngeal Dystonia, primarily affects the muscles which tense the vocal cords. This can result in sudden spasmodic voice loss often in the middle of a word, and may also occur concurrently with Adductor LD. Sometimes, the primary symptom of a subgroup of Adductor Laryngeal Dystonia is inspiratory stridor with breathing difficulties.

3. What are the treatment options?

Speech therapy is beneficial for many voice disorders, but is usually ineffective in Laryngeal Dystonia. Muscle relaxant drugs and psychotherapy relaxation techniques are also unhelpful. Before the nature of the condition was fully understood, early treatment usually involved total or selective laryngeal nerve section to stop the muscles spasms. Whilst this resulted in early benefit in many patients, subsequent regrowth of the nerve fibres almost inevitably resulted in recurrent voice problems after 1 to 2 years in more than two-thirds of cases and a permanently paralysed cord. More recently a technique to remove some cartilage from the front of the larynx and cause scarring where both vocal cords join to limit the spasms has been introduced (thyroplasty) with mixed voice quality results.

Andrew Blitzer, a Laryngologist in New York, pioneered treatment with botulinum toxin injections to the hyperactive laryngeal muscles in the mid-1980s. Botulinum toxin, the most potent neurotoxin known to man, blocks the acetylcholine muscle receptors and reduces muscle hyperactivity in a dose-dependent manner, though there are significant individual variations in the degree of muscle relaxation. Because the laryngeal muscles are hidden under the skin or inside the larynx, the treatment injections are given under electromyography (EMG) control for precise localisation under local anaesthetic as an Out-patient with few temporary side effects. Deactivation of the neuro-muscular receptors is permanent, but spontaneous neural re-sprouting regeneration occurs over a few months to cause progressive re-innervation and recurrent symptoms. Once the optimum individual dosage has been confirmed, long term management requires repeated laryngeal muscle injections every 3-4 months.

4. Neuro-Laryngology Service at The Harley Street ENT Clinic

Gerald Brookes, Consultant Neuro-Laryngologist, and Professor Renata Whurr, Speech & Language Therapist, pioneered the use of botulinum toxin for laryngeal dystonia in the UK in 1988 at The National Hospital for Neurology & Neurosurgery, a national referral centre for all the many different types of dystonia’s. Their joint clinic was soon established as the largest laryngeal dystonia treatment service in Europe. This team continues to maintain the NHS-funded Neuro-laryngology service at The Harley Street ENT Clinic, on the background of their extensive and unrivalled clinical experience in this specific field in the UK. They have particular expertise in the management of the rarer types of laryngeal dystonia, which often pose difficult technical challenges for other less experienced specialists.