SD meaning in Medical ?

Spasmodic dysphonia, also known as laryngeal dystonia, is a disorder in which the muscles that generate a person's voice go into periods of spasm. This results in breaks or interruptions in the voice, often every few sentences, which can make a person difficult to understand. The person's voice may also sound strained or they may be nearly unable to speak. Onset is often gradual and the condition is lifelong.

The cause is unknown. Risk factors may include family history. Triggers may include an upper respiratory infection, injury to the larynx, overuse of the voice, and psychological stress. The underlying mechanism is believed to typically involve the central nervous system, specifically the basal ganglia. Diagnosis is typically made following examination by a team of healthcare providers. It is a type of focal dystonia.

While there is no cure, treatment may improve symptoms. Most commonly this involves injecting botulinum toxin into the affected muscles of the larynx. This generally results in improvement for a few months. Other measures include voice therapy, counselling, and amplification devices. If this is not effective, surgery may be considered; however, evidence to support surgery is limited.

The disorder affects an estimated 2 per 100,000 people. Women are more commonly affected. Onset is typically between the ages of 30 and 50. Severity is variable between people. In some, work and social life are affected. Life expectancy is, however, normal.