Myasthenia gravis is an autoimmune disease affecting the nerve-muscle interface. The disease is more common in women (2:1). It typically presents between the ages of 30 and 40 in females and between the ages of 60 and 70 in males. No known risk factors exist. The typical symptoms of myasthenia gravis involve the eyes, specifically double vision and drooping eyelids. The symptoms usually arise after repetitive tasks (due to muscle fatigue) and improve with short periods of rest. Voice and speech-related symptoms include:
- Vocal fatigue
- Difficulty with controlling the pitch of the voice
- Hypernasal voice
- Mildly slurred speech
- Monotone voice
- Swallowing difficulty
- Weakness of the jaw muscles
The most reliable method of diagnosis is a blood test that detects the abnormal antibodies to the nerve-muscle receptor. Another method is the so-called “tensilon test.” The muscle in question is fatigued by a repetitive task and edrophonium (tensilon) is given to dramatically, but temporarily, reverse the fatigue. Other tests look at the muscles’ electrical firing (EMG) during repetitive tasks and their response to tensilon. The most common pitfall is a failure to recognize the often subtle symptoms of myasthenia gravis.
Voice problems correlated with myasthenia gravis include vocal fatigue, difficulty controlling pitch, and a monotone voice. The voice problem can stem from poor breath support, or from weakness causing disordered vocal fold movement. Speech disturbances include hypernasality (caused by weak palatal muscles) and dysarthria (particularly slurred speech, caused by articulatory imprecision).
Dysarthria is more frequently seen in younger patients diagnosed with MG, whereas dysphonia is more often seen in elderly men with MG. Typically, the symptoms appear and/or worsen with continuing or extended speech.
The treatment of speech and voice disorders in MG should occur on an individualized basis, and should take into consideration the underlying cause and severity of the problem. Speech therapy should occur in conjunction with medical treatment, with the Speech-Language Pathologist (SLP) planning treatment during peak medication times. The focus of speech and voice treatment in individuals with MG should be in providing compensatory strategies and environmental modifications to help increase intelligibility. Additionally, the patient should be educated on vocal hygiene, with specific emphasis on vocal rest.
The impact of MG on swallowing may occur gradually or suddenly. Swallowing muscles may become fatigued during a meal in as little as 1-20 minutes. A FEES examination is recommended for assessment because it can be used over an extended period of time to assess laryngeal fatigue and potential progression of aspiration throughout a meal. This will help ensure that the patient’s fatigue does not overwhelm their swallowing safety, and will allow for appropriate recommendations to be made.Leave a reply