MG Should Be Suspected in Patients with Voice Alterations, Case Report Says

A recent report described a rare case of a woman presenting with a sudden decrease in voice volume who was ultimately diagnosed and successfully treated for myasthenia gravis (MG).

The case study, “Hypophonia as only presenting symptom in myasthenia gravis — a diagnostic dilemma in poor countries: a case report,” appeared in the Journal of Medical Case Reports.

A subset of patients with MG may experience bulbar muscle weakness, which may affect speech and swallowing. Dysphonia, or difficulty speaking, is particularly rare as a primary clinical presentation of MG.

Researchers at Annapurna Neurological Institute and Allied Sciences, in Nepal, presented the case of a 51-year-old woman who came to a neurology clinic after a 15-day decrease in the tone and texture of her voice that worsened throughout the day. Though weakened, her voice was understandable. The patient had no complaints of choking, coughing or throat discomfort.

Despite having had constipation for several years, she had never visited the hospital. She did not smoke or drink alcohol. No family member had any known chronic disease.

Neurological examinations revealed normal muscle strength and balance, intact deep tendon reflexes — which determine muscle contraction upon tapping — and speech articulation. Although speech production was adequate and non-painful, its intensity was low.

She had visited an ear, nose, and throat department, leading to unsuccessful treatment for possible laryngeal disorder with hypophonia, or lower voice volume.

At the neurology clinic, the physicians considered differential diagnoses of MG, Parkinson’s, and a bulbar variant of motor neuron disease.

Both magnetic resonance imaging of the brain and spinal cord and laboratory parameters were normal. MG was then suspected as the other diseases were ruled out. Her quantitative MG (QMG) test score was 1 (mild) for speech. She had a positive result on the neostigmine test — a common way to diagnose MG — which resulted in a significant improvement in voice quality and in lessened fatigability.

Within one hour, the patient showed good quality of speech. The QMG test was then repeated, with a score of 0 (no symptoms). Then, a test conducted in India revealed the woman was positive for anti-acetylcholine receptor (AchR) antibodies, found in high levels. She was maintained on 60 mg of oral Mestinon (pyridostigmine) “with 12 hourly administrations and subsequently increasing to six hourly along with steroids,” the report said.

The patient showed a well-defined nodule in her anterior mediastinum — in front of the pericardium (the membrane enclosing the heart and great vessels) and below the thoracic plane — on computed tomography scans. She was then sent to the surgical department with a suspected thymoma — a tumor in the thymus.

A follow-up visit two months after the patient first went to the neurology clinic showed that the surgery had been successful and she was doing well. She had already been tapered off prednisolone (steroid), and was lowering her Mestinon dose. Her voice was clear and she had no complaints of fatigue. She was able to conduct her daily and work activities normally.

Overall, this case report illustrates that clinicians should have a “high index of suspicion” of MG even in patients presenting with uncommon manifestations such as hypophonia, the scientists said. “Early diagnosis and early necessary treatment from a multidisciplinary team enables improvement of MG and, in some cases, even total remission.”

They added, “The diagnosis for MG should not only rely on or wait for laboratory investigations.” This is particularly important in underdeveloped countries such as Nepal, where tests for MG-related autoantibodies are not available, the researchers said.