Myasthenia Gravis: A pain in the neck
Introduction
Myasthenia gravis is autoimmune disorder caused by an antibody-mediated blockade of neuromuscular transmission resulting in skeletal muscle weakness. The hallmark of myasthenia gravis is muscle weakness which gets worse on exertion and better with rest.
Case summary
We present a of 70 year old Indian male with complaints of neck pain for 2 weeks associated with pain in the bilateral shoulder girdles and mild weakness when he would lift his arms. He was not able to comb his hair or lift the head to look up after walking few steps. He had no significant past medical history. His examination revealed subtle left sided ptosis but ocular movement was full. He had no facial droop or tongue deviation. His neck movements and muscle tone was normal. He had mild weakness of the girdle muscles and hence was admitted to neurology for further management. Laboratory test revealed anti-AChR positive ANA and anti-acetylcholine receptor Ab was 50. Rapid nerve stimulation showed significant decremental response. He was started on pyridostigmine, IVIG for 5 days and oral prednisolone. The patient improved but a day later, he went into myasthena crisis with type 2 respiratory failure and respiratory acidosis, intubated and was put on ventilatory support. He was then weaned off and send for rehabilitation.
Discussion
This is an atypical presentation of MG with symptoms of neck pain which the GP had been treating almost for I week as cervical spondylosis. MG may affect any skeletal muscle, muscles that control eye and eyelid movement, facial expression, and swallowing are most frequently affected. The onset is sudden and the diagnosis is missed. There is no cure for MG but with current therapy the person can have normal life expectancy. These therapies are directed towards reducing and improving muscle weakness. The anti-acetylcholine receptor Ab titer and Nerve conduction study are helpful in diagnosing apart from the clinical evaluation. If the patent develops Respiratory failure he may need intubation and mechanical ventilation and Nasogastric feeding if dysphagia. Treatment options include like thymectomy (thymoma), steroids, anticholinesterase (mestinon and pyridostigmine ), immunoglobin and plasmapheresis.
Conclusion
The physicians should perform careful physical examination for patients presenting with muscle weakness, to enable early detection of atypical presentation of myasthenia gravis and commence early appropriate therapy.
