Which bedside test is used to support MG diagnosis by transiently increasing muscle strength after cooling?

Which bedside test is used to support MG diagnosis by transiently increasing muscle strength after cooling?

• A. Ice pack test
• B. Edrophonium test
• C. EMG
• D. Serum ACh receptor antibodies

Answer: (A)

The ice pack test is a simple bedside maneuver used when ocular MG is suspected. In myasthenia gravis, weakness worsens with use because fewer functional acetylcholine receptors are available at the neuromuscular junction. Cooling the affected muscle area, such as placing an ice pack over the eyelid, slows acetylcholinesterase activity and increases acetylcholine availability at the junction, transiently improving transmission. This can lead to a noticeable but temporary improvement in ptosis or diplopia, supporting a diagnosis of MG. The other options are not bedside cooling tests. The edrophonium (Tensilon) test uses a rapid acetylcholinesterase inhibitor but is pharmacologic and requires monitoring for adverse effects. Electromyography examines electrical activity (decrement on repetitive nerve stimulation or jitter on single-fiber EMG) rather than producing a short-term improvement with cooling. Serum ACh receptor antibodies reflect autoimmune involvement but do not demonstrate a reversible, cooling-induced improvement.

The ice pack test is a simple bedside maneuver used when ocular MG is suspected. In myasthenia gravis, weakness worsens with use because fewer functional acetylcholine receptors are available at the neuromuscular junction. Cooling the affected muscle area, such as placing an ice pack over the eyelid, slows acetylcholinesterase activity and increases acetylcholine availability at the junction, transiently improving transmission. This can lead to a noticeable but temporary improvement in ptosis or diplopia, supporting a diagnosis of MG.

The other options are not bedside cooling tests. The edrophonium (Tensilon) test uses a rapid acetylcholinesterase inhibitor but is pharmacologic and requires monitoring for adverse effects. Electromyography examines electrical activity (decrement on repetitive nerve stimulation or jitter on single-fiber EMG) rather than producing a short-term improvement with cooling. Serum ACh receptor antibodies reflect autoimmune involvement but do not demonstrate a reversible, cooling-induced improvement.