Ice test may not be reliable for myasthenia gravis

This case study describes a patient who received cosmetic botulinum toxin A (Botox) to the brow and subsequently developed variable unilateral ptosis who had a positive ice pack test. The ptosis was transiently improved after the test and gradually resolved over approximately three months. The authors therefore conclude that the ice test is not necessarily specific for myasthenia gravis.

They say that this patient highlights diagnostic difficulties in the setting of ptosis following Botox injection and regarding the specificity of the ice test for myasthenic ptosis.

This is the third patient documented to have variable ptosis after Botox injection to the brow and the second to have a positive ice test. All three patients had clinical evidence of neuromuscular junction impairment with fatigability and Cogan lid twitch sign. Ptosis in all three resolved within two to 12 weeks.

The current patient was a 52-year-old woman who presented with a one-week history of a drooping right upper eyelid. She did not have diplopia, limited ocular motility, or any other systemic signs or symptoms of generalized myasthenia gravis, and acetylcholine receptor antibody levels were normal.

The authors say that reports describing ptosis as a side effect of Botox generally have not mentioned variability, but the patients described in previous reports and in the present study indicate that variability may occur. This may create potential confusion regarding the diagnosis of myasthenia gravis, particularly if the patient is not questioned about or initially denies Botox injections.

They conclude that the ice test is not completely specific for myasthenia gravis but may, at times, improve ptosis resulting from other defects at the neuromuscular junction. They also say that wound botulism now is much more common because of illicit drug use, and the ice test also might be positive in this setting.