Ice Pack Test Helps Diagnose Ocular MG, Case Report Finds
The study, “Ice pack test in myasthenia gravis: a cool investigation at the bedside,” was published in the journal The Lancet.
A 65-year-old man was admitted to Centro Hospitalar Universitário de São João, in Portugal, with a drooping left eyelid, or ptosis, which had been present for one month, and double vision that was slowly developing for three days.
On examination, he also showed overactivity of his frontalis muscle, which is located in the forehead and elevates the eyebrows, but no other local neurological deficits.
The patient’s medical history revealed he had acute coronary syndrome (conditions associated with sudden, reduced blood flow to the heart) with ischemic heart failure and an irregular heartbeat, which were being treated with several medications. He had no personal or family history of neurological or autoimmune disorders.
Initial tests also found a normal blood count, as well as normal function of kidneys, liver and thyroid gland. A CT scan of the patient’s eye sockets also revealed no abnormalities.
Given this information, the clinicians made a preliminary diagnosis of MG and used the ice pack test to provide additional evidence. The benefit of this test, said the scientists, is that it can enable the differentiation of neuromuscular conditions such as MG from peripheral nerve or muscular disorders, as a neuromuscular condition would respond to cooling.
A nitrile glove filled with ice was placed on the patient’s left eyelid for two minutes, and the clinicians found that the ptosis receded by more than 2 mm. Yet, this improvement was temporary, lasting approximately seven minutes.
To further investigate the diagnosis, the clinicians ran several tests of the patient’s muscular function in the arm, hand, face and nose, which all came back normal.
However, he tested positive for anti-acetylcholine receptor antibodies, the most common cause of MG. This confirmed the team’s working diagnosis of ocular MG.
Following oral treatment with 60 mg pyridostigmine (sold as Mestinon and other names), the patient’s symptoms eased after 30 minutes, lasting nearly four hours. However, as some ptosis and double vision remained, he was given 60 mg pyridostigmine four times daily, with an additional 10 mg of prednisolone, a glucocorticoid medication, taken once daily.
Overall, “a single-fibre electromyography nerve-conduction test and the ice pack test are together highly sensitive and specific for ocular myasthenia gravis, but their results may be discordant,” the researchers wrote. “The combination of unilateral eyelid ptosis and a positive ice pack test with positive anti-acetylcholine receptor antibodies test will then confirm the diagnosis.”
“The ice pack test also helps to guide clinical decision making while waiting for the results of complementary investigations,” they added.