Myerson's sign is an important clinical neurological test used to assess the glabellar reflex. The test involves repetitive tapping on the glabella, which is the smooth area between the eyebrows. In a positive Myerson's sign, the patient continues to blink with each tap without habituation, which is often associated with Parkinson's disease and other neurological conditions.
The testing procedure for Myerson's sign is straightforward. First, position the patient comfortably and locate the glabella between the eyebrows. Then tap gently and repeatedly while observing the blink response. In a normal response, the patient blinks initially for two to three taps, then habituation occurs and blinking stops. However, in a positive Myerson's sign, the patient continues blinking with each tap without habituation.
Myerson's sign has significant clinical importance, particularly in diagnosing Parkinson's disease. It is found in seventy to ninety percent of Parkinson's patients and may appear early in disease progression. The sign results from degeneration of dopamine neurons in the substantia nigra, which affects the brain's ability to habituate reflexes. While it's also associated with other neurological conditions, it serves as a valuable screening tool for Parkinson's disease.