How is Lhermitte's sign performed?

Lhermitte's sign is a neurological sign that is produced when there is irritation of the cervical spine or lesions in the spinal cord, often associated with conditions such as multiple sclerosis. The test is performed by having the patient in a long sitting position and passively flexing the head while one of the hips is flexed.

The reason this method is effective is that flexing the head forward can elicit a "shock-like" sensation that radiates down the spine and into the limbs. This response is due to the stretching of neural pathways, which indicates possible dysfunction in the cervical spinal cord or the upper motor neurons. The additional hip flexion can help to further delineate whether the signs and sensations are localized to certain anatomical pathways.

In contrast, positioning the patient in supine with flexion of the head and oppositional shoulder or in a standing position with arms raised does not effectively replicate the clinical scenario necessary to test for this specific sign. Performing the maneuver in prone while extending the neck and back is not related to Lhermitte's sign at all, as this position does not create the necessary tension in the spinal cord pathways that is indicative of the sign. Therefore, method B is the most accurate and clinically relevant way to perform and