What is Lhermitte's sign?

Lhermitte's sign is characterized by a transient electrical sensation that runs down the spine when the neck is flexed. This phenomenon occurs due to demyelination of the cervical spinal cord, which is a common finding in conditions such as multiple sclerosis. When the neck is bent forward, it can trigger this sensation, often described by patients as feeling like an electric shock radiating down the spine and possibly into the limbs. It is a significant clinical sign that can help healthcare providers identify underlying neurological issues, particularly those related to spinal cord pathology.

The other choices do not accurately represent Lhermitte's sign. Constant numbness in the limbs relates to different types of neuropathies or nerve impairments, rather than the distinct sensation experienced with Lhermitte's sign. Memory loss is not directly associated with this symptom, as it pertains more to cognitive functions rather than somatic sensations. Visual disturbances also do not describe this phenomenon; such disturbances are related to optic nerve involvement in conditions like multiple sclerosis, but they are distinct from the electrical sensations described by Lhermitte's sign.