Complex sentence: Lhermitte's sign, sometimes called the Barber Chair phenomenon, is an electrical sensation that runs down the back and into the limbs when the practitioner pounds on the posterior cervical spine while the neck is flexed; caused by involvement of the posterior columns.
Split into simpler sentences: Lhermitte's sign, sometimes called the Barber Chair phenomenon, is an electrical sensation that runs down the back and into the limbs. It can also be evoked when a practitioner pounds on the posterior cervical spine while the neck is flexed; caused by involvement of the posterior columns.