E. Feindel, Tics and Their Treatment
“ By definition, then, a spasm is the motor reaction consequent on stimulation of some point in a reflex spinal or bulbo-spinal arc. To differentiate between the reflex, which is physiological, and the spasm, which is pathological, we may add as a corollary: the irritation provocative of the spasm is itself of pathological origin, and no spasm can occur without it. ”
