TICS OF THE CHIN
The muscles of the chin collaborate with other facial muscles in expressional movement, and are similarly liable to be the seat of tics.
Massaro[73] has observed an interesting series of isolated "geniospasm" occurring in twenty-six individuals of the same family during five generations. The characteristic feature of these spasms was an involuntary intermittent clonic contraction of the transverse muscles of the chin, suggesting the look of one seized with fear or with cold. The will did not always effect their inhibition, while emotion appeared to aggravate and distraction to abate their intensity. With sleep they vanished entirely.