Facial nerve paralysis. Facial nerve paralysis most commonly causes a unilateral, but sometimes bilateral, paralysis of the muscles responsible for facial expression. Patients often present unable to move the lip or blink and with a droopy ear and severe ptyalism.
The Fourth World is an extension of the Three-World Model, used variably to refer to. Sub-populations socially excluded from global society; Hunter-gatherer, nomadic, pastoral, and some subsistence farming peoples living beyond the modern industrial norm.
-Marty and Doc discussing how to get back to 1985 from 1885. The fourth dimension is the portion of the space-time continuum which the DeLorean time machine was designed to utilize when travelling to the past or the future.