Tic douloureux, Parkinson's disease and the herpes connection.

Several cases encountered in psychiatric practice are described in which herpetic involvement of the trigeminal nerve appeared to be crucial to the pathophysiology of the patient's illness. A brief history of herpes is discussed in terms of the anatomy and physiology of the trigeminal nerve. Particular attention is given to the effects of intraneuronal herpes on gasserian ganglion and spinal nuclei discharge thresholds, as well as viral pathways directly impacting the substantia nigra. Evidence characterizing Parkinson's disease as one of several important manifestations of CNS herpes is covered.