Non-Parkinson movement disorders: Five new things.

SOLUTIONS TO THE MAJOR RIDDLES IN MOVEMENT DISORDERS ARE APPEARING AT A BREATHTAKING PACE: 1) loss-of-function mutations in PRRT2, which encodes a cell surface protein expressed in neurons, have been found in many patients with paroxysmal kinesigenic dyskinesias; 2) mutations in CIZ1, which encodes a protein involved in cell-cycle control at the G1-S checkpoint, have been identified in a small percentage of patients with cervical dystonia; and 3) finally, after many years of genetics and identification of more than 25 disease-associated genes, cellular studies related to the pathobiology of hereditary spastic paraplegia are converging on defects in modeling the endoplasmic reticulum and membrane trafficking. On the treatment front, the distinctive syndromes of faciobrachial dystonic seizures with anti-LRI1 antibodies and anti-N-methyl-d-aspartic acid encephalitis with orobuccolingual dyskinesias are becoming increasingly recognized by clinicians as imminently treatable conditions. Also on the treatment front, the first phase I trial of MRI-guided high-intensity focused ultrasound for essential tremor has been completed and intraoperative MRI is currently being used to place electrodes in the brains of patients with medically intractable dystonia. Definitive etiologies and efficacious treatments for non-Parkinson disease movement disorders are no longer wishful thinking.