Catatonia Secondary to Depolarization Block.

Catatonia is a severe psychomotor disorder that is associated with a 60-fold increased risk of premature death. Its occurrence has been associated with multiple psychiatric diagnoses, the most common being type I bipolar disorder. Catatonia can be understood as a disorder of ion dysregulation with reduced clearance of intracellular sodium ions. As the intraneuronal sodium concentration increases, the transmembrane potential is increased, and the resting potential may ultimately depolarize above the cellular threshold potential creating a condition known as depolarization block. Neurons in depolarization block do not respond to stimulation but are constantly releasing neurotransmitter; they mirror the clinical state of catatonia - active but non-responsive. Hyperpolarizing neurons, e.g., with benzodiazepines, is the most effective treatment.