Two roads to coma: the Scottish hypothesis

Clinical experience seems to indicate two separate types of entry to coma. Some patients follow a pathway characterized by confusion, hallucinations, mumbling delirium, myoclonic jerks, and seizures. The author has called this sequence of symptoms the high road to coma and hypothesized that its basic underlying pathophysiology involves increased neuronal firing rates. Other patients develop somnolence, lethargy, obtundation, and unresponsiveness without seizures or muscle twitches. This low road to coma involves either anatomical compression of the midbrain reticular formation or a metabolic or toxic disorder characterized by membrane stabilization and decreased neuronal excitability.