κῶμα

Kōma in Greek means deep sleep, lethargy, from koimān (to put to sleep, to lull). Hippocrates used the word for states of profound unconsciousness. The Greek word was a natural choice — the patient in a coma appears to be sleeping deeply. Eyes closed, breathing present, unresponsive. But the resemblance is superficial. Sleep cycles through stages of brain activity. Coma is a state of minimal brain activity. The comatose brain is not sleeping. It is barely running.

The Glasgow Coma Scale, developed by Graham Teasdale and Bryan Jennett in Glasgow in 1974, standardized the assessment of consciousness. The scale measures three responses: eye opening (1-4), verbal response (1-5), and motor response (1-6). A score of 3 is the minimum (deep coma, no responses). A score of 15 is the maximum (fully conscious). The scale transformed coma from a yes/no diagnosis into a graduated measurement.

The distinction between coma, vegetative state, and brain death was clarified in the late twentieth century. A coma typically lasts days to weeks. A persistent vegetative state preserves sleep-wake cycles but without awareness — the eyes open and close, but the person is not conscious. Brain death is the irreversible cessation of all brain function, including the brainstem. The three conditions look different, are caused by different mechanisms, and have different prognoses. The word 'coma' covers only the first.

Modern neuroscience has revealed that some patients who appear to be in vegetative states may have islands of awareness. Adrian Owen's 2006 study used fMRI to show that a patient diagnosed as vegetative could respond to commands by imagining specific activities — their brain lit up in the expected areas. The boundary between consciousness and unconsciousness, which the Greek word kōma treated as a simple line, turned out to be a gradient.