Coma

Coma implies total or near-total unresponsiveness from which the patient cannot be aroused by external or internal stimuli.

Despite vigorous stimulation, there is no purposeful movement and only posturing; brainstem reflexes may be absent or present.

Whereas the drowsy patient Opens in new window is conscious but lapsing at times into unconsciousness, in coma the patient is unconscious.

There are variations in the degree of coma:

• Deeper states — In its deepest stages, no reaction off any kind is obtainable; corneal, papillary, pharyngeal, tendon, and plantar reflexes are absent and the tone in the limb muscles is diminished,including brainstem reflex responses (i.e., lack of oculo- and pupillomotoric responses). Some cyclic autonomic activity such as the sleep-wake cycle and changes in motor tone may coexist.

• Lesser states — With lesser degrees of coma, papillary reactions, reflex ocular movements, and corneal and other brainstem reflexes are preserved in varying degree, and muscle tone in the limbs may be increased. Respiration may be varying.
• Lighter states — Lighter stages (sometimes denoted as semi-coma) can be identified by brief moaning to strong stimulation and associated observed changes in autonomic function.

In lighter states, with strong stimuli, the patient may be momentarily rousable; and there are no verbal responses or responses to painful stimuli.

The righting response of posture has been lost; reflexes and muscle tone are present but greatly reduced; breathing is slow, deep and rhythmic; the face and skin may be flushed.

In deeper stages, the patient is no longer rousable; s/he is deeply unconscious. Distinct stages of coma have identifiable physical signs ultimately culminating in brain death, but these are not discussed further in this entry — they are beyond psychiatry Opens in new window.