Stupor describes a state in which the patient can be roused only by vigorous and repeated stimuli and in which arousal cannot be sustained without repeated stimulation. Responses to spoken commands are either absent, curtailed, or slow and inadequate. Restless or stereotyped motor activity is common, and there is a reduction or elimination of the natural shifting of body positions. When left unstimulated, these patients quickly drift back into a deep sleep-like state. The eyes are usually found to be displaced outward and upward, a feature that is shared with sleep (see further on). Tendon and plantar reflexes, and the breathing pattern may or may not be altered, depending on how the underlying disease has affected the nervous system. In psychiatry, the term stupor had been used in a second sense—to denote an uncommon condition in which the perception of sensory stimuli is presumably normal but activity is suspended and motor activity is profoundly diminished (catatonia, or catatonic stupor).
These states, including coma, exist in a continuum, and an alternative practical method of making distinctions between them was given by Fisher, who suggested that a verbal command is required to overcome drowsiness whereas a noxious stimulus is required to overcome stupor. This allows for further gradations in the level of consciousness based on the intensity of stimulation that is necessary to produce arousal.
The patient who is incapable of being aroused by external stimuli or inner need, comatose. There are variations in the degree of coma, and the findings and signs depend on the underlying cause of the disorder. In its deepest stages, no meaningful or purposeful reaction of any kind is obtainable and corneal, pupillary, pharyngeal responses are diminished. In lighter stages, sometimes referred to by the ambiguous terms semicoma or obtundation, most of the above reflexes can be elicited, and the plantar reflexes may be either flexor or extensor (Babinski sign). As mentioned, the depth of coma and stupor may be gauged by the response to externally applied stimuli and is most useful in assessing the direction in which the disease is evolving, particularly when compared in serial examinations.
Relationship of Sleep to Coma
Persons in sleep give little evidence of being aware of themselves or their environment; in this respect, they are unconscious. Sleep shares a number of other features with the pathologic states of drowsiness, stupor, and coma. These include yawning, closure of the eyelids, cessation of blinking and reduction in swallowing, upward deviation or divergence or roving movements of the eyes, loss of muscular tone, decrease or loss of tendon reflexes, and even the presence of Babinski signs and irregular respirations, sometimes Cheyne-Stokes in type. Upon being awakened from deep sleep, a normal person may be confused for a few moments, as every physician knows from personal experience. Nevertheless, sleeping persons may still respond to unaccustomed stimuli and are capable of some mental activity in the form of dreams that leave traces of memory, thus differing from stupor or coma. The most important difference, of course, is that persons in sleep, when stimulated, can be roused to normal and persistent consciousness. There are important physiologic differences as well. Cerebral oxygen uptake does not decrease during sleep, as it usually does in coma. Recordable electrical activity—electroencephalographic (EEG) and cerebral evoked responses—and spontaneous motor activity differ in the two states, as indicated later in this chapter and in Chap. 18. The anatomic and physiologic bases for these differences are only partly known.
THE VEGETATIVE AND MINIMALLY CONSCIOUS STATES, LOCKED-IN SYNDROME, AND AKINETIC MUTISM
Several clinical conditions are juxtaposed to the continuum of drowsiness, stupor and coma. They stand apart as a result of special characteristics or by their underlying cause but, with the exception of the locked in state, they are each forms of diminished consciousness.