Although limited in some ways in comparison to the examination of the alert patient, the neurologic examination of the comatose patient is relatively simple. Watching the patient for a few moments often yields considerable information. The predominant postures of the limbs and body; the presence or absence of spontaneous movements on one side; the position of the head and eyes; and the rate, depth, and rhythm of respiration each give substantial information.
The state of responsiveness is then estimated by noting the patient’s reaction to sequentially more vigorous stimuli starting with calling his name, to simple commands, and then to noxious stimuli such as tickling the nares, supraorbital or sternal pressure, pinching the side of the neck or inner parts of the arms or thighs, or applying pressure to the knuckles. By this method, one can roughly estimate both the degree of unresponsiveness and changes from hour to hour. Vocalization may persist in stupor and will be the first response to be lost as coma appears. Grimacing and deft avoidance movements of stimulated parts of the body are preserved in stupor; their presence substantiates the integrity of corticobulbar and corticospinal tracts. Yawning and spontaneous shifting of body positions indicate a minimal degree of unresponsiveness. These signs have been elegantly summarized by Fisher based on his own observations. The widely adopted Glasgow Coma Scale, constructed originally as a quick and simple means of quantitating the responsiveness of patients with cerebral trauma, can be used in the grading of other acute coma-producing diseases as mentioned earlier in this chapter (see also Chap. 35). Several other scales such as the “FOUR Score” (Wijdicks et al, 2005) have been devised and are used in various units.
In all but the deepest stages of coma, meningeal irritation from either bacterial meningitis or subarachnoid hemorrhage will cause resistance to the initial excursion of passive flexion of the neck but not to extension, turning, or tilting of the head. Meningismus is a fairly specific but somewhat insensitive sign of meningeal irritation as commented in Chap. 1. Resistance to movement of the neck in all directions may be part of generalized muscular rigidity or dystonia or indicate disease of the cervical spine. In the infant, bulging of the anterior fontanel is at times a more reliable sign of meningitis than is a stiff neck. A temporal lobe or cerebellar herniation or decerebrate rigidity may also create resistance to passive flexion of the neck and be confused with meningeal irritation.
A coma-causing lesion in a cerebral hemisphere can be detected by careful observation of spontaneous movements, responses to stimulation, prevailing postures, and by examination of the cranial nerves. Hemiplegia is revealed by a lack of restless movements of the limbs on one side and by inadequate protective movements in response to painful stimuli. The weakened limbs are usually slack and, if lifted from the bed, they “fall flail.” The hemiplegic leg lies in a position of external rotation (this may also be caused by a fractured femur), and the affected thigh appears wider and flatter than the nonhemiplegic one. In expiration, the cheek and lips puff out on the paralyzed side of the face. A lesion in one cerebral hemisphere causes the eyes to be turned away from the paralyzed side (toward the lesion, as described below); the opposite occurs with brainstem lesions. In most cases, a hemiplegia and an accompanying Babinski sign are indicative of a contralateral hemispheral lesion; but with lateral mass effect and compression of the opposite cerebral peduncle against the tentorium, extensor posturing, a Babinski sign, and weakness of arm and leg may appear ipsilateral to the lesion (the earlier-mentioned Kernohan-Woltman sign). A moan or grimace may be provoked by painful stimuli applied to one side but not to the other, reflecting hemianesthesia. During grimacing in response to stimuli, facial weakness may be noted.