Porth's Essentials of Pathophysiology, 4e

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Nervous System

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TABLE 37-2 Descending Levels of Consciousness andTheir Characteristics Level of Consciousness Characteristics

Confusion

Disturbance of consciousness characterized by impaired ability to think clearly and to perceive, respond to, and remember current stimuli; also, disorientation State of disturbed consciousness with motor restlessness, transient hallucinations, disorientation, and sometimes delusions Disorder of decreased alertness with associated psychomotor retardation A state in which the person is not unconscious but exhibits little or no spontaneous activity A state of being unarousable and unresponsive to external stimuli or internal needs; often determined by the Glasgow Coma Scale

Delirium

Obtundation

Stupor

Coma

Data from Bates D.The management of medical coma. J Neurol Neurosurg Psychiatry. 1993;56:590.

hemisphere unilaterally and also spare the RAS, such as cerebral infarction, usually do not impair consciousness. Levels of Consciousness. Levels of consciousness reflect awareness and response to the environment. A fully conscious person is totally aware of his or her sur- roundings and able to react to stimuli in the environ- ment. 14,15 Levels of consciousness exist on a continuum that includes consciousness, confusion, delirium, obtun- dation, stupor, and coma 4 (Table 37-2). The earliest signs of diminution in level of conscious- ness are inattention, mild confusion, disorientation, and blunted responsiveness. With further deterioration, the delirious person becomes markedly inattentive and vari- ably lethargic or agitated. The person may progress to become obtunded and may respond only to vigorous or noxious stimuli. Because of its simplicity of application, the Glasgow Coma Scale has gained almost universal acceptance as a method for assessing the level of consciousness in per- sons with brain injury 16 (Table 37-3). Numbered scores are given to responses of eye opening, verbal utterances, and motor responses. The total score is the sum of the best response in each category. Additional elements in the initial neurologic evalua- tion of a person with brain injury include checking for abnormalities in the size of the pupils and their reaction to light, evidence of decorticate or decerebrate postur- ing, and altered patterns of respiration. 4,7 Pupillary Reflexes and Eye Movements. Although the pupils may initially respond briskly to light, they become unreactive and dilated as brain function deteriorates. A bilateral loss of the pupillary light response is indicative of lesions of the brain stem. A unilateral loss of the pupillary light response may be due to a lesion of the optic or oculomotor pathways. The oculocephalic reflex (doll’s-head eye movement) Other Manifestations of Deteriorating Brain Function

can be used to determine whether the brain stem cen- ters for eye movement are intact (Fig. 37-11). If the oculocephalic reflex is inconclusive, and if there are no contraindications, the oculovestibular test (i.e., cold caloric test, in which cold water is instilled into the ear canal) may be used to elicit nystagmus (see Chapter 38). Decorticate and Decerebrate Posturing. With the early onset of unconsciousness, there is some combative and purposeful movement in response to pain. As coma progresses, noxious stimuli can initiate rigidity and abnormal postures if the motor tracts are interrupted at specific levels. These abnormal postures are classified as decorticate and decerebrate. 7 Both are poor prognostic signs.

TABLE 37-3 The Glasgow Coma Scale Test

Score*

Eye Opening (E) Spontaneous

4 3 2 1 6 5 4 3 2 1 5 4 3 2 1

To call To pain

None

Motor Response (M) Obeys commands

Localizes pain

Normal flexion (withdrawal) Abnormal flexion (decorticate)

Extension (decerebrate)

None (flaccid)

Verbal Response (V) Oriented

Confused conversation Inappropriate words Incomprehensible sounds

None

*GCS Score = E + M + V. Best possible score = 15; worst possible score = 3.