Brain Death, Neuromuscular Disorders and Consciousness

Assessment of Consciousness, Motor Function, and Pupillary Responses

A change in level of consciousness is often among the earliest and most sensitive signs of neurological deterioration in the critically ill adult. Consciousness comprises two distinct components: arousal, which is mediated by the reticular activating system, and awareness, which is mediated by the cerebral cortex. A patient may demonstrate arousal through wakefulness or eye opening while lacking awareness, which involves the complex cortical capacity to interact meaningfully with the environment. Systematic bedside assessment allows the critical care nurse to track subtle shifts in both domains before catastrophic decompensation occurs.

The Glasgow Coma Scale evaluates three specific behavioral domains: eye opening (scored 1 to 4), verbal response (scored 1 to 5), and motor response (scored 1 to 6). When evaluating motor function, record the best motor response observed in any limb, while separately reporting any asymmetry between sides. A Glasgow Coma Scale score of 8 or less indicates severe impairment of consciousness; in this scenario, the bedside nurse must assess airway protection and ventilation immediately and prepare for intubation if clinically indicated and ordered. An acute drop of two or more points on the Glasgow Coma Scale warrants immediate bedside re-evaluation and urgent notification of the provider. For an intubated patient, document the verbal component as untestable because of intubation rather than assigning a verbal score of 1, and report the assessable components separately. To overcome verbal assessment barriers, clinicians may also utilize the Full Outline of UnResponsiveness score, which evaluates eye responses, motor responses, brainstem reflexes, and respiration without relying on verbal output.

Abnormal motor posturing provides critical diagnostic data regarding the extent of central nervous system compromise. Decorticate posturing involves abnormal flexion of the upper extremities with extension of the lower extremities, indicating dysfunction at the cerebral cortex or diencephalon. In contrast, decerebrate posturing presents as abnormal extension and pronation of the upper extremities accompanied by extension of the lower extremities. Decerebrate posturing suggests severe neurological dysfunction but does not, by itself, precisely localize a lesion.

Pupillary examination yields rapid insight into structural and metabolic insults. A unilaterally dilated and non-reactive pupil serves as a classic sign of uncal herniation causing compression of cranial nerve III. Bilateral fixed, dilated pupils may occur with severe midbrain injury or global hypoxic-ischemic injury; however, the critical care nurse must also consider systemic or topical medications and underlying ocular causes. Pinpoint, reactive pupils are characteristically associated with pontine hemorrhage or opioid toxicity.