Signs of Metabolic Injury
Signs of metabolic injury, implying an intact brainstem, are roving eye movements, a pupillary reaction to light (pinpoint pupils suggest opiates or a pontine lesion. Dilated reactive pupils are seen with adrenergic or anticholinergic drugs), a normal oculocephalic reflex (dollís eyes) consisting of abruptly rotating the head to one side while the eyes deviate in the opposite direction (this test should not be used in the trauma patient unless the cspine has been cleared), a normal oculovestibular reflex (instilling 50 ml of cold water into the auditory canal causes deviation of the eyes toward the water) and hyporeflexia.
Signs of Structural Injury
Signs of structural injury from trauma or stroke are fixed pupils, either large or pinpoint (pinpoint pupils suggest a pontine hemorrhage. Fixed midposition pupils implies brainstem damage. One fixed dilated pupil suggests impending uncal herniation), no extra-ocular movements, loss of oculocephalic and oculovestibular reflexes, differences in movements of arms and legs, asymmetry and increased deep tendon reflexes with upgoing toes (Babinskiís reflex) and decorticate or decerebrate posturing (arm flexion and leg extension in decorticate posturing represents injury to both cerebral hemispheres;
extension of the arms and legs in decerebrate posturing represents injury to the brainstem). Decerebrate and decorticate posturing may occur in metabolic derangements, but more commonly are seen with structural damage. Fixed ocular deviation is toward a cortical lesion.