neurologic disorders
Overview of Coma and Impaired Consciousness
Symptoms and Signs
Consciousness is decreased to varying degrees. Repeated stimuli arouse patients only briefly or not at all. Depending on the cause, other symptoms develop (see table Findings by Location* ): Eye abnormalities:Pupils may be dilated, pinpoint, or unequal. One or both pupils may be fixed in midposition. Eye movement may be dysconjugate or absent (oculomotor paresis) or involve unusual patterns (eg, ocular bobbing, ocular dipping, opsoclonus). Homonymous hemianopia may be present. Other abnormalities include absence of blinking in response to visual threat (almost touching the eye), as well as loss of the oculocephalic reflex (the eyes do not move in response to head rotation), the oculovestibular reflex (the eyes do not move in response to caloric stimulation), and corneal reflexes. Autonomic dysfunction:Patients may have abnormal breathing patterns (Cheyne-Stokes or Biot respirations), sometimes with hypertension and bradycardia (Cushing reflex). Abrupt respiratory and cardiac arrest may occur. However, hypotension may occur if impaired consciousness is caused by severe infection, severe dehydration, major blood loss, or cardiac arrest. Abnormalities include flaccidity, hemiparesis, asterixis, multifocal Myoclonus , decorticate posturing (elbow flexion and shoulder adduction with leg extension), and decerebrate posturing (limb extension and internal shoulder rotation). Other symptoms:If the brain stem is compromised, nausea, vomiting, meningismus, occipital headache, ataxia, and increasing somnolence can occur. 