neurologic disorders
Vegetative State and Minimally Conscious State
Symptoms and Signs
Patients in a vegetative state show no evidence of awareness of self or environment and cannot interact with other people. Purposeful responses to external stimuli are absent, as are language comprehension and expression. The following are present in patients in a vegetative state: Signs of an intact reticular formation (eg, eye opening) and an intact brain stem (eg, reactive pupils, oculocephalic reflex) Sleep-wake cycles, not necessarily reflecting a specific circadian rhythm nor associated with the environment More complex brain stem reflexes, including yawning, chewing, swallowing, and, uncommonly, guttural vocalizations Sometimes arousal and startle reflexes (eg, loud sounds or blinking with bright lights may elicit eye opening) Sometimes watering and tearing of the eyes Sometimes the appearance of a smile or frown Spontaneous roving eye movements—usually slow, of constant velocity, and without saccadic jerks The spontaneous roving eye movements may be misinterpreted as volitional tracking and can be misinterpreted by family members as evidence of awareness. Patients cannot react to visual threat and cannot follow commands. The limbs may move, but the only purposeful motor responses that occur are primitive (eg, grasping an object that contacts the hand). Pain usually elicits a motor response (typically decorticate or decerebrate posturing) but no purposeful avoidance. Patients have fecal and urinary incontinence. Cranial nerve and spinal reflexes are typically preserved. Rarely, brain activity, detected by functional MRI or electroencephalography (EEG), indicates a response to questions and commands even though there is no behavioral response (covert consciousness). The extent of patients' actual awareness is not yet known. In most patients who have such brain activity, the vegetative state resulted from traumatic brain injury, not hypoxic encephalopathy. Fragments of meaningful interaction with the environment are preserved. Patients in a minimally conscious state may do the following: Establish eye contact Purposefully grasp at objects Respond to commands in a stereotypic manner Answer with the same word 