20. Altered consciousness

Full consciousness is characterized by wakefulness, focused attention and normal cognitive function. A coma patient by definition has closed eyes, does not respond to commands and does not talk, an urgent situation that calls for the cause to be found as soon as possible. Coma can be caused by damage to brain tissue, hypoxia, metabolic dysregulation or intoxication. It can also be due to a brain herniation syndrome. The prognosis for postanoxic coma depends on how long the patient has been unconscious. If there is no obvious cause of the coma, the possibility of non-convulsive status epilepticus should always be considered. Delirium patients have impaired attention to and perception of their surroundings. Frontal injuries can produce a state of ‘lack of will’ (abulia). Coma can be followed by vegetative state or unresponsive wakefulness syndrome, in which the patient has no awareness of their surroundings. Brain death is a diagnosis that can only be made if strict conditions are met; this diagnosis is required for organ donation. The brainstem plays an important role in consciousness and impairments of consciousness: its functions and testing are discussed in Chap. 6 (sect. 6.1, 6.4 and 6.5). Chapter 18 deals with attacks of impaired consciousness and Chap. 19 with physiological changes in consciousness. This chapter looks at pathological impairments of consciousness, which can affect level and/or content (sect. 20.1). Rapid action to decide on a good strategy is important (sect. 20.2). In a case of cerebral herniation (sect. 20.3) the course of the condition follows a fixed pattern, depending on the type of herniation. Disturbances of the internal environment can involve metabolic dysregulation (sect. 20.4.1), intoxication (sect. 20.4.2) and status following anoxia (sect. 20.4.3). Coma can in fact be caused by non-convulsive status epilepticus (sect. 20.5). The next section (sect. 20.6) considers consciousness that is altered but not lowered. This chapter concludes with vegetative state following coma (sect. 20.7) and total loss of brain/brainstem function, i.e. brain death (sect. 20.8). Chapter 21 deals with structural coma again. The final chapter of the book (Chap. 30) discusses the neurological effects of internal medicine disorders systematically, again looking at coma.