The content of this section will be more clearly understood if a few of the introductory remarks to the later section on psychiatric diseases are anticipated here. The main thesis of the neurologist is that mental and physical functions of the nervous system are two aspects of the same neural process. Mind and behavior both have their roots in the self-regulating, goal- seeking activities of the organism, the same ones that provide impulse to all forms of mammalian life. But the prodigious complexity of the human brain permits, to an extraordinary degree, the solving of difficult problems, the capacity for remembering past experiences, and casting them in a symbolic language that can be written and read, and the planning for events that have yet to take place. The constant but sometimes meandering internal verbal experience of this ideation during waking was aptly named “stream of thought” by William James. Somehow there emerges in the course of these complex cerebral functions, a continuous awareness of one’s self and the operation of one’s psychic processes. It is this continuous inner consciousness that might be called mind. Whether this is an emergent property of various mental functions or simply their representation as an idea in the mind cannot be answered, but any wide separation of the mental from the observable behavioral aspects of cerebral function is probably illusory. Biologists and psychologists have reached this view by placing all known activities of the nervous system (growth, development, behavior, and mental function) on a continuum and noting the inherent purposiveness and creativity common to all of them. The physician is persuaded of the truth of this view through daily clinical experience, in which every possible aberration of behavior and intellect appears at some time or other as an expression of cerebral disease. Furthermore, in many brain diseases, particularly the forms of confusion addressed in the first chapter in this section on confusional states, one witnesses parallel disorders of the patient’s behavior and a dissolution or distortion of the introspective awareness of his own mental capacities.
The reader will find that Chaps. 19 and 20 are concerned with common disturbances of the sensorium and of cognition, which stand as cardinal manifestations of cerebral diseases. The most frequent of these are delirium and related acute confusional states, as well as disorders of learning, memory, and other intellectual functions. A consideration of these abnormalities leads naturally to an examination of the symptoms that result from focal cerebral lesions, which are discussed in Chap. 22, and of derangements of language, which are discussed in Chap. 22. As emphasized in those chapters, even these disturbances fall between the readily localizable functions of the cerebrum and those that can be assigned only broadly to large regions or systems of the brain.
Because the psychiatric causes of disordered thinking and behavior have special qualities that make them separable from most of the conditions considered in the next several chapters, they are discussed in Chaps. 47 to 49 at the end of the book, rather than here.
The striking state in which a patient with previously intact mentality becomes confused is observed daily on the medical, surgical, and emergency wards of a general hospital. Occurring, as it often does, during an infection with fever or in the course of a toxic or metabolic disorder (such as renal or hepatic failure) or as an effect of medication, drugs, or alcohol, it never fails to create problems for the physician, nurses, and family. The physician has to cope with the problem of diagnosis, often without the advantage of a lucid history, and any program of therapy is constantly impeded by the patient’s inattention, agitation, sleeplessness, and inability to cooperate. Nurses are burdened with the need to provide satisfactory care and a safe environment for the patient, and at the same time, maintain a tranquil atmosphere for other patients. The family must be supported as it faces the frightening prospect of a deranged mind with peculiar behaviors and all it signifies.