NERVOUS DISEASES. – Nervous diseases and mental illnesses together constitute the group of morbid conditions affecting the nervous system. Although the former constitute a fairly homogeneous and characteristic group, distinguished from the rest of medicine by a special semeiology, particular research techniques, and different therapy, their boundaries, both in relation to mental illnesses and to medicine in general and the other specialties, are by no means sharply defined, but become intertwined from case to case.
For the sake of clarity, it is useful to refer briefly to the functions of the nervous system. Alongside the psychic function, alterations of which belong to mental illnesses, there are, simplifying to the greatest extent, the motor and the sensory-sensory functions; nervous diseases are understood as those that chiefly affect these two functions. It should also be mentioned that a characteristic of the nervous system is not only a “deficit symptomatology” caused by interruption of the centers or conducting pathways of nerve impulses, but also “irritative syndromes” manifested by an excess of function. Thus, for example, in motor disorders, alongside a series which, in order of severity, ranges from diminished strength in one finger (asthenia) to the total loss of the capacity for movement of one or more limbs (paralysis), there is the appearance of involuntary movements ranging from fine tremors limited to a single segment (Jacksonian seizure of one hand) to a generalized convulsive attack. Similarly, in alterations of the sensory-sensory functions, alongside disorders ranging from diminished sensitivity to touch in a restricted area of skin (hypoesthesia) to the complete loss of sensations in half the body (hemi-anesthesia), there is a range of irritative disorders that may extend from tingling in one finger to intense pain in extensive regions of the body. This has touched only upon disturbances of the principal functions; but it is clear that a system as complex as the nervous system interferes with the organism’s entire activity. Thus, from case to case, nervous diseases may involve ocular, auditory, respiratory, sphincter, endocrine, and other disorders.
