NERVA, IMPERATORE ROMANO — Statue — Rome, Vatican Museums.
In the presence of a nervous disease, two diagnoses must be made: that of the location of the lesion and that of the nature of the lesion itself. The former is, for obvious reasons, almost peculiar to these diseases, and has given rise to a special semeiology, extending from the neurological examination to neuroradiology, neuro-ophthalmology, neuro-otology, and electroencephalography, all subsidiary branches of the simple physical examination of the patient. The lesion may be single (and as such must explain the entire symptomatology of the patient) or multiple; in the latter case, there may be diseases affecting a single system, e.g. only the motor pathways (systemic diseases), or those affecting several systems (non-systemic, disseminated diseases). The problem of diagnosing the nature of the disease is common to the other branches of medicine as well, and differs in nervous diseases only because the alterations develop in a tissue possessing particular characteristics of its own. Thus, for example, the onset, course, and spread of a disease will be closely linked to the anatomical position, the tissue’s capacity for reaction, and the functions of the tissue. It must also be borne in mind that multiple causes of different kinds may produce a similar symptomatology; consequently, the medical history and auxiliary investigations play a very important role in the diagnosis of diseases of the nervous system.
Nervous diseases may be classified, in relation to the causal factor, as infectious, neoplastic, degenerative, vascular, deficiency-related, and diseases caused by physical agents. This concise classification, without any claim to completeness, is intended merely to provide a rapid panoramic view of the subject in question. Forms of infectious origin, caused by pathogenic agents, whether microbes or viruses, comprise a series of diseases which, depending on their location, are called “meningitis” (when the meninges, that is, the coverings of the brain, are invaded), “myelitis” (when the spinal cord is involved), and “neuritis” (when the nerves are affected); such diseases may be diffuse or circumscribed. Cerebral abscesses, chorea of rheumatic origin, and syphilis of the nervous system (the meningo-vascular form, tabes, and progressive paralysis) may also be mentioned. Neoplasms or tumors comprise types of differing microscopic structure, according to the cells from which they originate. Thus there are “meningiomas” (arising from the meninges), “gliomas” (derived from the glial cells of the nervous parenchyma), and “neurinomas” (originating in the sheaths of the cranial or peripheral nerves). Degenerative diseases, often based on hereditary or familial factors, comprise a considerable group of morbid conditions of highly varied appearance. These include the spinocerebellar ataxias (Friedreich’s disease), cerebellar atrophies, myopathies, and Parkinson’s disease.
Cerebrovascular diseases are often related to essential and malignant hypertension and to heart disease; they may present with sudden and often transient episodes, such as vasomotor hypertensive crises, or with more serious episodes, such as hemorrhages and softenings, and finally sometimes with coma. They also occur in chronic and progressive forms, in which case psychic disturbances are present as well. Deficiency diseases are due to the absence of substances necessary for normal metabolism; the most common among them are beri-beri, pellagra, and Lichteim’s syndrome, which is accompanied by pernicious anemia; they generally manifest themselves through spinal-cord symptoms. Physical agents include trauma, which is responsible for cerebral and spinal-cord lesions (contusions, concussions, and commotions). Among the various diseases omitted from this list, only the most important will be recalled: epilepsy (v.), which presents with attacks ranging from “petit mal” (loss of consciousness lasting an instant) to “grand mal” (generalized convulsive seizures), provoked by various stimuli (mechanical, chemical, and physical) acting on the brain (symptomatic epilepsy), or by unknown causes (idiopathic epilepsy).