We believe the neurologist is greatly aided by knowledge of the neuropathologic changes that are produced by processes such as infarction, hemorrhage, demyelination, physical trauma, inflammation, neoplasm, and infection, to name the more common ones. Experience with the gross and microscopic appearances of these disease processes greatly enhances one’s ability to explain their clinical effects. The ability to visualize the abnormalities of disease in nerve and muscle, brain and spinal cord, meninges, and blood vessels gives one a strong sense of which clinical features to expect of a particular process and which features are untenable or inconsistent with a particular diagnosis. An additional advantage of being exposed to neuropathology is, of course, that the clinician is able to intelligently evaluate pathologic changes and reports of material obtained by biopsy. For many conditions there is a parallel representation of neuropathology through various imaging techniques. This allows the clinician to deduce the pathology from the imaging appearance and vice versa.
From the foregoing description of the clinical method, it is evident that the use of laboratory aids, including imaging in the diagnosis of diseases of the nervous system, is ideally preceded by rigorous clinical examination. As in all of medicine, laboratory study can be planned intelligently only on the basis of clinical information. To reverse this process is wasteful of medical resources and prone to the discovery of irrelevant information, and in some cases exposes a patient to unnecessary risk.
In the prevention of neurologic disease, however, one resorts to two other approaches, namely, the use of genetic information and laboratory screening tests. Biochemical screening tests are applicable to an entire population and permit the identification of neurologic diseases in individuals, mainly infants and children, who have yet to show their first symptom; in some diseases, treatment can be instituted before the nervous system has suffered damage. Similarly in adults, screening for atherosclerosis and its underlying metabolic causes is profitable in certain populations as a way of preventing stroke. Genetic information enables the neurologist to arrive at the diagnosis of certain illnesses and to identify patients and relatives at risk of developing certain diseases.
The laboratory methods that are available for neurologic diagnosis are discussed in the next chapter and in Chap. 2, on clinical electrophysiology. The relevant principles of genetic and laboratory screening methods for the prediction of disease are presented in the discussion of the disease to which they are applicable.
There are a growing number of neurologic diseases for which specific therapy is available. Through advances in neuroscience, their number is steadily increasing. Among the most sweeping changes, now that many infectious diseases of the nervous system are being addressed, have been entirely novel medications for stroke, multiple sclerosis, Parkinson disease, migraine, neuropathy, brain tumor, and epilepsy as summarized in a review of 200 years of neurology by Ropper. These therapies and the dosages, timing, and manner of administration of particular drugs are considered in later chapters in relation to the description of individual diseases and detailed in Samuels’s Manual of Neurologic Therapeutics, cited in the references. The neurologist should also be familiar with the proper application of surgical treatment when it is an integral part of the amelioration or cure of disease, as it is for brain tumor, degenerative and neoplastic diseases of the spine, cerebral aneurysm, extracranial arterial stenosis, and some congenital disease of the brain and spinal cord. There are, in addition, many diseases in which neurologic function can be restored to a varying degree by appropriate rehabilitation measures or by the judicious use of therapeutic agents.