NEUROLOGY

medical specialty concerned with the diagnosis and treatment of functional or organic disorders of the nervous system (i.e., the brain, spinal cord, and nerves). The modern science of neurology has developed in the past two centuries. The first scientific studies of nerve function in animals were done in the early 18th century by Stephen Hales and Robert Whytt, but clinical neurology was still relatively unexplored territory until the middle of the 19th century. Important contributions to neurological knowledge were made in the mid- and late 19th century. New knowledge was gained about the causes of aphasia, epilepsy, and about motor problems arising from brain damage. The mapping of the functional areas of the brain through selective electrical stimulation also began at this time. Despite these contributions, however, most new knowledge of the brain and nervous functions came from studies of animals and from the microscopic analysis of nerve cells. The diagnosis of neurological disease was greatly improved by Hans Berger's invention in the 1920s of the electroencephalograph, which records electrical brain activity. With this device, with the analysis of cerebrospinal fluid obtained by the spinal tap, and with the development of cerebral angiography (q.v.), neurologists were able to increase the precision of their diagnoses and develop specific therapies and rehabilitative measures. Further aiding the diagnosis of brain disorders were the development of computerized axial tomography (CAT scans) in the early 1970s and nuclear magnetic resonance (NMR) imaging in the 1980s, both of which yielded detailed, noninvasive views of the inside of the brain. (See brain scanning.) Another major development was the introduction of specific drug therapies for neurological conditions. The identification of chemical agents in the central nervous system and the elucidation of the roles these substances play in the transmitting and blocking of nerve impulses led in the mid- and late 20th century to a wide array of drugs that could correct or alleviate various neurological disorders. Neurological surgery, or neurosurgery, is a medical specialty related to neurology. It is perhaps the most difficult and delicate of the surgical disciplines, but it too has benefited from CAT scans and other increasingly precise methods of locating lesions and other abnormalities in nervous tissues. Neurological disorders have always been among the most subtle and baffling of human illnesses, and despite continuing advances in their field, neurologists remained unable to effectively treat many disorders of the nervous system.