Neurological Impairments and Nervous Disorders

Neurology is the study of human neuromuscular system, including the brain, spinal cord and roots, peripheral nerves, junctions between nerves and muscles, and the muscles themselves, in health and disease. Neurological impairment arises from an alteration of function in any of these structures and can result from a wide variety of etiologies, from inherited genetic conditions to obstructed blood flow to a particular part of the nervous system. Common neurological symptoms and related disabilities include problems with memory, attention, concentration, speech or language (aphasias); sleep disturbance; visual changes; dizziness or vertigo; fatigue; weakness; involuntary movements or muscle rigidity; pain; loss of sensation or abnormal sensations; and problems with coordination or gait.

Neurology has a long history, and knowledge of the structure and function of the nervous system, along with conceptions of neurological impairments and their related disabilities, can be roughly divided into three phases: the preclassical, classical, and scientific phases. During the preclassical period, from antiquity until the early nineteenth century, medical scientists described several neurological syndromes, including epilepsy (the “sacred disease” or “falling sickness”), migraine and cluster headaches, hemorrhagic stroke (apoplexy), paralysis, and a variety of psychiatric disorders. Anatomical knowledge during this period was largely limited to the gross anatomy of the brain, spinal cord, and peripheral nerves. Concepts of the nervous system's function were correspondingly guided by structural appearance, so that peripheral nerves were believed to be conduits for the flow of animal spirits or nervous fluid; or by extrapolation from simple observation or experimentation, such as the notion of reflex action. With a relatively short human lifespan, limited knowledge of the structure [Page 1141]and function of the nervous system, and the absence of effective medications or interventions, neurological disability during the preclassical era frequently involved chronic pain, paralysis, social stigma, and institutionalization.

The classical period of neurology, from the early nineteenth century to the mid-twentieth century, witnessed a dramatic growth in knowledge about the structure and function of the nervous system, and detailed clinical descriptions for dozens of neurological disorders along with their underlying pathology. During this period, neuroanatomy advanced beyond the surface structure to the microscopic descriptions of the nervous system, including individual nerve cells (neurons) and their connections, and provided a foundation for the understanding of normal function and pathophysiology. Physiological concepts were still closely tied to general concepts of nerve impulses and reflex action, but were integrated with psychological notions of inhibition, association, and representation. Many neurological disorders were first described during this period, including the aphasias or disorders of language (Paul Broca, Carl Wernicke, Ludwig Lichtheim), several brainstem stroke syndromes, general paresis and tabes dorsalis (syphilis of the brain and spinal cord), movement disorders such as Parkinson's and Wilson's diseases, multiple sclerosis (Jean Martin Charcot), hemi-transection of the spinal cord (Charles Éduoard Brown-Séquard), and muscular dystrophy (G. B. A. Duchenne).

Although several anesthetics, aspirin, and potent anticonvulsants (phenobarbital and phenytoin) were also developed during the classical period of clinical neurology, disability was still largely related to the progressive or fixed paralyses, chronic pain, and institutionalization, with the addition of traumatic brain lesions resulting from war injuries and generalized syndromes related to combat and advancing technology (“railway spine,” neurasthenia, shell shock).

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