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Neurology is regarded by many as one of the most difficult and exacting medical specialties. Students and residents who come to a neurology service for the first time may be intimidated by the complexity of the nervous system through their brief contact with neuroanatomy, neurophysiology, and neuropathology. The ritual they then witness of putting the patient through a series of maneuvers designed to evoke certain mysterious signs is hardly reassuring. In fact, the examination appears to conceal the intellectual processes by which neurologic diagnosis is made. Moreover, the students have had little or no experience with the many special tests used in neurologic diagnosis—such as lumbar puncture, EMG (electromyography), EEG (electroencephalography), CT (computed tomography), MRI (magnetic resonance imaging), and other imaging procedures—nor do they know how to interpret the results of such tests. Neurology textbooks only confirm their fears as they read the detailed accounts of the many unusual diseases of the nervous system.
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The authors believe that many of the difficulties in comprehending neurology can be overcome by adhering to the basic principles of the clinical method. Even the experienced neurologist faced with a complex clinical problem depends on this basic approach.
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The importance of the clinical method stands out more clearly in the study of neurologic disease than in certain other fields of medicine. In most cases, it consists of an orderly series of steps:
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The symptoms and signs are secured with as much confidence as possible by history and physical examination.
The symptoms and physical signs considered relevant to the problem at hand are interpreted in terms of physiology and anatomy—i.e., one identifies the disorder(s) of function and the anatomic structure(s) that are implicated.
These analyses permit the physician to localize the disease process, i.e., to name the part or parts of the nervous system involved. This is the anatomic, or topographic diagnosis, which often allows the recognition of a characteristic clustering of symptoms and signs, constituting a syndrome. This step is called syndromic diagnosis and is sometimes conducted in parallel with anatomic diagnosis.
Expert diagnosticians often make successively more accurate estimates of the likely diagnosis, utilizing pieces of the history and findings on the examination to either further refine or exclude specific diseases. Flexibility of thought must be practiced so as to avoid the common pitfall of retaining an initially incorrect impression and selectively ignoring data that would bring it into question. It is perhaps not surprising that the method of successive estimations works well in that evidence from neuroscience reveals that this is the mechanism that the nervous system uses to process information.
From the anatomic or syndromic diagnosis and other specific medical data—particularly the mode of onset and speed of evolution of the illness, the involvement of nonneurologic organ systems, the relevant past and family medical histories, and the laboratory findings—one deduces the pathologic diagnosis and, when the mechanism and causation of the disease can be determined, the etiologic diagnosis. ...