Adams and Victor's Principles of Neurology

particularly the mode and speed of onset, evolution,
and course of the illness, the involvement of nonneuro-
logic organ systems, the relevant past and family histo-
ries, and the laboratory findings—one deduces the
 
pathologic diagnosis
and, when the mechanism and cau-
sation of the disease can be determined, the 
 
etiologic
diagnosis
. This may include the rapidly increasing num-
ber of molecular and genetic etiologies if they have
been determined for a particular process. Expert diag-
nosticians often make successively more accurate esti-
mates of the likely diagnosis, utilizing pieces of the
history and findings on the examination to either fur-
ther 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 ques-
tion. 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.
5. Finally, the physician should assess the degree of dis-
ability and determine whether it is temporary or per-
manent (
 
functional diagnosis
); this is important in
managing the patient’s illness and judging the poten-
tial for restoration of function.
 
All of these steps are undertaken in the service of effective
treatment
, an ever-increasing prospect in neurology. As is
emphasized repeatedly in later sections, there is always a
premium in the diagnostic process on the discovery of
treatable diseases, but even when specific treatment is not
available, accurate diagnosis may, in its own right, func-
tion as a therapy, as uncertainty about the cause of a neu-
rologic illness may be more troubling to the patient than
the disease itself.
Figure 1-1, a procedural diagram by which the clinical
problem is solved in a series of sequential finite steps,

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