FOCAL NERVOUS SYSTEM
a focal lesion is localized to a specific area of the nervous system (anatomical
diagnosis), the pathology (pathological diagnosis) and etiology (etiological
diagnosis) of the lesion should be determined.
to reach a pathological diagnosis
pathological diagnosis can only be made by direct pathological evaluation
of a specimen obtained from the focal lesion. When direct evaluation of
a specimen is not possible, a tentative pathological diagnosis can be
made based on the clinical, neuroradiological, and neurophysiological
The clinical findings that are
most helpful to establish a tentative pathological diagnosis are those
related to the location of the lesion and the rate of progression of the
location of a lesion helps to establish a tentative pathological diagnosis
because certain pathological processes are more likely to occur in specific
areas of the nervous system than in others. Neoplasms in the neonatal
period occur more often in the supratentorial region than in the infratentorial
region. Single artery infarcts occur more often
in the middle cerebral circulation than in the posterior cerebral circulation.
The speed of progression of
a deficitóthe time it takes for a deficit to reach maximal neurological
impairmentómay help to differentiate neoplasms, acute cerebrovascular
accidents, and infections. Neoplastic processes progress relentlessly
during the neonatal period. Acute cerebrovascular accidents reach maximal
neurological impairment in minutes or hours. Infectious processes reach
maximal neurological impairment in hours or days.
The event surrounding the onset
of symptoms does not contribute as much to the formulation of a tentative
pathological diagnosis as the location of the lesion or the speed of progression
of the deficit, except with traumatic processes. In traumatic processes
the onset of symptoms is usually clearly related to the traumatic event.
to reach an etiological diagnosis
a tentative pathological diagnosis is reached, the etiological diagnosis
is determined by a combination of clinical, neuroimaging, and laboratory