The results of the examination are taken together to anatomically identify the
lesion. This may be diffuse (e.g., neuromuscular diseases, encephalopathy) or highly specific (e.g., abnormal sensation in one
dermatome due to compression of a specific spinal nerve by a tumor deposit). General principles include: • Looking for side to side symmetry: one side of the body serves as a control for the other. Determining if there is focal asymmetry. • Determining whether the process involves the peripheral nervous system (PNS), central nervous system (CNS), or both. Considering if the finding (or findings) can be explained by a single lesion or whether it requires a multifocal process. • Establishing the lesion's location. If the process involves the CNS, clarifying if it is cortical, subcortical, or multifocal. If subcortical, clarifying whether it is white matter, basal ganglia, brainstem, or spinal cord. If the process involves the PNS then determining whether it localizes to the nerve root, plexus, peripheral nerve, neuromuscular junction, muscle or whether it is multifocal. A
differential diagnosis may then be constructed that takes into account the patient's background (e.g., previous cancer, autoimmune diathesis) and present findings to include the most likely causes. Examinations are aimed at ruling
out the most clinically significant causes (even if relatively rare, e.g., brain tumor in a patient with subtle word-finding abnormalities but no increased
intracranial pressure) and ruling
in the most likely causes. ==References==