Cerebral. There are some potential distortions of body image that may accompany sensory loss helping to localize the sensory deficit to the cerebral cortex. Examples are anosodiaphora, which is a lack of concern over a profound loss of sensation or other neurological deficit; anosognosia, which reflects a lack of awareness of a profound sensory or neurological deficit; and asomatognosia, which represents loss of awareness of one half of the body. Additionally, the patient may manifest sensory neglect with a lack of orienting responses to unilateral stimuli. An aphasia and an increased susceptibility to distracting stimuli manifested as lack of attention or poor concentration are also signs localizing an accompanying sensory deficit to the cerebral cortex.
Thalamic sensory deficits may be associated with unilateral hyperpathia.
Cranial Nerves. As the medial lemniscal fibers course
through the brain stem they may be lesioned at any level. The level can be identified by an associated cranial nerve deficit (e.g., cranial nerve III in the midbrain or cranial nerve VII in the caudal pons). Patterns of multifocal sensory loss in the face, extremities, and trunk may represent multiple sclerosis. It is essential in such circumstances to look for typical findings of an internuclear ophthalmoplegia or an afferent pupillary defect on cranial nerve examination that might suggest remote or concurrent optic neuritis or a demyelinating plaque in the brain stem.
Bilateral facial weakness in a lower motor pattern may accompany mild distal extremity sensory loss in acute inflammatory demyelinating polyradiculoneuropathy.
Motor/Reflexes/Cerebellar/Gait. Motor power can be assessed and the distribution of any weakness found noted, such as the distal symmetrical weakness of peripheral neuropathy, which aids in localization of the deficit found on sensory examination. The examiner should look for atrophy of muscles and fasciculations that might suggest a peripheral nervous system process. Muscle tone should be assessed. Deep tendon reflexes are extremely important in the assessment of patients with sensory complaints because they are frequently abnormal in the patient with a lesion in the sensory axis. One should look for the antalgic gait of a painful limb, such as in lumbosacral radiculopathy, or the slapping gait associated with a proprioceptive deficit. Ataxia or pseudoathetosis of the extremities may be associated with a proprioceptive loss in the affected limb.
Autonomic Nervous System. The autonomic nervous system can be evaluated in a noninvasive manner at the bedside with the following assessments: blood pressure and heart rate response to standing, isometric exercise, heart rate variation with respiration, Valsalva ratio, and plasma norepinephrine levels with standing.y
Neurovascular. The size, character, and quality of heart sounds and gallop rhythms should be estimated. One should look for the stigmata of cardiogenic embolization: Osler nodes, Janeway lesions, and Roth spots are examples. The pulse is noted for 1 minute in a search for irregularities. The femoral artery, carotid artery, supraclavicular artery, and orbit are auscultated for evidence of bruits.
Associated Medical Findings. A good general medical examination of all systems is necessary to aid in generating a differential diagnosis for conditions affecting the sensory axis and can also aid in localization. Diseases commonly associated with peripheral nervous system dysfunction include cancer, diabetes mellitus, the acquired immunodeficiency syndrome, connective tissue disorders, alcohol abuse, uremia, myxedema, and paraproteinemias.
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