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Author: Admin | 2025-04-28
Central cervical spinal cord abnormality, typically a syrinxFindings that indicate involvement of multiple anatomic areas (eg, both brain and spinal cord lesions) suggest more than one lesion (eg, multiple sclerosis, metastatic tumors, multifocal degenerative brain or spinal cord disorders) or more than one causative disorder. The rate of symptom onset helps suggest likely pathophysiology: Nearly instantaneous (usually seconds, occasionally minutes): Ischemic or traumaticHours to days: Infectious or toxic-metabolic or autoimmune (eg, multiple sclerosis)Days to weeks: Infectious, toxic-metabolic, or immune-mediated Weeks to months: Neoplastic, or degenerative, or occasionally infectious due to chronic central nervous system (CNS) infection (eg, fungal infection)Degree of symmetry also provides clues.Highly symmetric involvement: A systemic cause (eg, a metabolic, toxic, medication- or substance–related, infectious, or postinfectious cause; vitamin deficiency)Clearly asymmetric involvement: A structural cause (eg, tumor, trauma, stroke, peripheral plexus or nerve compression, a focal or multifocal degenerative disorder)After location of the lesion, rate of onset, and degree of symmetry have been determined, the list of potential specific diagnoses is much smaller, so that focusing on clinical features that differentiate among them is practical (see table Some Causes of Numbness). For example, if initial evaluation suggests an axonal polyneuropathy, subsequent evaluation focuses on features of each of the many possible medications, toxins, and disorders that can cause these polyneuropathies. Testing is required unless the diagnosis is clinically obvious and conservative treatment is elected (eg, in some cases of carpal tunnel syndrome, for a herniated disk or traumatic neuropraxia). Test selection is based on anatomic location of the suspected cause: Peripheral nerves or nerve roots: Nerve conduction studies and electromyography (electrodiagnostic testing)Plexuses: Nerve conduction studies and electromyography and sometimes contrast MRIBrain or spinal cord: MRIElectrodiagnostic tests can help differentiate between neuropathies and plexopathies (lesions distal to the nerve root) and more proximal lesions (eg, radiculopathies) and between types of polyneuropathies (eg, axonal and demyelinating, hereditary and acquired). If clinical findings suggest a structural lesion of the brain or spinal cord or a radiculopathy, MRI is usually indicated. CT is usually a second choice but may be particularly helpful if MRI is not available soon enough (eg, in emergencies).After the lesion is localized, subsequent testing can focus on specific disorders (eg, metabolic, infectious, toxic, autoimmune, or other systemic disorders). For example, if findings indicate a polyneuropathy, subsequent tests typically include complete blood count (CBC), electrolytes, renal function tests, rapid plasma reagin test, and measurement of fasting plasma glucose, hemoglobin
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