Assessment of acute motor deficit

Acute motor deficits occur when there is either a sudden loss of connectivity between the central nervous system (CNS) and the muscles or there is dysfunction of the muscles themselves. Loss of connection can occur anywhere from the CNS to the motor-end plate. Acute motor deficits occur in a wide range of disease states. Careful questioning of a patient who reports sudden motor loss can help determine the exact anatomy of the motor deficit, any accompanying features, and the likely pathophysiology. The anatomical description of the deficit helps localise the site of dysfunction. This may include the brain, spinal cord, peripheral nerves, and muscles. Motor deficits can be intermittent, relapsing, or acute and catastrophic, although these features do not always help define the pathophysiology.

Once the probable site of dysfunction has been identified, consideration can be given to the likely type of process involved (vascular, trauma, infection, autoimmune/inflammatory, metabolic, compression, or other). Although a general knowledge of the different systemic pathologies is helpful, there can be considerable overlap in presentations. For example, a sudden loss of motor function might often appear to have a vascular cause, but other conditions, such as oedema related to a tumour in the white matter or chronic subdural haematoma, can present with a similar history, albeit less frequently.