Paralysis is a complete loss of voluntary movement. Weakness is a reduction in the force of voluntary movement, and is a result of pathology affecting the motor pathway at any point from the cerebral hemisphere to the muscle fibre (Box 17.1). Weakness can be life-threatening if respiratory muscles are involved.

• Stroke (Chapter 65), multiple sclerosis and spinal cord injury (Chapter 70) are the major central nervous system pathologies causing weakness.
• Guillain-Barré syndrome (GBS) (Chapter 71) is the commonest cause of acute neuromuscular paralysis.

Pathologies at different localizations produce distinctive syndromes (Table 17.1). They are broadly divided into upper motor neuron (UMN) or lower motor neuron (LMN) syndromes with specific features (Table 17.2). Combined UMN and LMN signs raise the possibility of motor neuron disease, but can also indicate dual pathology.

You need rapidly to identify those patients:

• With acute stroke, who may be candidates for thrombolysis (Chapter 65)
• At risk of neuromuscular respiratory failure
• Who require urgent imaging and/or neurosurgical opinion (Figure 17.1)

The clinical assessment is summarized in Table 17.3.

Diagnostic tests are directed by the clinical picture, although some tests should be considered for all patients (Table 17.4). Acute stroke and spinal cord/cauda equina syndromes require urgent neuroimaging.

Further management is directed by the working diagnosis.

• Patients with acute stroke should be admitted to a specialist stroke unit, have an assessment of their swallow performed, and be regularly monitored for deterioration and the development of complications (Chapter 65).
• Patients with GBS (Chapter 71) and myasthenia need regular vital capacity checks and involvement of ICU in the event of deterioration, but may be suitable for the general ward in the absence of respiratory compromise. The former group also requires monitoring for arrhythmia and other forms of autonomic disturbance, which are also seen with spinal cord infarction.
• In other spinal cord syndromes, admission and repeat neurological assessment is likely to be required to inform the need for and timing of surgical intervention.
• Patients with multiple mononeuropathies and rhabdomyolysis need admission for monitoring and treatment.
• Those with subacute CNS syndromes may be suitable for outpatient investigation, dependent on the presence of ongoing deterioration and the severity of the deficit.
• Patients with monoradiculopathy or mononeuropathy can usually be discharged if systemically well, not progressing and if a benign cause is likely.
• In all immobile patients, pressure sores, deep vein thrombosis, respiratory infection/aspiration and contractures need to be prevented and addressed.