Weakness & Paralysis

Key Features

• Loss of muscle power may result from

  • Central disease involving the upper or lower motor neurons

  • Peripheral disease involving the roots, plexus, or peripheral nerves

  • Disorders of neuromuscular transmission

  • Primary disorders of muscle

Clinical Findings

• Weakness resulting from upper motor neuron lesions

  • Characterized by selective involvement of certain muscle groups

  • Associated with spasticity, increased tendon reflexes, and extensor plantar responses

• Lower motor neuron lesions

  • Lead to muscle wasting as well as weakness, with flaccidity and loss of tendon reflexes

  • However, no change in the plantar responses unless the neurons subserving them are directly involved

  • Fasciculations may be evident over affected muscles

• In distinguishing between a root, plexus, or peripheral nerve lesion, the distribution of the motor deficit and of any sensory changes is of particular importance

• In disturbances of neuromuscular transmission, weakness is

  • Patchy in distribution

  • Often fluctuates over short periods of time

  • Not associated with sensory changes

• In myopathic disorders, weakness is

  • Usually most marked proximally in the limbs

  • Not associated with sensory loss or sphincter disturbance

  • Not accompanied by muscle wasting or loss of tendon reflexes, at least not until an advanced stage

Diagnosis

• See individual disorders

Treatment

• See individual disorders