Hemiparesis is weakness or impaired performance on one side of the body, including an arm and a leg. It is not the same as paralysis of one side (hemiplegia). The most common cause is stroke and cerebral palsy but can also be caused by brain tumours, multiple sclerosis or other disorders of the brain or nervous system.

A person with hemiparesis may have difficulty with motor control, impaired balance, and difficulty walking. Muscles may be rigid or spastic and tend to overflex, also precise timing of muscle contractions is impaired resulting in a very awkward gait. Patients with right-sided hemiparesis due to stroke may also have speech difficulties.

Botox treatment is the injection of Botulinum toxins into spastic muscles to paralyse them for up to 12 months. During this time physiotherapy can help improve muscle tone in opposing muscle groups. This treatment has met with some success in children with cerebral palsy. Other treatments include muscle relaxant drugs and surgery to correct overly short tendons.

Patients suffering from hemiparesis after a stroke may eventually regain full or partial mobility. Physical therapy and mirror therapy can be valuable tools to aid the return to full functionality.