- Clinical science
Spasticity is defined as a velocity-dependent increase in muscle tone that manifests with resistance to movement and involuntary muscle spasms and contractions. It is caused by a lesion in the descending motor pathways. Common etiologies of spasticity include multiple sclerosis, stroke, tumor, cerebral palsy, and spinal or peripheral nerve injury. Nerve conduction studies and imaging of the brain and/or spinal cord may be requested to determine the underlying etiology. The management of spasticity is broad and may include physical and occupational therapy, pharmacotherapy (i.e., muscle relaxants such as diazepam, tizanidine, baclofen, or dantrolene; paralytics such as botulinum toxin), or surgery.
- The mechanism of spasticity is not completely understood.
- It is thought that upper motor neuron damage leads to loss of descending inhibitory inputs → increased muscle stretch reflex → increased muscle tone
- Increased muscle tone and velocity-dependent resistance to movement
- Elicited by flexion and extension of various muscles with alternating speed
- Clasp knife phenomenon: initial resistance (“catch”) when a limb is moved rapidly, followed by a sudden decrease in resistance; observed in patients with upper motor neuron lesions
- Upper extremity flexors and lower extremity extensors are usually more affected.
- Must be distinguished from
- Involuntary muscle spasms or contractions
- Clinical diagnosis
- Further tests (e.g., nerve conduction studies or brain imaging) depend on the suspected underlying etiology.
- Physiotherapy: including splinting of the affected extremity
Medical therapy: The most commonly used medication is baclofen; however, a variety of treatments (single and/or in combination) may be used and depend on patient-specific factors and patient response.
- Oral muscle relaxants
- Oral alpha-2 adrenergic agonists
- Intramuscular injections: A, , or phenol
- Intrathecal infusion
Baclofen: central acting muscle relaxant
- Contraindications: renal failure
- Therapeutic guidelines: should always be started at a slow dose and gradually increased to minimize potential side effects (particularly hypotension, sedation, nausea, depression).
- Plasma half-life: 3–4 hours
- Baclofen: central acting muscle relaxant
- Oral muscle relaxants
Surgical therapy: for severe spasticity refractory to medical treatment
- Selective dorsal rhizotomy: surgical destruction of nerves in the lower spinal cord in order to reduce muscle tone to the lower extremities
- Orthopedic surgery
- Musculoskeletal deformity
- Impaired mobility
- Reduced functional independence
We list the most important complications. The selection is not exhaustive.
The prognosis of spasticity depends on the underlying condition.