Spasticity: A Medical Overview

Part 1 of a 3-part series on understanding and coping with spasticity.

By Rob Ingraham

Spasticity, the sudden, involuntary muscle contractions characteristic of many people with spinal cord injuries and disorders (SCI), is a complex secondary condition that, paradoxically, is a debilitating, painful burden for some, but an unexpected advantage for negotiating activities of daily living for others.

“Some folks welcome spasticity; for others it is the bane of their existence,” said Dr. David R. Gater, chief of Spinal Cord Injuries and Disorders at the Hunter Holmes McGuire VA Medical Center in Richmond, Virginia. Dr. Gater presented an overview of the medical issues surrounding spasticity at United Spinal’s recent consumer conference, Creating Your Future: Living with a Disability, in Orlando, Florida, August 27 and 28.

Physiology

The brain and spinal cord are made up of millions of complex circuits of information- carrying “neurons,” which are “excitable” cells designed to transmit electrical signals over long distances. These signals from the brain to all of the muscles and organs in the body are passed from one neuron to another by triggering a chemical signal that communicates the message across to the next neuron and so on, along the pathways of the central nervous system. The area of chemical transmission between one neuron and another is called the synapse.

Neurons that carry messages from the brain down to the spinal cord are called upper motor neurons (UMN); ones that branch out from the spinal cord to the muscles and tissues are called lower motor neurons (LMN). Synapses allow the UMNs to communicate with the LMNs, carrying sensory information up the body to the brain and motor information down from the brain to the muscles.

Immediately after SCI, the body’s reflexes are absent below the level of injury, a condition known a “spinal shock,” which lasts for a few weeks or months. Eventually the shock wears off and reflex activity returns, but the normal flow of nerve signals below the level of injury is interrupted. Those signals may not reach the reflex center of the brain. If all the body’s reflex centers cannot work together to moderate the body’s response to those signals, the reflex centers of the spinal cord attempt to moderate the response. But because the spinal cord is not as efficient as the brain, the signals sent back to the site of the sensation are often exaggerated, producing an overactive muscle response known as spasticity.

There are a number of different types of spasticity. With “extensor” spasms, the legs or arms straighten and become rigid; “flexor” spasms are the opposite—the limb pulls up toward the chest. “Clonus” is the repetitive jumping of the muscle, usually around the ankle, causing the foot to bounce repeatedly.

For people with SCI, the overall incidence of spasticity is between 40% and 68%. Tetraplegics, however, are most susceptible, with 89% of all individuals likely to experience spasticity. For paraplegics, the incidence is about 46% overall, with 82% of those with T-1 to T-7 injuries experiencing some form of spasticity; 45% of those with injuries at T-8 to T-12; and 26% of those with injuries form L-1 to S-5.

Gater noted that factors exacerbating spasticity— known as “nociceptive input,” which refers to the process of pain transmission and neurons receptive to painful sensations-are infections, pressure sores, deep vein thrombosis-dangerous blood clots in the veins of the inner thigh or leg—bladder distension, bowel impaction, cold weather, or fatigue.

Managing Spasticity

Gater outlined a number of spasticity management techniques. Physical stretching is one of the simplest but most time- and labor-intensive. Stretches must be held for 45-90 seconds and done five- to-seven times daily. Also, stretching reduces spasticity for only a few hours; if one stops, the spasticity will return.

Other non-medicinal treatments include cryotherapy, the therapeutic use of cold, applied focally for 15 to 20 minutes; and electrical stimulation, which reduces sensitivity to pain through electrodes applied to the skin and can be done while the patient is conscious.

Among oral medications used to manage spasticity:

• The benzodiazepines- Diazepam (Valium® manufactured by Hoffman- LaRoche) and Clonazepam (Klonopin® from Roche Laboratories; Rivotril® from Roche Products Ltd.)- which act on the central nervous system and result in a decrease of overactive muscles and fewer painful spasms.

• Baclofen (Lioresal® from Novartis Pharmaceuticals Corp.) also works through the central nervous system and helps improve passive range of motion and reduces muscles spasms, pain, and tightness.

• Dantroline sodium (Dantrium® from Proctor & Gamble Pharmaceuticals) acts at the muscle rather than the central nervous system where it interferes with muscle contraction.

• Tizanidine (Zanaflex® from Acorda Therapeutics) acts on the central nervous system and does not reduce muscle strength as much as other types of oral medication.

• Other drugs currently being studied include Clorazepate (Tranxene® from Abbott Laboratories) which has been reported to have less of an effect on sedation, memory, and recall and “4-aminopyridine” (Fampridine-SR® from Acorda Therapeutics) which may improve impulse conduction in nerve fibers where the insulating layer, myelin, has been damaged.

Chemodenervation is the use of chemicals injected directly into the muscle to interrupt the flow of nerve impulses to spastic muscles. Some of these agents include Botulinum Toxin Type A (Botox® from Allergen; Dysport® from IPSEN) and Botulinum Toxin B (Myobloc® from Solstice Neurosciences), as well as phenol and alcohol.

Surgical interventions can be effective, but they are irreversible. Procedures include: contracture release, where a tendon is cut to release a contractured muscle; tendon transfer, which moves the attachment point of a spastic muscle; osteotomy which removes a small wedge of bone to allow it to be reshaped or repositioned; and arthrodesis, which fuses together bones that normally move independently.

The fastest growing treatment option is intrathecal medication, where a small pump is implanted into the abdomen with a reservoir of medication—usually baclofen- -which is pumped through a small tube directly to the fluid surrounding the spinal cord. The advantages are that the medicine is sent directly to the nerve cells where it is needed; the dosage can be adjusted; less medication is needed, compared to oral treatments; the reservoir is easily re-filled and; the surgery is reversible. Disadvantages are that it is expensive; the tubing can become kinked or disconnected; and there is a risk of infection, baclofen overdose, pump dysfunction, and withdrawal symptoms.

Weighing the Options

Dr. Gater stressed that quality of life issues are a main determinant when assessing whether one should attempt medical treatment for spasticity. Individuals should ask themselves if their spasms affect functional tasks or prevent them from participating in activities; if the spasms are painful; if they require personal assistance, interfere with sleep, put them at risk of losing control of a car or power chair, or if spasticity increases the risk of medical problems such as pressure ulcers.

On the other hand, many individuals can take advantage of muscle spasms to help them perform activities of daily life, Gater said. Some can learn to trigger spasms in their hands and fingers to help pick up items or learn to use spasticity to empty their bladders or, transfer, dress, stand, or walk.

Spasticity can also improve circulation and may prevent deep vein thrombosis and edema-an abnormally large amount of fluid in the intercellular tissue. It may also reduce the risk of osteoporosis. Spasticity may also help control weight gain if a person is susceptible to obesity because regular muscular contractions burn calories.

But the disadvantages of severe spasticity are significant and debilitating, foremost being relentless pain due to the stress put on muscles and joints. There can also be orthopaedic deformities; severe difficulties with activities of daily living such as dressing, bathing, toileting; skin breakdown; sleeping problems; and depression.

Gater urges individuals with spasticity to regularly consult their physicians to determine the best options and stay abreast of new treatments. “Spasticity is always a balancing act,” he said.

Rob Ingraham is senior editor.

This article is the first in a 3-part series on spasticity, sponsored by an unrestricted educational grant from Acorda Therapeutics. Acorda had no influence on the content of this article or series.