Trigger Point Injections
Trigger points are tender areas within skeletal muscle that may result from a primary abnormality of the muscle itself, or they may occur as a secondary phenomenon when nerves that supply muscles become irritated. Conditions in which pain is thought to be due primarily to a muscular abnormality include fibromyalgia and myofascial pain syndrome. Intervertebral disc herniation with spinal nerve root irritation is an example of a condition in which muscular trigger points are a secondary rather than a primary phenomenon. In this instance, trigger points occur because irritated nerve roots in the spinal column continually stimulate associated muscles.
Painful Skeletal Muscle
Whatever their cause, trigger points are associated with pain and tenderness in skeletal muscle and can be identified on physical examination as palpable, tender bands or “cords” of muscular tissue. Pain from trigger points may be mild or severe. Although most resolve without treatment or with conservative measures such as heat, massage, or myofascial release therapy, some trigger points are persistently painful and disabling.
Treatment of Severe Trigger Point Pain
When trigger point pain is severe and refractory to conservative measures, trigger point injection with local anesthetic—with or without added steroid—may be helpful. Trigger points may be injected with tiny (30-gauge) needles of variable length placed through the skin and into the substance of the muscle. Risk is minimal and discomfort on injection can be minimized with inhaled nitrous oxide, if necessary. Five to ten trigger points may be injected in one session, and sessions are typically repeated at regular intervals in series and coordinated with physical therapy.
Resolution of Trigger Point Pain
For some patients, trigger point pain is a recurrent, intermittent problem that may be managed over the long term with occasional injections and a combination of conservative therapies. Other patients respond with long-lasting benefit from a single session of trigger point injections.
Botulinum toxin is increasingly being used for prolonged muscular relaxation in cases of refractory trigger point pain. This substance, marketed under the name Botox, binds irreversibly to the neuromuscular junction, paralyzing the muscle for a period of weeks or months, resulting in muscle relaxation and pain relief. Botox can be targeted to specific muscles using EMG-guided injection techniques