LOCALIZED CHRONIC PAIN
If pain is localized, a careful history should be taken of the probable mechanism of injury. This can indicate the forces involved and the potential structures that may have been damaged.
PERIPHERAL PAIN
Although chronic pain is a combination of peripheral sensation and central hyper-excitation within the spinal cord, there are some pain syndromes which are predominantly peripheral in origin:
Peripheral nerve or nerve root injury: A careful examination should establish whether the pain is within the distribution of a nerve root or peripheral nerve.
Joint dysfunction: Pushing on or stretching an individual joint such as a cervical facet joint may reproduce the individuals pain. This indicates the joint, or structures surrounding it, may be involved in the pain process.
Scar tenderness: Neuromas may be present in any scar. Gentling "rolling" the scar or pressure over it may recreate the patient's pain.
Trigger points: Trigger points are localized areas of muscle spasm which, when pressure is exerted on them cause pain referral into the painful site. Stretching the muscle may also recreate the pain.
TREATMENT: PERIPHERAL PAIN
Topical Medication: Acute sensitivity of the skin or allodynia, (means "light touch" not normally perceived as pain is felt as being exquisitely painful), may be effectively decreased by capsaicin cream. Capsaicin works by depleting substance P and needs to be rubbed on 3-4 times a day. It takes three weeks to effectively deplete substance P stores peripherally and centrally. The cream, made from red peppers, causes an intense burning sensation which patients might find intolerable. However, the burning usually lessens after a few days of use. The patients should be warned to wash their hands carefully afterwards and to avoid rubbing their eyes or severe irritation of the eyes will occur.
Emla cream, a mixture of lidocaine and prilocaine can be placed on small spots of acute tenderness. The cream should be placed as a thick layer with a transparent dressing placed over it. The cream should be left in place for four hours after which time it can be removed. The area will remain anesthetic for a further four hours. This may be effective in desensitizing small painful areas. There are many other over-the-counter preparations, as well as those prepared by herbalists etc., which, when rubbed onto areas of pain, are said to diminish the pain sensation. If the over-the-counter creams, lotions or sprays, do not financially embarrass the individual and are found to be effective, with minimal side effects, their use should not be discouraged.
Oral medications: In the acute phase of pain, non-steroidal anti-inflammatories are very useful . In chronic pain, the non-steroidals probably have more effect centrally than peripherally and tend to be less effective. In areas of inflammation the site of action is probably more peripheral. Some medications such as the alpha-1 blockers (prazocin) are useful in sympathetically maintained pain syndromes. Mexilitine, an oral analog of lidocaine, and sodium channel blockers may be effective in chronic pain associated with nerve damage.
Trigger Points: When trigger points (localized areas of muscle tenderness that on palpation reproduce pain in a distal site) are present, ischemic massage, cold spray and stretch techniques, ice massage and stretch, dry needling and local anesthetic injections all have a role. Any trigger point treatment should be accompanied by a home stretching and range of movement exercise program.
Peripheral nerve block: Knowledge of the anatomical location of the nerve, use of a nerve stimulator, and careful injection of local anesthetic can selectively block the nerve going to a pain area. If pain relief is nearly total this may indicate the pain is being mediated peripherally. For confirmation a second successful block should be performed at a later date. If the pain is centralized, although the peripheral skin area will be numb the patient's pain will be unrelieved. Care must be taken not to inject into the nerve. This causes extreme pain during the injection and may cause a neuroma to form within the substance of the nerve. A joint or inflamed bursa can also be injected with local anesthetic to gauge the contribution to the pain syndrome. Facet or zygapophyseal joint injections should be done under fluoroscopy (X-ray controlled) with contrast confirmation.
Physical therapy: In chronic pain, a physical therapist should use hands-on techniques. Joints that are stiff due to disuse or muscle spasm must be mobilized and stretched manually. Heat and ultrasound can be used to relax muscles to allow more effective mobilization. Mobilization of the joints and surrounding connective tissue is the key factor. The physical therapist should also be skilled at giving the patient specific exercises for home use and encouraging a general home exercise program.
TENS: Transcutaneous electrical nerve stimulation is a useful modality and should be trialed in most patients with chronic pain. The patient should be instructed on the placement of the electrodes and the frequencies to be trialed. When placed correctly a stimulation pattern should be felt over the painful region. If TENS does not help after one week, it is unlikely it will be of value. Fifty percent of patients in whom TENS was successful state that the effect appears to wear off over the next year. TENS is useful initially in approximately 60% of patients with chronic pain.
|
