Impairment due primarily to intractable pain may greatly influence an individual’s ability to function. Psychological factors can influence the degree and perception of pain: different individuals in similar circumstances may be impaired by pain to different degrees. A chronic pain syndrome may follow thalamic lesions, but this is rare. Chronic pain in this section covers the diagnoses of causalgia, posttraumatic neuralgia, and reflex sympathetic dystrophy. The new term complex regional pain syndrome, type I and type II, is not used here since it does not represent a single diagnostic criterion.
Causalgia is burning pain that develops in a distal extremity following trauma to a peripheral nerve. The burning pain is triggered by movement, light mechanical stimuli to the skin, and strong emotion. Other features include distal extremity swelling and skin that is smooth, mottled, cold, and sweaty. Sympathetic block frequently relieves the pain. In posttraumatic neuralgia, the burning pain in the distribution of a nerve does not have the other clinical features and does not spread.
Reflex sympathetic dystrophy (RSD) occurs without known nerve lesions and is precipitated by minor soft tissue trauma. Burning spontaneous pain and stimulus-evoked pain are most pronounced in the distal limb (allodynia, hyperpathia, and hyperalgesia). The affected limb is usually warmer acutely (less than 6 months) and then is colder. It is now generally believed that a central nervous system abnormality is present based on the autonomic changes of abnormal sweating and skin blood flow. The acute distal swelling usually responds to sympathetic block. In the chronic stage, trophic changes include alteration in nail and hair growth, thin shiny skin, osteoporosis, and restriction of passive movement. Postural or action tremor is not uncommon, while an associated movement disorder is relatively rare.
To rate these conditions for impairment, diagnosis is key and is based on clinical criteria. Besides the clinical findings previously described, a three-phase bone scan may show increased uptake in the acute and subacute periods. This study is known to have low sensitivity, 50%,17 and therefore cannot be used as a required criterion for the diagnosis. Plain x-rays may show patchy demineralization, particularly in a periarticular distribution, within months of the onset of RSD. Altered blood flow by laser Doppler flowmetry and abnormal function in the sudomotor reflex also support the diagnosis. It is difficult to examine individuals who are experiencing these symptoms; therefore, once the criteria for the diagnosis have been met, the impact on ADL is determined.
To rate an impairment for causalgia, posttraumatic neuralgia, and RSD in an upper extremity, use Table 13-22. If a lower extremity needs to be rated for casualgia, posttraumatic neuralgia, or RSD, use the station and gait impairment criteria given in
Table 13-15.