Management of causalgia after peripheral nerve injury

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Abstract
The authors report on a series of patients with severely painful disorders of peripheral nerves — they review the modern theories on the nature of causalgia and reflex sympathetic dystrophy. Peripheral causes include spontaneous discharges from neuroma sprouts, their sensitivity to adrenergic compounds, ectopic generator activity in abnormally myelinated fires and increased firing in dorsal root ganglia. Central causes include spontaneous activity of deafferented nerves in the dorsal horn and development of response to new receptive fields. The natural history of such disorders is poor — many patients suffering pain for 10 years or more — the clinical picture is characterized by spontaneous burning pain and allodynia and hyperpathia, chronicity, osteoporosis, skin and nail changes and deformities. The basis of treatment is sympathetic blockade using intravenous guanethedine on alternate days. At least 6 blocks are given as the majority of patients do not respond until the 5th or 6th block. Each block is followed by desensitization and intensive rehabilitation. The authors emphasize that sympathetic blockade is only one, albeit the most important, modality in a multi-faceted treatment programme. Surgical attempts to relieve pain almost uniformly failed — causing as they do further neuronal changes peripherally and centrally. Recurrences depend on the degree of initial response. Those who obtained virtually complete relief of pain had a lower recurrence rate but a high proportion needed repeated sessions of treatment at yearly intervals. Follow-ups must therefore be indefinite.