Physical therapy, muscle reeducation, and the proper use of assistive devices are all important in the rehabilitation of the patient. Recent advances that combine epidural stimulation of the lumbosacral cord with intensive treadmill training have allowed some paraplegic patients to attain standing and some degree of over-ground walking (Angeli et al).
Radiation Injury of the Spinal Cord
Delayed necrosis of the spinal cord and brain are recognized sequela of radiation therapy for tumors in the thorax and neck. Mediastinal irradiation for Hodgkin disease or for other lymphomas had been in the past a typical setting for the development of these complications up to decades later. A lower motor neuron syndrome, presumably a result of injury to the gray matter of the spinal cord, may also follow radiation therapy in which the cord was inside the zone of treatment, as described below.
An “early” type of radiation myelopathy (appearing 3 to 6 months after radiotherapy) is characterized mainly by spontaneous uncomfortable sensations in the extremities. The paresthesias may be evoked by neck flexion (Lhermitte symptom). In one of our patients there was impairment of vibratory and position sense in the legs, but no weakness or signs of spinothalamic tract damage. The sensory abnormalities disappear after a few months and, according to Jones, are not followed by the delayed progressive radiation myelopathy described below. The pathology of the early and transient radiation myelopathy has not been fully elucidated, but there is a spongy appearance of the white matter with demyelination and depletion of oligodendrocytes.
This is one of the most dreaded complications of radiation therapy. It is a progressive myelopathy that follows, after a variable latent period, the radiation of malignant lesions in the vicinity of the spinal cord. The incidence of this complication is difficult to determine because many patients die of their malignant disease before the myelopathy has fully evolved but it was in previous eras of delivery of radiation estimated to be between 2 and 3 percent (Palmer). According to Douglas and colleagues, patients who have undergone hyperthermia as an adjunctive treatment for cancer are particularly vulnerable to radiation myelopathy.
Clinical features The neurologic disorder first appears 6 months or more after the course of radiation therapy, usually between 12 and 15 months (latent periods as long as 60 months or longer have been reported). The onset is insidious, usually with sensory symptoms—paresthesias and dysesthesias of the feet or a Lhermitte phenomenon, and similar symptoms in the hands in cases of cervical cord damage. Weakness of one or both legs usually follows the sensory loss. Initially, local pain is absent, in distinction to the effects of spinal metastases. In some cases, the sensory abnormalities are transitory as in the syndrome described above; more often, additional signs make their appearance and progress, at first rapidly and then more slowly and irregularly, over a period of several weeks or months, with involvement of the corticospinal and spinothalamic pathways. The neurologic disturbance may take the form of a Brown-Séquard syndrome, but with progression it is usually overtaken by a transverse myelopathy.
Reagan and coworkers, who have had considerable experience with this condition, described yet another myelopathic radiation syndrome, namely, a slowly evolving amyotrophy, with weakness and atrophy of muscles and areflexia in parts of the body supplied by anterior horn cells of the irradiated spinal segments. Most patients with this form of the disease die within a year of onset. Knowledge of the pathology is incomplete. This syndrome is reminiscent of the delayed motor neuron myelopathy following electrical or lightning injury described in the next section. There is also an unusual paraneoplastic variety of poliomyelopathy and an even less common necrotic myelopathy, mentioned below and in Chap. 30.