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Restless legs syndrome may be either a primary or a secondary disorder. The primary form of the syndrome is often familial whereas the secondary form is mainly associated with uraemia, iron deficiency, or pregnancy. Almost all patients with restless legs syndrome show periodic leg movements during sleep.1 The pathogenesis of both restless legs syndrome and periodic leg movements is still speculative. Yokota et al have reported an association of periodic leg movements with spinal cord lesions.2 However, none of these patients had the typical clinical features of restless legs syndrome. Restless legs syndrome associated with myelopathy is documented in one patient with a Borrelia induced myelitis.3 We report three patients who developed a restless legs syndrome in close temporal association with spinal cord lesions.
Case 1 was a 35 year old woman who presented with a 3 week history of painless restlessness of her left lower leg that occurred only at rest, particularly in the evening and at night. The restlessness was partially relieved by walking. With the onset of these symptoms, the patient had noticed a numbness of her left hemibody below the breast. Nine months previously, a numbness of the right leg had subsided spontaneously within 1 week. On examination, the patient had decreased senses for touch, pain, and temperature over the left hemibody below the T6 dermatome. Examination of CSF disclosed a normal cell count, normal protein content, increased CNS synthesis of IgG, and positive oligoclonal bands. In MRI studies of the spinal cord, no abnormality was detected. Brain MRI was not performed. Transcranial magnetic stimulation showed a slightly prolonged central conduction time of motor evoked potentials recorded over the left abductor hallucis muscle. Otherwise, multimodality evoked potentials were normal. A myelitis due to multiple sclerosis accompanied by a symptomatic unilateral restless legs syndrome was diagnosed. The patient was treated with 500 mg prednisolone intravenously over 5 days without any clinical effect. However, a single dose of 100 mg levodopa plus benserazide led to a dramatic improvement of the restless legs syndrome. The levodopa treatment was continued and resulted in complete relief.
Case 2 was a 49 year old man who had a traumatic atlantoaxial dislocation that necessitated operative stabilisation of the cervical spine. Preoperative MRI studies had shown a compression of the medulla and the cervical cord. When we saw the patient 3 years later, he complained of a sensation of cold, pain, and restlessness in both lower legs that was present only at rest, particularly in the evening, and was relieved by walking around and rubbing the legs with cold water. The onset of these symptoms was only a few weeks after the accident. Clinical examination disclosed a mild dysarthrophonia and atrophic pareses of the left sternomastoid and the left trapezius muscle. Tendon reflexes were hyperactive and plantar responses were extensor bilaterally. The patient’s gait was spastic, but he was able to walk unassisted. In both legs, pain and temperature sensation were markedly reduced. The diagnosis of a restless legs syndrome secondary to a traumatic lesion of the medulla and the cervical cord was made. Treatment with 100 mg levodopa plus benserazide and 100 mg tramadol resulted in a satisfactory relief of the restless legs syndrome.
Case 3 was a 65 year old man who developed slowly progressive spastic tetraparesis and ascending sensory disturbances in both legs. An MRI study showed a cervical spondylotic myelopathy at the level C3-C6 and the patient underwent spinal cord decompression. Five years later, he was referred to our hospital because of an intense sensation of restlessness of both legs located in the feet and calves. The restlessness occurred when sitting and lying for more than 20 minutes. It was pronounced at night and improved when he was walking around. These symptoms had started simultaneously with the motor and sensory disturbances due to the cervical spondylotic myelopathy and did not improve postoperatively. On examination, the patient was mildly impaired in carrying out fine motor tasks and his gait was moderately spastic. He had reduced touch and vibration senses in both upper limbs. A restless legs syndrome due to a cervical spondylotic myelopathy was diagnosed. Treatment with pergolide resulted in an excellent control of the restless legs syndrome.
Our patients meet the criteria for the diagnosis of restless legs syndrome.4 Over a follow up period of at least 6 months, restless legs syndrome symptoms were sufficiently relieved by dopaminergic treatment. The association of myelopathy and restless legs syndrome may be merely coincidental. However, the close temporal relation between the onset of myelopathy and restless legs syndrome strongly suggests that restless legs syndrome was secondary to the spinal cord lesions.
The pathogenesis of restless legs syndrome and periodic leg movements is still speculative. In patients with myelopathy and periodic leg movements, it is hypothesised that a spinal cord lesion may permit the expression of a spinal periodic leg movements generator by interrupting descending inhibitory spinal pathways.2 Our finding of restless legs syndrome in three patients with myelopathy provides evidence that disinhibition of spinal pathways may also be involved in its pathogenesis.
In patient 1, restless legs syndrome was strictly confined to the left leg. Preceding transitory sensory disturbances of the right leg and CSF findings support the diagnosis of multiple sclerosis in this patient. Clinical findings suggest a spinal lesion at the thoracic level. Involvement above the spinal level cannot be excluded. However, clinically and neurophysiologically no supraspinal lesion was detected. Yokota et al described three cases of periodic leg movements associated with spinal lesions due to multiple sclerosis.2 Ferini-Strambi et al performed polysomnographic studies in 25 patients with multiple sclerosis and in an age and sex matched control group.5 The prevalence of periodic leg movements was significantly higher in the multiple sclerosis group (36%v 8%). Patients with multiple sclerosis with periodic leg movements had higher MRI lesion loads in infratentorial regions compared with patients with multiple sclerosis without periodic leg movements. However, spinal MRI was not done and clinical findings were not reported in detail. Thus, further studies are needed to elucidate the prevalence and the pathogenesis of restless legs syndrome and periodic leg movements in patients with multiple sclerosis.
In conclusion, our report suggests that restless legs syndrome may occur secondary to spinal cord lesions due to different causative diseases including multiple sclerosis, spinal cord injury, and cervical spondylotic myelopathy. Similar to idiopathic restless legs syndrome and other secondary forms, restless legs syndrome due to myelopathy may respond well to dopaminergic drugs.
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