Post-traumatic Origin of Unilateral Restless Leg Syndrome.

Abstract

Although restless leg syndrome (RLS) is often an inherited disorder, this symptom complex can also arise in association with various secondary causes, such as cerebral stroke, renal failure, lumbosacral radiculopathy, and peripheral neuropathy.1, 2 Clinical features of acquired forms of RLS, including those of sporadic cases, can be indistinguishable from manifestations of RLS occurring as a familial disorder.3-6 Similarly, unilateral presentations of RLS generally do not differ in symptomatology from those cases with bilateral involvement.2 Since the neurological substrate underlying RLS remains a mystery, acquired instances of this syndrome offer the potential for useful insights. In this report, a case is described in which unilateral RLS developed and persisted after ipsilateral leg trauma. A 34 year-old man has a 5-year history of dysesthetic and painful sensations limited to his right distal lower leg. They occurr predominantly in the evenings and often interfere with falling asleep. He described his overall severity of discomfort as “8” on a 0–10 scale. Other symptoms typical of RLS include “creepy-crawly” sensations also limited to his right distal leg and foot. Near-complete (though temporary) relief can be achieved by walking or by repetitive movements with his right leg. Rubbing an ice pack on the right foot and leg also can be helpful. Similar, milder symptoms typical of RLS (rated “3” on a 0–10 scale) can be experienced during the daytime after prolonged sitting. There are no signs or symptoms suggesting peripheral neuropathy (and a lower extremity nerve conduction velocity and EMG study was normal). The patient denied toxic exposures, use of dopamine receptor-blocking medication, renal impairment, iron deficiency, muscle spasms, localized back pain or radicular symptoms, prior leg injury, features of regional pain syndrome, or familial RLS. A detailed neurological examination was entirely normal. A sleep study did not show periodic limb movements during sleep. Medication trials with dopaminergic agonists and gabapentin were ineffective. Tramadol (50–650 mg each evening) provides good symptomatic relief, as has marijuana. An intriguing feature was the relationship between the onset of RLS and two episodes of trauma to his right lower extremity. The full range of RLS features, as described above, began one evening after the patient carried out a full day of a work activity that involved forceful and repeated stomping of his right foot against a shovel. Immediately afterwards, there wasn't bruising or localized tenderness in his right leg, and he could walk normally. However, several hours after the shovel work was completed, characteristic symptoms of RLS developed. These symptoms continued daily in an unchanged manner. Two years later, the patient again engaged in the same type of work with a shovel for several days. After engaging in vigorous stomping with his right foot, his persisting right-leg RLS symptoms became much worse. Again, there was no outward evidence for any injury, such as bruising or difficulty in walking. The increased symptomatology has continued to the present (now three years later). Currently, his RLS symptom rating (using International RLS Rating Scale questionnaire7) is 28.5 for the Part C score (indicative of severe RLS); his RLS ordinal score is 5–6 (severe RLS). Recurrent episodes of work-related pounding blows to a foot were associated with the initiation and, two years later, with worsening of strictly ipsilateral RLS. Temporary relief can be achieved by interventions typically effective for RLS, including a low-potency opiate drug and physical measures, such as walking or moving his right foot. While RLS (either sporadic or familial) can emerge at any age, the abrupt onset and exacerbation of unilateral RLS after the two episodes of foot trauma highlight a likely cause-and-effect relationship. Unilateral manifestations of RLS have been recognized since Ekbom's initial description of this disorder.8 In a recent series of 195 RLS cases, 17% were one-sided presentations and sometimes there was persisting unilateral symptomatology.2 For those instances of acquired RLS with strictly unilateral involvement, an associated neurological disorder, such as peripheral neuropathy, lumbosacral radiculopathy, or a prior cerebral stroke were present for more than half of them.2 However, no prior reports have linked repetitive foot trauma to the onset of RLS, as in the current case. This case report suggests that, in some instances, RLS might be acquired from everyday activities that might otherwise go unrecognized for producing neurological damage. The concept of peripheral injury leading to centrally-mediated movement disorders has always been a controversial topic.9 However, the medical literature includes many compelling reports suggesting such a relationship, including instances of dystonia, parkinsonism, tremor, segmental myoclonus, adult-onset tics, and the syndrome of painful legs and moving toes.10 Typical features of unilateral RLS have been described to arise as an outcome of prosthetic knee surgery.11 However, no other instances of trauma-induced RLS have been published. Given the chronology of events, the etiological relationship in the current case seems quite compelling. This experience raises an intriguing question as to whether the origin (or unmasking) of RLS in susceptible individuals might be related to lifelong episodes of weight-bearing and repeated trauma that feet and legs undergo from everyday activities. In the absence of insights into what leads to the emergence of typical RLS besides hereditary factors, searching for acquired causes like trauma may prove to be informative. The author conceived, organized, and executed the writing of this report, which pertains to a patient under his care. Ethical Compliance Statement: The author confirms that the approval of an institutional review board was not required for this work. The author has read the Journal's position on issues involved in ethical publication and affirms that this work is consistent with those guidelines. Funding Sources and Conflict of Interest: None. Financial Disclosures for the previous 12 months: The author has served as a consultant or advisor for the following pharmaceutical firms: Acorda, Biogen, Britannia, Cavion, Cynapsus, Intec, Jazz, Merz, NeuroDerm, Pfizer, Sage, SynAgile, Titan, and USWorldMeds, and has received speaker honoraria from Acadia, Lundbeck, and USWorldMeds. He is compensated for services as Editor-in-Chief of Clinical Neuropharmacology. The Parkinson's Disease and Movement Disorders Program that Dr. LeWitt directs has received clinical research grant support for conducting clinical trials from Acorda, Adamas, Biotie, Cavion, NeuroDerm, The Michael J. Fox Foundation for Parkinson's Research, The Parkinson Study Group, Roche, Sunovion (formerly, Cynapsus), and USWorldMeds.