LAUSR

Dear Editor Painful leg and moving toe syndrome is characterized by pain in the feet or lower limbs and spontaneous movement of the toes [1]. The variants of this syndrome include phenotypes affecting the upper limbs, with symptoms such as painful hands and moving fingers [2]. We present a case of chronic leg pain associated with involuntary ankle movements. A previously healthy 43-year-old woman presented with a 3-month history of involuntary movements of the left ankle, which appeared insidiously. She also reported an 18-month history of left leg pain. Paresthesia on the lateral aspect of the left leg and dorsum of the foot was noted. Ankle jerk was less brisk in the left side. The involuntary movements of the left ankle had a roving pattern with some jerky components (Video Segment 1). No spontaneous toe movements were observed. She did not have inner urge to move her ankle. The ankle movement was not attenuated by distraction maneuvers. No other involuntary movements were observed. There was no edema or trophic change of the left foot. The pain did not respond to various analgesics including gabapentin and pregabalin. Lumbar spinal magnetic resonance imaging revealed left-sided disc protrusions at the L3–4 and L4–5 levels. Nerve conduction studies showed decreased left common peroneal compound muscle action potential (CMAP) by more than 50% of CMAP of the right common peroneal nerve. Left lateral femoral cutaneous sensory nerve action potential (SNAP) also decreased by 75% of the SNAP of the right lateral femoral cutaneous nerve. Because the patient was not cooperative, needle electromyography could not be performed. Motor and sensory evoked potential studies showed no abnormalities. The ankle movements did not respond to clonazepam, baclofen, or anti-dopaminergic agents. The ankle movements resolved when the pain subsided spontaneously 6 months later (Video Segment 2). Although her ankle movements had a jerky component and a roving pattern, there was a random appearance unlikely to be mistaken for myoclonus or dystonia. The presence of pain and single-limb involvement differentiated her ankle movements from chorea. As the movement was consistent and was not distractible, a psychogenic etiology was unlikely. In addition, because pain related to a herniated disc of the lumbar spine or an injury of peroneal nerve is commonly self-limited [3], spontaneous remission of the pain and the ankle movement did not suggest that the movement was psychogenic. The absence of sympathetic dystrophy of the affected foot ruled out complex regional pain syndrome. The pathophysiology of painful leg and moving toe syndrome is currently poorly understood. Painful leg and Electronic supplementary material The online version of this article (doi:10.1007/s10072-017-2940-7) contains supplementary material, which is available to authorized users.