Adult-Onset Primary Limb Dystonia: Clinical Description of a Rare Entity

Objective: In this study we report on 5 patients with adult-onset primary lower limb dystonia. Background: Adult onset primary dystonia generally affects the cranio-cervical region and remains focal. Lower limb onset usually occurs in the childhood form of idiopathic dystonia and is uncommon in primary adult onset dystonia. Methods: The charts of patients with the diagnosis of primary dystonia seen at a movement disorder clinic were reviewed. Results: Clinical details of five patients with adult-onset lower limb dystonia are summarized below. Average age of onset was 51.6 years (3 F, 2 M). Family history of dystonia was negative in all cases. None noticed diurnal fluctuation. Four patients showed dystonic movements when walking, including one presenting with an action-induced dystonia when walking downstairs. One patient (5) had a dystonic foot posture even at rest. Investigations included DYT 1, copper, acanthocytes, CT or MRI of brain and spine, myelogram, electrophysiology, CSF, and other studies of secondary dystonia were all normal. Except for case 3, patients were unresponsive to treatment normally prescribed in dystonia including anticholinergics, levodopa, tetrabenazine, pimozide, and which were tried. Case 1: 56-year-old woman with a 3-year progressive history of involuntary jerky spasms of foot and leg. Exam showed an inverted gait with dorsiflexion of the foot and internal rotation of the leg. There were no other abnormal neurological signs. Case 2: A 54-year-old man with a 3-year progressive history of abnormal posturing of the foot. Exam showed inverted foot, plantar flexion and fanning of toes when walking. Case 3: A 42-year-old woman with a 2-year history of involuntary movements of the lower limb. Exam showed dystonic twisting of the leg. She had benefit from combined treatment of tetrabenazine, pimozide, and benzhexol. Case 4: A 52-year-old man with a 10-year history of an isolated action dystonia of the leg when walking downstairs. Exam showed flicking outwards of the leg with dystonia posturing. Case 5: A 72-year-old lady with a progressive 3-year history of inversion of ankle and foot. Exam showed dystonia with inverted foot and a striatal toe. Conclusion: The diagnosis of primary adult-onset limb dystonia was made as none of the patients had any other abnormal signs even on prolonged follow-up (mean 7.2 years). We conclude that there is a rare form of adult-onset primary dystonia with onset in the legs and no further spread.