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Hereditary essential tremor and restless legs syndrome.

Sir Essential tremor is usually considered to be a monosymptomatic disorder with variable clinical expression, about half of all cases demonstrating an autosomal dominant pattern of inheritance.' Possible associations with other movement disorders have been described, including Parkinson's disease.2 We report a patient with hereditary essential tremor and the restless legs syndrome. A 71-year-old woman complained of a tremor in her right upper limb. This had affected her writing since her teens but had become worse in recent months, also affecting the left arm. The tremor was exacerbated by anxiety and fatigue; alcohol had no relieving effect. Tremulousness of the voice had made it increasingly difficult for her to sing in the church choir. She also complained of discomfort in the legs when sitting, unrelieved by massage but improved by getting up and walking about, and by taking a hot bath. She 'could not relax' because of an uncontrollable urge to move her legs when at rest. Although present throughout the day, this was particularly evident at night and often prevented her from falling asleep. This symptom had also been present since childhood when she had been labelled a 'fidget' at school because of her restlessness in class. A significant exacerbation of these symptoms occurred during pregnancy. Both her father and paternal grandfather had been troubled by a similar tremor of the arms. Moreover, her father had always been 'fidgety' and unable to settle. Her only sibling, a non-identical twin sister, was unaffected, likewise her only son (aged 47). On examination, the patient had a distal tremor in the upper limbs, accentuated by posture. Writing showed intrusion of tremor and drawing of a spiral was impaired. Head titubation ('no-no') was also evident, and holding a single note revealed vocal tremor. Otherwise neurological examination was entirely normal; in particular, there were no dystonic features nor evidence of a peripheral neuropathy. Investigations (urea, creatinine, thyroid function tests, full blood count, serum vitamin B12 and red cell folate) were normal. Treatment with propranolol (40 mg bid) marginally improved her postural tremor, but had no effect on her restless legs. Clinically this patient had unequivocal hereditary essential tremor.1 Furthermore, she fulfilled the suggested diagnostic criteria for restless legs syndrome.3 Previous accounts of an association between hereditary essential tremor and restless legs are few. Bornstein reported a pedigree in which restless legs and hereditary tremor coincided in three patients over two generations, with a similar time of onset in each patient, and opined that the syndromes were 'somehow associated'.4 Bain et al found restless legs in three of 93 patients with hereditary essential tremor; restless legs and tremor were found to co-segregate.1 Jankovic has reported encountering several patients with the restless legs syndrome and an essential tremor-like tremor but gives no further details.5 The association between essential tremor and restless legs in our patient could be the chance concurrence of two relatively common movement disorders. Alternatively, it may be indicative of an underlying link. The differing pharmacological responsiveness of the two disorders argues against a shared pathophysiological mechanism. A linkage at the genetic level would therefore seem more likely. Like hereditary tremor, restless legs syndrome has been reported to present in childhood and adolescence as an hereditary condition with probable autosomal dominant transmission.6 It may be that in this family, genes for essential tremor and restless legs have cosegregated. In such families, identification of the genetic locus for one condition may thus facilitate definition of the other.