Movement Disorders, Third Edition by Watts Ray L. & Standaert David G. & Obeso José

Author:Watts, Ray L. & Standaert, David G. & Obeso, José [Watts, Ray L.]
Language: eng
Format: epub
Publisher: McGraw-Hill
Published: 2011-08-11T17:00:00+00:00

PRIMARY ORTHOSTATIC TREMOR

In orthostatic tremor, also referred to as “shaky leg syndrome,” first described by Heilman,66 there is a subjective feeling of unsteadiness during standing, usually for over 10 seconds. In severe cases falls may occur during walking. Standing may induce visible or palpable fine-amplitude ripping in the leg muscles (gastrocnemius or quadriceps). The diagnosis can be confirmed by a surface EMG recording of the above muscles with the patient standing with a typical 13–18-Hz pattern. Similar tremor can be recorded in all leg and trunk muscles, with the tremor disappearing when patient sits or lies down. Walking, sitting, and lying were unaffected. Standing involved a wide base, but gait was normal. There are no other abnormal neurological signs or symptoms. Patients find it harder to stand still and are forced to take a step to regain balance. Falls and injuries are uncommon, as patients start moving as soon as the sense of imbalance occurs. Within any individual patient the frequency of tremor remains unchanged in all of the muscles examined. Salient features of orthostatic tremor are outlined in Table 26–1.67 The etiology of this condition is unknown, and it is thought to arise from a central generator in the cerebellum or the brainstem. Gerschlager and colleagues reviewed 41 patients with orthostatic tremor to further elucidate the natural history and symptoms associated with this disorder. They found that ~25% patients had other features such as parkinsonism. Although, OT typically does not progress, Gerschlager and colleagues found that in 15% patients the condition gradually worsened and the tremor moved proximally to involve the trunk and arms.68 Symptomatic orthostatic tremor in pontine lesions is reported.69 In some cases slower frequency OT may be a component of parkinsonian tremor and may respond to levodopa.70 The term pseudo-OT has been employed in this setting.

TABLE 26–1. FEATURES OF ORTHOSTATIC TREMOR

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