Intention Tremor of the Legs in Essential Tremor: Prevalence and Clinical Correlates

The aim of this study was to estimate the prevalence and assess the clinical correlates of intention tremor in the legs in essential tremor (ET) patients. The cerebellar features of ET are of growing interest to clinical neurologists. Arm tremor has an intentional component in many ET patients. Intention tremor in the legs, however, has never been systematically evaluated. One hundred twenty-eight ET patients were enrolled in a clinical-epidemiological study at Columbia University (New York, NY). A videotaped neurological examination included 10 toe-to-target movements with each foot. Videotapes were independently reviewed by two movement disorder neurologists who noted the presence versus absence of intentional leg tremor. Two patients underwent quantitative computerized tremor analysis to study the physiological characteristics of the tremor. Thirty-five patients (27.3%) had intentional leg tremor, in 21, tremor was unilateral and in 14 it was bilateral. The 35 patients with intentional leg tremor did not differ from the remaining 93 in their clinical characteristics. Analyses comparing the 14 patients with bilateral intentional leg tremor to the 93 with no intentional leg tremor showed trends toward longer disease duration and more-severe intentional arm tremor in the former. Tremor analysis showed a 3-fold increase in average tremor amplitude from movement onset to the point just before touching the target. Our data suggest that intentional leg tremor, another cerebellar feature, is common in ET patients. The tremor may be associated with longer disease duration and more-severe intentional arm tremor, but these preliminary trends need to be assessed in larger study samples.