After reexamining individuals under the new classification, essential tremor plus (ET-plus) appears to be more common than essential tremor (ET) in individuals with Parkinson disease and lower limb tremor, according to a study published in Parkinsonism & Related Disorders.
This study included 283 patients with Parkinson’s and a score ≥1 in at least 1 leg on the Fahn-Tolosa-Marin Tremor Rating Scale. The slim majority (58.3%) of participants were men with a tremor duration of 25.6±17.9 years and aged 65.0±16.0 years. Of the 133 individuals previously diagnosed with ET under the old classification, 110 were reclassified as ET-plus under the new criteria, 20 stayed with their original ET classification and 3 were categorized with indeterminate tremor. Patients with ET-plus were also found to be considerably older at the onset of tremor and to have a longer disease duration.
Individuals who took part in the study were part of a separate chart-review study conducted at Toronto Western Hospital in Canada and assessed under their original diagnoses, which included several tremor types. After reviewing medical history and physical examinations, participants were reclassified by tremor type using the new criteria.
The researchers concluded that ET in pure form, thought to be the most common tremor type, is less common than ET-plus in patients with lower limb tremor when utilizing the new diagnostic criteria. The main limitation of the study was a concentration on lower limb tremor. The researchers’ goal is to encourage future studies using the new classification criteria on a larger demographic or wider range of tremor types.
Rajalingam R, Breen DP, Lang AE, Fasano A. Essential tremor plus is more common than essential tremor: Insights from the reclassification of a cohort of patients with lower limb tremor [published online June 20, 2018]. Parkinsonism Relat Disord. doi: 10.1016/j.parkreldis.2018.06.029