The spiral axis: A comparison of unaffected first-degree relatives of essential tremor cases vs. controls

Elan D. Louis, Hollie N. Dowd, Mazen Elkurd

Research output: Contribution to journalArticlepeer-review

Abstract

We previously observed that during a spiral drawing task, in essential tremor (ET) cases, the tremor wave forms align along a single predominant axis. This interesting clinical feature can distinguish ET from dystonia cases. We now investigate whether the unaffected relatives of ET cases also express this trait, albeit perhaps in a milder form. To address our aim, we assessed the spiral axis in 237 unaffected first-degree relatives of ET cases (FD-ET), comparing them to 105 controls (Co). A movement disorder neurologist assessed four hand drawn spirals for the presence of a single identifiable tremor orientation axis. A spiral axis score (range = 0–4 [a single axis on 4 spirals]) was assigned to each enrollee. FD-ET had higher spiral axis scores than Co. In a contingency table, the distribution of spiral axis scores differed in the two groups: FD-ET (highest) and Co (lowest) (ordinal chi-square test p = 0.014). Furthermore, when spiral axis scores were examined as a continuous measure, the groups differed (Mann-Whitney test p = 0.03) - with the means being 0.51 (FD-ET) and 0.26 (Co). These data have scientific implications. They (1) show that such axes are more common in relatives of ET cases than controls, and (2) raise the possibility that the spiral axis may be an early subclinical feature of ET.

Original languageEnglish (US)
Article number117330
JournalJournal of the Neurological Sciences
Volume422
DOIs
StatePublished - Mar 15 2021

Keywords

  • Clinical features
  • Essential tremor
  • Family study
  • Spiral axis

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology

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