The spiral axis as a clinical tool to distinguish essential tremor from dystonia cases

Abstract

Background: Tremor is a common feature of a variety of neurological disorders. In genetic studies of essential tremor (ET), investigators need to screen potential enrollees by mail or telephone to exclude those with other neurological conditions, especially dystonia. In clinical settings, the differentiation of ET and dystonia may also be very challenging. We hypothesized that the spiral axis, described below, is a useful screening tool to distinguish ET cases from dystonia cases. Methods: We analyzed the hand-drawn spirals of 135 individuals enrolled in a genetics study at Columbia University Medical Center. Each of the four spirals was assessed for the presence of a single identifiable tremor orientation axis, and a spiral axis score (range = 0 – 4) [a single axis on all 4 spirals] was assigned to each enrollee. Results: There were 120 ET cases and 15 cases with dystonic tremor. Most (101/120, 84.2%) ET cases had an axis score ≥1 vs. only half (8/15, 53.3%) of the dystonia cases (p =0.02). Receiver Operator Curve (ROC) analysis revealed that the use of a spiral axis score ≥2 as a cut off would exclude 60.0% of dystonia cases while including 67.5% of ET cases. Conclusion: Handwritten spirals appear to have a single predominant axis in more ET than dystonia cases. The evaluation of this axis has moderate diagnostic validity as a screening tool to distinguish ET cases from those with dystonia. Although this study did not assess the utility of this tool in clinical practice settings, future studies should do so.

Distinguishing features between valproate-induced tremor and essential tremor

“…ET); patients and evaluator were not aware of the study hypothesis. Additionally, in a second stage, after including all patients, we carried out blinded evaluations to the underlying diagnosis for the presence of tremor axis in the Archimedes spirals . The Internal Review Board of the University Hospital of Guanajuato approved the study protocol, and patients provided informed consent to participate in the study.…”

Effect of Primidone on Dentate Nucleus γ-Aminobutyric Acid Concentration in Patients With Essential Tremor

“…ET cases were recruited from several sources, including a clinical-epidemiological study of ET, 14 one of the author’s (E.D.L.) neurological practices, and study advertisements.…”

Essential tremor: diagnosis and management

“…In writing and Archimedes spiral samples, the axis of essential tremor is commonly in the 8-2 o’clock in right handed drawing and 10-4 o’clock in left handed drawings (see video). This is seen in script writing, especially with vertical letters such as “h,” “l,” and “p.”77 This can help to differentiate essential tremor from dystonia, in which this axis is uncommon. On examination, up to 20% of patients with essential tremor will have a unidirectional, non-oscillatory head jerk (“head snap”) during the finger-to-nose examination as the finger nears the nose.…”