Contents lists available at ScienceDirect Journal of the Neurological Sciences journal homepage: www.elsevier.com/locate/jns Shaky and unsteady: Dynamic posturography in essential tremor Shweta Prasad a,b , Selva Ganapathy Velayutham c , Venkateswara Reddy Reddam b , Albert Stezin a,b , Ketan Jhunjhunwala a,b , Pramod Kumar Pal b, ⁎ a Department of Clinical Neurosciences, National Institute of Mental Health & Neurosciences (NIMHANS), Hosur Road, Bangalore 560029, Karnataka, India b Department of Neurology, National Institute of Mental Health & Neurosciences (NIMHANS), Hosur Road, Bangalore 560029, Karnataka, India c Department of Neurological Rehabilitation, National Institute of Mental Health & Neurosciences (NIMHANS), Hosur Road, Bangalore 560029, Karnataka, India ARTICLE INFO Keywords: Essential tremor Dynamic posturography Balance control Cerebellar dysfunction ABSTRACT Background: The spectrum of symptoms exhibited by patients with essential tremor (ET) extends far beyond the classical tremor. This study aims to explore and establish the presence of subtle balance abnormalities in ET using dynamic posturography (DP). Methods: DP was performed on 18 patients with ET and 26 controls. Diagnosis of ET was based on the Consensus Statement of the Movement Disorder Society on Tremor. Dynamic stability which included the overall balance index, anterior-posterior index and mediolateral index, and limits of stability were measured. Results: Patients with ET had significantly impaired balance indices. Impairment of dynamic stability revealed poor static balance control in all directions. Lower limits of stability scores indicated a smaller range of motion prior to which patients have to shift foot balance. No correlations were observed between age at evaluation, age at onset, duration of illness and the balance indices. Conclusions: Dynamic posturography reveals significant balance impairment in patients with ET which is un- related to the age at onset, age at evaluation or duration of illness. This finding concurs with pre-existing reports and adds to the growing body evidence of cerebellar involvement in ET. 1. Introduction Essential tremor (ET) is a highly prevalent movement disorder [1], classically associated with an action tremor of the upper limbs, occa- sionally involving the head, legs and trunk. ET was always considered to be a monosymptomatic disorder with a relatively benign course. In fact, according to the diagnostic criteria for ET, the presence of other abnormal findings on a neurological examination is indicative of a disorder other than ET [2]. However, this view has been under scrutiny due to several reports suggesting a symptom complex extending beyond the tremor. Patients with ET have been reported to suffer from a variety of symptoms ranging from gait and balance impairments to alterations in cognition [3–5]. Although gait and balance impairment has been known for several decades, the reports were usually anecdotal, with the impairment at- tributed to old age rather than the disease [6]. Singer et al. [7], pro- vided the first proof of balance and gait impairment in ET. Post this, several studies have concurred with this finding either through the utilization of clinical examinations and scores or complex laboratory analysis [8–16]. An increase in the number of missteps during tandem gait has been consistently reported in studies which have focused on abnormalities in neurological examination in patients with ET [7–9,11,14,15]. Gait analysis has shown a reduction in the velocity of normal and tandem gait, increased step variability and step width, and a reduction in stride length [8,9,11,12,15]. Posturographic assessment has revealed significant impairments of both static and dynamic bal- ance control in patients with ET [8,10,12,13,16]. However, the actual implication of this impairment is still unclear and the need for ther- apeutic intervention is doubtful [17]. The presence of subtle cerebellar dysfunction in ET has been pre- viously reported [18,19]. In view of this, gait and balance abnormalities should be expected in this disorder. There are limited studies which have utilized dynamic posturography (DP) to assess the balance im- pairment in ET [8]. This study aims to explore and establish the pre- sence of subtle balance abnormalities in ET by DP. https://doi.org/10.1016/j.jns.2017.12.003 Received 2 August 2017; Received in revised form 24 October 2017; Accepted 1 December 2017 ⁎ Corresponding author. E-mail address: pal.pramod@rediffmail.com (P.K. Pal). Abbreviations: AAO, age at onset; API, anterior-posterior index; BMI, body mass index; DP, dynamic posturography; ET, essential tremor; HT, head tremor; LOS, limits of stability; MLI, mediolateral index; OBI, overall balance index; SP, static posturography Journal of the Neurological Sciences 385 (2018) 12–16 Available online 05 December 2017 0022-510X/ © 2017 Elsevier B.V. All rights reserved. T