Introduction

Essential tremor (ET) is a progressive neurological disease and is considered the most common movement disorder.1 Depression, anxiety, and age are associated with increased functional disability in ET, regardless of tremor severity.2 ET is also associated with a wide range of impairments, such as ataxia, postural instability, impaired tandem walking, and decreased gait speed.1,3–5 Compared with a control group without ET, individuals with ET demonstrate decreased Berg Balance Scale scores, decreased single limb stance times, and increased Timed Up and Go times, which could indicate an increase in the risk of falls.1 A 2013 review indicates that gait and balance deficits in patients with ET are well documented in the literature.6

Typically, individuals with ET will seek medical management to reduce tremor, such as pharmaceutical remedies or deep brain stimulation (DBS). Although DBS can diminish tremor, prolonged bilateral DBS is linked with postural instability and impairments in gait and balance in individuals with ET.1,7 There is a paucity of research investigating rehabilitation for individuals with ET and prolonged DBS with these deficits.

The potential impairments, activity limitations, and participation restrictions associated with ET warrants an examination of the role of physical therapy (PT) to address movement dysfunction. The purpose of this case report is to describe the development, implementation, and outcomes of a novel PT plan of care for a patient with ET. Although the individual in this case report has ET and prolonged DBS, the intervention described is broadly applicable to individuals with ET without DBS.

Case report

A 61-year-old, Caucasian male presented to an outpatient, multidisciplinary neurological clinic with a diagnosis of ET of at least 9 years. The patient, a high school-educated retired army veteran, lived with his wife and four children in a multi-level home.

Past medical history included depression, headaches, left elbow fracture, tobacco use (one pack per day), and hypertension. Prescribed medications at the time of the examination were Inderal XI (Propranolol) and Cymbalta (Duloxetine). Past pharmacological management was unknown. Past surgical history consisted of a repair of right knee and left shoulder injuries of unknown pathology, hernia repair, and bilateral DBS to the subthalamic nuclei approximately 9 years before the PT examination.

He perceived initial improvements following the DBS. Over time, the tremor returned, his speech worsened, and he experienced increased dizziness and falling, specifically on stairs and when negotiating tight spaces. The patient reported a falls frequency of two falls per week at the time of the examination.

The patient was referred to the clinic by his neurologist, having not had any previous speech, occupational, or physical therapy. His chief complaints to the physical therapist were increased falls, specifically when walking down the stairs, and bilateral upper extremity tremor.

Based on the history and systems review, vestibular dysfunction (e.g., dizziness while driving), cerebellar dysfunction (e.g., loss of balance in tight spaces), and impaired strength were identified as potential factors contributing to the patient’s reported deficits. The physical therapist completed an examination to determine specific impairments pertaining to the subjective reports of falls and postural instability (Table 1).

Standardized outcome measures were administered to assess balance, postural stability, and falls risk based on patient presentation and findings during subjective and objective testing. The physical therapist prioritized obtaining information about the risk of falls when selecting appropriate outcome measures and gaining insight about static and dynamic mobility. These included the Berg Balance Scale (BBS),8 Functional Gait Assessment (FGA),9 Five-Times-Sit-to-Stand test (5×STS),10 and 10-meter walk test (10MWT).11 Baseline results are in Table 2. The standardized outcome measures indicated a risk of falls and results below normative values.

Additional important examination findings included subjective reports of dizziness from head turns, difficulty with vertical eye gaze, inability to perform tandem gait, a wide base of support, difficulty with stairs, and inability to perform gait with eyes closed. These deficits are consistent with ET and prolonged DBS.

Clinically, individuals with ET can present similarly to individuals with cerebellar diseases.4,12–14 Interventions that improve postural control, balance, coordination, and functional mobility for individuals with cerebellar diseases are described.15–18 Given the similar clinical presentations of individuals with ET and cerebellar disorders,5 interventions designed to improve proximal stability, balance, and coordination with functional movements were selected as primary components of the PT plan of care. Furthermore, principles of body awareness training (BAT) and visual motor coordination (VMC) were applied to the PT interventions and are described in the following intervention section. BAT and VMC were incorporated to enhance the patient’s ability to self-reflect throughout therapy and in his home environment.

The patient received 14 individual 60-minute sessions of PT over 8 weeks (Table 3). Over the 8 weeks, the PT plan of care included integration of the principles of BAT and VMC with the training triumvirate (proximal stability, balance, and functional movements) (Figure 1). These three domains of training were addressed in each session and exercises frequently overlapped these domains. An example of this overlap was the design of the exercise of sit to stand transitions: an inherently functional movement with an emphasis on proper mechanics and repetition (functional movement training), reaching the limits of stability (balance training), and engagement of the core (proximal stability training).

The goal of BAT is to enhance a person’s awareness of movements and one’s body attempting to reach the limits of stability, especially during slow repetitive movement, and reflecting upon performance.19–21 Although it is indeterminate if individuals with ET experience deficits specifically with body awareness, given this patient’s presentation of decreased balance and postural stability and the benefits of BAT to address these deficits in another neurological population (stroke), the principles of this approach were trialed.19–21 The focus during training for this patient included principles of BAT, such as self-reflection during movements and awareness of changing pressures on the soles of his feet.

Proximal stability training involved core strengthening exercises with the inclusion of cues that guided the patient’s attention to increasing awareness of his body in space during activities such as weighted trunk rotation. Balance training involved progressively reaching his limits of stability during activities in a standing position such as reactive stepping. Functional movement training involved increasing body awareness during functional movement patterns such as multi directional gait training.

Consistency of interventions across multiple sessions, therapist-guided verbal cues, and adequate time during and after activities for reflection aimed to improve the patient’s understanding of his performance and body positioning. The consistency of interventions was particularly helpful to promote increased focus on body awareness and control as he then did not have to devote attention and cognitive load to always learning a new exercise. Toward the end of the plan of care (sessions 9–14), motor and cognitive loads were added to the training as a means to increase complexity and intensity.

Given the influence of visual feedback on movement,22 VMC was implemented. VMC is the integration of “both visual and motor abilities with the environmental context to accomplish a goal.”23^,p.207

Integrating visual input into motor abilities was a key component to enhance the overall treatment. VMC was used to heighten information about body movements. Altered functional movement patterns, hypothesized because of poor visual integration, were noted in the examination and during subsequent therapy sessions. Given the patient’s presentation and the known cerebellar influence on saccade generation,18 exercises to heighten vestibulo-ocular reflex (VOR) functioning and saccades were incorporated.

VMC was incorporated into balance and proximal stability training through hand or target tracking. The introduction of VMC into functional movement patterns occurred within realistic and salient activities.

Outcome measures were reassessed during sessions 8 and 14. These time points coincided with the outpatient PT regulations requiring reassessments every 30 days. Currently, there are no established minimal clinically important difference (MCID) or minimal detectable change (MDC) values for individuals with ET for any of the outcome measures in this study. Comparisons of data to the MCID and the MDC, therefore, are based on studies involving individuals with community-dwelling older adults,24 vestibular disorders,25,26 or movement disorders.27–30 Following 8 eight weeks of intervention, the patient demonstrated a clinically meaningful change in the 5×STS, FGA, and BBS. These results indicate a decrease in the risk of falls. At the time of discharge, the patient reported one fall since the PT evaluation, an improvement from the pre-PT frequency of two falls/week.

Discussion

There is a paucity of research describing the effectiveness of rehabilitation interventions for individuals with ET and limited evidence examining PT for those with prolonged DBS in those with ET. This case report describes a novel PT approach that emphasized balance, functional movement, and proximal stability training with an integration of principles of BAT and VMC for a 61-year-old patient diagnosed with ET who underwent bilateral DBS 9 years prior. His presentation was consistent with characteristics of ET3,4 and prolonged DBS.29 In addition, there were similarities of his presentation to those with cerebellar diseases.1,17,18,31–33

The outcome measures encompassed constructs reflective of the interventions that promoted body awareness and visual integration during balance, complex movements, and functional patterns. The patient demonstrated clinically significant improvements in outcome measures of balance and functional mobility as well as a decreased fall risk, although it is noted that the measures of clinical significance and cut-off scores for fall risk were in populations other than ET. Future research is needed to establish psychometric properties of these outcome measures for individuals with ET. Improvements in gait speed were demonstrated although clinical significance was not achieved. Gait training was incorporated, but the emphasis was on body awareness, VMC, and balance during gait, not solely increasing gait speed.

Attributing his improvements to this specific PT plan of care is indeterminate given the retrospective case report design. Given the patient’s level of inactivity prior to therapy, there is the potential that improvements were due to participation in physical activity, regardless of type. In the future, utilization of an A–B–A design would help determine if improvements are attributable to the PT intervention and if those effects endure. Delaying intervention for active fallers to obtain a baseline, however, may warrant further discussion regarding the ethical implications. Larger scale trials with more rigorous research designs are needed to examine the effects of PT for those with ET and the value of integrating BAT and VMC with training.

This case report provides a description of interventions used including BAT and VMC for clinicians who would like to trial this approach for individuals with similar presentations. This case report supports referrals by physicians to neurologic physical therapists for evaluation and treatment of individuals with ET to improve balance and functional movements and decrease falls risk.