© Springer International Publishing Switzerland 2017
Hsin Fen Chien and Orlando Graziani Povoas Barsottini (eds.)Movement Disorders Rehabilitation10.1007/978-3-319-46062-8_66. Rehabilitation in Essential Tremor
(1)
Morton and Gloria Shulman Movement Disorders Centre and the Edmond J. Safra Program in Parkinson’s Disease, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada
Keywords
Essential tremorPhysiotherapyNonpharmacological treatmentRehabilitationIntroduction
Essential tremor (ET) is one of the most prevalent disorders in neurology, affecting 0.4–0.9 % in the general population of all ages, reaching even higher prevalence with advancing age, ranging from 4.6 to 6.3 % for individuals above 65 years old [1]. Although the term “benign ET ” was historically used to describe it as a monosymptomatic disorder with no pathological changes on brain tissue examination, it is not unusual to observe cases in which the progressive and potentially disabling nature of ET is evident, leading to significant disability and affecting quality of life with prominent interference with activities of daily living. In addition, there is heated debate about the validity and caveats of a series of recent studies highlighting the possible pathological changes in addition to a high prevalence of nonmotor symptoms and imaging abnormalities. Another recent development in the understanding of this field is the general concept that the entity as a single disease may not exist and what we refer to as ET is in fact the phenomenological expression of a series of different disorders [2, 3].
In spite of controversies and significant developments, treatment remains limited and includes pharmacotherapy, surgery and nonpharmacological therapy . The focus of this review is to discuss non-pharmacological therapies , mostly related to rehabilitation.
Clinical Features of ET
The phenomenological hallmark of ET, as its designation suggests, is the postural and kinetic tremor of the upper extremities present in up to 95 % of cases. However, any body part can be affected, including more commonly the head (30 %), lower extremities (10–15 %), and voice (20 %), in the vast majority of cases in combination [4]. The two most consistent risk factors for ET are age and a family history of tremor. In spite of ≥50 % of the affected individuals presenting a positive family history, the objective identification of genes related to increased susceptibility and monozygotic forms of ET has been difficult [5]. Recent studies have linked LINGO1, FUS, and TENM4 genes with a higher risk of developing ET; however, further studies are needed to confirm their pathogenicity [6].
As mentioned above, in recent years, studies have shown that individuals with ET may develop nonmotor symptoms , such as cognitive deficits, depression, anxiety, balance disorder, hearing impairment, olfactory dysfunction, and sleep problems with a significant impact on quality of life [7]. Again, these topics and studies are currently a matter of heated debate among experts in the field.
The same observation is valid for pathological changes in ET. These findings in the central nervous system include a reduction in cerebellar Purkinje cells and restricted Lewy bodies in the locus ceruleus in a limited number of autopsied cases [8]. Brain imaging also shows changes in the cerebellum. A recent study using functional MRI and EEG showed an association between tremor and activity in the ipsilateral cerebellum and contralateral thalamus [9]. However, pathological and imaging changes are still a matter of controversy in the literature.
Pharmacological and Surgical Therapies
Pharmacological Approach
Oral pharmacotherapy in ET comprises different medications, including beta-blockers, anticonvulsants (primidone and topiramate ), and benzodiazepines . Treatment may bring varying degrees of improvement in tremor severity in approximately 50 % of the patients, although this proportion diminishes as the disease progresses to more severe stages [10]. In general, treatment choice is based on the degree of psychological, social, and functional disability, and according to the general health status, as all pharmacological choices carry a significant risk of inducing adverse effects.
First-line therapy agents include propranolol and primidone. Propranolol is a nonselective β-adrenergic receptor antagonist and is the only pharmacotherapy approved through the US Food and Drug Administration (FDA). Initial doses of 20 mg twice a day are usually recommended (10 mg, twice a day in elderly patients). Doses can be titrated up to 60–320 mg/day. Common side effects are bradycardia and bronchospasm. Primidone is an anticonvulsant drug and the initial dose is 50 mg at bedtime (25 mg in elderly patients). Typical maintenance daily dose is 250–750 mg/day. The most frequent side effects are somnolence and dizziness. Second-line therapies include benzodiazepines (i.e., alprazolam), gabapentin, pregabalin, and topiramate.
Botulinum toxin type A (BTXA) has been proven to be effective in ET patients with tremors of the upper extremities [4]. Furthermore, BTXA is also effective in ET patients with head and voice tremors.
Essential tremor is classically marked by alcohol responsiveness. Ethanol improves tremor at relatively low levels, usually within 20 min for 3–5 h, sometimes followed by a rebound tremor augmentation [11]. Alcohol provides reduction in tremor amplitude, but not frequency. Given the significant improvement in tremors, alcohol addiction needs to be monitored in ET patients.
Surgical Approach
Deep brain stimulation (DBS) is the surgical treatment recommended for patients with disabling ETs. In 1997, the FDA approved DBS as a treatment for ET [12]. The ventrolateral thalamus and the posterior subthalamic area (PSA) are the typical targets for DBS in ET. Compared with unilateral implants, bilateral implants significantly reduce tremors; however, with a higher risk of side effects from stimulation (balance and posture). The effect is safe, with effects that are quite significant and long-lasting in most cases [13]. Thalamotomy is a surgical option that is equally as effective for refractory tremors in ET patients, but is limited because of an increased relative risk of adverse effects, especially with bilateral surgery.
Nonpharmacological Therapy and Rehabilitation
Although symptoms of ET may be controlled with medication or surgical interventions, it is of interest to explore and employ additional forms of therapy to assist with functionality. As already summarized, both medications and surgical interventions have several potential side effects and may not provide the best benefits in terms of overall motor function. Therefore, rehabilitation is in the pipeline not only for ET, but for most chronic neurological conditions. The interventions described below should typically be used in parallel with other forms of treatment or as the sole intervention.
Tremor
Resistance Training
The resistance training (RT) program is an exercise intervention consisting of sessions of biceps curl, wrist flexion, and wrist extension movements performed with both limbs with sets of repetitions. Exercises may be performed with loads. A preliminary study reported that fine manual dexterity and upper limb strength were improved in ET patients after an RT program [14]. The findings of this preliminary study provided initial evidence that RT is worthy of further investigation as a therapy for improving functionality in ET patients.
A recent study investigated whether a generalized upper limb RT program improves manual dexterity and reduces force tremor in older individuals with ET [15]. Ten ET patients and 9 controls were recruited to participate in a 6-week program of upper-limb RT. A battery of manual dexterity and isometric force tremor assessments were performed before and after the RT to determine the benefits of the program. The 6-week, high-load, RT program produced strength increases in each limb for the ET and healthy older group. These changes in strength were associated with improvements in manual dexterity and tremor, particularly in the ET group. The least affected limb and the most affected limb exhibited similar improvements in functional assessments of manual dexterity, whereas reductions in force tremor amplitude following the RT program were restricted to the most affected limb of the ET group. These findings suggest that a generalized upper limb RT program has the potential to improve aspects of manual dexterity and reduce force tremor in older ET patients.
Inertial Loading
Inertial loading has been postulated to have an effect on the strength of motor unit training and the synergistic/competitive interaction between central and mechanical reflex tremor components in individuals with ET. A research study recruited 23 patients with ET and 22 controls and first defined the one-repetition maximum (1-RM) load, which is the maximal load that can be successfully lifted (wrist extensors) through the full range of motion [16]. Subsequently, the participants were asked to hold their hand in an outstretched position while supporting sub-maximal loads (no-load, 5, 15, and 25 % of 1-RM). Hand postural tremor and wrist extensor neuromuscular activity (electromyography [EMG]) were recorded. Results showed that inertial loading resulted in a reduction in postural tremor in all ET patients. The largest reduction in tremor amplitude occurred at between 5 and 15 % loads, which were associated with spectral separation of the mechanical reflex and central tremor components in a large number of ET subjects. Despite an increase in overall neuromuscular activity with inertial loading, EMG tremor spectral power did not increase with loading. The authors concluded that the effect of inertial loading on postural tremor amplitude appears to be mediated in large part by its effect on the interaction between the mechanical reflex and central tremor components.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
