What is tremor?
Tremor is defined as an involuntary, rhythmic, and often oscillatory movement of one or more body parts. Tremor can involve the hands, legs, chin, jaw, head, voice, and torso. Tremor can be bilateral or unilateral meaning involving both or one side of the body respectively. Tremor occurs for a variety of reasons. In adults, three common causes of tremor are drug induced tremor, Parkinson disease or other parkinsonian states, and essential tremor. This article discusses the latter.
What is essential tremor?
Essential tremor, or ET for short, is movement disorder characterized by progressively worsening action tremor of the hands that affects men and women nearly equally. It is one of the most prevalent movement disorders with an estimated prevalence of 1% across all age groups. The term essential in the name refers to the absence of an obvious cause for the tremor.
Essential tremor follows a bimodal distribution pattern. That is, the onset of tremor peaks in the third and seventh decade of life. Overall incidence however increases with advancing age. When tremor begins early on in life, it tends to be milder and more slowly progressive. Late onset tremor on the other hand cane be more disruptive and rapidly progressive. Additionally, early onset tremor is more often than not inherited with rates of inheritance as high as 70%.
Essential Tremor diagnosis:
ET is diagnosed primarily on clinical grounds with little need for advanced testing such as MRI imaging. To truly make the diagnosis of ET, a patient must have tremor affecting the bilateral upper extremities for three or more years, with or without involvement of the head, voice, or lower limbs.
Unlike a parkinsonian tremor, ET is primarily an action tremor of the hands with little to no presence at rest that typically interferes with activities of daily living such as writing, dressing, eating, drinking, and grooming. Later in disease stages, 20% of patients develop a resting component and up to 40% develop a tremor of the head and or voice. The tremor can accentuate with fine motor tasks such as inserting a key into a lock making them difficult to perform and disabling patients.
ET can be worsened by excessive caffeine intake, heightened states (such as sadness, anxiety, excitement, anger), certain medications (such as antidepressants, antipsychotics, and antiemetics), and fatigue. One interesting feature of ET which is often used in making the diagnosis is improvement of the tremor after the ingestion of alcoholic beverages. If patients present with this described movement disorder, have a typical family history, and a physical exam that excludes features of other movements disorders such as dystonia or Parkinson disease they are diagnosed with ET.
Essential Tremor treatment:
Decision to start treatment for ET is largely dependent on the degree of disability resulting from the presence of tremor. This includes not only impairment in activities of daily living due to tremor, but societal impact secondary to being seen with a tremor. Other factors to consider include the patient’s medical comorbidities and other prescribed medications. Once the diagnosis is made and treatment other than lifestyle modifications is desired, a tiered approach is typically employed.
First, patients are offered one of the two first line treatments, Propranolol and Primidone. The former should be avoided in the case of comorbid asthma. If not tolerated or not successful at treating symptoms, the two can be combined or the Neurologist may choose to move on to second line agents. These include Topamax, Gabapentin, and Zonisamide (three anti-seizure medications) or Clonazepam (an anxiolytic). These agents can be used in isolation or combination.
Should oral medications fail, a trial of Botox injections in the affected limb can be employed if feasible. Alternatively, an external stimulator worn on the wrist of the most affected limb can be used to suppress tremor with variable results. This device is called Cala Trio.
If all interventions fail, there are now two surgical techniques FDA approved for the treatment of refractory ET. The more ancient technique is Deep Brain Stimulation (DBS). This method consists of delivering electrical stimulation to a target in the motor center of the brain in an effort to suppress tremor. This is accomplished by using an implantable power generator (in the chest) and implantable leads to carry electrical stimulation to the target. This is an invasive surgery that involves opening the skull and surgical complications include bleeding, stroke, and infection of the hardware. Depending on the placement success, this therapy can result in some side effects from the electrical stimulation including tingling, slurred speech, trouble with ambulation, and neck pulling to name a few.
Alternatively, MRI Guided Focused Ultrasound Treatment (MRgFUS) can be used. This technique is non-invasive and involves using MRI guidance to burn the portion of the motor center that is thought to generate tremor using an ultrasound beam. Complete elimination of tremor is often not always possible, therefore, therapy is often aimed at reducing tremor intensity to non-disabling levels while causing as little side effects as possible.
Dr. Oliver Achi, Neurologist, Medical Director of Neurology Services, Iberia Medical Center
Appointments with Dr. Achi: 337.374.7242