essential tremor (Parkinson’s disease)

A common neurodegenerative disorder of fast, involuntary, and rhythmic movements that primarily affects people older than age 50, although it can start early in midlife (and in rare circumstances, in early adulthood or even adolescence). Other terms for this condition are familial tremor (when it has a hereditary component) and benign essential tremor. The classic symptoms of essential tremor include:

• Intentional tremor (tremor that worsens with reaching or other directed movement)

• Postural tremor (tremor that worsens while holding a non-resting position such as the arms extended)

• Symmetric symptoms (tremors that affect both sides fairly evenly, although tremor may be more pronounced on the dominant side)

• Head involvement that produces a side-to-side motion, as if signaling “no”

• Tremors disappear during sleep

It is sometimes difficult to distinguish between essential tremor and Parkinson’s disease when tremor is the primary symptom. The most significant differentiating factor is whether the tremors are most pronounced during activity or at rest. The tremors of Parkinson’s disease are usually most prominent at rest and tend to diminish or cease with activity. The tremors of essential tremor intensify during activity and diminish at rest. other tremor characteristics further support the diagnosis.

Essential tremor progresses slowly, as symptoms typically emerge over several decades. in some people, symptoms may be present for several months or even a few years and then seem to disappear for several years before reemerging. The longer a person has essential tremor the more severe the symptoms tend to become, although for most people symptoms are not as debilitating as are the symptoms of Parkinson’s disease. When essential tremor is mild enough that it does not interfere with the person’s ability to manage the regular activities of daily living, treatment is not necessary. Propanolol (such as the brand name drug Inderal), a beta-adrenergic (blocker) antagonist medication, relieves symptoms for many people who have moderate tremor. An anticonvulsive medication, primidone, taken alone or in combination with propanolol, is effective for moderate to severe symptoms, though it tends to be sedating. Other anticonvulsants including topiramate (Topa-max), lamotrigine (Lamictal), and possibly gabapentin (Neurontin) may be useful. The antipsychotic clozapine (clozaril) has been found useful in a randomized controlled trial as well as open label trials. The antidepressant mirtazapine (Remeron) has also been reported to help in an open label trial. some people also experience relief from antianxiety medications such as benzodiazepines (diazepam, alprazolam) paroxitine (Paxil), and buspirone (BuSpar). Botulinum toxin injections have been found to be potentially helpful in open label studies, but often with resultant muscle weakness. occasionally essential tremor symptoms do not respond to medications; in that case surgery such as deep brain stimulation (DBS) of the thalamus or thalamotomy may be an option.

Although researchers estimate that essential tremor is about 10 times more common than Parkinson’s disease, they know less about what causes it. unlike Parkinson’s disease, essential tremor appears to involve no neurotransmitter depletion or other detectable change in brain function. However, the same parts of the brain—especially the motor thalamus—appear to be involved in generating tremor activity, as deep brain stimulation or ablation to these areas can end the tremors. About half of people who have essential tremor have a family history of the disease, in which case doctors call the condition familial. in the late 1990s scientists isolated several gene mutations that appear to be present in people who have the familial form. This discovery prompts hope that gene therapy will allow more effective treatment in the future.