Essential tremor (ET) is a common movement disorder in which a high frequency (typically 5-6 hz) tremor occurs in the hands, variably accompanied by a head and/or vocal tremor. It affects 5% of those aged 65 or over. The tremor ordinarily is abolished by ingestion of alcohol, and is increased by nervousness and medications or situations (e.g. stress) that increase adrenalin levels. ET often runs in families, and is generally not associated with brain lesions. ET may not be a single entity. (Hopfner and Deuschl, 2018)
Unsteadiness is not a prominent part of the essential tremor picture, but occasionally it can accompany the tremor. The tremor can often be documented and partially quantified by having the patient draw a spiral. As this is easily simulated, it is obviously not entirely objective.
Tremulous spiral (from Frucht, 2018).
Essential tremor is a control system problem, and is a type of oscillation, that is enabled by activation of a muscle. Generally speaking, in systems, oscillation is caused by feedback loops that have delays or are too high gain. Presumably the gain here is increased by activation of the muscles, and the delay is intrinsic. Oscillations in electrical systems can sometimes be eliminated by compensation techniques. The cerebellum would be a likely site for damage to a compensation system in ET.
Essential tremor is generally easily distinguished from the common tremor of Parkinsonism, which is slower and present at rest. Essential tremor generally affects the hands, sometimes also the head and voice. It is not present at rest -- when the hands are simply on the knees (for example), there should be no tremor. The tremor is typically seen with the arms extended.
Other postural tremors include psychogenic tremor, cerebellar tremor, dystonic tremor, and task specific tremors.
The head tremor is usually a "yes-no" tremor -- that is, the head pitches forward and backward, about 2 times/second.
The voice tremor manifests itself as a "quavery" voice. Sometimes there are other types of voice problems too -- straining or hoarseness. It can be seen with video-stroboscopy.
Essential tremor is often seen in older people, who are also commonly affected by imbalance. There is probably also an added risk to balance from essential tremor (Singer et al, 1994). As many of the medications below also have unsteadiness as a side effect (e.g. klonopin, gabapentin), there can sometimes be confusion as to whether a drug is helping or hurting.
The good news is that ET is very treatable.
Major medications for essential tremor Drug Initial Dose Typical Dose Side effects Primidone 12.5-25 mg/day at bedtime 50-750 mg/day at bedtime or in 2 divided doses. The main breakdown product is phenobarbital (a barbituate). Sedation, confusion, unsteadiness are all side effects. Klonopin 0.5 mg in AM 0.5 mg Addiction, sleepiness Propranolol 20-60 mg/day, typically as extended release 120 mg/day as extended release Bradycardia, erectile dysfunction, low blood pressure gabapentin 300-900/day, in divided doses 1200 mg/day dizziness, weight gain, sedation Levetiracetam 250 mg at night 500 mg/day Drowsiness, sometimes mood alteration including anger topiramate 25-50 mg/day at bedtime 50-100 mg/day Glaucoma, word finding problems, nausea, confusion, tingling in hands and feet zonisamide 25 mg/day at bedtime 50-100 mg/day Similar to topiramate.
This table was extensively modified from Frucht, 2018.
Beta blockers (such as propranolol), benzodiazepines (such as klonopin), and a very low dose of primidone (50 mg) are all commonly used in treatment.
A small amount of propranolol (such as 20 mg) is sometimes used by public speakers with this tremor. It is taken about 30 minutes prior to the stressful event. Beta-blockers reduce the effects of adrenalin, and may also block muscle spindles. A common dose of propranolol for essential tremor is 60 mg/day.
Benzodiazepines (i.e. drugs resembling Valium including klonazepam and alprazolam) and primidone increase the effects of GABA (an inhibitory neurotransmitter). Thus the two main types of treatments are somewhat independent. Benzodiazepines are very addictive, and their use needs to be with great caution. Primidone is somewhat effective (Findley et al, 1985). It breaks down into the barbituate phenobarbital, but according to Sasso et al (1991), phenobarbital does not affect hand tremor. We find this inference suspicious and think that phenobarbital is likely the active ingrediant.
Topiramate, a seizure medication, has also been reported to improve ET (Ondo et al, 2006). Unfortunately, the effect was small and very close to the effect of placebo. We see no reasonable role for topiramate in the treatment of ET.
Gabapentin, nimodipine and pregabalin are also occasionally used. We have never seen a successful treatment with these drugs in our patients.
Of course, one should avoid ingesting substances that increase anxiety or cause agitation -- caffeine should be avoided as well as decongestants containing pseudoephedrine and related substances. Also drugs that increase or cause tremor such as sodium valproate (a seizure medication), or venlafaxine (an antidepressant) should generally be avoided.
Treatment of tremor with Botulinium toxin can work, but the mechanism is through creating weakness.
ET can be treated with high effectiveness with thalamotomy or deep brain stimulation (Zesiewicz et al, 2005; Zaaroor et al, 2018). Each surgical procedure entails risk of serious complication -- including for example personality changes. Of course, any treatment that involves drilling a hole into the head and putting in electrodes is going to be more dangerous than nearly any other method of dealing with ET.
We have encountered patients who can turn their tremor on or off, using a small box that controls a stimulator. This treatment seems most appropriate for persons who have very severe and disabling tremor, refractory to medication.