Tremor

Tremor is an involuntary, rhythmic oscillation of one or more body parts. The hands, arms, legs or vocal cords can be affected. It is important to note that tremor is only a symptom. The causes of tremor can be very different. That is why a classification is also so difficult *.

Tremors can affect different parts of the body. Accordingly, we then speak of hand tremors, arm tremors, leg tremors or head tremors. Even the vocal cords may be affected. Vocal tremors cause a shaky voice that is sometimes difficult to understand.

The tremors may also only occur in certain situations and be absent in others. A distinction is made here between, among other things, a resting tremor, which occurs during physical relaxation, and an action tremor, which becomes apparent during purposeful movements.

Based on the combination of tremor characteristics and other neurological findings, the physician may combine the tremor into a tremor syndrome. This distinction is very important with regard to further treatment options, since the individual forms of tremor respond very differently to different forms of treatment.

Some forms of tremor respond very well to surgical therapy. In the following, we will discuss these subtypes in more detail:

The treatment of tremors depends largely on the underlying disease. Diagnosis and therapy are carried out by neurologists with experience in the field of movement disorders. The corresponding experts at Inselspital can be found at the Center for Parkinson's Disease and Movement Disorders (ZfPB).

Drug therapy

Drug therapy is the treatment of choice *:

• Essential tremor initially should be treated with primidone or propranolol, a beta-blocker, or a combination of both. Efficacy and side effects limit their use. Topiramate and gabapentin have good success in some patients and should be used as second-line therapy.
• Parkinson's disease tremor usually improves with proper dopaminergic therapy to treat akinesia and rigor. If the tremor remains unchanged, anticholinergics (e.g. biperides), propranolol, or clozapine can be tried.
• There is no established drug therapy for Holmes tremor, and medication treatment for Holmes tremor has rarely been successful. In isolated cases, success of L-dopa, levetirazetam, clonazepam, and clozapine is observed.
• There is also no established drug therapy for dystonic tremor. Medication treatment is based on expert opinion. Trihexyphenidyl, propranolol, lioresal, and clonazepam are suggested.

In cases where medication therapy shows only slight improvement of the tremor or cannot be applied at all due to drug intolerance, the possibility of functional neurosurgical therapy exists.

In general, there are two surgical procedures available for the treatment of tremors:

1. Classic lesioning
2. Novel deep brain stimulation (DBS)

DBS is among the most effective treatments for essential tremor and Parkinson´s disease tremor. It is indicated for those cases of essential tremor and PD tremor that do not respond adequately to drug therapy *, *, *.

The motor thalamus (VIM) and posterior subthalamic area (PSA) are established anatomic targets for successful treatment of essential tremor. In this case, the superiority of DBS over a lesion of the motor thalamus, called thalamotomy, was demonstrated in a randomized trial *.

Although the tremor-suppressing effect of both treatment forms is comparable, both therapeutic methods differ with regard to side effects. Side effects such as speech disorders (dysarthria), gait unsteadiness, sensory disturbances and cognitive impairment are significantly less frequent with DBS and are also reversible in most cases.

The major disadvantage of lesioning is the irreversibility of the treatment – regardless of whether it involves classical procedures with probes for thermocoagulation or modern ultrasound treatments. Since the stimulation intensity can be individually adjusted during deep brain stimulation, optimal settings can be worked out for each patient. As a rule, tremors can be satisfactorily reduced without any limiting side effects.
For these reasons, the importance of thalamotomy has decreased. The treatment of choice at Inselspital is mainly deep brain stimulation. However, thalamotomy is still a good treatment alternative in certain cases *. The choice of therapy (DBS versus thalamotomy) must be carefully considered in each individual case.

More about deep brain stimulation

Generally, the same side effects apply as with all stereotactic functional DBS procedures. Specific risks associated with PSA stimulation for the treatment of tremor may include muscular twitching or cramping, speech disorders, or sensory insensitivity. Speech disorders are the most common side effect. However, these stimulation-induced side effects are usually reversible.