Essential Tremor
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Name and student number
Kathryn Kacperek – z3376276

The Media Item
http://www.youtube.com/watch?feature=player_embedded&v=RjSFuxrsgW8#!

Table of Contents
1. Introduction
2. Neurological Context
2.1 What is Essential Tremor?
2.2 Causes of ET.
2.3 Pathophysiology
2.4 Treatment options for ET.
2.41 Medications
2.4.2 Deep brain stimulation
2.4.3 Gamma Knife radiosurgery
3. References

1. Introduction
Posted by Swedish on the 3rd of August 2012, the chosen multimedia item is an informational YouTube video, describing the progressive neurological condition known as Essential Tremor (ET). It also explains, in more detail, one of the three main treatment options (gamma knife radiosurgery).
The study of ET is fairly important. As described in the video above, Essential Tremor is actually the most common movement disorder – more common, in fact, that Parkinson’s disease. While it is not life-threatening, the uncontrollable shaking of a person’s hands, head, arms, voice, tongue and even trunk, may be embarrassing and cause problems with daily activities such as writing, eating and drinking, potentially reducing a patients’ quality of life.
As a sufferer of a mild form of the condition, this media idem is of particular interest to me. Further researching this topic and gaining a better understanding of different treatment options is something that may be very beneficial.

2. Neurological Context
2.1 What is Essential Tremor?
As outlined above, ET is a common neurotically disorder, prevalence 0.4-3.9%, (E. D. Louis et al. 1998). It is characterised by the involuntary and rhythmic trembling of particular parts of the body, but typically the upper extremities such as the hands and arms. Unlike Parkinson’s disease, in which a tremor is most pronounced when a limb is at rest, ET involves kinetic tremors, i.e. those occurring during voluntary movement, or postural tremors, i.e. those occurring when maintaining a position against gravity.
The condition is often progressive (E. D. Louis et al. 2003), increasing in severity and spreading to other parts of the body, although this process is usually quite slow.

2.2 Causes of ET
ET is generally considered a to be largely a genetic disorder (W. J. Weiner, 2011), however recent studies such as those of Louis et al 2008, have been able to show that high concentrations of certain neurotoxins, namely harmane (a potent b-caroline alkaloid) and lead, correlatewith higher tremor severity, suggesting that environmental impact may be playing a large role as well.

2.3 Pathophysiology
While the underlying mechanism behind ET is still unknown studies suggest the presence of cerebellar dysfunction and have shown the existence of microscopic changes in the cellebellum of most ET cases (J.E. Axelrad et al, 2008). This is characterized by cerebellar degenerative changes such as a reduction of Purkinje cells, dendrite swelling and an increase in the number of proximal swellings of the Purkinje cell axons (torpedoes). Brains of these patients have no Lewy bodies (abnormal collections of protein that develop inside nerve cells), (Weiner 2011).
Studies such as that performed by Axelrad et al, 2008, have also shown the existence of a second type of ET, one in which Lewy bodies are present, mainly in the locus ceruleus, and very few torpedoes are found.
This may suggest that ET is actually a family of diseases, rather a single disease entity.

2.4 Treatment options for ET

2.4.1 Medications
This is usually the first cause of actions taken in the treatment of ET. Only when medications are become ineffective or do not work to begin with, are the other options really considered.

Propranolol (Inderal):
In many cases this beta-blocker is fairly effective, usually decreasing tremor amplitude, although not frequency. It works by blocking B-adrenergic receptors in the heart and other smooth muscles and is usually used as a method of controlling blood pressure. Propranolol has side effect such as dizziness, fatigue, vomiting and diarrhoea and must not be taken by people who suffer from asthma, certain heart problems and poorly controlled diabetes.

Primidone (Mysoline):
Primidone is a drug commonly used in suffers of certain kinds of epilepsy as it helps control seizure activity. It works by slowing the central nervous system and is a good option for patients with ET, with its side-effect usually minimal and infrequent. Primidone should be taken with meals.

In some cases Propranolol and Primidone are taken in combination and a variety of second-line drug therapies such as Nadolol, Methazolamide, Topiramate or Botox are occasionally used.


2.4.2 Deep brain stimulation

This is an invasive surgical approach to treatment and should only be undertaken where the condition has disabling effects and when medicated treatments have been tried and are not satisfactory. During the surgery, electrodes are implanted into certain areas of the brain which will then deliver electrical stimulation to the thalamus, blocking signals that cause tremors. Patients are able to turn the electrical stimulation on and off and the genitor will need to be replaced every 3-5 years, resulting in further surgeries.

2.4.3 Gamma Knife radiosurgery

Gamma knife radiosurgery is a safe procure that involves non-invasive surgery, in which highly focused gamma radiation beams are used to target the ventral intermediate nucleus, largely reducing tremors in most patients and in some cases, stopping them completely. The results from gamma knife radiosugery are comparably favourable to those of deep brain stimulation, in relation to the rate of tremor relief and the complications. This option is of particular importance to those patients who have disabling tremors and are not candidates for the surgery alternative.

3. References


Axelrad, J. E., Louis, E. D., Honig, L. S., Flores I., Ross, W., Pahwa, R., . . .Vonsattel, J. P. G. (2008). Reduced Purkinje Cell Number in Essential TremorA Postmortem Study. Arch Neurol,65(1),101-107

Louis, E. D. (2011). Essential tremor. Handbook of Clinical Neurology, 100(3), 434-448.

Louis, E. D., Factor-Litvak, P., Gerbin, M., Slavkovich, V., Graziano, J. H., Jiang, W., Zheng,W. (2011). Blood harmane, blood lead, and severity of hand tremor: Evidence of additive effects. NeuroToxicology, 32(2), 227-232.

Louis, E. D., Ford, B., Wendt, K. J., Cameron, G, (1998). Clinical Characteristics of Essential Tremor: Data From a Community Based Study. Movement Dirorders, 13(5), 803-808.

Young, R.F., Li, F., Vermeulen, S., Meier, R. (2010). Gamma Knife thalamotomy for treatment of essential tremor: long-term results. J Neurosurg, 112(6),1311-1317.

Essential Tremor. (2011). Wemove worldwide education and awareness for movement disorders. Retrieved October 2, 2012 from www.wemove.org/et/et_pt.html

Fung, V. (n.d). Essential Tremor, Brain Foundation. Retrieved October 2, 2012 from www. brainfoundation.org.au

NINDS Essential Tremor Information Page. (2011). Retrieved October 2, 2012 from
www.ninds.nih.gov/disorders/essential_tremor/essential_tremor.htm

Richard Senelick. (2012). Essential Tremor and Deep Brain Stimulation. WebMD. Retrieved October 2, 2012 from www.webmd.com/brain/essential-tremor-brain-stimulation