Most patients will report tremor that starts from one upper extremity and then affects the other. It is almost always limited to the upper extremities. Tremor is initially intermittent but overtime becomes persistent. The amplitude is worsened by hunger, emotion, fatigue and extremes of temperature. Tremors may also involve the head and face. The tremor is noticed to resolve during sleep and ethanol intake may temporarily reduce its amplitude in up to 70% of cases. There is a family history of tremor in up to 60% of cases. When a tremor is visible, it should be considered pathologic [6]. During physical examination, features of Parkinson disease like rigidity and bradykinesia should be ruled out.

• Movement Disorder

  William Ondo, Overview of the Medical Treatments of Hyperkinetic Disorders, Hyperkinetic Movement Disorders, (40-48), (2012). Julián Benito‐León and Elan D. Louis, Essential Tremor, Hyperkinetic Movement Disorders, (71-94), (2012). [doi.org]

  Electronic address: [email protected]. 10 Movement Disorder Group, Columbia University Medical Center, 710 West 168th Street, 3rd Floor, #350, New York, NY 10032, United States. [ncbi.nlm.nih.gov]

• Disability

  […] tremor severity or disability. [ncbi.nlm.nih.gov]

  No tremor related disability was present before the age of ten. However, 55% of young people with ET had disability and 25% reported social handicap by the age of 20 years old. [tremor.org.uk]

• Surgical Procedure

  Surgical procedures, such as deep brain stimulation of the ventral intermediate nucleus of the thalamus, offer treatment for refractory tremor. The epidemiology, pathogenesis, and medical and surgical treatment of ET will be discussed in this paper. [ncbi.nlm.nih.gov]

  These include drug therapies and surgical procedures. [bestpractice.bmj.com]

  Patients who fail to respond to medication may be treated with surgical procedures such as Deep Brain Stimulation (DBS) or thalamotomy. [insightec.com]

  Surgery If medicine treatment is not effective and the tremor is severe, a surgical procedure may be an option. There are two main surgical procedures that may be considered - thalamotomy and thalamic deep brain stimulation. [patient.info]

• Chills

  Photo Credit Dolly Faibyshev for The New York Times Work Out and Chill? Cool temperature workouts may be the answer for those who want to exercise without becoming a hot mess. [nytimes.com]

  An elastic diaphragm was attached to the scalp and connected to the ultrasound transducer so that it could be filled with chilled, degassed water. Patients were then transferred into the bore of the magnet for the treatment. [nejm.org]

• Suggestibility

  This finding supports the presence of cortical or transcortical motor loops that are likely involved in essential tremor and suggests a possible link with the cerebellar-thalamic-cortical pathway. [ncbi.nlm.nih.gov]

• Tremor

  Tremor-Dominant Parkinson's Disease (PD) Initially, patients with tremor-dominant Parkinson’s disease (PD) demonstrate tremor with relatively mild bradykinesia and rigidity. [insightec.com]

  tremor Saturnine tremor Static tremor Toxic tremor Tremor due to orthostatic hypotension Tremor of palate Tremor opiophagorum Tremor, drug or toxin induced Tremor, due to orthostatic hypotension Tremor, dystonic Tremor, dystonic tremor Tremor, essential [icd9data.com]

  About 20% of patients with essential tremor also have resting tremor, but the resting tremor is often milder than the postural and kinetic tremors. [doi.org]

  Vocal tremor is often worsened by head tremor, and reduction in head tremor may also improve the voice. [movementdisorderscenter.org]

  Tremor improvement was sustained at last follow-up in 96% of patients who experience tremor relief. [ncbi.nlm.nih.gov]

• Dystonia

  The severity of the dystonia and the presence of more generalized dystonia may alter the thinking about optimal targeting. [ncbi.nlm.nih.gov]

  Dystonia is manifested an involuntary sustained contraction of muscles producing abnormal movements or postures. Examples of dystonia include writer's cramp, torticollis or wry neck (cervical dystonia), and involuntary eye closure (blepharospasm ). [bcm.edu]

  G24.09 Other drug induced dystonia G24.1 Genetic torsion dystonia G24.2 Idiopathic nonfamilial dystonia G24.3 Spasmodic torticollis G24.4 Idiopathic orofacial dystonia G24.9 Dystonia, unspecified G25 Other extrapyramidal and movement disorders G25.0 [icd10data.com]

• Action Tremor

  A 64-year-old female with essential tremor (ET) presents for evaluation of deep brain stimulation (DBS) candidacy. Examination revealed subtle dystonic features as well as a disabling postural-action tremor. [ncbi.nlm.nih.gov]

  See Tremor. es·sen·tial trem·or ( ĕ-sen'shăl trem'ŏr ) An action tremor of 4-8 Hz frequency that usually begins in early adult life and is limited to the upper limbs and head; called familial when it appears in several family members. essential tremor [medical-dictionary.thefreedictionary.com]

  Action tremor refers to tremor occurring with voluntary muscle contraction and is subdivided into postural tremor, isometric tremor and kinetic tremor. [movementdisorders.org]

• Irritability

  Effects of essential tremor on quality of life Uncontrollable shaking can reduce a person’s quality of life in many ways, including: difficulties with everyday activities, such as writing, getting dressed or eating irritation and stress caused by the [betterhealth.vic.gov.au]

• There are no laboratory investigations to diagnose essential tremors. Laboratory studies are only considered if the history and physical examination are not indicative of essential tremor. Some of these laboratory studies are: Serum electrolytes, blood urea nitrogen, serum creatinine, thyroid function test, and liver function tests. These tests will help to identify other cause of tremors. Serum ceruloplasmin should also be done to rule out Wilson disease [7]. 
• Electromyography can be used to assess frequency, amplitude and rhythmicity. Accelerometry can also be used.
• Computed tomography and magnetic resonance imaging are normal in patient with essential tremor. However these imaging techniques are done to rule out structural and/or inflammatory lesions of the brain [8]. 

• Gliosis

  The minimal foreign body reaction and gliosis around the electrodes 12 years after implantation supports the long-term safety of DBS. [ncbi.nlm.nih.gov]

• Lymphocytic Infiltrate

  Lymphocytic infiltration was seen by L26 immunoreactivity with CD3 (T cells) staining predominating over CD20 (B cells). Cerebellar axonal spheroids and Purkinje cell loss were found. [ncbi.nlm.nih.gov]

• The initial management of essential tremor is medical. Propranolol and primidone are the bases of maintenance medical management of this condition. Usually, propranolol is started first in younger patients while primidone is started first in older patients [9]. 
• These drugs generally reduce tremor amplitude in 70% of cases. Some other medications that may be tried if these are unsuccessful are beta-1 receptor antagonist, beta-2 receptor antagonist and clonazepam. Others are Botulinum toxin, topiramate, gabapentin, clozapine and mirtazapine. Alcohol may be used in patients who only require intermittent tremor reduction [10].
• Patients with disabling, medically intractable upper extremity tremors should be considered for surgery. Surgical procedures that can be performed include thalamic ventralis intermedius nucleus deep brain stimulation and stereotactic thalamotomy. Both of these procedures offer a high rate of tremor reduction in the contralateral arm as well as reducing head and voice tremor. Thalamic stimulation is however now being considered the procedure of choice as it has the advantage of being adjustable.
• There is a very high risk of dysarthria and cerebral hemorrhage in bilateral thalamotomy. 

The mortality rate in essential tremor is basically the same as that for the general population. There is however disability from essential tremor with up to 15% of affected individuals being seriously disabled. There is a generally a decreased quality of life primarily due to loss of function.

The cause of essential tremor is still unknown. In absence of any consistently associated pathologic findings, some hypothesis have been promulgated. One of such is the possible involvement of the cerebellar-brainstem-thalamic-cortical circuits. Another is that it is as a result of an abnormally functioning central oscillator that is involves the inferior olivary nucleus. A third hypothesis is that the pathophysiology of essential tremors is diverse.

Some of the factors that have been linked to its etiology include a potent tremor-producing neurotoxin called Harmane and increased glucose consumption in the medulla. There are also multiple etiologies that have been linked with genetics [2].

The prevalence of essential tremor is about 5.6% of the general United States population, and only about 11% of those affected seek medical attention. The prevalence in the internal community is about 3.9%. It has a bimodal peak age of occurrence, in late adolescence/early adulthood and in the older age group and the mean age of occurrence is between 35 to 45 years. It usually manifests by age 65 years and the amplitude of the tremor increases over time. The race demographic has not been well studied but there appears to be a higher prevalence in Caucasians than in African-Americans. It occurs with equal frequency in both sexes [3].

• The pathophysiology, like the etiology is multifactorial with many of the causes likely to be genetic. Transmission may be autosomal-dominant with incomplete penetrance. Some susceptibility loci have been identified [4]. 
• There are other proposed methods of pathogenesis.
• There is increased blood concentration of harmane in the blood of affected individuals and this is likely due to metabolic alterations. PET scans have also showed bilateral overactivity of cerebellar circuitry and increased regional blood flow in the medulla of individuals with essential tremor.
• Findings during autopsy like loss of Purkinje cells, dentate nucleus abnormalities, and lewy bodies in the locus ceruleus are pathologic abnormalities of the brain stem that support the hypothesis that essential tremor is a neurodegenerative disease [5].

There is no known way to prevent this condition. Small quantities of alcohol have been shown to reduce tremors. The potential for abuse should however be considered.

Essential tremors are also known as kinetic tremor as they intensify when the muscle groups are put in play [1].  It is the most common movement disorder and it usually affects both upper extremities. The etiology is unknown but there is a debate as to whether or not it is a neurodegenerative disease.

• Definition: Essential tremor is a movement disorder characterized by involuntary movement of some muscle groups. It typically affects the upper arms and sometimes the face and head. No underlying disease is usually found to be responsible for these movements.
• Cause: The cause is unknown. It is however believed to have some familial links as genes can be passed from parents to offspring. It may also be due to abnormal functioning of the part of the brain responsible for movement. 
• Symptoms: The main symptom is tremor and it is sometimes the only symptom. It is most likely going to start from one hand and then extend to the other. There may also be head nodding and quivering of the voice due to the effect of the tremors.
• Diagnosis: This is usually gotten from the history and physical examination. Laboratory tests will be ordered to rule out other causes of tremors, if no cause it found, it is essential tremor. Imaging tests like MRI will also be done to rule out brain disease. Some test may be required to check the intensity of the tremor.
• Treatment: Treatment involves the use of drugs to control the tremors. If the drugs fail, some surgical techniques may be employed.

1. Elias WJ, Shah BB. Tremor. JAMA 2014; 311:948.
2. Louis ED. Treatment of Essential Tremor: Are there Issues We are Overlooking?. Front Neurol. 2011;2:91.
3. Louis ED, Barnes LF, Ford B, Pullman SL, Yu Q. Ethnic differences in essential tremor. Arch Neurol. May 2000;57(5):723-7
4. Busenbark KL, Nash J, Nash S, et al. Is essential tremor benign? Neurology 1991; 41:1982.
5. Ross GW, Dickson D, Cersosimo M. Pathological investigation of essential tremor. Neurology. Apr 2004;62(7) S5:A537-A538.
6. Tan EK, Lum SY, Prakash KM. Clinical features of childhood onset essential tremor. Eur J Neurol. Dec 2006;13(12):1302-5
7. Jankovic J, Fahn S. Physiologic and pathologic tremors. Diagnosis, mechanism, and management. Ann Intern Med 1980; 93:460.
8. Nicoletti G, Manners D, Novellino F, et al. Diffusion tensor MRI changes in cerebellar structures of patients with familial essential tremor. Neurology 2010; 74:988.
9. O'Brien MD, Upton AR, Toseland PA. Benign familial tremor treated with primidone. Br Med J (Clin Res Ed). Jan 17 1981;282(6259):178-80.
10. Pahwa R, Busenbark K, Swanson-Hyland EF, et al. Botulinum toxin treatment of essential head tremor. Neurology 1995; 45:822.