Essential tremor (ET) is a neurological disease that causes a hand or arm to shake during activities such as writing or eating. The tremor can also progress to involve the neck, voice, jaw, or other body regions.
This article explores recent research on the neurological and genetic causes of ET.
What is an Essential Tremor?
The first noticeable symptom often with essential tremor is that writing or fine hand movements, such as when texting, are difficult due to shaking. For others, it may be first noticed when eating or pouring a drink into a glass. Essential tremor usually starts in the hand and arm, but sometimes it is first seen as an involuntary head movement or voice tremor.
While this article explains the neurological causes of essential tremors, keep in mind that for people with ET there are often huge emotional impacts from the disease. It causes anxiety, frustration, and decreased self-esteem for many, especially when it starts at a young age.
Symptoms of Essential Tremor:
An essential tremor usually starts as mild and barely noticeable, but it usually worsens over time. Estimates range from 2-5% worsening of tremors per year. Additionally, as the years progress, the tremor can spread to other body regions, including motor features and cognitive problems.[ref]
For most people, essential tremor begins with the hand or arm on one side of the body. It is usually noticed when using the hand, such as in eating, writing, lifting lightweight objects, or tying shoelaces. It can gradually progress to other parts of the body, such as a tremor in the voice or an involuntary head nodding.
ET is different from the tremor seen in Parkinson’s disease, which occurs when hands are at rest instead of in use. Plus, ET doesn’t affect walking or other movement issues also seen in Parkinson’s.
Causes:
Tremors are caused by rhythmic, oscillatory movement of a body part at a constant frequency. The antagonistic muscles — think push then pull — are alternating contractions at a constant rate. It is a neurological disorder driven by changes in the neurons in the brain region that controls muscle movement.[ref]
Essential tremor (ET) has been studied for decades, but there are still elements of the cause that are not fully known.
Here’s what current research shows:
Neuroimaging studies show changes to the cerebellum (brain region) in people with ET.[ref]
Some studies show that Purkinje cells are affected. Purkinje cells are large neurons in a specific layer of the cerebellum. They are important in movement and controlling excitatory neurons.[ref]
Excess Activation: A 2020 study published in Science combined animal models, clinical data, and brain tissue from autopsies to examine what is going on in the brain with ET. The researchers found that people with ET have excessive brain wave oscillations in the cerebellum.
The 2020 study showed that patients with ET likely have excess synapses in between climbing fibers (a type of nerve cell) and the Purkinje cells in the cerebellum. Normally, excess synapses get pruned away as the brain develops into adulthood. But for ET patients, the excess synapses remain, which results in too many neuronal connections and overactivation. One specific protein – glutamate receptor delta 2 (GRID2 protein) – may hold the key (at least it seems to in mice).[ref][article]
GABA is an inhibitory neurotransmitter that ‘turns off’ neurons to keep them from firing excessively. A postmortem study on people who had essential tremor showed a decreased number of GABA-A and GABA-B receptors in a specific region of the cerebellum.[ref]
Lack of inhibition combined with excess synapses — all come together to show excess activation in the part of the brain that controls muscle movement.
What causes the changes in the brain?
So we have excess activity in the brain, causing oscillations in movement. But what triggers ET to occur?
Both genetic and environmental factors are thought to contribute to ET. Twin studies show that the genetic component is about 50-60%, which leaves a large portion due to environmental factors such as toxic exposure.[ref]
Toxic exposure: Several studies point to environmental factors that contribute to ET. Exposure to lead, harmane, pesticides, and organic solvents.[ref]
- Harmane is a β-carboline alkaloid found in animal foods. Grilling or frying increases the concentration of β-carboline alkaloids in meat. β-carboline alkaloids are also found in tobacco, alcohol, soy sauce, tabasco, toasted bread, and coffee.[ref] Harmane levels are elevated in ET patients compared to a healthy control group.[ref][ref][ref]
- Lead has been shown in animal studies to damage Purkinje cells in the brain. And a study of ET patients found that blood lead levels were high when compared to an age-matched control group.[ref]
- Pesticide exposure, especially long-term, is linked to higher odds of having an essential tremor. The study showed a more than 4-fold increase in risk for workers exposed to pesticides for 16 years or more.[ref]
- Heavy metal exposure, including mercury, manganese, and lead, are neurotoxic and linked to tremors.[ref]
These environmental toxins increase oxidative stress and thus may lead to neuronal dysfunction in the cerebellum.[ref]
Essential Tremor Genotype Report:
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Lifehacks for Essential Tremor:
Talk with your doctor, first: If you notice a tremor, a doctor can help you rule out other pathologies (Parkinson’s, dystonia, dementia, etc.) and determine if you have ET.
Treatments and Medications (Prescriptions):
Your doctor can also help figure out if a tremor is due to side effects from a medication. Medications or drugs that have tremors as side effects include:[ref]
- Cytostatics (vincristine, cisplatin, paclitaxel, doxorubicin, cytosine-arabinoside, ifosfamide, 5-fluorouracil, methotrexate)
- Immunomodulators (ciclosporin, tacrolimus, interferons)
- Anticonvulsant drugs (valproate, carbamazepine, phenytoin, lamotrigine)
- Dopamine receptor blockers/medications depleting dopamine (neuroleptics, metoclopramide, tetrabenazine)
- Antidepressants (tricyclic antidepressants and selective serotonin/norepinephrine reuptake inhibitor, lithium)
- Antiarrhythmics (amiodarone, mexiletine, procainamide)
- Calcium antagonists (nifedipine, amlodipine)
- Hormones (thyroxine, calcitonin, progesterone, corticosteroids)
- Sympathomimetics (bronchodilators, β2-agonists)
- Phosphodiesterase inhibitors (theophylline, aminophylline caffeine)
- amphetamine
- nicotine
- psilocybin
- cocaine
- alcohol withdrawal
If you suspect you have ET, there are prescription medications that your doctor may want you to try, such as propranolol (beta-blocker) or primidone (anticonvulsant). Topiramate (antiepileptic) is another medication sometimes used with ET.[ref][ref]
Botox injections in the wrist are also sometimes recommended. Clinical trials show that it improves tremors for about half the patients, but it can also cause weakness in the wrist and reduced grip strength.[ref]
Cala Trio:
This wrist-worn device (it looks like a watch) is marketed to stop essential tremor. It is prescription only, so talk with your doctor about it. https://calatrio.com/
TENS / Electrical Stimulation:
Applying electrical stimulation to a muscle causes it to contract, so it makes sense that the right frequency of stimulation could affect and perhaps improve a tremor.
An analysis of studies on electrical nerve stimulation showed that stimulation had been tested both in-phase with the tremor and out-of-phase. TENS and FES (functional electrical stimulation) have been tested on several nerves in the arm, elbow, or wrist. As you can imagine, the results of these clinical trials varied widely, with some showing positive results and others showing no effect (or worsening).[ref]
Overall, electrical stimulation seems to have a positive effect when applied appropriately. This type of therapy may be something to work on with a good practitioner who knows what they are doing. Expect to experiment a bit with different frequencies and nerve placements.
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