Essential tremor (ET) is a common neurological disorder characterized by involuntary shaking. While many people might develop ET without a clear cause, a significant portion experience what’s known as familial tremor. This form of tremor is passed down through families, highlighting a genetic component in its development. Understanding the causes of familial tremor is crucial for those with a family history of this condition and for researchers working towards better treatments.
What is Familial Tremor?
Familial tremor is essentially essential tremor that runs in families. It’s not a separate disease but rather a subtype of ET where genetics play a significant role. If you have essential tremor and at least one close relative also has tremors, you are likely experiencing familial tremor. This hereditary aspect distinguishes it from sporadic ET, where no clear genetic link is identified.
Genetic Causes of Familial Tremor
The primary cause of familial tremor is genetic. Research suggests that about half of all essential tremor cases are familial, meaning they are inherited. The most common pattern of inheritance is autosomal dominant.
Autosomal Dominant Inheritance Explained
In autosomal dominant inheritance, only one copy of an altered gene from one parent is needed to cause the condition. If a parent has familial tremor due to this genetic alteration, there is a 50% chance that each of their children will inherit the gene and potentially develop tremors. This explains why familial tremor often appears across multiple generations within a family.
While the autosomal dominant inheritance pattern is well-established, the specific genes responsible for familial tremor are still being researched. Scientists believe that multiple genes may be involved, and the exact genetic mutations can vary between families. Ongoing research is focused on identifying these genes to better understand the mechanisms behind familial tremor and potentially develop targeted therapies.
Risk Factors for Familial Tremor
The most significant risk factor for familial tremor is having a family history of the condition.
- Family History and Genetics: As mentioned, if you have a parent with familial tremor, you have a 50% chance of inheriting the altered gene. This genetic predisposition is the strongest risk factor.
- Age: While familial tremor is caused by genetics, the symptoms often manifest later in life. Essential tremor, including the familial type, is more common in individuals aged 40 and older. Therefore, even with the genetic predisposition, symptoms might not appear until later adulthood.
It’s important to note that while genetics plays a crucial role in familial tremor, not everyone who inherits the gene will necessarily develop significant tremors. The severity and onset of symptoms can vary, even within the same family.
Symptoms of Familial Tremor
The symptoms of familial tremor are largely the same as those of essential tremor in general. The key differentiator is the family history, not a distinct set of symptoms. Common symptoms include:
- Action Tremor: Tremors primarily occur when you are moving or attempting to move. This is in contrast to resting tremors seen in Parkinson’s disease.
- Hand Tremors: Hands are most commonly affected, often in both hands, and worsen during activities like writing, eating, or drinking.
- Head Tremors: The head can also be affected, sometimes manifesting as a “yes-yes” or “no-no” motion.
- Voice Tremor: In some cases, the voice can become shaky or tremulous.
- Aggravating Factors: Stress, fatigue, caffeine, and temperature extremes can worsen tremor symptoms.
It’s crucial to remember that the presence of these symptoms along with a family history of tremor strongly suggests familial tremor.
Familial Tremor vs. Other Tremors
Distinguishing familial tremor from other tremor types, especially sporadic essential tremor and Parkinson’s disease tremor, is important for accurate diagnosis and management.
- Familial Tremor vs. Sporadic Essential Tremor: Both present with similar symptoms. The primary difference is the presence of a family history in familial tremor. Sporadic ET occurs in individuals without a known family history of the condition. The underlying causes of sporadic ET are less clear and may involve a combination of genetic and environmental factors, or de novo genetic mutations.
- Familial Tremor vs. Parkinson’s Disease Tremor: While both involve tremors, they differ in several key aspects:
- Timing: Familial tremor is typically an action tremor, while Parkinson’s tremor is often a resting tremor, most noticeable when the hands are at rest.
- Associated Symptoms: Parkinson’s disease is associated with other symptoms like slow movement (bradykinesia), rigidity, and postural instability, which are not characteristic of essential tremor. Familial tremor is primarily characterized by tremor, although some individuals may develop mild balance issues later in life.
Diagnosis and Management
Diagnosing familial tremor involves a neurological examination, assessment of symptoms, and a detailed family history. Genetic testing is not routinely used for diagnosis but may be considered in research settings or in complex cases.
Management of familial tremor focuses on alleviating symptoms, as there is currently no cure. Treatment options include:
- Medications: Beta-blockers (like propranolol) and anti-seizure medications (like primidone) are commonly prescribed to reduce tremor severity.
- Lifestyle Modifications: Avoiding caffeine and managing stress can help minimize tremor symptoms.
- Physical and Occupational Therapy: These therapies can help individuals adapt to living with tremors and improve daily functioning.
- Surgical Options: In severe cases that are unresponsive to medication, surgical procedures like deep brain stimulation (DBS) or focused ultrasound thalamotomy may be considered.
Conclusion
Familial tremor, a hereditary form of essential tremor, is primarily caused by genetic factors, most notably autosomal dominant inheritance. Understanding the genetic basis and risk factors associated with familial tremor is essential for individuals with a family history of tremors. While there is no cure, various treatment options are available to manage symptoms and improve the quality of life for those affected. Ongoing research into the specific genes involved in familial tremor holds promise for developing more targeted and effective therapies in the future.
Essential tremor care at Mayo Clinic
March 29, 2023
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