The hummingbird sign refers to a specific hand tremor that can occur in people with Parkinson’s disease. Parkinson’s disease is a progressive neurodegenerative disorder that affects movement and motor control. As Parkinson’s disease progresses, people may develop tremors or trembling in their hands, arms, legs, jaw, and face. The hummingbird tremor is a type of hand tremor that causes the hand to shake back and forth very quickly, resembling the constant fluttering of a hummingbird’s wings.
What causes the hummingbird tremor in Parkinson’s disease?
The hummingbird tremor is caused by the damage and death of neurons in a part of the brain called the substantia nigra. The substantia nigra is responsible for producing dopamine, a chemical messenger that helps control smooth, coordinated muscle movements. In Parkinson’s disease, the loss of dopamine-producing neurons leads to abnormal signaling in the brain and a lack of control over movement.
The underlying cause of the cell death in the substantia nigra is still not fully understood, but likely involves a combination of genetic and environmental factors. Risk factors for developing Parkinson’s disease include older age, family history, and exposure to certain toxins.
As dopamine levels decrease, it leads to the motor symptoms of Parkinson’s disease. The lack of dopamine causes increased excitation of the areas of the brain that control movement. This results in the over-activation of muscles, causing tremors and other Parkinson’s symptoms.
The very rapid, fluttering tremor of the hummingbird sign is due to oscillations in the neural networks that regulate movement as they try to compensate for the dopamine deficiency. The frequencies of the oscillations lead to the characteristic 4-8 Hertz tremor.
What are the characteristics of the hummingbird tremor?
The main characteristics of the hummingbird tremor in Parkinson’s disease include:
- High frequency (4-8 Hz) back-and-forth motion
- Occurs while the hands are at rest
- Affects one or both hands
- Fingers may flex and extend involuntarily
- Thumb may rub against forefingers in “pill-rolling” motion
- Intensity can increase with stress or excitement
- Tremor usually diminishes with intentional movement
The high frequency trembling has been likened to the constant flapping of a hummingbird’s wings, which beat approximately 5 times per second, giving rise to the name “hummingbird sign.” The tremors usually occur at rest and may worsen with stress or strong emotions. Carrying out an intentional movement can temporarily reduce the trembling.
How is the hummingbird tremor different from other Parkinson’s tremors?
There are a few key ways that the hummingbird tremor differs from other tremors that can occur in Parkinson’s disease:
- Frequency – The hummingbird tremor has a very rapid frequency of 4-8 Hz compared to the slower frequencies of other Parkinson’s tremors (3-6 Hz).
- Rest tremor – Hummingbird tremor occurs at rest, while postural or action tremors occur with maintenance of posture or movement.
- Distribution – Hummingbird tremor mainly affects the hands, while other tremors may impact a wider distribution, involving the arms, legs, trunk, jaw or face.
- Medication response – Hummingbird tremor may not respond as robustly to dopaminergic medication compared to other Parkinson’s tremors.
- Progression – The hummingbird tremor tends to emerge later in the Parkinson’s disease course, while other tremors often present earlier.
Identifying key features like the high frequency and rest-specific nature of the trembling can help clinicians recognize the hummingbird sign.
What other symptoms may occur with the hummingbird tremor?
In addition to the hand tremors, people with Parkinson’s disease who experience the hummingbird sign may also have:
- Bradykinesia – Slowness of movement
- Rigidity – Stiffness of the limbs or trunk
- Postural instability – Impaired balance and coordination
- Masked facial expressions – Reduced facial expressiveness
- Micrographia – Small, cramped handwriting
- Foot dystonia – Curling of the toes
- Hypophonia – Quiet, monotonous speech
- Stooped posture – Leaning or tilting of the neck and head
The hummingbird tremor is usually accompanied by bradykinesia and rigidity in the affected limbs. Many people also develop the typical Parkinson’s masked facial appearance and reduced arm swing when walking.
What tests diagnose the hummingbird tremor?
There are no specific tests that diagnose the hummingbird tremor. However, doctors may use various assessments and tools to diagnose Parkinson’s disease and identify the hummingbird sign, including:
- Medical history – Looking for risk factors, description of symptoms, medication history, and more.
- Neurological exam – Assessing motor function, coordination, reflexes, and possible tremors.
- Tremor analysis – Using sensors to measure tremor frequency, amplitude, and variability.
- DATscan – Imaging test assessing dopamine transporter binding.
- Other imaging – MRI or CT scanning to rule out other neurological conditions.
There are no blood or laboratory tests that can diagnose Parkinson’s disease. The diagnosis is based mainly on the clinical examination and the physician’s observation of symptoms.
What causes the hummingbird sign to occur in Parkinson’s disease?
The specific factors that cause some individuals with Parkinson’s disease to develop a hummingbird tremor while others do not are still under investigation. However, researchers believe there are a few contributors that lead to the manifestation of this unique tremor pattern:
- Dopamine deficiency – The degree of dopamine loss differs, leading to variations in symptoms.
- Differences in brain circuits – The topology of each person’s neural networks varies.
- Medications – Some Parkinson’s medications may induce dyskinesia and fast tremors.
- Genetics – There may be gene variants that predispose some people.
- Environment – Toxins or conditions causing more extensive midbrain damage.
Overall, it appears that more severe dopamine deficiency along with an individual’s unique neural wiring lead to the hyper-excitability and synchronized oscillations that generate the high-frequency hummingbird tremor.
What is the treatment for the hummingbird tremor?
Unfortunately, the hummingbird tremor in Parkinson’s disease can be difficult to treat. Standard Parkinson’s medications like carbidopa-levodopa, dopamine agonists, MAO-B inhibitors, and anticholinergics may help reduce other symptoms, but often provide incomplete relief for the hummingbird tremor specifically.
Some treatment approaches that may help manage the hummingbird tremor include:
- Medication adjustments – Finding the right dose, combination, or timing of Parkinson’s medications.
- Deep brain stimulation – Targeting deep brain nuclei that modulate abnormal network activity.
- Occupational therapy – Exercises and adaptive strategies to improve function.
- Physical therapy – Stretching, resistance training, and CBDs to strengthen muscles.
- Limb weighting – Wrist weights or splints to load and stabilize the limb.
- Botulinum toxin – Injections to paralyze overactive muscles temporarily.
Multidisciplinary and individualized treatment plans are often needed to address this difficult-to-treat tremor. Research is ongoing to find better therapies for the hummingbird sign.
What is the prognosis for Parkinson’s patients with hummingbird tremor?
The prognosis for Parkinson’s disease patients with a hummingbird tremor depends on the individual characteristics and response to treatment. However, some general observations indicate that:
- The tremor may be resistant to medication in up to 25% of patients.
- The amplitude of the tremor often worsens over time.
- The tremor frequency tends to remain stable.
- Severe tremors can significantly impact quality of life.
- Functional disability may progress more rapidly.
- Levodopa-induced dyskinesias may develop sooner.
- There is a higher risk of gait impairment and falls.
- Patients may require care facility admission sooner.
While concerning, the hummingbird tremor does not necessarily indicate the overall Parkinson’s disease will progress more quickly. With proper management and therapy, many patients live productive lives for years after the tremor develops. However, increased difficulties with functional activities are common and should be addressed.
Takeaways on the Hummingbird Tremor and Parkinson’s Disease
In summary, key takeaways on the hummingbird tremor in Parkinson’s disease include:
- It is a rest tremor of the hands characterized by a rapid, fluttering motion.
- The 4-8 Hz frequency resembles a hummingbird’s wing beats.
- Caused by dopamine deficiency and excessive excitation of motor pathways.
- Does not robustly respond to standard Parkinson’s medications.
- Can significantly impair hand function and quality of life.
- Requires a multidisciplinary approach to management.
- Prognosis is variable; functional disability is common.
- More research needed to better understand and treat it.
Identifying and properly managing the hummingbird tremor presents an important goal for improving outcomes in Parkinson’s disease. Increased recognition and study of this unique symptom pattern will enable better solutions for those affected.
Frequently Asked Questions
How common is the hummingbird tremor in Parkinson’s disease?
The hummingbird tremor is relatively uncommon, occurring in approximately 5-10% of Parkinson’s disease patients. It tends to emerge in the later stages of the disease, on average about 15 years after diagnosis.
Can anything make the hummingbird tremor better or worse?
The tremor may worsen with stress, anxiety, excitement, fatigue, or certain medications. Concentrating on a motor task, resting the hand, or loading/stabilizing the limb may temporarily dampen the tremor. But in general it persists at rest.
Does the hummingbird tremor occur when sleeping?
Most Parkinson’s tremors disappear with sleep. However, in rare cases, the hummingbird tremor can persist and disrupt sleep. This is likely related to subconscious muscle contractions.
Can the hummingbird tremor affect other body parts besides the hands?
Typically, the hummingbird tremor affects the hands, wrists, and forearms. But in some cases, the lower limbs can also be involved. The face, jaw, and neck are less often affected.
Are there exercises or home remedies to help with the hummingbird tremor?
Light hand weights, splints, adaptive utensils, and exercises like stretching and resistance training may help strengthen muscles and reduce trembling. Relaxation techniques, good sleep hygiene, and avoiding stimulants can also help in some cases.
Conclusion
The hummingbird sign refers to a high frequency rest tremor of the hands seen in a subset of patients with Parkinson’s disease. While the exact cause is still under investigation, it appears linked to more extensive dopamine deficiency and individual differences in brain circuitry. This troublesome symptom is generally more difficult to treat than other Parkinson’s tremors. A multimodal approach is required to manage the trembling and associated disability. Increased recognition and research focused on the hummingbird tremor will pave the way for better understanding and care.
