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Boxing Reflex (Myrtiform Tremor)

What is Boxing Reflex (Myrtiform Tremor)?

The boxing reflex, also known as myrtiform tremor, is a brief, involuntary, rhythmic shaking of the upper limbs that resembles the motion of a boxer’s gloves punching forward and backward. The movement is typically fast‑acting (20‑30 Hz), symmetrical, and most noticeable when the hands are placed together or when the patient is asked to “hold their hands together as if in a boxing stance.”

Although the term is relatively obscure, it is recognized in neurology as a type of post‑ural tremor that can signal disruption of the cerebellar–brainstem pathways or dysfunction of the basal ganglia. The reflex is usually triggered by sudden changes in posture, startle stimuli, or specific voluntary tasks, and it tends to disappear when the arms are relaxed or supported.

Because the phenomenon is uncommon, many patients first encounter it during a routine neurological exam or when evaluating unexplained tremor. Understanding its underlying causes is essential, as the boxing reflex can be an early herald of serious neurologic disease.

Common Causes

Boxing reflex (myrtiform tremor) is not a disease itself but a sign that can appear in a variety of conditions. The most frequent etiologies include:

• Essential Tremor (ET) – a hereditary, action‑dominant tremor that may present with a boxing‑like pattern during specific tasks.
• Parkinson’s disease (PD) – especially in the early “off” state or with medication fluctuations.
• Cerebellar degeneration – such as spinocerebellar ataxia, alcoholic cerebellar degeneration, or cerebellar infarcts.
• Multiple system atrophy (MSA) – a rapidly progressive neurodegenerative disorder with prominent autonomic and motor signs.
• Drug‑induced tremor – most commonly from β‑agonists, lithium, valproic acid, or high‑dose caffeine.
• Hyperthyroidism – excess thyroid hormone increases β‑adrenergic activity leading to fine tremor that can accentuate with posture.
• Peripheral neuropathy with sensory ataxia – loss of proprioceptive input can cause a compensatory, rhythmic arm movement.
• Lesions of the brainstem or thalamus – strokes, tumors, or demyelinating plaques that interrupt the cerebello‑thalamic circuit.
• Wilson’s disease – copper accumulation affecting basal ganglia and causing various tremor patterns.
• Functional (psychogenic) tremor – a tremor without an organic lesion, often modifiable by distraction.

Associated Symptoms

The boxing reflex rarely occurs in isolation. Patients frequently report—or are observed to have—additional neurologic or systemic signs, such as:

• Gait instability or ataxia
• Rigidity or bradykinesia (slowness of movement)
• Micrographia (small handwriting)
• Speech changes: slurred, monotone, or rapid “tremulous” speech
• Vertigo or dizziness
• Autonomic dysfunction: urinary urgency, constipation, orthostatic hypotension
• Muscle cramps or stiffness
• Fatigue, weight loss, heat intolerance (in hyperthyroidism)
• Visible tremor in other body parts (head, voice, legs)

When to See a Doctor

Because a boxing reflex can be a clue to serious neurologic disease, you should schedule a medical evaluation if you notice any of the following:

• The tremor is new, progressive, or worsening over weeks to months.
• It interferes with daily activities (e.g., writing, using utensils, buttoning clothes).
• You have accompanying balance problems, drooping eyelids, or sudden weakness.
• There are signs of autonomic dysfunction (e.g., fainting on standing, severe constipation).
• You have a personal or family history of Parkinson’s disease, essential tremor, or other movement disorders.
• Recent changes in medication, caffeine intake, or thyroid symptoms occur.

Prompt evaluation helps differentiate a benign tremor from a potentially progressive neurodegenerative condition.

Diagnosis

Diagnosing the boxing reflex involves a systematic approach that blends clinical observation with targeted testing.

1. Detailed History

• Onset, progression, and triggers (posture changes, stress, caffeine, medications).
• Family history of tremor or neurodegenerative disease.
• Associated systemic symptoms (weight loss, heat intolerance, visual changes).
• Medication review – especially β‑agonists, antipsychotics, lithium, or thyroid drugs.

2. Neurological Examination

• Observation of the tremor while the patient holds hands together, extends arms, or performs finger‑nose testing.
• Assessment of gait, coordination (heel‑to‑shin, rapid alternating movements), and muscle tone.
• Screen for rigidity, bradykinesia, and postural instability.

3. Laboratory Studies

• Thyroid panel (TSH, free T4)
• Copper studies (serum ceruloplasmin, 24‑hr urinary copper) if Wilson’s disease suspected
• Basic metabolic panel to rule out electrolyte disturbances
• Serum drug levels when toxicity is considered

4. Neuroimaging

• MRI of the brain – best for detecting cerebellar atrophy, brainstem lesions, or demyelination.
• CT scan – useful in acute settings (e.g., suspected hemorrhagic stroke).

5. Electrophysiological Tests

• Electromyography (EMG) and accelerometry can quantify tremor frequency and differentiate organic from functional tremor.
• DaTscan (dopamine transporter SPECT) – helps distinguish Parkinsonian from non‑Parkinsonian tremor.

6. Specialized Evaluations

• Genetic testing for hereditary ataxias or familial essential tremor when indicated.
• Autonomic testing (tilt table, sweat test) if MSA is a concern.

Treatment Options

Treatment is tailored to the underlying cause and the severity of the tremor. Below is a pragmatic, step‑by‑step guide.

1. Address Primary Etiology

• Essential Tremor – First‑line: propranolol (non‑selective β‑blocker) 40‑80 mg daily; alternatively, primidone 125‑250 mg daily. Consider gabapentin or topiramate if refractory.
• Parkinson’s Disease – Optimize levodopa/carbidopa dosing; add MAO‑B inhibitors (selegiline, rasagiline) or dopamine agonists (pramipexole, ropinirole) for tremor control.
• Hyperthyroidism – Anti‑thyroid medications (methimazole, PTU) or definitive therapy (radioactive iodine, surgery) usually resolve the tremor.
• Drug‑induced Tremor – Discontinue or taper the offending agent; substitute with an alternative when possible.
• Cerebellar Lesion – Surgical removal (tumor) or targeted rehabilitation after stroke.

2. Symptomatic Pharmacotherapy

• Beta‑blockers (propranolol, atenolol) – reduce adrenergic contribution.
• GABA‑ergic agents – primidone, clonazepam, or benzodiazepines can dampen tremor amplitude.
• Topical agents – β‑blocker gel (e.g., propranolol gel) for focal hand tremor.
• In refractory cases, botulinum toxin injections into forearm flexors/extensors may reduce tremor amplitude.

3. Non‑pharmacologic Strategies

• Physical & occupational therapy – focus on coordination drills, weighted utensils, and adaptive devices.
• Stress‑reduction techniques – mindfulness, yoga, or biofeedback; stress often amplifies tremor.
• Limit caffeine, nicotine, and alcohol (excess) as they can exacerbate the reflex.
• Use of wearable tremor‑suppressing orthoses (e.g., weighted wrist cuffs) for short‑term functional improvement.

4. Surgical Options (for severe, medication‑resistant cases)

• Deep Brain Stimulation (DBS) of the ventral intermediate nucleus (VIM) of the thalamus – highly effective for essential tremor and Parkinsonian tremor.
• Focused Ultrasound Thalamotomy – a non‑invasive alternative approved for essential tremor.

Prevention Tips

While you cannot always prevent the development of a neurologic disorder, certain lifestyle habits can reduce the risk of a boxing reflex emerging or worsening.

• Maintain a balanced diet rich in antioxidants (berries, leafy greens) to support neuronal health.
• Exercise regularly – aerobic activity improves cerebellar perfusion and reduces tremor severity.
• Limit stimulants: caffeine < 200 mg/day, avoid nicotine and illicit drugs.
• Adhere to prescribed medication regimens and report side‑effects promptly.
• Get routine thyroid screening if you have a family history of thyroid disease.
• Practice good sleep hygiene; chronic sleep deprivation can accentuate tremor.
• Stay up‑to‑date on vaccinations and infection control, as some viral infections (e.g., COVID‑19) have been linked to transient tremor.

Emergency Warning Signs

Key Take‑aways

The boxing reflex (myrtiform tremor) is a distinctive, rhythmic hand tremor that often points to an underlying neurologic or systemic disorder. Recognizing the sign, understanding its potential causes, and seeking timely evaluation are crucial steps to prevent progression and to implement effective treatment. If you notice the characteristic “boxing” motion in your hands—especially with other neurologic signs—consult a neurologist or your primary‑care provider promptly.

For further reading, consult reputable sources such as the Mayo Clinic, CDC, NIH, and the Cleveland Clinic.

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