FND Education Project

REFERENCE · RECOVERY TECHNIQUE

Specialist Botulinum-Toxin Review for Functional Dystonia

Page role: Additional specialist treatment review. New standalone specialist-option page; it was not a numbered original entry. The page states that the small pilot trial does not support routine injection. See the collection index for the original technique groupings.

Most likely fit: A movement-disorder specialist has identified a particular muscle target and a limited goal—such as reducing selected painful tonic overactivity to enable care or rehabilitation—or suspects a coexisting nonfunctional dystonia for which injection is indicated. Routine injection solely because a functional posture is present is not supported. [A small pilot randomized trial found no added benefit over placebo before cognitive behavioural therapy; selected use remains uncertain]

Not the same as: A cure for FND, a diagnostic test, an injection into every visibly tight muscle, or a reason to postpone active rehabilitation and complication care.

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What this treatment is—and what the evidence says

Botulinum toxin, often known by brand names including Botox, reduces release of a chemical signal from a motor nerve to an injected muscle. The effect develops over days, usually reaches its strongest point later and then wears off over months. It does not directly treat the full nervous-system process involved in functional dystonia.

The only small randomized trial focused on persistent functional dystonia compared botulinum toxin with placebo before all participants received individualized cognitive behavioural therapy. Fourteen people were randomized and ten completed follow-up. Both groups improved, but botulinum toxin did not add benefit over placebo at twelve weeks. The study was too small to answer every question about selected face or neck patterns, but it does not support routine injection.

Anatomy in everyday language

The neuromuscular junction is where a motor nerve communicates with a muscle. Botulinum toxin reduces release of acetylcholine, the chemical messenger used there, so the injected muscle becomes weaker for a period.

That effect can spread beyond the intended target. In the neck, weakening the wrong dose or distribution can worsen head control or swallowing. In a forearm or hand, it can reduce grip or finger control. In a calf or foot, it can affect standing or walking. Accurate muscle identification matters because a visible posture may involve several muscles, compensation, pain or a fixed joint—not one simple overactive target.

Questions before an injection

  • What exact diagnosis or coexisting diagnosis is being treated?
  • Which muscle or muscles are the targets, and how were they identified?
  • Is the goal pain, hygiene, range, walking, hand use or another activity?
  • What benefit is realistic, and when should it begin?
  • What weakness or other adverse effects could interfere with function?
  • How will rehabilitation use any temporary change?
  • When will benefit and harm be reviewed before another injection?

An immediate change at the time of injection occurs too soon to be the toxin’s pharmacological effect. It may still be a real experience, but it should not be used alone to confirm diagnosis or predict longer-term benefit.

Seek urgent advice for swallowing or breathing difficulty, marked generalized weakness or another severe unexpected reaction after injection, following the treating service’s instructions.

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Do not pressure the person either to accept or refuse injection. Help write down the specific goal and track function over the expected onset and wearing-off period. A temporary change, no change or worsening should be reported without treating it as proof for or against FND.

Know the service’s instructions for adverse effects. If injection is intended to open a rehabilitation opportunity, help the person follow the agreed practice plan without forcing the newly weakened muscle or joint.

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For Clinicians and the Care Team

Selection and differential boundary

Revisit the phenotype and potential coexistence of functional with nonfunctional dystonia. Specify distribution, fixed versus dynamic pattern, active and passive range, objective tonic muscle activity, pain, contracture, task effect and the function that might be gained or lost by focal weakness. Do not use injection response as a standalone diagnostic test.

For cervical targets, distinguish sternocleidomastoid, splenius capitis/cervicis, levator scapulae, trapezius, scalene and deeper cervical contributions according to the actual pattern; translate these as front/side/back-of-neck and shoulder-blade muscles for the person. For upper- or lower-limb targets, map joint actions and compensations rather than inferring the target from posture alone. Use appropriate anatomical, EMG or ultrasound guidance according to target and specialist practice.

Explicit decision and review procedure

  1. Confirm the diagnostic formulation and document uncertainty or comorbidity.
  2. Define one measurable goal and why focal chemodenervation is expected to help it.
  3. Record baseline posture, pain, passive/active range, strength, swallowing or gait as relevant, task function and assistance.
  4. Discuss the pilot-trial result, uncertainty, time course, temporary nature and target-specific risks through shared decision-making.
  5. Select muscle and dose using specialist standards; avoid injecting diffuse “tightness” without a target hypothesis.
  6. Coordinate a time-limited rehabilitation plan that uses any reduced overactivity without forcing range.
  7. Review at an appropriate interval using the predefined functional goal and adverse effects.
  8. Do not repeat automatically. Continue, modify or stop according to net benefit and diagnostic formulation.

Evidence boundary

In Vizcarra and colleagues’ double-blind pilot trial, 14 adults with persistent functional dystonia were randomized to onabotulinumtoxinA or placebo before 12 weekly individualized CBT sessions; 10 completed the study. Clinical assessments did not differ between groups at 12 weeks, and the authors concluded that CBT improvement was unaffected by prior toxin. The sample was small and does not exclude every selected topographical use, but it provides no basis for routine BoNT treatment of functional dystonia.

Focused review discusses occasional targeted use, particularly with objective painful spasm, while also noting immediate responses inconsistent with the drug’s delayed mechanism. Present both the uncertainty and procedure-related risks. Community reports of temporary benefit, no benefit or worsening are individual experiences, not effectiveness estimates. [1][2][3]

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Research and Sources

Citation Full citation
[1] Vizcarra JA, Lopez-Castellanos JR, Dwivedi AK, Schmerler DA, Ries S, Espay AJ. OnabotulinumtoxinA and cognitive behavioral therapy in functional dystonia: a pilot randomized clinical trial. Parkinsonism & Related Disorders. 2019;63:174–178. FND-CIT-0093. https://doi.org/10.1016/j.parkreldis.2019.02.009
[2] Frucht L, Perez DL, Callahan J, et al. Functional dystonia: differentiation from primary dystonia and multidisciplinary treatments. Frontiers in Neurology. 2021;11:605262. FND-CIT-0021. https://doi.org/10.3389/fneur.2020.605262
[3] Gros P, Bhatt H, Gilmour GS, Lidstone SC. Rehabilitation for functional dystonia: cases and review of the literature. Movement Disorders Clinical Practice. 2024;11(8):1018–1024. FND-CIT-0055. https://doi.org/10.1002/mdc3.14121

Detailed technique page created September 12, 2026 · Clinical and accessibility review pending

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