Cervical dystonia is a condition that causes the neck muscles to tighten or spasm, leading to abnormal head positions and pain.

The main questions it aims to answer are:

• Do ultrasound-guided BoNT injections improve quality of life more than injections without ultrasound?
• Are ultrasound-guided injections as safe as injections without ultrasound?

Researchers will compare:

• BoNT injections with ultrasound guidance
• BoNT injections without ultrasound guidance (based only on body landmarks)

Participants will:

• Receive both types of injections during the study (one first, then the other)
• Complete questionnaires about quality of life, movement, pain, and mood
• Attend follow-up visits over about 8 months About 37 adults with cervical dystonia will take part. The study will take place at the Fondazione IRCCS Istituto Neurologico Carlo Besta in Milan, Italy.

Cervical dystonia (CD) is the most common type of focal dystonia and is characterised by sustained or intermittent involuntary contractions of the neck muscles. These contractions lead to abnormal head postures and movements, frequently associated with pain and tremor, and have a major impact on quality of life.

The established treatment for CD is repeated intramuscular injections of botulinum toxin type A (BoNT-A), usually every 12 to 16 weeks. BoNT-A blocks acetylcholine release at the neuromuscular junction, producing a temporary and reversible chemodenervation of the target muscle. Clinical benefit generally appears within a few days, peaks after 2 to 4 weeks, and gradually wears off after 3 to 4 months, requiring repeated injections. Although this therapy is effective and safe, its clinical success largely depends on the accuracy of muscle targeting. Suboptimal precision in injections can lead to unsatisfactory outcomes, persistence of symptoms, or treatment discontinuation.

Several approaches are used in clinical practice to guide injections. The conventional method relies on palpation and anatomical landmarks, is widely available, and requires limited resources. However, it depends heavily on the injector's experience and may result in inaccurate targeting. Ultrasound (US) guidance, on the other hand, allows direct, real-time visualisation of the cervical muscles and adjacent structures. This technique may increase accuracy, optimise toxin distribution, and lower the risk of misplaced injections and adverse events.

Cadaveric studies have demonstrated higher accuracy of US-guided injections compared with landmark-based methods, and preliminary clinical studies suggest that US guidance may improve outcomes. However, these studies have been limited by small sample sizes, lack of randomisation, or non-blinded assessments. Robust evidence from randomised controlled trials is still lacking, and therefore the clinical superiority of US guided injectionsance remains uncertain.

US-guided injections also require additional equipment, time, and operator training. This may limit their widespread adoption in routine clinical practice unless a clear advantage over landmark-based injections is demonstrated. Addressing this knowledge gap is essential to inform clinical decisions and optimise the management of CD.

The present study has been designed to evaluate the impact of US-guided BoNT-A injections compared with injections based only on anatomical landmarks in adults with idiopathic CD. The primary objective is to determine whether US guidance provides superior improvements in quality of life. Secondary objectives include assessing the effects of the two techniques on motor and non-motor symptoms, as well as comparing their safety.

A total of approximately 37 participants with idiopathic cervical dystonia and a documented good response to prior BoNT-A therapy will be recruited at the Fondazione IRCCS Istituto Neurologico Carlo Besta in Milan, Italy. Each participant will undergo two treatment cycles, one with US guidance and one without, in randomised order. The duration of participation for each individual will be about 8 months. By directly comparing two widely used approaches, this trial will provide high-quality evidence to guide clinical practice and improve care for people with cervical dystonia.

Inclusion Criteria:

• Minimum age 18 years old
• Clinical diagnosis of Idiopathic Cervical Dystonia
• On a stable dose of other medications (if any) used for focal dystonia treatment (e.g. anticholinergics and benzodiazepines) for at least 3 months prior to screening and expected to be maintained throughout the study
• Treatment non-naïve to BoNT type A therapy for CD
• At least 4 months have passed between the last BoNT injection at screening
• Good clinical response to previous BoNT injections, on stable dosing and treatment scheme
• Informed Consent as documented by signature.
• Ability to perform study requirements (to attend assessment and treatments)

Exclusion Criteria:

• Diagnosis of other types of Cervical Dystonia (Inherited and Acquired)

  • Concomitant diagnosis of diseases that contraindicate the use of botulinum toxin, such as myasthenia gravis
  • Known hypersensitivity or allergy to Botulinum-A Toxin
  • Women who are pregnant or breast feeding
  • Intention to become pregnant during the study
  • Lack of safe contraception
  • Other clinically significant and unstable concomitant disease states (e.g., renal failure, hepatic dysfunction, cardiovascular disease, etc.).
  • Inability to follow the procedures of the study, e.g., due to language problems, psychological disorders, dementia, etc. of the participant
  • Participation in another study with investigational drug within the 30 days preceding and during the present study
  • Previous enrolment into the current study

Participants and outcome assessors will be blinded to the injection technique. Injectors cannot be blinded for practical reasons. To maintain blinding, the ultrasound device will be present in all procedures. For participants randomized to the non-ultrasound group, the ultrasound probe will be positioned but the device screen will be turned off, so that the procedure appears identical to an ultrasound-guided injection.