Highlights from

TOXINS 2019

International Neurotoxin Association (INA) annual meeting

Copenhagen 16-19 January 2019

Diagnosis and treatment

A much discussed topic in Copenhagen was cervical dystonia, the most frequent focal dystonia in clinical practice with a prevalence of approximately 50 per million. Women are far more frequently affected by this painful chronic condition, characterised by involuntary patterned contractions of cervical musculature, resulting in postural changes of the head, neck, and shoulder. Disease onset peaks in the fourth and fifth decades of life. In up to 25% of the patients, there is a family history of this disorder that is mainly managed by repeated botulinum toxin injections.

Prof. Alberto Albanese (Humanitas Research Hospital, Italy) recounted his historical knowledge on early observations about cervical dystonia, which dates back to Dante and Virgil who met the seers: "Each of them appeared strangely distorted between the chin and the start of the chest, since the head was reversed towards the body, and they had to move backwards, since they were not allowed to look forward." Prof. Albanese explained that in cerebellar processing of neck proprioceptive information, the effects of combined cerebellar and cortical stimulation in cervical dystonia patients are opposite from those in healthy volunteers. Phenomenological subtypes of cervical dystonia include stiff head and neck, i.e. caput and collum obstitum.

Diagnosis of cervical dystonia is based on clinical features: rotational posture (torticollis) and lateral tilt (laterocollis). Still, the average interval between symptom onset and diagnosis is 44 months, as there are no validated diagnostic criteria and a lack of confirmatory diagnostic testing [1]. Cervical dystonia may increase in severity depending on activity/posture. That is why it is important to assess patients with regard to action and posture, Prof. Cynthia Comella (Rush University Medical Center, USA) said.

All botulinum toxin products labelled for cervical dystonia

Prof. Albanese welcomed the fact that all botulinum toxin products are labelled for cervical dystonia. Unique to dystonia affecting the cervical region is that high doses are required compared with other focal dystonia, he added. Prof. Comella further mentioned deep brain stimulation. Surgical procedures, however, are a second-line alternative. She emphasised that no oral medications, such as levodopa, anticholinergics, baclofen, clonazepam, or tetrabenazine have been approved for use in cervical dystonia and adverse effects are frequent. According to Prof. Comella, botulinum toxin is the treatment of choice. Treatment of peripheral muscles with botulinum toxin A can lead to modification of brain-motor-control, she said. Originally it was assumed that botulinum toxin reduced pain only by the decrease of muscle spasms. However, the current understanding is that it can also directly act on nociceptors by inhibiting the release of neuropeptides. Botulinum toxin A demonstrated improvement in clinical scores and a reduction of pain. In an open-label study, including 97 patients with focal dystonia and hemifacial spasm, 64% of the patients experienced moderate or marked improvement in motor symptoms and 74% in pain symptoms after treatment with botulinum toxin A. According to a Cochrane review of botulinum toxin A therapy for cervical dystonia, there is an average of 18.7% Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) improvement from baseline at 4 weeks after injection [2]. Recommendations for managing cervical dystonia in patients with a poor response to botulinum toxin by the British Neurotoxin Network consist of improvements in practice by using a flexible, non-stereotype strategy and correct botulinum toxin targeting with the lowest dose required.

Determination of dominant abnormal movement

Prior to botulinum toxin treatment, Prof. Albanese suggested identification of the primarily involved muscles as opposed to compensatory activity for simple cases. His rule of thumb: muscles that cause the most dominant movement of head/neck and are clinically hyperactive and painful should be injected. The injection technique has to be precise. Movement (affected and compensatory muscles), weakness (lack of activation, atrophy), and pain (contraction, stretching, independent of muscle activity) are to be assessed. For clinical examination, initial inspection serves to allow detection of hypertrophy/atrophy and recognition of the muscles involved in abnormal postures and movements. Palpation is used for identification of size and activation of superficial muscles, and evoked muscle pain.

For complex or unclear cases, Prof. Albanese recommends the use of electromyography (EMG) mapping. EMG recordings show muscle activity at rest and during voluntary tasks. Ultrasound may be used for visual recognition of muscles and their contractile activity, and to measure muscle size (quantify botulinum toxin-induced atrophy). EMG and ultrasound may be used for targeting, especially when targeting deep muscles.

Treatment algorithm

Prof. Albanese was convinced that there was a need to develop practical management guidelines for botulinum toxin injections with the aim to increase patient satisfaction and to assess whether EMG in combination with ultrasound would help in targeting dystonic muscles in patients with cervical dystonia. As currently no consensus exists on the practical issues involved in performing guided injections, he proposed a new algorithm based on simultaneous support of EMG plus ultrasound in botulinum toxin injections. After conducting a prospective 12-week study in which patients with cervical dystonia received botulinum toxin treatment according to the algorithm, the speaker concluded that algorithm-based treatment is feasible and efficacious.

A randomised, double-blind study, comparing botulinum toxin injections administered with and without EMG guidance, revealed that those in the EMG guided group had a greater magnitude of improvement and a larger number of patients with a marked improvement [3].

  1. Tideringston et al. J Neurol Sci (2013).
  2. Castelão M et al. Cochrane Database Syst Rev. 2017 Dec 12;12:CD003633.
  3. Comella CL et al. Neurology. 1992 Apr;42(4):878-82.

The content and interpretation of these conference highlights are the views and comments of the speakers/authors.