Cervical dystonia - improving the effectiveness of botulinum toxin therapy

Abstract

Introduction: Cervical dystonia is the most frequent form of focal dystonia. It is characterised by involuntary muscular contractions resulting in abnormal head/neck and shoulder movements and postures, which can be associated with tremor and pain. Local intramuscular injections of botulinum toxin type A (BoNT-A) is the treatment of choice, being both effective and well-tolerated. However, a considerable number (c. 30%) of patients discontinue this treatment. The aim of this review was to analyse the factors possibly responsible for treatment failures of cervical dystonia (CD), with special regard to the new classification known as the 'Col-Cap' concept and non-motor symptoms.

Clinical implications: Several factors analysed in this review are responsible for effective treatment: proper diagnosis of dystonia and exclusion of pseudodystonias, correct recognition of dystonia pattern and identification of new patterns according to the Col-Cap concept, muscle selection and precise injections under electromyography (EMG) and/or ultrasonography (US) guidance. Furthermore, concomitant diagnosis and treatment of non-motor symptoms such as depression, anxiety, fatigue, sleep problems, phobias and stigmatisation are crucial in obtaining the best overall effect of the treatment. Primary and secondary immunisation and non-responsiveness seem to be marginal problems nowadays due to a low potential of new BoNT-A formulations to produce neutralising antibodies.

Future directions: There is a need for new and relevant scales combining the Col-Cap concept patterns with non-motor symptoms and quality of life. There is also a lack of specific rehabilitation protocols which could enhance BoNT-A treatment results.

Keywords: Col-Cap concept; botulinum toxin; cervical dystonia; primary non-responsiveness; secondary non-responsiveness; treatment failures.