Patient selection and injection techniques for botulinum neurotoxin in oromandibular dystonia

Abstract

Oromandibular dystonia (OMD) is a form of focal dystonia that involves the masticatory, lower facial, labial, and lingual musculature. It is a disabling disorder which had limited treatment options until the recent introduction of botulinum toxin (BoNT) as the recommended first-line therapy by most experts and evidence-based literature. Owing to the complex relationship between the muscles of mastication and surrounding muscles, there is a wide variety of dynamic clinical presentations, making clinical recognition and the corresponding approach to BoNT injection therapy difficult. In this review, the authors provide a framework for practical clinical approaches, beginning with the recognition of clinical subtypes of OMD (jaw-opening, jaw-closing, jaw-deviating, lingual, peri-oral, and/or pharyngeal dystonias), followed by patient selection and clinical evaluation to determine function interferences, with injection techniques illustrated for each subtype. Careful stepwise planning is recommended to identify the muscles that are primarily responsible and employ a conservative approach to dosing titration. Treating physicians should be diligent in checking for adverse events, especially for the first few injection cycles, as muscles involved in OMD are small, delicate, and situated in close proximity. It is recommended that future studies should aim to establish the clinical efficacy of each subtype, incorporating muscle targeting techniques and patient-centred outcome measures that are related to disturbed daily functions.

Keywords: Abobotulinum toxin; Botulinum toxin; Jaw-closing; Jaw-opening; Lingual dystonia; Meige’s syndrome; Onabotulinum toxin; Oromandibular dystonia; Perioral; Segmental craniocervical dystonia.

Fig. 1

(A) View of the medial and lateral pterygoid muscles, showing its origin and insertion; (B-D) Surface anatomy (B), mandibular approach (C), and intraoral approach (D) for botulinum toxin injection of medial pterygoid muscle; (E-G) Surface anatomy (E), lateral approach (F), and intraoral approach (G) for botulinum toxin injection of lateral pterygoid muscle. Black dots denote approximate injection sites of medial (C) and lateral (F) pterygoid muscles.

Fig. 2

(A) Inferior view of the floor of the mouth, showing the submentalis complex; (B) Surface anatomy of submentalis complex; (C) The sign X denotes approximate injection sites of digastric muscles.