Lateral pterygoid: superior and inferior heads.

Action: opening and slight protrusion of jaw.

Involvement of the inferior head is the usual cause of jaw opening dystonia.

Anatomy of the Lateral Pterygoid



The examiner should palpate immediately beneath the zygomatic arch, and request the patient to open and clause their jaw: the opening of mandibular notch is easily palpated (note that the that mandibular notch is formed by the gap between the coronoid process anteriorly and the mandibular condyle posteriorly.

Typically under EMG guidance, the needle is passed horizontally through the notch into the lateral pterygoid which can be activated by jaw opening.

Potential side-effects: The maxillary artery is relatively superficial and is therefore potentially prone to trauma from the injecting needle, potentially resulting in haematoma formation.

Alternatively, the muscle may be injected intraorally, also with EMG guidance. The lateral pterygoid plate is palpated, and the needle is placed between this plate and the coronoid process of the mandible. The needle should be oriented parallel to the length of the muscle. Once the needle is in position, the patient is asked to produce lateral excursions of the jaw to confirm proper placement.
7.5 u Botox

Anatomy of the Mandible