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Oromandibular dystonia is a rare condition of hyperkinetic motor dysfunction in the orofacial area. It is a centrally mediated disorder of unknown aetiology and manifested by a sustained contraction of masticatory muscles, involving one or both lateral pterygoids, and pushing the mandible forward. The prognosis is poor and the treatment is symptomatic. This paper describes a case of a 38-year-old woman referred for a locked left TMJ who was diagnosed as having an oromandibular dystonia. A step-by-step diagnosis and treatment procedure is described.
Clinical Relevance: Knowledge of oromandibular dystonia may be valuable as rare medical diseases can be masked by common dental problems.
Article
Oromandibular dystonia is a hyperkinetic motor disorder of unknown aetiology. Its mechanism is not well understood and thought to be due to decreased neurotransmission of dopamine in the basal ganglia, as this disorder has been observed in patients with long-term use of dopamine receptor blocking drugs, such as neuroleptics.1 It is also hypothesized that, following a dental treatment, a disturbance in local neuronal circuitry might lead to an alteration of synaptic transmission in the basal ganglia which, in turn, might provoke a central reorganization of somatic representation in the thalamus. This hypothesis is not fully supported from the various dental reports and should be further examined.1,2
Several criteria have been used in the classification of dystonia. These include:
Onset (whether inherited as primary or acquired as secondary to trauma medications);
Age;
Anatomical region of distribution: focal, segmental, multifocal or generalized.2
Oromandibular dystonia is a focal type of dystonia. Prevalence of this focal dystonia (29.5 cases among 100,000 individuals) is more frequent in elderly women.3,4
Clinical manifestations include pulling and twisting of the mandible forward or laterally, speech alteration and, occasionally, swallowing difficulty. All these manifestations depend mainly on the musculature involved. Typically, the lateral pterygoid, anterior digastric, platysma, orbicular oris, buccinator and tongue muscles are affected. The mandible shakes and, occasionally, temporomandibular disorders, such as open locks, can happen.3 Patients can sometimes control or suppress movements by holding an object in their mouth, massaging the cheeks or touching the chin. This is referred to as the ‘geste antagonistique’.5 Oromandibular dystonia can extend into the neck muscles3 but patients are strongly advised to have a Magnetic Resonance Imaging (MRI) of the brain to rule out a major brain disease (including tumour). Electromyogram (EMG) recordings of involved muscles can be helpful. Sometimes, oromandibular dystonia can extend to the cervical area.3 There are a number of treatments for this condition but the most common include:
Baclofen at doses 30–80 mg/day;
Botox injection of 20–50 units per muscle involved.3,6,7
The absolute and comparative efficacy and tolerability of drugs in dystonia, including anticholinergic and antidopaminergic drugs, is poorly documented and no evidence-based recommendations can be made to guide prescribing.8
Case Report
A 38-year-old Caucasian female patient reported to the Department of Prosthodontics complaining of an open lock of the mandible. History revealed that she had had this condition for more than 3 months. She mentioned that her problem started during a dental treatment in which the dentist tried to adjust the occlusion but was unable to solve the problem. She consulted four other local medical and dental practitioners, who tried several procedures without any relief of the lock. Despite treatment with a muscle relaxant, Muscerol® 2 tablets TID (Paracetamol 450 mg and Chlormezazone 100 mg) for several weeks, the pain persisted.
Her medical history was normal and she was in good health. She didn't smoke, had no allergies and was not taking permanent medications. Extra-oral examination revealed an open lock of the mandible in a protrusive posture with a slight deviation towards the left side. All her masticatory and facial muscles were tense. Intra-oral examination was limited to tongue movements, which were difficult. The OPG findings revealed a normal configuration of the condyles, the right condyle in its normal position and the left one in front of the eminence. All her remaining teeth were endodontically treated and crowned. She also had crowns on implants on the upper right side. There was no indication of her dental condition before the completion of all the prosthetic work (Figure 1).
Figure 1. Note the absence of natural teeth landmarks and the left condyle outside the fossa.
Unlocking the jaw manually was not possible. It was decided to place the patient on Baclofen, a drug used for the relief of chronic muscle spasm (10 mg per day for 5 days) and retry. A few days later, unlocking was still unsuccessful. It was thought that the failure to unlock was due to the spasms of the muscles under tension for three months. Finally, the patient was admitted to hospital and the unlocking procedure was successful under general anaesthesia (Figure 2).
Figure 2. Occlusion re-established with condyles in place.
The patient was still under the effect of Baclofen when she returned the next day. She was able to close her mouth but was in an Angle's Class III jaw relationship (Figure 3). Alginate impressions and a bite registration were taken in order to mount the models on an articulator. A temporary stabilization splint was inserted. Her freeway space was measured and found to be 13 mm. It was concluded that the problem was due to the loss of vertical dimension, which brought the mandible forward, creating the locking. The spasms were thought to be time related (remaining in this position for three months). She was asked to open her mouth with caution, eat a soft diet, continue taking the Baclofen and was forbidden to bite on her front teeth until the delivery of the stabilization splint. The splint was made of a 2 mm thick and hard polyvinyl (Thermoforming material, Zahn Laboratory division, Henry Schein Inc Melville, USA), by a vacuum-forming technique (Henry Schein Inc Melville, USA). Cold cure acrylic was then added to raise the bite and produce a freeway space of 4 mm, thus reducing it by 9 mm (Figure 4). The patient was asked to wear it only at night and remove it during the day. The Baclofen treatment was maintained for one month and the patient felt that she had improved, but the mandible was always in a forward position when she removed the splint. This confirmed our diagnosis. It was decided to move a step forward, remove all her actual prosthetic work and replace it by new temporaries at the newly acquired occlusion.
Figure 3. Protrusion of the mandible in the intercuspal contact position.Figure 4. Splint inserted. Note the gap between anterior teeth resulting from raising the bite.
A wax-up on an articulator was made at the splint level (Figure 5) and new temporaries fitted in the mouth (Figure 6). The patient was asked to test this new occlusion for one more month and gradually stop the Baclofen at a rate of every other day for two weeks, reduced to every four days for two more weeks before stopping it completely.
Figure 5. Wax-up following the same height of the new vertical dimension obtained with the splint.Figure 6. Replacement of all the prosthetic work by new provisional acrylic teeth.
It was decided to complete the final prosthetic work if she felt comfortable and pain free. She finally came back six weeks later with a recurrence of the lock. She mentioned new clinical symptoms: her mandible shook continuously and she had difficulty swallowing and speaking. Her sister noticed that the symptoms disappeared during sleep. She finally explained that she felt the tension coming back gradually and was in this state one week after she stopped the Baclofen. She waited for one more week then decided to come back and ask for help.
From the new information and the clinical outcome it was obvious that her problem was not occlusally related and we had to look elsewhere. New clinical symptoms in concomitance with the gradual reduction of the Baclofen made us think of a focal dystonia, and specifically an oromandibular dystonia.
She was referred to a neurologist. Magnetic Resonance Imaging (MRI) and Electromyogram (EMG) recordings revealed that her problem was due to a spasm of the lateral pterygoid muscles. Baclofen was increased to 50 mg per day with no real improvement. Finally, a botulinum toxin A (Botox) was injected at a dose of 50 units per muscle and the patient became symptom free for six months. She decided to complete her prosthetic work in Syria, for financial reasons, and left with the provisional teeth.
Discussion and conclusion
This case was confusing for many reasons. The patient came with an apparent open lock of the left TMJ in a forward position. This lock prevented her mandible from shaking. The second confusing factor was the absence of any natural landmark as the patient's remaining teeth were crowned and the missing ones were replaced by conventional bridges or implants. The fact that no medical or dental practitioner could relieve her, that she had a huge loss of vertical dimension and that she was in a constant protrusive posture, apparently explained the spasms and satisfied the occlusal theory.
Her constant spasm for three months justified the use of Baclofen as a centrally antispasmodic drug. Her improvement was also related to the occlusal theory by restoring the vertical dimension without any credit given to the drug. However, all these steps were necessary to uncover the new symptoms that validated the oromandibular dystonia discovery. The use of Botox was justified because the patient felt nausea and drowsiness while taking higher doses of Baclofen and asked if she could stop the medication. She was warned that Botox would cure her temporarily, as the toxin takes effect for a few months, and the sprouting of new nerve fibres would cause a relapse of the disease, so she would have to repeat the injections. After several injections, the toxin would no longer be effective and she could be required to switch to another type of Botox (type B or C). Nevertheless, the patient insisted on having the Botox treatment. It was decided to give her the injections as this treatment was described clearly in the literature.3,9 A maxillofacial surgeon performed the procedure.
Oromandibular dystonia is difficult to diagnose as there is no special laboratory test for it and it is often masked by other dental conditions, such as a temporomandibular disorder, and treated as such.2,3,10
In conclusion, it is important to consider oromandibular dystonia as a possible diagnosis when a patient is apparently not responding to a TMD or any treatment of an occlusal problem. The onset of the disease must also be kept in mind, especially in view of the scant literature on its cause and onset.2 Although the patient stated that her oromandibular dystonia started after dental treatment, this could not be definitely ascertained.
