Treatment of oromandibular dystonia
As an initial treatment, we prescribe medicine for mild cases. Most patients show some improvement. There is no specific medicine for oromandibular dystonia. We use combinations of various drugs and continue to gradually increase the dose while evaluating the effects and side effects of the treatment. Pharmacotherapy takes several months. As the elderly tend to develop side effects, we increase the dose slowly in such patients. If a patient’s symptoms do not improve, we apply muscle afferent block (MAB) therapy by injecting local anesthetic into the affected muscles (13,14,17,18,20-22,26) or via the intramuscular injection of botulinum toxin (botulinum therapy) (22,24,26).
1. Muscle afferent block (MAB) therapy
MAB therapy, which involves the local injection of diluted lidocaine and ethanol, aims to reduce the effectiveness of muscle spindle afferents without causing unfavorable weakness. Its effect has been shown to be mediated by the blockade of either muscle afferents or gamma motor efferents. In a previous study, the T-reflex of the hand muscles was attenuated whilst their power was preserved after the intramuscular injection of lidocaine, and the muscle spindle afferents or gamma motor efferents that tonically control the sensitivity of the spindles were postulated to be blocked by MAB. In another study, the mean post-MAB response of the jaw elevator muscles (70%), which was evaluated on a self-rating scale, was significantly higher than that of the depressor muscles (38%) (17,18), and it was suggested that by the different numbers of muscle spindles supplying these muscles were responsible for these results. Therefore, MAB therapy is indicated for jaw elevator muscles (the masseter, temporalis and medial pterygoid muscles), but not for jaw depressor muscles (the lateral pterygoid and digastric muscles), which contain fewer muscle spindles.
·EMG recordings
We use surface electrodes to take EMG recordings from superficially located muscles such as the masseter and temporal muscles, whereas we use needle electrodes for deeper muscles like the lateral pterygoid and medial pterygoid muscles or genioglossus muscles. We choose the target muscles for injection based on the patient's symptoms and the results of EMG recordings from the masseter, temporalis, lateral pterygoid (the inferior head), medial pterygoid, genioglossus, trapezius, and sternocleidomastoid muscles, etc.
·Injection
The injection volume (2 to 10 ml) of 0.5% lidocaine delivered to the target muscle is determined according to the size of the target muscle and its contraction force: 3-5 ml for the lateral pterygoid, medial pterygoid, and digastric muscles; 5-10 ml for the masseter, temporal, genioglossus muscles; and 10 ml for the trapezius and sternocleidomastoid muscles.
During the contraction of the target muscle, we slowly inject 80% of the total lidocaine dosage into one site within the bulkiest portion of the muscle using a hollow EMG needle and a standard EMG instrument for guidance. During the injection, we specifically check the subject for any pain, numbness, or weakness. After confirming the absence of these symptoms, we then slowly inject ethanol. The remaining 20% of the lidocaine is added to the ethanol at the same needle site by reversing the connector. We only inject lidocaine in the first treatment session. In the subsequent sessions, a one-tenth volume of 99.5% ethanol is added to the lidocaine at the same needle site using a triple connector.
·Follow-up
The treatment begins to have a noticeable effect soon after the injection, but the effect only lasts for a short period. After repeated injections, the effects of the injections gradually last longer. Eventually, the effects of such injections can last for 6 months or more.
2. Botulinum therapy
Botulinum toxin is produced by Clostridium botulinum, a Gram-positive anaerobic bacterium. Botulinum toxin is a neuromuscular blocking agent. It exerts its paralytic action by rapidly and strongly binding to presynaptic cholinergic nerve terminals. It is then internalized and ultimately inhibits the exocytosis of acetylcholine by decreasing the frequency of acetylcholine release. Without its nerve supply, the muscle fiber withers away. The muscle strengthens again as the nerves regenerate.
·EMG recordings
We use surface and needle electrodes to take EMG recordings in the same manner as described for MAB therapy. We choose the target muscles for injection based on the patient’s symptoms and the results of EMG recordings from the masseter, temporal, lateral pterygoid (the inferior head), medial pterygoid, digastric (the anterior belly), genioglossus, trapezius, and sternocleidomastoid muscles, etc.
·Injection
Botulinum toxin (Botox) is reconstituted with normal saline. Appropriate doses of the toxin are injected into several sites within the bulkiest portion of the target muscle during contraction using a monopolar hollow-bore EMG needle and an EMG instrument for guidance. In the first injection, we only inject a small dose of the toxin due to the large interindividual variation in its effects.
·Follow-up
The treatment first begins to have a noticeable effect a few days after the injection. The effect usually lasts a minimum of 3-4 months; however, some patients experience a lasting effect. We record the degree of jaw opening and bite force after treatment as objective assessments of the therapeutic effect. The injections should be repeated over time if the effects disappear.
Video 4. Jaw closing dystonia before and after botulinum therapy
Video 5. Tongue protrusion dystonia before and after botulinum therapy
3. Surgery
If long-term extremely forceful dystonic elevator muscle contraction results in masticatory muscle tendon-aponeurosis hyperplasia or hyperplasia of the coronoid process (Fig. 9), surgery, e.g., coronoidotomy, might be required (Fig. 10) (22,25,26). We approach, and all incisions are made in the mouth, so no surgical scars remain on the face. The operation takes 1.5-2 hours. As postoperative mouth opening training is important, the patient has to remain in hospital for about two weeks.
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Fig. 9. A case of hyperplasia of the coronoid process. Note the enlargement of the bilateral coronoid process and the hypertrophy of the mandibular angle (a). The enlargement impinges on the zygomatic arch during mouth opening. The maximal extent of mouth opening was only 17 mm (b). After bilateral coronoidotomy (c), the maximal extent of mouth opening increased to over 40 mm (d).
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Fig. 10. This patient could not open her mouth at all due to involuntary contracture of the bilateral temporalis and masseter muscles (a). Radiographs of the temporomandibular joints showed normal findings. Bilateral coronoidotomy via the intraoral approach was performed under general anesthesia. Just after the operation, the patient was able to open her mouth by 50 mm (b).
Video 6. Jaw closing dystonia before and after coronoidotomy
4. Other therapies
Neurosurgical procedures such as stereotactic surgery or deep brain stimulation, transcranial magnetic stimulation, psychotherapy, and acupuncture have been used to treat other focal dystonias such as blepharospasm, cervical dystonia, and hemifacial spasm. However, there are insufficient data on their safety and effectiveness against oromandibular dystonia.
5. Treatment of other involuntary movements
Pharmacotherapy is the main treatment for oral dyskinesia (14). Bruxism is generally treated with oral medication or splinting. At our department, we also apply botulinum therapy if the patient’s symptoms fail to improve after these general methods. Masticatory muscle-tendon aponeurosis hyperplasia requires surgery under general anesthesia. At our department, we perform surgery for patients with hyperplasia due to masticatory muscle tendon-aponeurosis hyperplasia, masseteric hypertrophy, or hyperplasia of the coronoid process, which can induce excessively forceful masticatory contractions over the long-term.
Video 7. Oral dyskinesia before and after pharmacotherap
Video 8. Oral dyskinesia before and after denture adjustment
6. Hospitals capable of treating dystonia
Only a limited number of physicians specialize in involuntary movements, even among neurologists. Few neurologists are able to diagnose and treat dystonia. I have listed below hospitals that are capable of treating focal dystonia such as blepharospasm and spasmodic torticollis. There are no hospitals that specialize in oromandibular dystonia. Neurologists are able to diagnose oromandibular dystonia; however, it is difficult to diagnose in cases in which the muscles of the jaw and/or mouth show exhibit abnormal contractions, and it requires skill to accurately inject Botox into the affected muscles. The listed hospitals will use the same medication as we do to treat patients with mild oromandibular dystonia. If you are currently living in Japan but would find it difficult to visit our hospital, we recommend that you consult one of the following hospitals.
·Links (Hospitals)
Hokkaido
Kanto
National Center Hospital, National Center of Neurology and Psychiatry
Kawasaki Municipal Tama Hospital
St. Marianna University School of Medicine Hospital
Teikyo University Medical Center
Tokyo Medical University Hospital
Tokyo Women's Medical University Hospital
Aoyama Hospital Tokyo Women's Medical University
Tokyo Metropolitan Neurological Hospital
Toho University Ohashi Medical Center
Shin-Etsu
Tokai
Kansai
Ijinkai Takeda General Hospital
Kansai University of Health Sciences, Attached Clinic
Shikoku
Kyusyu
University of Occupational and Environmental Health
7. Medical tourism
Once a diagnosis of dystonia is made, the treatment will differ depending on the degree of the patient’s symptoms. Patients with milder symptoms will receive oral medication or undergo MAB therapy. MAB therapy and oral medication therapy both take several months. However, botulinum therapy for the mouth closing muscles (masseter, temporalis, and medial pterygoid muscles) is possible as an outpatient. In the case of injections into the muscles of the palate or tongue, dysphagia might occur after treatment, although our department has experienced no such cases; therefore, it is safer for you to stay in hospital for a short period after such injections. If you prepared to be hospitalized for a brief period, botulinum therapy and surgery are possible. Botulinum therapy takes about 3-5 days. Surgery such as coronoidotomy requires two-week stay in hospital. Pharmacotherapy and surgery are covered by the Japanese national health insurance system, but botulinum therapy based on the site and muscles injected cannot be covered by the insurance.
Recently, medical tourism; i.e., when patients visit different regions or countries to obtain medical services, has become increasingly common. Therefore, if you require treatment for involuntary contractions of the mouth and/or jaw including botulinum therapy, visiting our center as a medical tourism might be an appropriate option. Kyoto has many attractions including UNESCO World Heritage Sites (Figure 10) and Michelin-starred restaurants. In addition, the ancient city has something to offer in all four seasons, e.g., cherry blossoms in spring, autumn leaves, the Gion Festival, Jidai Matsuri, and Daimonji. Our hospital provides special private rooms, which are almost like a luxurious hotel (Hospitalization). The treatment of oromandibular dystonia can be performed for visitors to Kyoto. We welcome dystonia patients from all over the world.
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Figure 11. Some of cultural attractions in Kyoto. Temple of the Golden Pavilion (a), Kiyomizu Temple (b), Fushimi Inari Shrine (c)