Involuntary movements of the stomatognathic system, e.g., oromandibular dystonia or dyskinesia, can result in excessive involuntary muscle contractions in the mouth, jaw, tongue, and lips. These contractions can cause various symptoms including failure to chew foods, problems with mouth opening or closing, muscle pain, lateral shifting of the jaw, and difficulty in swallowing or speaking. We apply a comprehensive range of treatments including medication, injections of local anesthetic (muscle afferent block therapy) or botulinum toxin (Botox), and surgery, for such involuntary movements.

Involuntary movements of

the stomatognathic region

Dr. Kazuya Yoshida

Department of Oral and Maxillofacial Surgery,

National Hospital Organization, Kyoto Medical Center

1-1 Mukaihata-cho, Fukakusa, Fushimi-ku, Kyoto 612-8555, Japan

Tel: 81-75-641-9161, Fax: 81-75-643-4325


I. Introduction

1. Symptoms of involuntary movements and other conditions

The mouth and jaw play important roles in various functions such as eating, chewing, speaking and swallowing. However, various problems can occur if the muscles that move the jaw and mouth are subjected to excessive involuntary contraction. These problems include failure to chew foods (masticatory disturbance); problems with mouth opening (trismus) or closing; involuntary movements of the mouth, tongue, and/or lips; tremors; muscle pain; lateral shifting of the jaw (jaw deviation); and difficulties with swallowing (dysphagia) or speaking (dysarthria). Such symptoms can be caused by dystonia of the mouth and/or jaw (oromandibular dystonia), temporomandibular joint disorders, oral dyskinesia, bruxism, fibromyalgia, psychogenic movement disorder, and/or masticatory muscle tendon-aponeurosis hyperplasia. The cause of the symptoms may be one of these diseases, however more than one disease may coexist. A variety of involuntary movements can occur in the orofacial region, most of which are not diagnosed correctly. In fact, the misdiagnosis of oromandibular dystonia as temporomandibular joint disorder, psychogenic disease, bruxism, or temporomandibular joint ankylosis is very common. Most patients that are diagnosed by dentists or oral surgeons are initially treated with dental appliances. In fact, 80% of our patients with jaw closing dystonia, the most common type of oromandibular dystonia, initially visited dentists or oral and maxillofacial surgeons. None of these patients were diagnosed with dystonia. Accordingly, they did not receive appropriate treatment, and their conditions deteriorated. In addition, dental students are not taught about involuntary movements other than oral dyskinesia and bruxism, and thus, probably do not recognize the symptoms of dystonia.

2. Triggers and causes

Involuntary movement is defined as movement that is not under the control of the brain. Movement disorders are neurological conditions that affect the speed, fluency, quality, and/or ease of movement. Abnormal fluency or speed of movement might manifest as excessive or involuntary movement, or slow or absent voluntary movement. There are various kinds of involuntary movements, e.g., dyskinesia, dystonia, tics, tremors, athetosis, myokymia, myoclonus, and chorea. The causes of involuntary movements remain unclear. However, dystonia is considered to be caused by functional abnormalities of the basal ganglia, which controls movement and posture, and can also develop in patients who have been taking oral psychiatric drugs for long period. The symptoms of dystonia are often observed after dental treatment (insertion of a new denture, tooth extraction, etc.) or a trauma involving the jaw or mouth. However, even though dental care can trigger the condition it does not directly cause it. Dystonia patients who experience mouth-related symptoms caused by involuntary contractions of the muscles of the jaw and/or tongue, particularly when they try to speak, often have professions that require them to speak regularly such as receptionists, sales staff, announcers, and teachers. Talking in a very stressful state for a long period of time can also contribute to dystonia and could be considered to be a kind of occupational dystonia, which is a type of dystonia in which the same movement is repeated excessively during a particular occupation, e.g., by a musician or craftsman causing muscle cramps.

3. Clinical and research history

I have been administering botulinum therapy for dystonia since 1992 and have treated many patients. I have also conducted research with Prof. Jun Kimura and Prof. Hiroshi Shibasaki at the Department of Neurology, Faculty of Medicine, Kyoto University. In addition, I have performed clinical research on involuntary movements such as dystonia as a Research Fellow (PD) of the Japan Society for the Promotion of Science with Dr. Ryuji Kaji (Utano National Hospital) at his laboratory of electrophysiology at Kyoto University. The following individuals, all of whom are considered authorities on involuntary movements and dystonia, also worked at the same laboratory: Dr. Takahiro Mezaki (Sakakibara Hakuho Hospital), Dr. Nagako Murase (Nara Medical Center, Department of Neurology), Dr. Toshiaki Suzuki (Kansai Medical University), Dr. Takashi Sakamoto (National Center of Neurology and Psychiatry), Dr. Shinichi Matsumoto (Osaka Neurological Institute, Department of Neurology), Dr. Takenori Abe (Nakamura Memorial Hospital, Department of Neurology).

At the Department of Oral and Maxillofacial Surgery at Kyoto Medical Center, we specialize in involuntary movements of the oral and facial area. We apply a comprehensive range of treatments for such involuntary movements, including medication, injections of local anesthetic (MAB therapy) or botulinum toxin (Botox), and surgery. There are no other departments that specialize in involuntary movements of the stomatognathic system. Accordingly, patients with involuntary movements of the orofacial region are referred to us from many hospitals. In addition, when patients require neurological, neurosurgical, or psychiatric treatment or examinations, they can be examined at our hospital’s Neurology, Psychiatry, or Neurosurgery departments. Due to these advantages, we receive numerous queries from all over Japan, and many patients come to our department for treatment from abroad.

II. Involuntary movements of the stomatognathic region

1. Dystonia

Dystonia (dys: abnormal, tonia: tension) is a neurological movement disorder. It is defined as a syndrome characterized by sustained muscle contractions that cause twisting or repetitive movements and abnormal postures in the affected body parts. Dystonia follows Parkinson's disease (a neurological movement disorder associated with bradykinesia, tremor, rigidity, and postural instability) and essential tremor (a common movement disorder characterized by involuntary, rhythmic oscillatory movements resulting from alternating or irregularly synchronous contractions of antagonist muscles) as the third most common movement disorder. The age at onset of dystonia varies from infancy to old age, and the condition tends to be more generalized in cases in which it displays an earlier onset.

·Oromandibular dystonia

Oromandibular dystonia is a focal dystonia that manifests as involuntary masticatory and/or lingual muscle contractions. Oromandibular dystonia includes jaw closing dystonia (Fig. 1), jaw opening dystonia (Fig. 2), tongue protrusion dystonia (Fig. 3), jaw deviation dystonia (Fig. 4), and jaw protrusion dystonia (Fig. 5) (ref. 13,17-22, 26). Oromandibular dystonia is easily misdiagnosed as a temporomandibular joint disorder or psychosomatic disease, and hence, patients with the condition often visit many hospitals and departments before being correctly diagnosed. Note, the patients whose photos are shown on my website have consented to this.

Fig. 1. A case of jaw closing dystonia. When this patient begins to speak, the jaw closing muscles (masseter muscles) go into involuntary contraction. As the result, she cannot open her mouth. The patient also suffers from blepharospasm (spasm of the eyelids). This combination of conditions is called Meige syndrome.

Video 1. Jaw closing dystonia (Meige syndrome)

Fig. 2. A case of jaw opening dystonia. During speaking, the patient’s jaw opening muscles (lateral pterygoid muscles) contract involuntarily, and the contractions gradually become stronger until she cannot speak any more. The patient shows no symptoms during eating or at rest.

Fig. 3. A case of tongue protrusion dystonia. When the patient begins to talk, her tongue gradually protrudes out of her mouth. The patient does not exhibit tongue contraction during other movements such as eating or swallowing.

Video 2. Tongue protrusion dystonia

Fig. 4. A case of jaw deviation dystonia. This patient exhibited lower jaw deviation (approximately 8mm to the right) during mouth closing. This was due to an involuntary contracture of the left lateral pterygoid muscle. The patient has displayed this symptom for a long time. The deviation was even present at rest. The mandible can sometimes deviate in temporomandibular joint disorders; however, it will deviate to the affected side during mouth opening in such conditions. The patient did not exhibit any abnormal findings on magnetic resonance imaging (MRI) of the temporomandibular joint.

Fig. 5. A case of jaw protrusion dystonia. This patient displays jaw protrusion due to involuntary contractions in the bilateral lateral pterygoid muscles. The patient has displayed the symptom at rest for a long time. Her temporomandibular joint did not display any abnormal findings. She is able to guide her jaws into the intercuspal position.

2. Clinical features of oromandibular dystonia

The clinical characteristics of oromandibular dystonia include the following (13,26):

·Stereotyped pattern of muscle contraction

The pattern of muscle contraction and the orientation of the abnormal posture or movement are constant in each patient. Patients with oromandibular dystonia exhibit stereotypical jaw muscle contractions according to the subtype (jaw closing, jaw opening, jaw deviation, jaw protrusion, or tongue protrusion dystonia) of oromandibular dystonia they are suffering from; i.e., jaw opening in jaw opening dystonia and jaw closing in jaw closing dystonia, etc.


Dystonia often starts with a specific task, especially in its early phase, e.g., writer's cramp might develop during writing, but not during other highly discrete hand movements such as handling a knife or chopsticks. The symptoms can later extend into other tasks and other body parts, and might eventually be present at rest. The symptoms of oromandibular dystonia patients often appear task-specifically only at the time of speaking or chewing.

·Sensory tricks

Sensory tricks are physical movements or positions that are able to temporarily interrupt dystonia, and patients might be aware a particular sensory trick that provides some relief from their symptoms. The symptoms of oromandibular dystonia can sometimes be temporarily ameliorated via the use of sensory tricks. For example, gently touching the lips, chin, teeth, or jaws with a handkerchief or mask; chewing gum; talking; biting on a toothpick or tobacco; or placing a finger underneath the chin might cause the symptoms to subside temporarily.

·Overflow phenomenon

The overflow phenomenon involves the activation of muscles that are unnecessary for a task, which hampers purposeful movement. For instance, dystonic contracture of the masticatory muscles can expand to the orbicularis oris muscle, orbicularis oculi muscle, neck and shoulder muscles.

·Morning benefit

The symptoms of dystonia tend to be milder in the morning, with large interindividual variations in their duration, while temporomandibular joint disorders caused by bruxism-related masticatory muscle tension tends to be worst upon awakening. This finding is important for differential diagnosis.


Co-contraction reflects a loss of the reciprocal inhibition of muscle activities, causing involuntary simultaneous contractions of agonist and antagonist muscles. This phenomenon is known to affect the masticatory muscles. For example, jaw elevator muscle contraction during mouth opening can prevent the mouth from opening, and jaw depressor muscle contraction during speaking or eating can interfere with speech or mastication.

·Flip-flop phenomenon

The symptoms of dystonia can abruptly appear or disappear in relatively mild cases, and they sometimes suddenly fully disappear during treatment.

In some cases of involuntary movement, none of the abovementioned features are present. We diagnose such patients as having a psychogenic movement disorder. The features of this entity are inconsistency in the pattern, distribution, and velocity of the involuntary movements in addition to spontaneous recovery or recurrence.

3. Dyskinesia

Dyskinesia (dys: abnormal, kinesia: movement) refers to repeated involuntary movements such as licking of the lips or chewing-like movements. Oral dyskinesia consists of abnormal, involuntary, uncontrollable movements that predominantly affect the tongue, lips, and jaw. They often vary in complexity, distribution, and severity. They might go unnoticed or result in social embarrassment, traumatic oral injuries, speech difficulties, chewing or eating disorders, an inability to wear dentures, or problems at work. In some cases, repeated dyskinetic movement results in frequent contact with the teeth, causing ulcers to form or trauma (Fig. 6).

Fig. 6. In this patient, repeated dyskinetic movement of the lower lip resulted in it being penetrated.

Video 3. Oral dyskinesia

4. Bruxism

Bruxism is clenching of the teeth when not chewing and is associated with forceful lateral or protrusive jaw movements. It results in the patient grinding or rubbing their teeth together. Bruxism usually occurs during sleep. It is sometimes done so forcefully or so often that it damages the occlusal surfaces of the teeth, particularly the molar teeth, and can contribute to temporomandibular joint syndrome. If, because of long-term excessive bruxism-related contractions, the masticatory muscles and tendons become stronger, it might result in hypertrophy of the masseter muscles, hyperplasia of the mandibular coronoid process and masticatory muscle hyperplasia tendon-aponeurosis hyperplasia. Masticatory muscle tendon-aponeurosis hyperplasia is a new disease entity that is characterized by limited mouth opening due to contracture of the masticatory muscles, resulting from hyperplasia of the tendons and aponeuroses.

III. Diagnosis of oromandibular dystonia

When diagnosing patient’s that exhibit involuntary movements we record their medical history and symptoms and make careful diagnosis. During this process, it is necessary to differentiate oromandibular dystonia from temporomandibular joint disorder, bruxism, oral dyskinesia, hyperplasia of the mandibular coronoid process, and masticatory muscle hyperplasia tendon-aponeurosis hyperplasia.

Fig. 7. Muscles that can be injected to treat involuntary contractions. Also, the genioglossus muscle, tensor veli palate muscle, and the muscles involved in facial expression can contract involuntarily.

1: zygomaticus major muscle, 2: orbicularis oris muscle, 3: mentalis muscle, 4: masseter muscle, 5: temporalis muscle, 6: coronoid process, 7: posterior belly of the digastric muscle, 8: anterior belly of the digastric muscle, 9: buccinators muscle, 10: sternocleidomastoid muscle, 11: trapezius muscle, 12: platysma, 13: medial pterygoid muscle, 14: lateral pterygoid muscle

1. Self-check for oromandibular dystonia

If you have symptoms such as involuntary movements or contractions involving the mouth and/or jaw muscles, you might have oromandibular dystonia. Please check any of the following statements that apply to you.

1. ( ) You experience unconscious contractions of the mouth and/or jaw muscles.

2. ( ) The direction of the movement (mouth closing, opening or tongue protrusion) is always the same.

3. ( ) The symptoms only appear during a specific task (speaking, eating, or mouth opening, etc.).

4. ( ) When something (chewing gum, candy, or a mouth piece, etc.) is in your mouth, the symptoms are temporarily relieved.

5. ( ) The symptoms do not occur during sleep.

6. ( ) Your symptoms are less severe or absent in the morning. However they gradually become worse during the day.

7. ( ) You are taking or have previously taken psychiatric drugs.

8. ( ) The severity of your symptoms is affected by tension or relaxation.

9. ( ) The symptoms first occurred after dental treatment or a tooth or jaw injury.

10. ( ) You are being treated for other forms of dystonia (spasmodic torticollis, blepharospasm, writer's cramp, etc.)

If you checked 2-3 answers, you might have oromandibular dystonia.

If you checked 4-5, you are likely to have oromandibular dystonia.

If you checked more than 6, you are highly likely to have oromandibular dystonia.

2. Contact us

If you wish us to diagnose and/or treat your oromandibular dystonia, please fill in the detailed questionnaire below and email it to Dr. Kazuya Yoshida ( as an attachment or fax it to +81-75-643-4325. Alternatively, you could post it to: Department of Oral and Maxillofacial Surgery, Kyoto Medical Center, 1-1, Mukaihata-cho, Fukakusa, Fushimi-ku, Kyoto 612-8555, Japan. Please note that due to the number of inquiries we receive from patients, it might take us some time to reply. We take care to manage patients’ personal information in an appropriate manner; however, transmitting personal information over the internet carries a risk of it being lost or disclosed. This site is my own (Dr. Kazuya Yoshida). Personal questions about medical care for other physicians at the Kyoto Medical Center cannot be accepted. If you have been treated elsewhere, you should have your physician write a letter of introduction. Also, if you are on any oral medication, we ask you to bring your prescription to your initial consultation.

3. Sending images and video

To obtain a definitive diagnosis, you should visit our hospital. However, if it is difficult for you to do this due to travel constraints, please make a video recording your involuntary movements, and email me it as an attachment using such as Hightail. We take care to manage patients’ personal information in an appropriate manner; however, transmitting personal information over the internet carries a risk of it being lost or disclosed. Any images and video data received are stored on a password-protected computer in a responsible manner. We keep the computer room locked when unattended and always strive to prevent theft.

4. Remote diagnosis

If you have the typical symptoms of dystonia, I will be able to say whether you are likely to have dystonia based on the information images, questionnaire results, and video you provide. However, for a definitive diagnosis you must visit our department to undergo electromyography (EMG), muscle palpation, and other tests such as X rays, computed tomography (CT), and MRI. Furthermore, in some cases consultations with the departments of Neurology, Psychiatry or Neurosurgery are also necessary. Please note that we cannot be held responsible for remote diagnoses based solely on questionnaire results and/or images.

5. Appointment for an initial consultation

If you wish to visit our department but you have been treated somewhere else already, please get your doctor to write a letter of introduction. Please tell your doctor to fill out a request form which can be downloaded from the Regional Medical Liaison Office’s website, and fax it to our hospital to make a reservation for your initial consultation. If it is not possible for your doctor to fax the form, you cannot make an appointment on your own. We ask you to make an appointment for 10:30 or earlier on Monday through Thursday. On Friday, we perform surgery under general anesthesia. If you have to travel far, and contact Dr. Kazuya Yoshida ( in advance, you can make reservation for the afternoon and be hospitalized immediately after your initial visit. However, because of the condition of the ward we cannot always offer the type of room you request (a large room, private room, special private room, etc.). In addition, you should check my schedule before visiting the hospital because I am occasionally absent because of business trips or scientific conferences. Alternatively, you can call our clinic on 075-641-9161, extension 3141. In addition, if you are taking any oral medication we ask you to bring your prescription.

·Getting to Kyoto Medical Center

By Keihan trains:

The center is 8 minutes walk from Fujinomori station on the Keihan line.

By Kintetsu trains:

At the JR Tokaido Shinkansen station or Kyoto station change to the Kintetsu line and then transfer to the Keihan line at Tanbabashi station. The center is 8 minutes walk from Fujinomori station (Fig. 8)

By JR trains:

Get on the JR Nara line at Kyoto station. The center is 12 minutes walk from JR Fujinomori station (Fig. 8).

Alternatively, get on the JR Nara line at Kyoto station, get off at Tofukuji station and transfer to the Keihan line. The center is 8 minutes walk from Fujinomori station.

By car:

The center is 7 minutes from the Kyoto Minami interchange of the Meishin Expressway.

(There are limited spaces in the parking lot, please use the tour bus and public transport as much as possible.)

Access to Kyoto Medical Center

Bus service timetable

Google Maps

Fig. 8. Map of the area around Kyoto Medical Center

6. Oromandibular dystonia questionnaire

Please fill out the following questionnaire. You can check more than one answer. If none of the example answers are applicable, please provide as much specific information as you can.

Full Name:

Gender: Male ( ), Female ( )

Date of birth: year ( ), month ( ), day ( )





1. What kind of symptoms do you have?

Clenching teeth ( ), Mouth opening ( ), Lateral or frontal shifting of the jaw ( ), Tongue protrusion ( ), Contraction around the mouth ( ), Movement of the tongue ( ), Movement of the lips ( ),

Other, please describe them specifically ( )

2. What problems does your condition cause?

Can not eat ( ), Can not talk ( ), Can not open mouth ( ), Pain ( ), Difficulty in swallowing ( ), Discomfort ( ),

Other, please describe them specifically ( )

3. How long have you had the symptoms?

( ) year(s), ( ) month(s), ( ) day(s)

4. Were your symptoms triggered by something?

No ( ), Yes ( )

If yes: Dental treatment ( ), Injuries to the mouth or jaw ( ), Oral medication ( ),

Other, please describe ( )

5. What part(s) of your body is affected?

Mouth ( ), Mandible (lower jaw) ( ), Maxilla (upper jaw) ( ), Lips ( ), Cheek ( ), Neck ( ), Eyelid ( ),

Other, please describe ( )

6. When do you experience symptoms?

During speaking ( ), During eating ( ), During mouth opening ( ), During swallowing ( ), Always ( ),

Other, please describe specifically ( )

7. Is there anything that temporarily eases the symptoms?

No ( ), Yes ( ), Depends on time ( )

If yes: Putting something in my mouth ( ), Touching my jaw with my hand or fingers ( ), Touching my mouth with a handkerchief or mask ( ),

Other, please describe specifically ( )

8. Do you have symptoms when you are sleeping?

No ( ), Yes ( ), Not sure ( )

Other, please describe ( )

9. Do the symptoms change over time?

No ( ), Yes ( ), There is a difference from day to day ( )

No symptoms upon awakening ( ), The symptoms become worse from morning to night ( ),

Other, please explain specifically ( )

10. Have you ever taken psychiatric drugs? Or are you now taking them?

No ( ), Yes ( )

If yes: For ( ) year(s), ( ) month(s), ( ) day(s)

Which drug(s)? ( )

11. Have you ever been treated for another form of dystonia or muscle contraction?

No ( ), Yes ( )

If yes: Spasmodic torticollis (cervical dystonia) ( ), Blepharospasm (spasms of the eyelids) ( ), Writer's cramp (hand dystonia) ( ), Hemifacial spasm (hemifacial-cramp) ( ), Other ( )

12. Which clinical departments have you visited so far for treatment?

None ( ), Department of Neurology ( ), Dentistry ( ), Oral and Maxillofacial Surgery ( ), Neurosurgery ( ), Otolaryngology ( ), Psychiatry ( ), Acupuncture ( ), Other ( )

13. What kind of examinations have you had?

None ( ), MRI ( ), CT ( ), EMG ( ), X-ray ( ), Blood test ( ), Genetic testing ( ), Other ( )

14. Have you had your symptoms treated?

No ( ), Yes ( )

If yes: Oral medication ( ), Botulinum therapy (Botox) ( ), Acupuncture ( ), Magnetic stimulation ( ), Surgery ( ),

Other ( )

15. Do you have any other medical condition now?

No ( ), Yes ( )

If yes: what? ( )

And where were you treated? At the Department of Neurology ( ), Psychiatry ( ), Orthopedics ( ),

Psychosomatic ( ), Surgery ( ), Internal medicine ( ), Other ( )

16. Please add any other information or questions.

( )

Please email your responses to the above questions to Dr. Kazuya Yoshida as an attachment ( or fax them to +81-75-643-4325). Alternatively, you can post them to: Department of Oral and Maxillofacial Surgery, Kyoto Medical Center, 1-1, Mukaihata-cho, Fukakusa, Fushimi-ku, Kyoto 612-8555, Japan.

The above data will only be used for diagnostic purposes. We take care to manage personal information in an appropriate manner. Due to the number of inquiries we receive from patients, we might have to wait for some time for a reply.

IV. 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.


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.


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 toxin 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.


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.


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.





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).



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 pharmacotherapy

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)


Nakamuta Memorial Hospital

Hokkaido Medical Center


National Center Hospital, National Center of Neurology and Psychiatry

Kawasaki Municipal Tama Hospital

Kanto Rosai Hospital

Juntendo University 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


Shinsyu University Hospital


Sakakibara Hakuho Hospital


Ijinkai Takeda General Hospital

Shinko Hospital

Kansai University of Health Sciences, Attached Clinic

Kyoto Medical Center


Tokushima University Hospital


Kaizuka Hospital

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.




Figure 11. Some of cultural attractions in Kyoto. Temple of the Golden Pavilion (a), Kiyomizu Temple (b), Fushimi Inari Shrine (c)

·Links (Kyoto tourism)

Kyoto City Tourism Association

Kyoto Travel Guide

Kyoto Prefecture's Web Site

Kyoto Prefecture Tourism Guide

World Heritage Map

JAPAN: the Official Guide

Japan Video Topics


V. Research

We have studied the activities of the masticatory muscles (the masseter, temporalis, lateral pterygoid, and medial pterygoid muscles) and other muscles associated with mastication (digastric and sternocleidomastoid musles, etc.) via the simultaneous recording of incisal point and condylar movements and examined the role of reflexes in the functional roles of these muscles (1-12).

We have also researched movement disorders such as oromandibular dystonia, dyskinesia, and bruxism, as well as diseases caused by abnormal muscle contracture of the masticatory muscles, such as masseteric hypertrophy, hyperplasia of the coronoid process, masticatory muscle tendon-aponeurosis hyperplasia, and temporomandibular joint disorders (13-29). Furthermore, we have electrophysiologically studied the movement and perception of the stomatognathic system using non-invasive brain function measurement techniques such as electroencephalography (movement-related cortical potentials, contingent negative variation, somatosensory evoked potentials), EMG (surface and needle EMG, evoked EMG), magnetoencephalography (MEG) (movement-related MEG, somatosensory evoked magnetic fields), and near-infrared spectroscopy (15,16,19,21-27). We are currently attempting to determine how the central nervous system regulates the movements of the mandible and tongue; chewing; and perception in the lips, tongue, gums, and palate, as well as the changes that occur during involuntary movements of the stomatognathic system, e.g., the changes in movement-related cortical potentials, which are indicative of activity in the supplementary motor area in the basal ganglia in preparation for exercise. The amplitudes of these potentials differ significantly between some of the movements. The amplitudes of potentials associated with lateral movements are identical and tend to be larger than those of potentials associated with mouth opening and closing. In addition, these signals tended to predominantly occur in the ipsilateral hemisphere during right- and left-sided movements whereas their hemispheric distribution was symmetrical during mouth opening and closing (15,16,19). These potentials exhibit decreased amplitudes in oromandibular dystonia (19,21). Also we have recorded somatosensory MEG responses using soft palate stimulation and observed the responses in the bilateral secondary sensory cortex (23) and perception in the tongue (27,29).

VI. References

1. Yoshida K, Inoue H. EMG activity of the superior and inferior heads of the human lateral pterygoid muscles in internal deranged patients. Advanced Prosthodontics Worldwide, Proceedings of the World Congress on Prosthodontics, 258-259, 1991.

2. Yoshida K, Fukuda Y, et al. A method for inserting the EMG electrode into the superior head of the human lateral pterygoid muscle. Journal of Japan Prosthodontic Society, 36: 88-93, 1992.

3. Yoshida K. An electromyographic study on the superior head of the lateral pterygoid muscle during mastication from the standpoint of condylar movement. Journal of Japan Prosthodontic Society, 36: 110-120, 1992.

4. Yoshida K, Inoue H. An electromyographic study of the lateral pterygoid muscles during mastication in patients with internal derangement of TMJ. Journal of Japan Prosthodontic Society, 36: 1261-1272, 1992.

5. Yoshida K. Untersuchung zum Entlastungsreflex von Kaumuskeln während des Zerbeißens von Nahrung. Deutsche Zahnärztliche Zeitschrift, 48: 588-590, 1993.

6. Yoshida K. An electromyographic study on unloading reflex of the masticatory muscles. Journal of Japan Prosthodontic Society,37: 227-235, 1993.

7. Yoshida K. Elektromyographische Aktivität der Kaumuskeln während Kiefergelenkknacken.Schweizer Monatsschrift für Zahnmedizin, 105: 24-29, 1995.

8. Yoshida K. Elektromyographische Aktivität des M. pterygoideus lateralis bei Patienten mit Kiefergelenkknacken und Diskusverlagerung. Deutsche Zahnärztliche Zeitschrift, 50: 721-724, 1995.

9. Yoshida K. Kiefergelenkknacken und Diskusverlagerung aus der Sicht der Elektromyographie der Kaumuskeln. In: Siebert GK (ed): Atlas der Zahnärztlichen Funktionsdiagnostik, Carl Hanser, München, 44-50, 1996.

10. Yoshida K. Masticatory muscle responses associated with unloading of biting force during food crushing. Journal of Oral Rehabilitation, 25: 830-837, 1998.

11. Yoshida K. Koordination der Kaumuskeln während der Kaubewegung aus der Sicht der Kondylusbewegung bei Patienten mit Diskusdislokation. Deutsche Zahnärztliche Zeitschrift, 52: 816-820, 1998.

12. Yoshida K. Eigenschaften der Kaumuskelaktivität während verschiedenen Unterkieferbewegungen bei Patienten mit Diskusverlagerung ohne Reposition. Stomatologie, 96: 107-121, 1999.

13. Yoshida K, Kaji R, et al. Muscle afferent block for the treatment of oromandibular dystonia. Movement Disorders, 13: 699-705, 1998.

14. Yoshida K, Kaji R, et al. Muskelafferenzblockierung mittels lokaler Injektion von Lidocain bei Kaumuskelspasmus. Deutsche Zahnärztliche Zeitschrift, 53: 197-199, 1998.

15. Yoshida K, Kaji R, et al. Cortical potentials associated with voluntary mandibular movements. Journal of Dental Research, 79: 1514-1518, 2000.

16. Yoshida K, Kaji R, et al. Cortical distribution of Bereitschaftspotential and negative slope potential preceding mouth opening movements in human subjects. Archives of Oral Biology, 44: 183-190, 1999.

17. Yoshida K, Kaji R, et al. Muscle afferent block therapy for oromandibular dystonia. Japanese Journal of Oral and Maxillofacial Surgery, 46: 563-571, 2000.

18. Yoshida K, Kaji R, et al. Factors influencing the therapeutic effect of muscle afferent block for oromandibular dystonia: implications their distinct pathophysiology. International Journal of Oral and Maxillofacial Surgery, 31, 499-505, 2002.

19. Yoshida K, Kaji R, et al. Movement-related cortical potentials prior to jaw excursions in patients with oromandibular dystonia. Movement Disorders, 18, 94-100, 2003.

20. Yoshida K. Muskelafferentzblockierung in der Behandlung der oromandibulären Dystonie -Unterschiedliche Wirkung auf Kau- und Zungenmuskulatur-. Nervenarzt, 74: 516-522, 2003.

21. Yoshida K, Iizuka T. Jaw-deviation dystonia evaluated by movement-related cortical potentials and treated with muscle afferent block. Journal of Craniomandibular Practice, 21, 295-300, 2003.

22. Yoshida K. Temporomandibular joint disorders and sleep. Iizuka T, Inoue H (eds), Manual of Temporomandibular Joint Disorders. Nagasue, Kyoto, 186-193, 2004.

23. Yoshida K, Maezawa H, et al. Somatosensory evoked magnetic fields to air-puff stimulation on the soft palate. Neuroscience Research, 2006 55, 116-122, 2006.

24. Yoshida K, Iizuka T. Botulinum toxin treatment for upper airway collapse resulting from temporomandibular joint dislocation due to jaw-opening dystonia. Journal of Craniomandibular Practice, 24 217-222, 2006.

25. Yoshida K. Coronoidotomy as treatment for trismus due to jaw-closing oromandibular dystonia. Movement Disorders, 21, 1028-1031, 2006.

26. Miyawaki S, Yoshida K. Involuntary movements in the orofacial region. Cyclopedia of Mouth and Teeth. Asakura, Tokyo, 282-296, 2008.

27. Maezawa H, Yoshida K, et al. Somatosensory evoked magnetic fields following the tongue stimulation using needle electrodes. Neuroscience Research, 62, 131-139, 2008.

28. Maezawa H, Matsuhashi M, Yoshida K, et al. The magnetic artifacts derived from dental metals in magnetoencephalography. Japanese Journal of Cognitive Neuroscience, 11: 258-267, 2010.

29. Maezawa H, Yoshida K, et al. Evaluation of tongue sensory disturbance by somatosensory evoked magnetic fields following tongue stimulation. Neuroscience Research, 71, 244-250, 2011.

30. Maezawa H, Tojyo I, Yoshida K, et al. Recovery of impaired somatosensory evoked fields induced by tongue stimulation after improvement of tongue sensory deficits. Journal of Oral and Maxillofacial Surgery. 74, 1473-1482, 2016.

31. Yoshida K. Surgical intervention for oromandibular dystonia-related limited mouth opening: long-term follow-up. Journal of Cranio Maxillofacial Surgery. 45, 56-62, 2017.

32. Yoshida K. How do I inject botulinum toxin into the lateral and medial pterygoid muscles? Movement Disorders Clinical Practice 4, 285, 2017 doi:10.1002/mdc3.12460

33. Yoshida K. Clinical and phenomenological characteristics of patients with task-specific lingual dystonia: possible association with occupation. Frontiers in Neurology. 8, 649, 2017 doi:10.3389/fneur.2017.00649

34. Yoshida K. Sensory trick splint as a multimodal therapy for oromandibular dystonia. J Prosthodont Res. 62, 239-244, 2018 doi:10.1016/j.jpor.2017.09.004

35. Yoshida K. Computer-aided design/computer-assisted manufacture-derived needle guide for injection of botulinum toxin into the lateral pterygoid muscle in patients with oromandibular dystonia. Journal of Oral & Facial Pain and Headache. 32, e13-e21, 2018 doi: 10.11607/ofph.1955

36. Yoshida K. Multilingual website and cyberconsultations for oromandibular dystonia. Neurology International. 10, 7536, 2018 doi: 10.4081/ni.2018.7536

37. Yoshida K. Botulinum neurotoxin injection for the treatment of recurrent temporomandibular joint dislocation with and without neurogenic muscular hypertrophy. Toxins. 10, 174; doi: 10.3390/toxins10050174

38. Yoshida K. Oromandibular dystonia screening questionnaire for differential diagnosis. Clinical Oral Investigation. 23, 405–411, 2019. doi: 10.1007/s00784-018-2449-3

39. Yoshida K. Botulinum neurotoxin therapy for lingual dystonia using an individualized injection method based on clinical features. Toxins. 11, 51, 2019. doi: 10.3390/toxins11010051

40. Yoshida K. Development and validation of a disease-specific oromandibular dystonia rating scale (OMDRS). Frontiers in Neurology. 11, 583177, 2020. doi: 10.3389/fneur.2020.583177

41. Yoshida K. Sphenopalatine ganglion block with botulinum neurotoxin for treating trigeminal neuralgia using CAD/CAM-derived injection guide. Journal of Oral & Facial Pain Headache. 34, 135–140, 2020. doi: 10.11607/ofph.2510

42. Yoshida K. Clinical characteristics of functional movement disorders in the stomatognathic system. Frontiers in Neurology. 11: 23, 2020. doi: 0.3389/fneur.2020.00123

43. Yoshida K. Mouth opening retaining appliance after coronoidotomy for the treatment of trismus: effects on pain during postoperative training and maximal extent of mouth opening. Clinics in Surgery. 5, 2737, 2020.

44. Yoshida K. Prevalence and incidence of oromandibular dystonia: an oral and maxillofacial surgery service-based study. Clinical Oral Investigation. 25, 5755-5764, 2021. doi: 10.1007/s00784-021-03878-9

45. Yoshida K. Effects of botulinum toxin type A on pain among trigeminal neuralgia, myofascial temporomandibular disorders, and oromandibular dystonia. Toxins. 13, 605, 2021. doi: 10.3390/toxins13090605

46. Yoshida K. Behandlungsstrategien bei oromandibulärer Dystonie. Fortschritte der Neurologie Psychiatrie. 89, 562-572, 2021. doi: 10.1055/a-1375-0669

47. Yoshida K. Is botulinum toxin therapy effective for bruxism? Anti-Aging Medicine. 13: 394-398, 2017.

48. Yoshida K. Clinical Application of Botulinum Neurotoxin for Diseases in the Stomatognathic System. Journal of Japanese Dental Society of Anesthesiology. 48, 33‒40, 2020.doi:

49.Yoshida K. Oromandibular dystonia. Clinical Neuroscience. 38, 1118-1121, 2020.

The publications listed above are representative of my studies on involuntary movements. I have listed other literature at ResearchGate. In addition, studies on sleep apnea syndrome have been compiled on the following website: Treatment and research of sleep apnea syndrome from clinical and neurophysiological aspects in the stomatognathic system.

1. Books

1. Principles and Practice of Movement Disorders: Expert Consult. Fahn S, Jankovic J, Hallett M, Saunders, 2011.

2. Psychogenic Movement Disorders and Other Conversion disorders. Hallett M, Lang AE, Jankovic J, Fahn S, Cambridge University Press, 2011.

3. Movement Disorders: 100 Instructive Cases. Reich SG, CRC Press, 2008.

4. Manual of Botulinum Toxin Therapy. Truong D, Dressler D, Hallett M, Cambridge University Press, 2009.

2. Links

·Societies and institutes

The Movement Disorder Society

American Academy of Neurology

World Federation of Neurology

International Federation of Neurology

Movement Disorder Society of Japan

National Institute of Neurological Disorders and Stroke

UCL Institute of Neurology

BCM Parkinson's Disease Center and Movement Disorders Clinic

Societas Neurologica Japonica

Japanese Society of Clinical Neurophysiology

·Patient groups

Dystonia Medical Research Foundation


Bachmann-Strauss Dystonia & Parkinson Foundation

Benign Essential Blepharospasm Research Foundation (BEBRF)

National Spasmodic Torticollis Association (NSTA)

Spasmodic Torticollis/Dystonia, Inc.

The Dystonia Society

Action for Dystonia, Diagnosis, Education and Research (ADDER)

Dystonia Europa

Australian Spasmodic Torticollis Association

Blepharospasm Australia

Dystonia Ireland

Dystonian Friends Association

Deutsche Dystonie Gesellschaft e.V.

Bundesverband Torticollis e. V.

Österreichische Dystonie Gesellschaft

Schweizerische Dystonie-Gesellschaft

Association de Malades atteints de Dystonie (AMADYS)

Asociación de Lucha contra la Distonia en España (ALDE)

Associazione Italiana per la Ricerca sulla Distonia (ARD)

Associacao Brasileira dos Portadores de Distonias

Associação Portuguesa de Distonia

Nederlandse Vereniging van Dystoniepatiënten

Belgische Zelfhulpgroep voor Dystoniepatienten v.z.w.

Svensk Dystoniförening

Dansk Dystoniforening

Norsk Dystoniforening