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.