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Botulinum Toxin Injection Therapy for Lingual Dystonia: A Case Report
J Oral Med Pain 2022;47:152-155
Published online September 30, 2022;  https://doi.org/10.14476/jomp.2022.47.3.152
© 2022 Korean Academy of Orofacial Pain and Oral Medicine

So-Yeon Bae │ Ji-Rak Kim

Department of Oral Medicine, School of Dentistry, Kyungpook National University, Daegu, Korea
Correspondence to: Ji-Rak Kim
Department of Oral Medicine, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu 41940, Korea
Tel: +82-53-600-7324
Fax: +82-53-426-2195
E-mail: jirak@knu.ac.kr
https://orcid.org/0000-0002-1326-3948
Received August 23, 2022; Revised September 2, 2022; Accepted September 2, 2022.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Lingual dystonia is an uncommon focal type of oromandibular dystonia that only affects the tongue. Although the use of several treatment modalities has been attempted to reduce involuntary tongue movements, such as anticonvulsants and anticholinergics, the results do not seem promising, and the efficacy of such treatments is unpredictable among patients. This case report describes botulinum toxin injection for a patient with lingual dystonia with favorable clinical results. Botulinum toxin injection to the muscles of the tongue could be an alternative treatment option for lingual dystonia.
Keywords : Botulinum toxin; Lingual dystonia; Muscle dystonia
INTRODUCTION

Dystonia is a movement disorder characterized by lasting and involuntary muscle contractions that cause abnormal movements or postures [1]. Oromandibular dystonia (OMD) is a subtype of dystonia that can manifest as tooth grinding, clenching, opening, deviation, or protrusion, or a combination of these, depending on the affected muscles, resulting in stuttering, dysphagia, and cosmetic disfigurement [2,3].

The symptoms of OMD usually occur between the age of 40 and 70 and is more common in women (female-to-male ratio, 1.3-2:1) [4]. The prevalence of OMD was estimated to be about 68.9 per million [5]. OMD can be inherited or acquired or occur secondary to idiopathic nervous system pathologies. Neuropathological abnormalities may occur due to the use of drugs, such as dopamine agonists, anticonvulsants, and calcium channel blockers, or secondary to neurological disorders, including Huntington’s disease, cerebral palsy, infectious diseases, toxins, vascular diseases, and psychological causes [1].

Although OMD is diagnosed based on clinical features, its various forms and their severity make it complicated. Furthermore, there is no confirmatory diagnostic test. Hence, the diagnosis is made on a case-by-case basis; patient information, history, neurological examination, and confirmation via intramuscular electromyography are key [6]. Patients with OMD are managed with medication, muscle afferent nerve blocks, sensory trick appliances, physiotherapy, and botulinum toxin injection therapy.

Lingual dystonia is an idiopathic rare subtype of OMD having a prevalence of 4% [1,7]. It can be treated using a comprehensive range of various treatment options [2]. This case report elaborates on the use of botulinum toxin injection therapy for lingual dystonia treatment.

This study protocol was approved by the Institutional Review Board of Kyungpook National University Dental Hospital (approval no. KNUDH-2022-07-04-00), and the need for collecting written informed consent was waived by the committee.

CASE REPORT

A 74-year-old female patient visited the Department of Oral Medicine, Kyungpook National University Dental Hospital, with chief complaints of a spontaneous, dull pain in both cheeks, hypersalivation, and difficulty in pronunciation for the last 3 months. She visited the department of neurology at the hospital; however, no neurological abnormalities were detected. She had been diagnosed with osteoporosis, shoulder arthritis, and gastrointestinal disorders.

During physical examination, she complained of pain in both the masseter muscle areas during mouth opening and palpation. Her tongue was continuously curled to the left, and the mandible had a left-ward deviation. The masseter and the muscles of the tongue exhibited involuntary movements. There were no specific findings in the panoramic and temporomandibular joint radiographs. When the history of the present complaints was elucidated, it was found that the repetitive movements of the tongue and masseter had started 4 years prior. At the time, there was no history of drug consumption or trauma and no abnormal findings in the neurological examination. According to the classification proposed by Albanese et al. [1], the patient’s symptoms were indicative of OMD and resultant local myalgia of the bilateral masseter muscles.

The patient was given options, such as botulinum toxin injection, splint, and pharmacological therapy; she opted for the pharmacological therapy first. To reduce excessive muscle contraction by blocking acetylcholine in the central nervous system, trihexyphenidyl (4 mg/day) was prescribed. Diazepam (2 mg/day) was prescribed to induce muscle relaxation by increasing the inhibitory effect of γ-aminobutyric acid. After 3 weeks of treatment, involuntary movements of the mandible and tongue persisted. The patient arbitrarily stopped medication and underwent botulinum toxin injection in the bilateral masseter muscles at a dermatology clinic. After the procedure, the involuntary movements of the mandible improved. However, the tongue symptoms persisted; the patient requested for botulinum toxin injections to relieve the lingual dystonia (Fig. 1).


Sixteen units of botulinum toxin (Botulax; Hugel, Inc., Chuncheon, Korea) was injected into six points of the bilateral superior longitudinal muscles and two units each into two points of the left inferior longitudinal muscle (Fig. 2). Three days after the injection, the patient’s difficulty in pronunciation worsened but resolved after a few days. On follow-up examination after 2 weeks, the involuntary movements had decreased compared with the initial visit; however, the curling and laterotrusion movement to the left persisted. An additional 21 units of botulinum toxin was injected into the same area (Fig. 3). To alleviate movement to the left, the dorsal and ventral points of the left posterior area were supplemented with 0.5 units each. Two months after the initial injection, both the mandibular and tongue involuntary movements had significantly decreased.


The patient’s before-and-after state of lingual dystonia was evaluated using Yoshida’s rating scale (Table 1) [2]. Her mastication scale decreased from 3 (takes a long time to consume soft food) to 1 (takes a long time to consume anything); speech scale, from 4 (inaudible) to 1 (hard to speak clearly); pain scale, from 3 (numeric rating scale: 5-7.5) to 2 (numeric rating scale: 2.5-5); discomfort scale, from 3 (moderate to severe) to 2 (mild to moderate); and total score, from 12 to 6 points (Table 2). After botulinum toxin injection, the patient’s overall discomfort had decreased.

DISCUSSION

OMD, including lingual dystonia, is managed with medications, muscle afferent blocks, sensory trick splints, myomonitors, and botulinum toxin injections. If patients do not respond to any of these treatments, surgical interventions, such as coronal arthroplasty, are recommended. Several medications, such as anticholinergics, benzodiazepines, anti-parkinsonism drugs, anticonvulsants, and dopamine receptor antagonists, are also being used to manage OMD [6,8]. For lingual dystonia, the therapeutic effects of these medications are unstable even if patients overcome the side effects of the drug.

There are several case reports of effective symptomatic relief in patients with lingual dystonia without major adverse effects with botulinum toxin injection [2,3,7,9,10]. Yoshida’s lingual dystonia subtype classification from previous literature can be applied to this case [2]. In Yoshida’s article [2], in cases of curling and laterotrusion type of dystonia similar to this case, the appropriate injection amount to minimize adverse reactions is between 10 and 40 units; in this case, a total of 37 units were injected twice within a span of 2 weeks.

In our case, an initial smaller dose was injected to minimize the side effects. Because the effect of botulinum toxin peaks at about 10 days [11], supplemental doses are considered after 2 weeks depending on the symptom severity of the patient. In cases of laterotrusion type of dystonia, the literature describes the administration of botulinum toxin into the genioglossus muscle on the side contralateral to the affected side; however, because electromyography-guided injection was not possible in this hospital, botulinum toxin could not be correctly injected into the genioglossus muscle. Thus, although movements had decreased compared with those before the injection, the symptom reduction was not satisfying to the patient.

In Yoshida’s article [2], mild and transient dysphagia developed in 3.7% of the total injections (12.5% of patients) from a total of 172 patients, and the side effects spontaneously disappeared within a few days to 2 weeks. In this case, there was no dysphagia, but the patient developed worsening difficulty with pronunciation 3 days following the injection. However, 2 weeks after the injection, the difficulty in pronunciation resolved, and the involuntary movements had decreased to some extent when compared with those before the intervention. An additional injection of 21 units 2 weeks after the initial injection (16 units) did not cause any side effects. Due to poor patient compliance and loss to follow-up, it was not possible to confirm how long the effect lasted after one injection, making it difficult to evaluate whether repeated injections showed similar or better efficacy than a single shot.

Patients with lingual dystonia suffer from repetitive muscle movement, affecting their quality of life. Botulinum toxin injection into the genioglossus and/or other muscles improved the quality of life [12]. Using the OMD questionnaire-25, all the patients achieved satisfactory results with good safety and tolerability. Among them, patients with lingual and additional jaw deviation dystonia reported the highest improvement.

At present, the etiology of lingual dystonia is still unknown; thus, complete cure cannot be guaranteed. Abnormal movement of the tongue muscle can interfere with significant daily activities, such as chewing, swallowing, and speaking, causing occupational and aesthetic problems, and consequently, social disability. Thus, social disabilities need to be resolved through symptomatic relief. In most cases, administration of oral therapeutics to treat lingual dystonia is unsatisfactory. Treatment with botulinum toxin injection may be beneficial in the management of lingual dystonia.

CONFLICT OF INTEREST

No potential conflict of interest relevant to this article was reported.

Figures
Fig. 1. Prior to injection, continuous involuntary movement of the tongue was observed. Curling (A) and laterotrusion of the tongue to the left (B).
Fig. 2. Injection site. Six points into the bilateral superior longitudinal muscles (A) and two points into the left inferior longitudinal muscle, each two units (B). A total of 16 units were injected.
Fig. 3. Additional injection site. Six points into the bilateral superior longitudinal muscles (A) and two points into the left inferior longitudinal muscle, each 2.5 units (B). To alleviate movement to the left, the botulinum toxin was injected into the dorsal and ventral left posterior area, 2.5 units each plus 0.5 units (3 units), making a grand total of 21 units.
Tables

Rating scale to evaluate oromandibular dystonia [2]

Point Mastication Speech Pain Discomfort
0 Normal Normal No pain No discomfort
1 Takes a long time to consume anything Hard to speak clearly Numeric rating scale: <2.5 Mild
2 Soft food only Difficult to comprehend Numeric rating scale: 2.5-5 Mild to moderate
3 Takes a long time to consume soft food Not audible to less than half of speech Numeric rating scale: 5-7.5 Moderate to severe
4 Liquids only Not audible to more than half of speech Numeric rating scale: >7.5 Severe

Comparison of the rating scale before-and-after botulinum toxin injection

Rating scale First visit 2 months after injection
Mastication 3 1
Speech 4 1
Pain 2 2
Discomfort 3 2
Total 12 6
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