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Year : 2011  |  Volume : 22  |  Issue : 5  |  Page : 729-730
Trismus as a first presenting complaint in a case of myasthenia gravis

Department of Dental Surgery, Christian Medical College and Hospital, Vellore 632 004, India

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Date of Submission12-Jul-2010
Date of Decision13-Oct-2010
Date of Acceptance27-Jul-2011
Date of Web Publication7-Mar-2012


The initial presentation of myasthenia gravis as trismus is very rare and no previous reports have been found in the literature. A 35-year-old male presented to the outpatient unit of our department with inability to clench well and to open his mouth. Physical examination revealed that he had clinical findings consistent with the signs and symptoms of myasthenia gravis. He was immediately referred to a neurologist, who confirmed that he was in an advanced stage of myasthenia gravis with severe deficit to his respiratory muscles and he was promptly treated. He is presently on a maintenance drug therapy. To our knowledge, this is the first reported case of myasthenia gravis whose initial presentation was trismus. This case presents a rare but important diagnosis that should be added to the differential diagnosis of trismus.

Keywords: Diagnosis, myasthenia gravis, trismus

How to cite this article:
Simon SS, Challu AP, Chacko RK. Trismus as a first presenting complaint in a case of myasthenia gravis. Indian J Dent Res 2011;22:729-30

How to cite this URL:
Simon SS, Challu AP, Chacko RK. Trismus as a first presenting complaint in a case of myasthenia gravis. Indian J Dent Res [serial online] 2011 [cited 2023 Mar 30];22:729-30. Available from:
Trismus can be a result of various causes. In most instances, local inflammation or other pathology accounts for most cases of trismus. [1],[2] Neuromuscular causes for trismus are rare and a neurological condition like myasthenia gravis has rarely been implicated as a cause for trismus. [1],[2]

   Case Report Top

A 35-year-old man presented to our department with the chief complaint of progressive trismus for past 3 months following a dental extraction. He had no previous history of medical relevance. He also gave a history of lethargy and drowsiness during the day, combined with sleepless nights. He said that occasionally he had difficulty in keeping his head aright. He had been to various dentists and physicians with this complaint, but had no relief. Evidently, the patient was unable to fully open the mouth and also effectively occlude the teeth.

Intraoral examination showed no carious teeth and no signs of oral inflammation. On clinical examination, he could not occlude his teeth however hard he tried to bite. Attempts to register his bite with marking paper proved negative with the paper failing to register any of his occlusion [Figure 1]. He had a limited interincisal mouth opening [Figure 2].
Figure 1: Failing to register occlusion

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Figure 2: Limited interincisal opening

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Clinical examination revealed ptosis of eyelid [Figure 3] and physical examination revealed extreme weakness of his skeletal muscles. After a through process of elimination of local etiological factors, we were able to diagnose that the reason for the patient presenting with trismus could be a neurological disorder. The patient was promptly referred to the Department of Neurology for expert opinion. The concerned clinicians conducted a through examination and confirmed that the patient was a case of myasthenia gravis (MGFA III B), thyoma (Stage IV). He was immediately admitted as an inpatient and started on treatment. He is now stable and on therapy.
Figure 3: Ptosis of the eye lids

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   Discussion Top

Myasthenia gravis is a neuromuscular disease leading to fluctuating muscle weakness and fatigability. It is an autoimmune disorder. The hallmark of myasthenia gravis is fatigability. [3] Muscles become progressively weaker during periods of activity and improve after periods of rest. Muscles that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are especially susceptible. In most cases, the first noticeable symptom is weakness of the eye muscles. In others, difficulty in swallowing and slurred speech may be the first signs. This disease affects the neuromuscular junction/synapse and trismus is due to involvement of the masticator muscles. Diagnosis of myasthenia gravis is dependent on neurological and biochemical investigations. The condition responds to medical treatment.

Trismus is defined as a tonic contraction of the muscles of mastication. More recently, the term "trismus" has been used to describe any restriction to mouth opening. [3],[4] Trismus can dramatically affect the quality of life in a variety of ways. Mastication is compromised and communication is more difficult when one is suffering from trismus. Not only is it difficult to speak with the mouth partly closed, thus impairing articulation, but also trismus can decrease the size of the resonating oral cavity, and thus diminishes vocal quality.

Severe trismus makes it difficult or impossible to insert dentures. It may make oral examination difficult, if limited mouth opening precludes adequate visualization of the site. Oral hygiene is affected and swallowing is more difficult.

The patient who presented to us came with a history of progressive bulbar, ocular, facial, proximal muscle weakness for last 3 months. He also had a significant fatigability and diurnal variation of the symptoms. After the diagnosis of myasthenia gravis was made, a thymectomy was done for him. He had four cycles of chemotherapy with Carboplatin 550 mg and Etoposide 150 mg. However, we deduce that the presenting complaint of difficulty in opening and closing the mouth had improved, since the patient was not referred back to us.

Since the causes of trismus vary, the diagnosis of the underlying disease causing the trismus is essential before planning management of the complaint. It is therefore our inference to include myasthenia gravis in the differential diagnosis of trismus.

   References Top

1.Eanes WC. A review of the considerations in the diagnosis of limitedmandibular opening. Cranio 1991;9:137-44  Back to cited text no. 1
2.Dhanrajani PJ, Jonaidel O. Trismus: Aetiology, differential diagnosis andtreatment. Dent Update 2002;29:88-92,94.  Back to cited text no. 2
3.Howard JF Jr. Myasthenia gravis. A Manual for the health care provider.Chap 10. Greek: Myasthenia gravis foundation of America; 2008. p. 100-7.  Back to cited text no. 3
4.Lee JS, Iranmanesh A, Schmidt BL, Fischbein NJ, McKenna SJ. Limited oral opening in a 43-year-old man. J Oral Maxillofac Surg 2005;63:103.  Back to cited text no. 4

Correspondence Address:
Sibu S Simon
Department of Dental Surgery, Christian Medical College and Hospital, Vellore 632 004
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-9290.93467

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  [Figure 1], [Figure 2], [Figure 3]


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