Congenital Disorders
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- Hypertrophy of the coronoid process causes interference of the coronoid against the anteromedial margin of the zygomatic arch.
- Pierre-Robin syndrome
- Trismus-pseudo-camptodactyly syndrome
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Infections | - Trismus is a typical symptom of masticatory space infections.
- Infections causing Trismus could be odontogenic or non-odontogenic in nature.
- Odontogenic infections include pulpal infections, periodontal infections, and pericoronal infections.
- Non-odontogenic infections include tonsillitis, tetanus, meningitis, parotid abscess, and brain abscess.
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Trauma | - Fracture or dislocation of the zygomatic arch,
- Hemarthrosis/Hematoma,
- Temporomandibular Joint (TMJ) contusion,
- Intra-articular bone islands/foreign bodies,
- Displaced meniscus,
- Injury to muscles of mastication.
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Iatrogenic | - 3rd molar extraction-related inflammation,
- Inaccurate nerve block injection procedure,
- Puncturing medial pterygoid muscle or vessels,
- Radiotherapy for head and neck cancer
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Neoplasia | - Malignant tumors involving the mandible, muscles of mastication, and associated structures.
- Primary tumors or neoplastic diseases occurring in many parts of the body could metastasize to the epipharyngeal region, parotid gland, mandible, or temporomandibular joint.
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Radiotherapy | - Involvement of the medial pterygoid muscles during the radiotherapy around the head and neck region.
- When the muscles of mastication are within the field of radiation, fibrosis may lead to Trismus. It is attributed to the ischemia caused by endarteritis obliterans.
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Temporomandibular Disorders
| - TMJ disorders are divided into intra-articular or extra-articular.
- Intra-articular causes include fibrous ankylosis, anchored disc phenomenon, bilateral anterior disc displacement without reduction, arthritis, and unilateral condylar hypoplasia.
- The extra-articular covers all myofascial-related causes.
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Drugs | - Due to secondary effect of some drugs
- Succinylcholine, Phenothiazines, Tricyclic Antidepressants, Metaclopramide, Phenothiazines.
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Psychogenic | - Hysteria is a cause of Trismus. Electromyography is a useful test in diagnosing Hysterical Trismus.
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Miscellaneous | - Trismus can be associated with multiple sclerosis, pseudobulbar palsy, lupus erythematoses, scleroderma, acquired deformity e.g. burns, and neck flexion deformity.
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