Highlights MMTAH is a new clinical entity, misdiagnosed as temporomandibular joint disorder. MMTAH is diagnosed based on a square mandible, cord-like masseter muscle aponeurosis, and limited mouth-opening. Aponeurectomy combined with coronoidectomy is the treatment of choice for a better prognosis. It is important to evaluate the patient’s compliance with mouth-opening training before surgery.

Highlights Temporomandibular disorders (TMD) are diseases of the temporomandibular joint and masticatory muscles, and are often difficult to be diagnosed. Determining the cause of facial asymmetry and jaw deviation are quite challenging. The morphologic and functional characteristics of masticatory muscles are maintained by sensory and motor innervation from the trigeminal nerve. Trigeminal schwannoma is a rare benign tumor originating from the Schwann cells. We experienced a case of masticatory muscle disuse atrophy during long-term follow-up after resection of intracranial trigeminal schwannoma.

Introduction Mucoceles are mucous extravasation phenomena resulting from spontaneous ductal rupture or, less commonly, a traumatic cutting of a salivary excretory duct. Occasionally, the appearance of a mucocele closely resembles a neoplastic lesion, and it can be difficult to diagnose. Presentation of case A 74-year-old Japanese male patient was referred to our clinic with painless swelling related to the upper right canine-premolar area. Preoperative imaging of the lesion revealed that it was fluid-filled and the histopathological biopsy suggested a myxoid tumor. We excised the lesion with the patient under general anesthesia, using safety margins based on the histology of the biopsy specimen to reach the definitive diagnosis and treatment. The final pathological diagnosis was a mucocele in the vicinity with an aberrant small salivary gland. Follow-up visits showed complete healing of the epithelium, and no recurrence has been observed during the subsequent 30 months. Discussion In cases with a difficult definitive diagnosis based on medical history, diagnostic imaging and pathological examination, it is important to proceed carefully with the possibility of a tumor in mind. Conclusion This case emphasizes that some mucous cysts are challenging for clinicians in terms of diagnosis and treatment due to an uncommon presentation.