2020 Volume 32 Issue 2 Pages 77-83
Jacob's disease is defined as a condition wherein a false joint-like relationship resembling a mushroom-like osteochondroma forms between the zygomatic arch and the coronoid process that keeps increasing in size. We report a case of coincident Jacob's disease and masticatory muscle tendon-aponeurosis hyperplasia. The patient showed favorable prognosis post surgery. The patient was a 27-year-old man, who was referred to our department because of long-term trismus. The patient was observed to have an enlarged mandible with a maximum mouth opening range of 4 mm. Lateral and protrusive excursion movements on both sides of the mandible were 4 mm and 6 mm. A computed tomography (CT) scan revealed a 26 x 18 x 18 mm mushroom-like opaque lesion at the top of the left coronoid process and the zygomatic arch that was in contact with it was deformed. A magnetic resonance imaging scan revealed a strike root appearance on both masseter muscles. The patient was diagnosed with suspected left coronoid process neoplastic lesion and bilateral masticatory muscle tendon-aponeurosis hyperplasia. Under general anesthesia, left coronoidectomy was first performed using a combination of intraoral and extraoral methods. However, since a hard tension was palpated on the anterior edges of both masseter muscles at the time of mouth opening, right coronoidectomy and bilateral aponeurotomy of the masseter muscle were performed. The mouth opening range was 63 mm at the end of the operation. Histopathology of the neoplastic lesion in the coronoid process confirmed the presence of thick fibrous tissue and premature hyaline cartilage-like tissue at the tip of the lesion. An osteochondroma was noted below due to cancellous tissue with a transitive medullary cavity. Thus, the patient was diagnosed with coincident Jacob's disease and masticatory muscle tendon-aponeurosis hyperplasia. Mouth-opening training was started four days after the surgery and continued for three months. 12 months after the operation, the patient is doing well with a mouth opening range of 60 mm with no signs of recurrence.
