Background: The aneurysmal bone cyst is a well known but rare bony lesion that is known to affect the lower jaw. Its name is actually a misnomer as it is neither a cyst or a a vascular aneurysm. Rather it is an osteolytic bone lesion which is characterized by being comprised of serum or a sponge-like blood material that usually contains osteoclast-like giant cells. It has a wide variability in presentation from a small asymptomatic lesion that is coincidentally found on an x-ray to a much larger expansile lesion that has eroded through the outer cortex causing some external facial deformity.
The unusual nature of the aneurysmal bone cyst has led to debate about its origin. The historic explanation is that it was caused by increased venous pressure in the bone and subsequent vascular rupture…hence its traditional name. More contemporary thought has been modified to be an arteriovenous malformation within the bone. While it can occur independently, it is also known to be caused from pre-existng bone lesions such as giant cell tumors, osteoblastomas and fibrous dysplasia.
Case Study: A 14 year-old female presented with swelling over the jaw on the left side of her face for the past four months. External examination showed a non-tender and firm consistency to the jaw swelling. X-rays showed a large expansile multilocular lesion of the left mandible which extended between the apical roots of the second premolar and first and second molars., suggest of a benign odontogenic tumor. A CT scan shows an expansive lesion with hydraulic-appearing outer margins that wrapped around the inferior alveolar nerve canal.
Under general anesthesia a mucoperiosteal flap was raised to expose the thinned out outer bony cortex. The expanded cortex was opened revealing a serous liquid fill. The cavity was thoroughly curetted with preservation of the nerve. It was grafted with a combination of demineralized bone powder and platelet-rich plasma as a putty-like material. The diagnosis of aneurysmal bone cyst was confirmed by subsequent histopathologic diagnosis.
At one year followup she was pain-free with a normal appearing left jawline. An x-ray showed the cavity site was slowing filling in with bone with no signs of recurrence.
Case Highlights:
1) Aneurysmal bone cysts are not uncommon in the lower jaw and can present as an external facial swelling along the jawline.
2) An expansile bony jaw lesion that is filled with serous or bloody fluid indicates an aneurysmal bone cyst.
3) Enucleation and allogeneic bone grafting is an effective treatment for this type of osteolytic jaw lesion.
Dr. Barry Eppley
Indianapolis, Indiana