Intraoral endoscopic enucleation of a solitary bone cyst of the mandibular condyle

Abstract

Solitary bone cysts are benign osteolytic lesions rarely involving the mandibular condyle. They are considered pseudocysts due to the absence of epithelium and their pathogenesis is unknown. These lesions are also known with a variety of synonyms, such as traumatic bone cysts, simple bone cysts, haemorrhagic bone cysts and unicameral cysts. The authors report a case of a solitary cyst of the condylar head treated by enucleation and curettage via an intraoral endoscopic-assisted surgical approach, which avoids the risk of facial nerve injury, reduces the patient’s hospitalization and speeds up functional recovery.

Introduction

Recently, endoscopic-assisted techniques have been implemented by different surgical specialties, following the new concept of minimally invasive surgery. In the head and neck region, these techniques were initially limited to laryngeal, nasal and paranasal sinus surgery, but they have gradually expanded into craniofacial, temporomandibular joint (TMJ), and cosmetic facial surgery.

In the specialty of maxillofacial surgery, condylar fracture treatment was one of the first indications for endoscopic surgery, with the possible benefits of less visible scars, reduction in facial nerve deficit, and quicker functional rehabilitation compared to open surgery. Whilst the literature on this topic is quite relevant , other endoscopic-assisted procedures are rarely mentioned . In this paper, the authors report a rare case of a condylar lesion of the mandible treated with an intraoral endoscopic-assisted approach. The clinical evaluation, radiographic studies and operative technique are described. Histological diagnosis of the lesion showed a solitary bone cyst.

Case report

A 42-year-old Caucasian female patient was referred to the authors’ clinic because of the onset of progressive swelling in the left pre-auricular region, developing over the previous 3 months. The patient reported no significant past medical history, and she did not remember any episode of head or jaw trauma.

On presentation, her clinical examination showed a Class I dental occlusion. Her maximal interincisal opening was 35 mm, mouth opening and closing movements were normal, and lateral excursion movements were symmetrical; no pathological clicks were identified. She felt uncomfortable during mastication, with mild tenderness over her left TMJ, but she did not refer any pain at rest. Moderate swelling was visible in that area; palpation was normal for consistency, with slight tenderness.

She presented with a transcranial radiograph, obtained from her primary care physician, which showed a radiolucent lesion, confined to the left condylar head, with defined borders ( Fig. 1 A ). She had no other previous imaging for comparison.

Fig. 1
Preoperative imaging, with a black arrow indicating the lesion. (A) A transcranial X-ray of the left condyle. (B) T2-weighted MRI shows a condyle widely filled with a hyperintense signal, indicative of liquid. (C and D) CT, sagittal/coronal view and axial view. Notice the slight expansion of the bony cortices of the left condyle, with hypodense tissue replacing the marrow and a small break in the anterior-medial cortex of the head.

Further radiological investigations were requested. A computer tomography (CT) scan was obtained to define the real extent of the lesion and the integrity of the cortical bone. This revealed a 1.0 cm × 1.3 cm isolated unilocular lesion of the left condylar head, without trabecular pattern or bony septa inside, not extending to the condylar neck. It showed an eggshell-like cortex, denoting expansion and cortical lyses of the anterior-medial wall ( Fig. 1 C and D).

Magnetic resonance imaging (MRI) indicated that the content of the lesion was liquid, showing a diminished T1 and an increased T2 marrow signal, whilst the surrounding soft tissues were normal ( Fig. 1 B).

The clinical hypotheses of a benign lesion suggested the possibility of a minimally invasive surgical approach to the head of the condyle.

Surgery was performed under general anaesthesia with nasotracheal intubation. Local anaesthesia with mepivacaine and adrenaline was injected intraorally into the retromolar area, the ascending ramus and more superiorly towards the condylar neck. A mucoperiosteal incision, approximately 3 cm in length, was performed from the molar region to the anterior ascending ramus. Subperiosteal blunt dissection was extended from the angle of the mandible up to the lateral surface of the ramus, the sigmoid notch and the condylar neck. Then, an Obwegeser ramus retractor was used to gain access to the area. Through the same intraoral incision, a 30°, 4 mm Storz rigid Hopkins endoscope was introduced along the lateral surface of the mandibular ramus, protected by a special fibreoptic housing and a cheek retractor (Synthes ramus/condyle endoscopic set, Synthes, West Chester, Pennsylvania, USA). Once the condylar neck was identified, the temporomandibular ligament was detached and the condylar head became visible ( Fig. 2 A ). Medially, it presented an eggshell cortex, where the pinhole break observed in the CT was sought and identified. Through this entry point, a J-curette was used to enlarge the bony window. Then, straw-coloured fluid leaked out of the lesion, revealing a hollow cystic cavity without any apparent capsule. A round burr was used to enlarge the opening, to facilitate the removal of the content of the lesion ( Fig. 2 B).

Fig. 2
Three stages of endoscope-assisted surgery. (A) The temporomandibular ligament has been detached and reflected cranially. On the left lateral side, a special cheek retractor is visible, behind the neck and the head of the condyle. On the right medial side, a common dissector pulls apart the external pterygoyd muscle from the condyle. (B) The pinhole break on the anterior medial wall of the condyle is widened with a burr. (C) The enlarged hole is visible.

Traditional Blakeslee–Weil forceps, routinely used in sinus surgery, were the instrument of choice to scrape small tissue fragments from inside the lesion. These fragments were sent for histological examination. The endoscope was pushed forward and the remnants on the lateral aspect of the condyle were scraped out ( Fig. 2 C). The empty cavity and surrounding tissues were irrigated with saline and hemostasis was obtained. The wound was closed with a running 3-0 absorbable suture.

The procedure lasted about 95 min, and bleeding was negligible. There were no intraoperative complications and the postoperative course was uneventful. The patient was given specific instructions for a soft diet and prescriptions for appropriate antibiotics and analgesics. Functional recovery was complete, with unchanged maximal interincisal opening, protrusive and lateral excursion movements; facial nerve function was normal. The histology report showed fibrotic tissue without epithelial lining, compatible with a diagnosis of solitary bone cyst. 6 months after surgery a new CT scan and MRI were taken, showing evident and progressive bone healing ( Fig. 3 A and B ). The patient had follow up appointments about twice a year, she remained asymptomatic and, 27 months after surgery, another MRI revealed a residual lesion, smaller than the previous one. Since then no more images have been taken, as the authors consider the absence of symptoms and the progressive reduction of the hollow cavity in the condyle satisfactory targets for the clinical outcome ( Fig. 4 ).

Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Intraoral endoscopic enucleation of a solitary bone cyst of the mandibular condyle
Premium Wordpress Themes by UFO Themes