Literature review
We reviewed the cases of 11 individuals with craniofacial chondroblastoma who were described in 11 previously published papers (Table
1 [
9‐
19]). Including our case, the review included five male and seven female patients (median age, 44.5 years; range, 27–66 years). In eight cases, the radiographic examinations revealed destroyed the TMJ and mandibular condyle; temporal bones were affected in five cases. In four cases, the chondroblastomas affected the anatomical structures of the middle ear, producing hearing loss. In some cases, the clivus and sphenoid sinus were destroyed. In the earliest (1971) included case, curettage was used to remove the lesion, but it recurred and remained. Therefore, a second operation was required. In addition, there was a tendency for treatments to involve complete excisions. The pre-auricular approach was used in five cases. Three cases used the endoscopy and rhinoscopy, and one case employed the middle cranial fossa approach. To reduce damage to the anatomical structures around the TMJ and minimize postoperative dysfunction, the middle cranial fossa approach has also been used in recent years. The advantage of this approach is that it is easy to secure a surgical field and access the dura mater [
19]. In addition, some cases used the transpetrosal-transzygomatic approach, the modified auriculotemporal approach using a U-shaped incision, and the retro-auricular approach. Reconstruction using the temporalis muscle flap was performed in two cases, and there were two cases that involved the use of the temporal fascia layer and one that used the nasoseptal flap. In two cases, reconstruction of the surgical defect was performed using a fat graft. In 11 cases, the treatment resolved the chondroblastoma.
Table 1
Summary of characteristics for patients with craniofacial chondroblastomas (from 11 reports)
| 30/F | • Fronto-zygomatic area • Anterior superior EAC | • Not described | • Temporal area swelling • Plugged ear sensation • Conductive hearing loss | • 1st OP: curettage • 2nd OP: excision (1 month after 1st OP) | • Not described | No recurrence (2 years) |
| 27/M | • TMJ • Mandibular condyle • Temporal bone | • Not described | • TMJ swelling • Mouth opening deviation | • Subtotal excision (extended pre-auricular, temporal approach) | • Not described | No recurrence (1 year) |
Watanabe et al. (1999) [ 11] | 43/F | • TMJ • Temporal bone • Middle ear • EAC | • 15 x 20 | • Chronic otitis media • Conductive hearing loss | • Complete excision (retro-auricular approach) | • Surgical defect (Temporal muscle flap) | No recurrence (4 years) |
| 57/F | • TMJ • Mandibular condyle | • 20 x 20 | • TMJ swelling • Mouth opening deviation • TMJ clicking | • Complete excision (pre-auricular approach to deep sub-fascia) | • Not described | No recurrence (1 year) |
| 38/M | • Temporal bone • Zygomatic arch | • 30 | • Temporal area swelling • Conductive hearing loss | • Complete excision (middle cranial fossa approach) | • Not described | No recurrence (1.25 years) |
| 49/F | • Mandibular condyle | • 20 | • TMJ swelling • Pre-auricular pain, swelling • Trismus | • Complete excision (pre-auricular approach) | • Not described | No recurrence (8 years) |
| 27/F | • Clivus • Carotid canal | • 28 x 20 x 19 | • Headache • Diplopia • Facial dysesthesias | • Complete excision • Endoscopic endonasal approach | • Surgical defect (nasoseptal mucosal flap) | No recurrence (3 months) |
Hiraumi et al. (2016) [ 16] | 64/M | • TMJ • Middle cranial fossa • Superior semicircular canal • Foramen spinosum • Facial nerve • Otic capsule | • Not described | • Vertigo | • Complete excision (transpetrosal-transzygomatic approach) | • Eardrum, EAC (temporal fascia flap) • Surgical defect (abdominal fat) | No recurrence (5 years) |
Marano et al. (2019) [ 17] | 46/M | • Mandibular condyle | • 21 x 10 x 17 | • TMJ pain, swelling | • Complete excision (pre-auricular approach) | • Not described | No recurrence (1.5 years) |
| 40/F | • Sphenoid sinus | • 22 x 20 | • Dizziness • Headache | • Complete excision • Rhinoscopic surgery | • Not described | Not described |
Tomioka et al. (2020) [ 19] | 66/F | • TMJ • Temporal bone • Middle cranial fossa • EAC | • 35 x 25 x 20 | • Hearing loss • Mouth opening deviation • TMJ clicking | • Complete excision (modified auriculotemporal approach via U-shaped incision) • Endoscopic surgery | • Parietal bone (temporal muscle flap, titanium mesh plate) | No recurrence (5.5 years) |
Present case | 52/M | • TMJ • Mandibular condyle • Temporal bone • EAC | • 28 x 28 x 37 | • TMJ swelling, asymmetry • TMJ pain on palpation • Mouth opening deviation • Eyebrow paralysis | • Complete excision (pre-auricular approach) | • Anterior wall of the EAC (temporal fascia flap) • Surgical defect (inguinal fat graft, TPFF) | No recurrence (1.5 years) |
When the tumor occurs in the craniofacial region, as in the present case, pain in the pre-auricular region, occlusal abnormalities, trismus, and TMJ clicking have been reported. Further, the patient may also experience a “plugged ear” sensation, hearing loss, dizziness, and otorrhea. Radiographic examinations usually show well-marginated, ovoid-shaped masses with rarefaction. This imaging finding suggests that the tumor is benign, but is insufficient to confirm a differential diagnosis relative to other bone tumors. Therefore, a histological examination is necessary. The characteristic histological findings of a chondroblastoma include the presence of multinucleated giant cells and a chondroid matrix. These cells show immunoreactivity with the s-100 protein, which differentiates a chondroblastoma from a chondrosarcoma or an aneurysmal bone cyst. Unlike our case, chondrosarcoma of the craniofacial region occurs mainly in patients younger than 20 years of age. Radiographically, chondrosarcoma shows malignant characteristics with ill-defined margins. It also shows histologic features, such as cytologic atypia, as, which are not seen in chondroblastoma [
20]. An aneurysmal bone cyst is an osteolytic lesion surrounded by connective tissue, that, unlike chondroblastoma, occurs mainly in patients under 30 years of age [
21]. Radiographically, aneurysmal bone cysts are characterized by osseous expansion accompanied by a thin peripheral shell of bone. Histological findings include a hemorrhagic cystic space [
22]. Considering our patient's age, clinical symptoms, radiographic and histologic characteristics, the likelihood of the lesion being a chondrosarcoma or aneurysmal bone cyst was low. Therefore, we decided not to perform further immunologic analysis, such as the s-100 protein test.
To date, the pre-auricular approach has been considered the gold standard surgical method for accessing the TMJ. The indication for a pre-auricular approach is any operation that requires access to the upper condyle and TMJ. Efforts have been made to minimize incision scars by using the crease in front of the tragus. Among the modified approaches to TMJ, the post-auricular approach has the advantage of hiding the incision line behind the ear, even in patients with tendencies to develop keloids. However, the post-auricular approach to the TMJ cannot avoid transecting the EAC. Therefore, a wide dissection is necessary to prevent ankylosis of the EAC and external otitis [
23]. Some authors have extended the post-auricular incision to the cervical region to enable the excision of a TMJ chondroblastoma and have used a neck dissection to diagnose the metastases of tumors [
24]. According to a report published in 2009, some mandibular condylectomies have been performed using a modified trans-oral approach. The flap elevation was performed using a buccal mucosa incision, and the coronoid process was cut at the sigmoid notch level to access the condyle. After the condylectomy, the fragment of the coronoid process was realigned and fixed in its original position. We suggest that this approach is a new method for treating TMJ lesions [
25].
The most important point of our case is that a very large (approximately 37 mm) chondroblastoma that was affecting the TMJ was successfully removed. The main tumor had aggressive characteristics and had destroyed the mandibular fossa of the temporal bone, but it was delicately removed, avoiding perforation of the dura mater. Additionally, half of the lateral condyle neck was damaged by the tumor, but the condyle head was preserved to the extent possible to preserve the vertical height of the mandibular ramus. Therefore, the patient did not complain of facial asymmetry, trismus, or deviations when opening his mouth. The anterior part of the articular disc was invaded by the main tumor and resected, and an inguinal free fat graft was connected to the remaining posterior part of the articular disc. Although the patient did not experience abnormal occlusion or a masticatory disorder, it was unreasonable to expect significant improvement in mouth opening due to the loss of half of the articular disc.
The main deficiency associated with the diagnosis of this patient was that the region of the EAC that had been invaded by the tumor was incorrectly diagnosed, based on the preoperative CT, as fluid collection due to external otitis. Hence, the destruction of the EAC was not predicted. Due to this tentative diagnosis, a preoperative puretone audiometry (PTA) examination was not performed. Sensorineural hearing loss (SNHL), at 2 kHz, was detected during postoperative PTA, which may have caused the postoperative tinnitus. We could not confirm whether SNHL existed prior to the operation. If we had preoperatively confirmed SNHL, we could have used minimally invasive surgery to avoid worsening the SNHL. Preoperatively, the patient complained of eyebrow muscle paralysis, which might have been expected due to tumors affecting the temporal branch of the facial nerve. Paralysis of the right eyebrow and ptosis of the right eyelid worsened after the operation. This observation suggests that additional facial nerve damage was caused intraoperatively due to electric cauterization or overly aggressive traction.
Complete surgical excision is the most effective treatment for a chondroblastoma. When en bloc excision is not possible, curettage may be considered as a treatment option. The recurrence rate following complete surgical excision is 20%; however, when treated with curettage, there is a 50% probability of recurrence [
26]. In our case, the tumor was very large and had aggressive characteristics, prompting the decision to perform a complete surgical excision, with wide margins. This was chosen over curettage to reduce the chance of recurrence.
The reconstruction of damaged craniofacial areas, especially at the cranial base, is a very delicate operation. The TPFF receives its blood supply from the superficial temporal artery and has a high survival rate, even after radiation therapy. In addition, deep and superficial temporal fascia layers have the advantage of being thin, flexible, and adjustable in length; therefore, they are useful for reconstructing skull base defects. The TPFF is used to reconstruct lateral skull base defects and prevent CSF leakage; they are also used to rebuild defects in the ventral skull base by passing the TPFF through the infratemporal fossa. The modified TPFF can be used to reconstruct anterior skull base defects via the supraorbital epidural corridor [
27]. The use of a superficial temporal fascia flap to reconstruct a burned ear has been reported [
28].
Although most authors insist that the surgical excision of chondroblastomas is the most effective treatment, there is an argument that suggests that invasive methods should be avoided. Among the recently published papers, several cases involving the use of a microscope and an endoscope have been reported. The microsurgical instruments were used to access the main mass by drilling through the tympanic region and the mandibular condyle. Although a safety margin could not be obtained, there was the advantage of preserving the functioning of the cochlea, facial nerve, jugular vein, and TMJ. Recurrence was observed in some of the cases treated in this manner; however, they were well managed using radiotherapy [
29].
There is a debate about the role of radiation therapy in chondroblastoma treatment. In one report, radiation therapy helped prevent recurrence after complete resection of the chondroblastoma [
30]. Thus, radiation therapy may be considered to reduce the frequency of chondroblastoma recurrence, but it also increases the possibility of malignancy. Therefore, radiotherapy is not essential [
31].