Squamous cell carcinoma is the most common malignancy of the external auditory canal, middle ear, and mastoid. Surgical resection is the cornerstone of treatment, with T1 lesions of the external auditory canal treated by lateral temporal bone resection and more advanced lesions treated by subtotal or total temporal bone resection.
Clinical features
Patients with cancer of the temporal bone most often present when aged 60 years or older, although any age group, including children, can be affected.
Symptoms and signs of temporal bone lesions are summarized as follows:
· Otalgia (80-85%)
· Otorrhea (40-75%)
· Facial paralysis (25%)
· Hearing loss (45-80%)
· Tinnitus (8-10%)
· Vertigo
· Auricular lesion
· External canal mass (10%)
· Parotid mass (19%)
· Skin lesions
· CN V, IX, I, XI deficits (30%)
Workup in malignant tumors of the temporal bone
Routine preoperative testing includes complete blood counts (CBCs), electrolyte level tests, renal function tests, liver function tests, coagulation.
Imaging studies can include the following:
· HRCT and MRI scan- Imaging is important in TBMs for accurate tumor and node staging as many patients have limited findings on physical examination. Highresolution computed tomography of the temporal bone offers the most accurate method for the evaluation of bone erosion due to malignancies. However, a reported limitation of CT is its inability to distinguish between tumor and fluid in the middle ear, soft tissue or mucosal thickening in the absence of bone erosion. Also, spread along fascial planes and neurovascular structures can be difficult to detect. MRI can provide excellent differentiation between soft-tissue tumor margin, muscle and soft-tissue infiltration, and can help in distinguishing tumor from obstructive inflammatory changes. In addition, obstruction of the sigmoid sinus and encasement of the petrous internal carotid artery are better detected on MRI than CT, because of the vascular signal void seen on precontrast MRI and the flow enhancement of the sigmoid sinus seen on postcontrast MRI. Tumor extension, specially cranial spread into the middle and posterior cranial fossa and caudal spread into the infratemporal fossa, is also better detected on MRI. Enhanced T1-weighted spin-echo images with fat-signal suppression are most suitable for this purpose. MRI has also made it possible to confidently diagnose perineural spread of malignancies. Fat saturation gadolinium-enhanced magnetic resonance (MR) scans are often capable of detecting subtle tumor tracking along the fifth and seventh cranial nerves, as well as other nerves that travel through the many foramina of the skull base, before the lesions have grown sufficiently large to affect the surrounding bone.
· Chest radiography - If the histology indicates squamous cell carcinoma, obtain plain radiographs or CT scans of the chest to rule out metastasis
· CT scanning of the chest, abdomen, or pelvis - This is not necessary unless the biopsy specimen of the temporal bone tumor reveals a tumor with a known propensity for metastasis
· Carotid angiography with balloon occlusion Xenon test - If the carotid artery is suspected to be involved
Other tests include the following:
· Audiometry - An audiogram is obtained prior to performing any major procedure on the ear or temporal bone; audiograms provide baseline hearing thresholds for future comparison
· Biopsy - to determine whether the lesion in the ear is benign or malignant.Histologic examination is important because, although CT scanning provides important preoperative staging information, systematic pathologic evaluation of the specimen is crucial for staging and treatment.
Management of Temporal Bone Malignancy
Surgery is the primary treatment of choice in TBMs. Radiotherapy is used as an adjuvant treatment to surgery except in advanced tumors requiring palliation. The role of chemotherapy is not established in TBMs.
Surgical techniques for temporal bone malignancies
· Modified lateral temporal bone resection
· Lateral temporal bone resection
· Subtotal temporal bone resection
· Total temporal bone resection
· Lateral temporal bone resection
This is the primary surgery of choice in T1 and T2 tumors. The approach entails a complete canal wall up mastoidectomy with an extended facial recess opening. The EAC is resected en bloc along with the tympanic membrane, the malleus after disarticulation and removal of the incus, with the medial limit defined at the level of the incudostapedial joint. Some authors advocate that routine superficial parotidectomy be done with lateral temporal bone resection (LTBR), specially in T2 tumors.
Fig2: Lateral Temporal Bone Resection
· Subtotal Temporal bone resection
This is used in T3 and T4 tumors and is an extension of the LTBR. After the steps of LTBR are performed, this procedure extends medially in a piecemeal fashion and includes IAC identification, facial nerve exposure and removal of the otic capsule with preservation of the petrous apex. Care must be taken to remove adequate bone around the tumor. The capsule of the temporomandibular joint and, if necessary, the condyle of the mandible is resected when found involved. If the tumor extends into the mastoid and dural involvement is suspected, middle and posterior fossa craniotomies might be necessary to achieve adequate exposure. Generally, the dura is a good barrier for tumor spread and it must be removed only when necessary. If the dura is found infiltrated, its incision is undertaken and it is excised until free margins are reached. If the facial nerve is invaded by the tumor, it should be included in the specimen. The facial nerve may otherwise be re-routed to give access to the tumor. The sigmoid sinus and jugular bulb are preserved unless infiltrated. If there is any area of uncertain tumor clearance around the jugular bulb or the lower cranial nerves it is advisable to leave a vascular clip in situ for the site to be identified and targeted during postoperative radiotherapy.
Fig 3: Subtotal Temporal Bone resection
Total temporal bone resection
This procedure is used in advanced T4 tumors. It may be performed with or without resection of the pinna. Bone is resected superiorly for 3 cm above the temporal line to expose the middle fossa dura and behind the sigmoid sinus by a similar amount to leave a residual margin of healthy bone. Medial dissection extends through the labyrinth and exposes the intrapetrous carotid artery. Inferiorly, the sigmoid sinus and jugular bulb are mobilized from surrounding bone. The sternocleidomastoid and digastric muscles are freed from the mastoid tip. At this stage in the procedure, the ascending ramus of the mandible is transected with a Gigli saw or a drill, and this and the head and coronoid process are dissected free and removed. A total parotidectomy is completed, and the specimen is removed en bloc. The residual tip of the petrous bone is then removed with a high-speed drill. Resection of the carotid artery can also be accomplished if the contralateral cerebral blood supply has been proven to be adequate by angiography and preoperative balloon occlusion.
Selection of surgical procedure.
The optimal surgical strategy for SCC of the temporal bone remains controversial. A review of the literature shows that many authors often adopt an individualistic approach to primary tumor and neck nodes management. Sleeve resection with retention of the pinna is still supported as a treatment of T1 tumors of the EAC . We do not perform SRs at our center where LTBR is the accepted mainstay for T1 and T2 tumors. Both LTBRs and subtemporal bone resections (STBRs) are accepted techniques in T3 tumors . In T4 tumors, although STBR is the surgery of choice, the application of total temporal bone resection (TTBR) in advanced T4 tumors is a matter of debate. The management of more advanced tumors (T4) is particularly challenging as a result of the complex anatomy and the proximity of intracranial structures. The palliative benefits of TTBR like decreased pain and improved hygiene in comparison with radiotherapy. Although recent studies reported an improvement in terms of surgical morbidity and survival in patients who have undergone TTBR, this procedure is still associated with significant postoperative deficits. STBR performed by a combination of en bloc and piecemeal resection techniques followed by postoperative radiotherapy could be a reasonable choice in patients with T4 tumors. Tumors of the EAC can involve the parotid gland either by direct extension or through nodal dissemination of the disease because one of the first echelon lymph nodes involved in SCC of the temporal bone is the intraparotid or periparotid node. Preformed pathways around the EAC like the cartilaginous fissures of Santorini, the petrosquamous suture line and the bony foramen of Huschke are suspected to facilitate easy spread of tumor anteriorly. This is the main reason why some surgeons prefer to associate superficial parotidectomy with LTBRs, specially if tumor is found to be eroding the anterior wall of the EAC. The incidence of parotid involvement in SCC of the EAC has been reported to be between 10 and 62% of patients . But there is no recorded benefit of performing a routine superficial parotidectomy in terms of better survival rates. It is well known that nodal dissemination in TBMs is uncommon and hence many authors avoid performing a routine superficial parotidectomy for the sake of nodal clearance . We do not include superficial parotidectomy as a routine procedure in all T2 cases and prefer to perform it in T2 tumors only if there is evidence of involvement of the anterior wall of the EAC. However, in T3 tumors, we routinely perform a superficial parotidectomy. In T4 tumors and when there is evidence of involvement of the parotid gland per se, we perform a total parotidectomy. Though lymph nodes involvement is relatively rare (10–36%) in TBMs, the presence of nodal metastasis, seen in advanced stages, has an adverse outcome on survival. Although some studies have reported a poor survival rate in the presence of nodal metastasis, others have not found this to be statistically significant. With this background it is difficult to justify a routine neck dissection in a N0 neck, specially in T1 and T2 tumors. A positive neck at presentation is a sign of aggressiveness of the primary tumor. Therefore, when there is clinical or radiological evidence of neck nodes involvement one must pursue an aggressive neck dissection. In N0 neck, we perform a frozen section of the level II lymph nodes and proceed with neck dissection only when this is positive for metastasis. In Nþ necks, we perform routine neck dissection to involve the parotid and the level II lymph nodes. Although radiotherapy has proven to be an effective adjuvant therapy, its role as a primary treatment modality for TBMs is not established. Postoperative radiotherapy is used to improve local and regional control of the disease. It is indicated in T3 and T4 tumors and also in T1 and T2 tumors where there is evidence of bone invasion, a positive margin, perineural invasion or nodal metastasis.
CONCLUSION
Despite the fact that significant attention has being focused on TBMs in the last few decades, there is still need to comprehensively study the entire gamut of histological varieties, refine the existing tumor staging system or develop novel ones and standardize treatment protocols. Radical surgery is the mainstay of treatment of TBMs in all tumor stages. Advances in neuroradiology, skull base surgical techniques and neuroanesthesia have made surgical resection of even advanced tumors in this area feasible with minimal morbidity. Adjuvant radiotherapy is indicated in T2, T3 and T4 tumors and is considered in T1 only in case of incomplete resection. `