Revising the Indications of Transtemporal Surgical Approaches in the Modern Endoscopic Era of Skull Base Surgery: A Dying Art

Abstract

Objectives  The aim of the study is to emphasize and explore the possible transtemporal approaches for spectrum of complicated lateral skull base pathologies.

Design  Retrospective analysis of complicated lateral skull base pathologies was managed in our institute between January 2017 and December 2019.

Setting  The study was conducted in a tertiary care referral center.

Main Outcome Measures  The study focused on the selection of approach based on site and extent of the pathology, the surgical nuances for each approach, and the associated complications.

Results  A total of 10 different pathologies of the lateral skull base were managed by different transtemporal approaches. The most common complication encountered was facial nerve palsy (43%, n  = 6). Other complications included cerebrospinal fluid (CSF) collection (15%, n  = 2), cosmetic deformity (24%, n  = 4), petrous internal carotid artery injury (7%, n  = 1), and hypoglossal nerve palsy (7%, n  = 1). The cosmetic deformity included flap necrosis ( n  = 2) and postoperative bony defects leading to contour defects of the scalp ( n  = 2).

Conclusion  Surgical approach should be tailored based on the individual basis, to obtain adequate exposure and complete excision. Selection of appropriate surgical approach should also be based on the training and preference of the operating surgeon. Whenever necessary, combined surgical approaches facilitating full tumor exposure are recommended so that complete tumor excision is feasible. This requires a multidisciplinary team comprising neurosurgeons, neuro-otologist, neuroanesthetist, and plastic surgeons. The surgeon must know precise microsurgical anatomy to preserve the adjacent nerves and vessels, which is necessary for better surgical outcomes.

Introduction

The anatomy of the temporal bone, its complex, intimate, and intricate anatomical relationship to the skull base structures makes the management of the lesions in the vicinity very challenging. The temporal bone has five parts: squamosal, petrous, mastoid, tympanic, and styloid process. Temporal bone pathologies usually present with symptoms of hearing deficit (conductive, sensorineural, mixed), vestibular dysfunction, facial nerve dysfunction, mastication difficulties, and dysphagia. Imaging plays an essential role in the determination of the exact location of the lesion along with the relationship of the lesion with surrounding neurovascular structures and may suggest the differential diagnosis of pathologies. Computed tomography (CT) and magnetic resonance imaging (MRI) are often complementary to each other, and in most cases, both are required. To evaluate the relationship of the internal carotid artery (ICA) with the tumor/lesion, magnetic resonance angiography or digital subtraction angiogram is considered often.

A surgical approach is defined as the route taken for the surgical procedure from an opening to the target. Various approaches are currently available for the management of temporal bone pathologies. ^{1 2} Usually, two or more approaches are combined for the same lesion; therefore, intimate knowledge of anatomy and multidisciplinary evaluation are essential factors to be considered in choosing an appropriate approach for this complex area. This ensures both effective treatment of pathology and better functional and cosmetic outcomes. The knowledge of the structures we encounter in any particular approach is vital along with the judgment of which are to be preserved, mobilized, or removed. It determines the success of choosing the particular surgical corridor for particular lesion and accessibility. The selection of the approach used depends upon the type of pathology whether benign or malignant, site of origin, and extension which may be confined to temporal bone or extending to the adjacent areas of the neck, infratemporal fossa, and in the “exo” and “endo” cranial regions or both. Rhoton Jr ² classified the temporal approaches into three categories.

1. Approaches through the surface of the temporal bone forming the middle fossa floor. Examples include classical/extended middle fossa approaches and subtemporal infratemporal fossa approaches.

2. Approaches directed through presigmoid transmastoid bone. Examples are retrolabyrinthine, translabyrinthine, and transcochlear.

3. Post aural transtemporal approaches: examples are fish infratemporal fossa approaches (Type-A, B, C) and far lateral skull base approaches.

It is essential to consider multiple factors during the surgical planning to get a good functional outcome, which is cosmetically appealing with minimal morbidity at the end. It includes proper skin flap design without compromising its vascularity, especially while doing the revision cases. Proper dissection and preservation of muscle and musculoperiosteal flap are also important to ensure a tight cerebrospinal fluid (CSF) closure as well as obliteration of the surgical cavity at the end of surgery. The approach should give adequate exposure and straight-line access to the pathology with minimal to no brain retraction and be versatile enough to expand intraoperatively. The need for preoperative embolization and intraoperative measures to tackle blood loss is planned well before the intervention. The present review enumerates the challenging case scenarios that we have managed through the transtemporal approaches.

Patients and Methods

Study Group

Ten patients, ranging in the age group from 2.5 to 55 years, underwent surgical management for rare pathologies involving the temporal bone region over 3 years (between January 2017 and December 2019), were included in this study. Patients were evaluated, and the same surgical team operated on all the cases. Patients were followed up for an average of 18 months. The medical records were analyzed retrospectively.

Results

A total of 10 different pathologies concerning the temporal bone managed through the transtemporal bone approaches (which include: extended cortical mastoidectomy, radical mastoidectomy, modified transcochlear approach, extended middle fossa approach, and infratemporal fossa approaches). The most common complication encountered was facial nerve palsy (43%, n  = 6). Other complications included CSF collection (15%, n  = 2), cosmetic deformity (24%, n  = 4), petrous ICA injury (7%, n  = 1), and hypoglossal nerve palsy (7%, n  = 1). The cosmetic deformity included flap necrosis ( n  = 2) and postoperative bony defects leading to contour defects of the head ( n  = 2; Table 1 ).

Table 1. Pathologies managed by transtemporal approaches.

S. no	Age	Gender	Diagnosis	Approach	Complication
1	55	M	Paradoxical CSF Rhinorrhoea	Post auricular extended cortical mastoidectomy and repair of fistulous tract	None
2	2.5	M	Facial nerve hemangioma	Post auricular radical mastoidectomy with excision	Facial nerve palsy
3	45	F	Left petrous apex recurrent chondrosarcoma	Modified transcochlear approach	Facial nerve palsy, CSF collection
4	21	M	Right recurrent benign fibrosseous lesion of temporal bone	Modified transcochlear approach	Flap necrosis, post auricular cosmetic deformity
5	60	F	Right glomus jugulare	Infratemporal fossa A	Facial nerve palsy Skin flap necrosis
6	32	M	Left glomus jugulare	Post auricular transmastoid jugular foramen approach	Facial nerve palsy
7	45	M	Right hypoglossal schwannoma	Post auricular transmastoid suboccipital approach	Facial nerve paresis, hypoglossal palsy
8	51	M	Right middle ear adenoma	Extended middle fossa approach	ICA injury
9	50	M	Left infratemporal fossa nerve sheath schwannoma	Preauricular transzygomatic infratemporal fossa approach	Facial nerve palsy CSF collection
10	18	F	Right temporal anaplastic meningioma	Preauricular transzygomatic subtemporal approach	Cosmetic deformity

Abbreviations: CSF, cerebrospinal fluid; ICA, internal carotid artery.

Surgical Techniques

Extended Cortical Mastoidectomy

Extended cortical mastoidectomy involves complete exenteration of mastoid air cells with skeletonization of surrounding anatomical structures, while a conventional cortical mastoidectomy involves removal of the mastoid cortex and opening of the mastoid antrum.

Extended mastoidectomy is performed using microsurgical cutting and diamond burr with continuous suction and irrigation. The initial step was by using postauricular incision; skin flaps and musculoperiosteal flap were raised; outer mastoid cortex air cells were drilled out followed by opening of the mastoid antrum and identification of the lateral semicircular canal, which is the most reliable landmark in the temporal bone and helps in the identification of facial nerve and bony labyrinth. Bone is removed from the sinodural angle and along the superior petrosal sinus. The mastoid air cells are exenterated from the sinodural angle, tegmen, and posterior fossa dural plate areas.

Case Scenario

Paradoxical CSF Rhinorrhea

A 55-year-old gentleman is a known case of left vestibular schwannoma, he underwent left Retro-mastoid-sub-occipital (RMSO) craniectomy and excision of the tumor 11 years ago. During that surgery the left eighth cranial nerve was sacrificed, while the left seventh cranial nerve was preserved. Now, he presented with left hemi-facial spasm and left-sided gait ataxia, on MRI there was an evidence of recurrence of the lesion for which he underwent re-exploration of left RMSO craniectomy and gross total excision recurrence was done. Two months after the second surgery, he came with complaints of watery discharge from the nose. CT cisternography showed a CSF tract from the operated cavity filling the mastoid cavity through the supra labyrinthine tract into the middle ear and through the Eustachian tube into the nasal cavity. The patient was planned for extended cortical mastoidectomy and repair of the fistulous tract. The left postauricular incision was made followed by extended cortical mastoidectomy. Tegmen, posterior fossa dural plate, labyrinthine block, and sigmoid sinus were delineated and preserved. CSF leak through the supralabyrinthine cell tract was identified ( Fig. 1A and B ) and demarked to be reconstructed with musculoperiosteal tissue and fat. Aditus was blocked with fat. Fibrin glue was applied ( Fig. 1C ).

Fig. 1.

( A ) Coronal CT cisternography was showing CSF collection at the postoperative cavity and draining to the mastoid cavity through supralabyrinthine cell tract ( arrow ); ( B ) Supralabyrinthine air cells ( arrow ) identified after an extended cortical mastoidectomy; ( C ) Tract repaired with musculoperiosteal tissue, fat plug, and tissue glue ( arrow ); ( D ) Hyperintense lesion filling the right mastoid antrum and middle ear cavity; ( E ) Exposure of the vascular tumor in the mastoid cavity after radical mastoidectomy, and ( F ) postoperative MRI showing near-total removal. CSF, cerebrospinal fluid; CT, computed tomography; MRI, magnetic resonance imaging.

Radical Mastoidectomy

Extended cortical mastoidectomy is the preferred approach in cases where hearing preservation is required. However, there are many situations where hearing is already lost, and the pathology involves the middle ear cleft where a more radical approach is needed in the form of radical mastoidectomy. The difference between a radical mastoidectomy and extended cortical mastoidectomy is that the posterior canal wall was taken down along with the removal of middle ear structures like ossicles (except stapes footplate) along with the obliteration of Eustachian tube opening into the middle ear. The facial nerve within the fallopian canal was delineated and preserved.

Case Scenario

Temporal Bone Hemangioma

A 2.5-year-old male child presented with a history of right ear bleeding and discharge with a mass in external auditory canal (EAC). Clinical evaluation showed a fleshy mass in the right EAC, with the normal facial nerve. CT scan showed evidence of soft tissue density filling the EAC, middle ear, and mastoid antrum. MRI showed an evidence of contrast-enhancing lesion filling the mastoid ( Fig. 1D ) and EAC. Possibility of rhabdomyosarcoma was suspected because of the presenting age. The patient was planned for radical mastoidectomy. Through a post aural incision, cortical mastoidectomy was done; tegmen and sigmoid sinus plate were identified, and the mastoid tip was removed. A highly vascular mass was noted, filling the mastoid cavity and involving the middle ear ( Fig. 1E ). This was gradually debulked with cautery. During dissection, the disease was found involving the tympanic and mastoid segment of the facial nerve. The involved segment was resected, and the cut end was anastomosed using the greater auricular nerve graft. The histopathology showed hemangioma; hence the possible site of origin of hemangioma was thought to be facial nerve. During follow-up, the patient had grade IV facial nerve paralysis. Primary hemangioma of the facial nerve is a rare entity, and in a pediatric population, it is still rarer.

Modified Transcochlear Approach

Radical mastoidectomy is chosen in cases where the petrous apex/bony labyrinth is spared. However, in cases with the disease involving the middle ear cleft but extending into the labyrinth or a primary disease of the petrous bone with hearing loss, a transcochlear approach can be used. The transcochlear approach is mainly useful for lesion involving the petrous apex and adjoining areas with hearing loss. House and Hitselberger have initially described the transcochlear approach; it includes identification of the internal auditory canal, posterior rerouting of the facial nerve, and removal of the cochlea and petrous apex with the preservation of middle ear and EAC ³ . In modified transcochlear approach, we combine the removal of the middle ear and external auditory canal with posterior re-routing of the facial nerve; this widens the exposure and allows better control of the temporal carotid artery and ease the complete removal of petrous apex lesion. ⁴ We had two rare cases involving the temporal bone, (1) Petrous apex recurrent chondrosarcoma and (2) Fibrous dysplasia of temporal bone which were managed by the modified transcochlear approach.

Case Scenario

Petrous Apex Chondrosarcoma

A 45-year-old female presented with complaints of neck mass with headache, who had undergone surgery 4 years back and was a histologically proven case of petrous chondrosarcoma. MRI brain showed a large peripherally enhancing lobulated lesion in cerebellopontine angle ( Fig. 2A and B ) extending from lower pons to C2 level, at the site of jugular foramen with the cystic component in cerebellar hemisphere associated with cerebellar edema. The pathology replaced the temporal bone (petrous and mastoid part). There was also a well-defined lesion in the left side of the mid-neck. A left craniotemporocervical incision was made. Through a modified transcochlear approach, the tumor debulking was performed, and complete excision was done ( Fig. 2C and D ). Through the same incision, the tumor in the neck was excised. The dural repair was done with the artificial dura and tumor cavity was obliterated with fat. Skin closure was done in multiple layers.

Fig. 2.

( A ) The multilobulated hyperintense lesion in the left CP angle replacing the entire left temporal bone on T2W MRI. ( B ) Sagittal section of T2W MRI showing d hyperintense lesion causing compression of the left cerebellar hemisphere; ( C ) Tumor cavity after excision through a modified transcochlear approach ( D ) posterior fossa dural defect. ( E ) A hetero-intense lesion in the right temporal bone, displacing the right temporal lobe and the right cerebellum; ( F ) Exposure of the tumor and ( G ) postoperative CT showing complete tumor removal and tumor cavity. CP, cerebellopontine; MRI, magnetic resonance imaging; T2W, T2-weighted.

Fibrous Dysplasia of Temporal Bone

A 21-yearold male presented with right-sided painless swelling behind the ear with ear discharge for 4 years. He had undergone two surgeries for the same complaints in the past 8 years. After the second surgery he developed facial nerve palsy. The histopathology showed fibrous dysplasia. CT showed a well-defined lytic lesion replacing the entire temporal bone, with the displacement of the cerebellum. MRI showed well-defined large nonenhancing lesion involving the right temporal bone with significant compression on the intracranial structures ( Fig. 2E ). Due to multiple recurrences, we planned for a radical excision. A right craniotemporocervical incision was made ( Fig. 2F ), and the tumor was gradually debulked and separated from the middle fossa dura. As the tumor was densely adherent to the posterior fossa dura, during resection, there was rent in the dura, which was repaired using artificial dura. Due to multiple surgeries, there was skin flap necrosis, which was managed nonsurgically. Cranioplasty was planned at a later stage.

Extended Middle Fossa Approach

Transcochlear approach is preferred for lesions of the petrous apex with hearing loss and is a more radical approach. However, for lesions of the petrous apex with preserved hearing, one can use the middle fossa approach which is a more conservative approach. A classical middle fossa approach provides a subtemporal extradural approach to the middle fossa floor and is most commonly used for the excision of vestibular schwannoma situated laterally in the internal auditory canal. ^{5 6} The extended middle fossa approach provides exposure to the lesion that extends to the petrous apex and supraclival region.

Case Scenario

Middle Ear Adenoma

A 51-year-old male, with a known case of right middle ear adenoma who had undergone surgery 3 years ago, presented with a headache. MRI showed a sharp contrast-enhancing lesion in the right petrous temporal bone ( Fig. 3A ), right half of clivus and right occipital condyle encasing right ICA with the involvement of IAM with the encasement of intracanalicular part of right seven to eight cranial nerve complex extending into the ipsilateral cerebellopontine angle and mastoid air cells which were suggestive of recurrence. The CECT head showed the right frontotemporal craniotomy cavity with residual lesion along the lateral and posterior margins of the surgical cavity.

Fig. 3.

( A ) Isointense lesion on T1W MRI involving the right petrous part of the temporal bone the temporal ICA is seen inside the lesion; ( B ) Tumor cavity after excision through extended middle fossa approach ( C ) T2W MRI showing a heterointense multilobulated lesion involving the left infratemporal region causing significant compression of the oropharynx, parotid region, and intracranial extradural extension with minimal displacement of the temporal lobe; ( D ) Tumor cavity and craniotomy defects are well visualized. ( E ) Postoperative CT scan showing complete tumor removal. Posterior fossa dural defect. ICA, ; internal carotid artery; CT, computed tomography; MRI, magnetic resonance imaging; T2W, T2-weighted.

The patient underwent near-total excision by extended middle fossa approach ( Fig. 3B ). During the procedure, the patient had petrous carotid artery injury, which was managed with muscle plug and pressure. Postoperative CT angiography was done to rule out rebleed and aneurysm, which was normal. Postoperatively patient was subjected to radiotherapy (RT). The patient is under follow-up for the past 1.5 years and has no increase in the size of the lesion.

Infratemporal Fossa Approaches

The above discussed approaches are used for lesions primarily affecting the temporal bone region including the petrous apex. However, for lesions extending from the temporal bone to the infra-temporal fossa (ITF) or lesions primarily in the ITF, we need more extensive approaches. ITF is a potential space bounded by greater wing of sphenoid superiorly, and part of the temporal bone; medially by superior constrictor muscle and pterygoid plates; posteriorly by the glenoid fossa, styloid process, and carotid sheath; laterally by zygoma, mandible, parotid, and masseter muscle. Transtemporal approaches was described by Ugo Fisch (A, B, C), while the preauricular approach was described by Sekar et al. ^{7 8} Fisch approaches are primarily used for lesions involving middle ear cleft with extension into jugular bulb, petrous apex, clivus, and nasopharynx. The preauricular approach gives adequate access to the petrous apex, clivus superior and inferior infratemporal fossa and nasopharynx with no middle ear or mastoid involvement.

Preauricular Transzygomatic Infratemporal Fossa Approach

Case Scenario

Infratemporal Fossa Schwannoma

A 50-year-old male presented with left-sided facial and neck swelling for 20 years. CECT showed a well-encapsulated multilobulated lesion involving the entire left ITF causing a significant bulge into the oropharynx leading to the erosion of the greater wing of the sphenoid. The lesion was abutting the CCA, and ICA while the internal jugular vein (IJV) was compressed. On MRI ( Fig. 3C ), the lesion was displacing the left temporal lobe superiorly with edema of temporal lobe and effacement of temporal horn.

The left-sided pre-auricualr cranio-cervical incision pre-auricualr cranio-cervical incision was marked, skin flap was raised zygomatic root was identified and zygomatic osteotomy was performed to gain access into the ITF. Hypoglossal; nerve, glossopharyngeal nerve, spinal accessory were identified and preserved and IJV, external carotid and internal carotid were identified and vascular control was taken. Facial nerve main trunk was identified; the superficial lobe of parotid was dissected along with facial nerve after dividing the main trunk. Temporal craniotomy was done, and the tumor was dissected; intracranial and extradural tumors were removed in piecemeal. Dura was breached during its removal from the medial part of the tumor. Dural repair was done by muscle patch; skull base repair was done using fat, fascia, glue, and Oxidized cellulose, ITF filled with fat; facial nerve reconstruction was done by end to end anastomosis using 9.0 Vicryl. Glue was placed around the facial nerve reanastomosis; hemostasis was achieved, and suturing was done after the closure of craniotomy. Due to complete involvement of the infratemporal fossa and the widening of the stylo-mandibular tunnel, the lesion was excised without the need of mandibular management (mandibulotomy or mandibulectomy) ( Fig. 3D ). Due to the large tumor volume, the facial nerve was unduly stretched; hence an attempt to dissect it from the tumor was not made as it would lead to irreversible damage of the nerve fibers. The nerve trunk was sharply cut and anastomosed after tumor excision.

Type-A Infratemporal Fossa Approach

Case Scenario

Glomus Jugulare

A 60-year-old female presented with right aural mass associated with pulsatile tinnitus. The otoscopic evaluation showed bleeding pulsatile mass in the right external auditory canal with normal facial nerve function. Audiometry showed a moderately severe conductive hearing loss. She also had isolated hypoglossal nerve palsy. CT showed evidence of soft tissue density in the jugular bulb with the widening of the jugular foramen ( Fig. 4A ). MRI showed an evidence of a lesion with classical salt and pepper appearance, filling the jugular foramen. CT angiogram/venogram showed a filling defect in the jugular bulb and proximal jugular vein. RT is one of the mainstay treatment modalities for glomus jugulare. However, there are certain indications in which surgical excision should be preferred. The reason for choosing surgery over RT in two patients included in this series is the involvement of 12th cranial nerve in one patient and young age (32 years) in the second case. The patient was planned for surgical excision via a transtemporal route. The craniotemporocervical incision was made; control of the major vessels was obtained in the neck followed by extended canal wall mastoidectomy. Vertical and tympanic segments of the facial nerve were mobilized; a tumor in the middle ear and external auditory canal was gradually debulked with bipolar electrocautery. The tympanic bone was drilled, and jugular foramen was exposed. Sigmoid sinus was extraluminally packed and obliterated following, which IJV was ligated and cut. Lateral wall of IJV along with the tumor in the IJV ( Fig. 4B ), jugular bulb, and hypotympanum were removed with the preservation of medial wall of IJV ( Fig. 4C ). Brisk bleed from the inferior petrous sinus was controlled with Surgicel and gel foam. The tumor cavity was obliterated with fat, and blind-sac closure of the EAC was performed. Another case of a hypoglossal schwannoma presenting as jugular foramen lesion was also managed with this approach successfully with some modifications ( Fig. 4D and E ).

Fig. 4.

( A ) The lesion in the right jugular foramen causing erosion of caroticojugular crest (phelps sign); ( B ) Excision of the tumor ( arrow ) from the right jugular bulb and IJV; ( C ) Tumor cavity after excision; ( D ) Hyperintense lesion in T1 contrast MRI, involving the left jugular foramen ( E ) postoperative CT showing the tumor cavity. IJV, internal jugular vein; MRI, magnetic resonance imaging.

Discussion

Skull base surgeons have the choice of various surgical approaches. It is not the approach to the field but the pathology and its extent that dictate its approach ( Fig. 5 ). Although some of these pathologies are very rare, surgeons should be aware of their rare presentation and be prepared to enlist other surgeons for complementary expertise. Thorough knowledge of anatomy and the vital structures that are crossing the surgical corridor should be evaluated in preoperative imaging to plan the surgical steps and anticipate which structures can be saved or sacrificed. This is necessary to prevent major complications like paradoxical CSF rhinorrhea.

Fig. 5.

Various transtemporal approaches. ( A ) Location of pathologies and appropriate surgical approaches explained on an axial section of NCCT of temporal bone; ( B ) Location and extent of pathologies on a coronal section and the appropriate approaches; ( C ) coronal section and ( D ) sagittal section, depicts the location and extent of pathology that can be handled by preauricular transzygomatic subtemporal approach. NCCT, non-contrast computed tomography.

Paradoxical CSF rhinorrhea refers to the drainage of CSF through middle ear cleft and its exit via the nasal cavity. It may result from congenital middle ear defects, iatrogenic causes (post tumor excision), traumatic causes, or neoplastic intracranial lesions adjacent to the middle ear. CSF rhinorrhea is a rare complication after surgery for vestibular schwannoma. It may occur through opening up of mastoid air cells while drilling the internal auditory canal (IAC) or via the vestibule or oval window. ⁹ The significant factors that increase the risk of CSF rhinorrhea following vestibular schwannoma surgery are large tumor size, type of approach (retrosigmoid > translabyrinthine), and hyper pneumatized mastoid. ^{10 11} CT cisternogram of temporal bone plays an essential role in diagnosing this entity and also in determining the path of CSF drainage preoperatively. ¹⁰ Treatment modalities include conservative management, lumbar drainage, or mastoid exploration with obliteration of cell tract and Eustachian tube obliteration. In our case, we had a CSF leak through supralabyrinthine cell track alone, and other possible routes are ruled out, that is why we decided an extended cortical mastoidectomy and obliteration of the cell tract, which worked out very well and subsequently the patient was symptom-free during follow-up.

Temporal bone hemangiomas are very rare. These are benign tumors of the middle ear, which usually originate from either the geniculate ganglion of the facial nerve or the fundus of the internal auditory canal. They usually present with hearing deficits, tinnitus with or without facial nerve palsy. ¹² Capillary hemangiomas are more common in geniculate ganglion whereas in IAC cavernous hemangiomas are more common. ¹³ The common differential diagnosis for these lesions is facial nerve schwannomas and meningioma. Treatment of choice for these lesions is surgery. Type of surgery depends on site, size, and extension of the lesion. The treatment aims at total tumor removal with preservation or restoration of facial nerve function and hearing. ¹² Because of the young age in our case, we planned radical mastoidectomy, and total excision was performed. The site of origin in our case was facial nerve near the geniculate ganglion, so we proceeded with nerve excision and nerve grafting.

Based on tissues of origin, the petrous apex lesions are classified into (1) developmental lesion, (2) inflammatory lesions, (3) benign, (4) malignant, (5) vascular, and (6) osseous lesions. Recent advances in MRI and CT imaging increase the chances of early diagnosis of petrous apex lesion and possible preoperative diagnosis. ¹⁴ The most common lesions encountered in petrous apex are cholesterol granuloma, meningioma, schwannoma, and chordoma.

Chondrosarcomas are rare malignant tumors of petrous bone that are formed by the cartilage matrix producing tumor cells. ¹⁵ They are usually low-grade tumors exhibiting an indolent growth pattern and most commonly seen at synchondrosis near the temporo-occipital junction. The most common presentation of these lesions is a diminution of hearing and cranial nerve palsies. Surgical resection is the treatment of choice; however, piecemeal surgical resection has been associated with increased chances of local recurrence. ¹⁶ RT has a role in high-grade tumors. ¹⁷ Because of recurrence, our case underwent radical excision through extended transcochlear approach followed by RT.

Fibrous dysplasia is a localized abnormal proliferation of connective tissue with segments of immature bone interspersed in between, encountered in facial and temporal bones. It may present with swelling, pain, and hearing loss in cases of the temporal bone. They may have a syndromic presentation where the patient may also have endocrinopathies and cutaneous pigmentation. Modern-day imaging allows us to diagnose this condition quickly, and conservative surgery is preferred. ¹⁸ However, in circumstances of multiple recurrences, as in our case, a more radical approach is advised.

Middle ear adenoma is a rare benign epithelial tumor that arises from middle ear mucosa. These lesions do not have any specific clinical presentation, usually associated with hearing deficits, tinnitus, and vertigo. The closest differential diagnosis is middle ear carcinoid tumor. Other differential diagnoses include schwannomas, meningiomas, and paragangliomas. ¹⁹ Total excision is the treatment of choice; however, in rare scenarios, they can recur despite being benign. In such recurrent cases, there is a role of adjuvant RT. In our case, as the patient had multiple recurrences after near-total excision, he underwent RT. The horizontal portion of ICA and the cochlea limit the inferior exposure to the level of inferior petrosal sinus, trigeminal ganglion anteriorly, TMJ and petrous ICA laterally, and superior semicircular canal and vestibule posteriorly. Complications include temporal lobe injury due to retraction, paradoxical CSF rhinorrhea, ICA injury, trigeminal injury, and postoperative hematoma. The main advantage of the approach is that hearing can be preserved. ²⁰ Our patient also had petrous ICA injury that was managed with muscle plug and pressure. Postoperative CT angiography was done to rule out rebleed and aneurysm and it was normal.

The Fisch infratemporal fossa approaches were mainly described for lesions extending anteriorly and medially. The preauricular transzygomatic transmandibular infratemporal approach is useful for lesion arising in the ITF and intracranial tumor arising in relation to the greater wing of the sphenoid. ²¹ In the case of jugular foramen exposure, removal of the styloid process along with anterior transposition of facial nerve facilitates a good exposure of jugular foramen. Whenever there is a need for wide jugular foramen exposure for large lesions, then that can be accessed by removing the transverse process of atlas and lateral suboccipital craniotomy or craniectomy. ²² We have managed a very large ITF schwannoma and an anaplastic meningioma through preauricular transzygomatic subtemporal approach.

The most common tumors to occur in the region of jugular foramen are paragangliomas, schwannomas, and meningiomas. Some of the rare tumors include chondroma and chondrosarcoma. These lesions most commonly present with loss of hearing, multiple lower cranial nerve palsies, vestibular symptoms, and tinnitus. The jugular foramen lesions can be reached through a lateral corridor via transtemporal approaches, posterior approach via translabyrinthine or transcochlear route, or anterior approaches like Fisch infratemporal approach. ²² Selection of appropriate approach depends on the nature of pathology and its extension. In our series, we have managed two jugular paragangliomas and one hypoglossal nerve schwannoma through Fisch Type-A infratemporal approach.

Transtemporal approaches pose particular problems to the surgeons because they have to negotiate ICA, sigmoid sinus, lower cranial nerves, seventh and eighth nerve complex, and inner ear for hearing and balance to be preserved. A skull base tumor often extends into different anatomical compartments that necessitate combined approach. ²² Due to the overlap of neurosurgery and otology in this area, often collaboration between neurosurgeon and otologist is mandatory. Key to success in transtemporal approach is adequate exposure, careful attention to tissue plane while elevating the skin flap to prevent inadvertent injury to the frontal branch of the facial nerve, and to maintain the flap vascularity to prevent flap necrosis. It is also important to plan musculoperiosteal flap and muscular flaps for the reconstruction at the end of surgery. During major vessel handling, it is crucial to catch the subadventitial plane and neck control is mandatory to prevent vascular complications. The facial nerve is the most common cranial nerve at risk during transtemporal surgery. Monitoring facial nerve function during the surgical procedure is mandatory whenever the facial nerve is being handled. Even with careful dissections, some degree of temporary facial nerve palsy is common due to the disturbance of its vasculature. ²² Postoperative surveillance of the nerve functioning is quite essential, especially in cases of lagophthalmos to prevent exposure keratitis. Eye moisturization using lubrication and taping of the eyelids should be initiated as early as possible. Permanent tarsorrhaphy or gold weight implantation may also be considered to avoid chronic exposure keratitis. In cases of lower cranial nerve palsies, to improve the swallowing and speech rehabilitation, a unilateral cricothyroid approximation can be done on the paralyzed side. In some studies, the cricothyroid approximation has proven to aid patients in swallowing abilities and improve their speech qualities. ²³

Due to the proximity of dural space around the temporal bone, the patients undergoing transtemporal approaches are at a greater risk of developing immediate or delayed onset CSF leak. It is important to recognize the CSF leak early and decide the need for conservative management, lumbar drainage, or re-exploration as early as possible. The cosmetic deformity may arise even with careful surgical planning and reconstruction. The surgical cavity should be reconstructed with a free graft or implant at the time of surgery or a later date. ²¹

Conclusion

Our series shows that acceptable results were obtained when standard microsurgical principles and techniques were applied through the transtemporal approach for complex skull base lesions. We had three cases of multiple recurrent uncommon lesions, which were successfully managed by surgery. Selection of appropriate surgical approach primarily should be based on the training and preference of the operating surgeon. Combined surgical approaches facilitating full tumor exposure are recommended so that complete tumor excision is feasible. This requires a multidisciplinary team comprising neurosurgeons, neuro-otologist, anesthetist, and plastic surgeons. It should be tailored based on the individual lesion, to obtain adequate exposure and complete excision. It is important to follow an extradural strategy for huge exocranial pathologies. The surgeon must know precise microsurgical anatomy to preserve the adjacent nerves and vessels, which is necessary for better surgical outcomes.