Keywords
infratemporal fossa - preauricular transzygomatic - pterional craniotomy
Introduction
The preauricular transzygomatic surgical approach (PTZA) for infratemporal fossa (ITF)
can be used to achieve a complete resection of a variety of tumors arising from or
extending into the ITF. This approach can be tailored to the individual tumor and
its extensions. This approach is designed for ITF lesions with or without extension
to pterygopalatine fossa (PPF), sphenoid sinus, and minimal extension into cavernous
sinus. Two types of preauricular approach for ITF are preauricular transzygomatic
ITF approach and preauricular frontotemporal orbitozygomatic approach.
The earliest publications addressing surgical approaches to the ITF appeared in the
19th century and focused on the treatment of sphenopalatine neuralgia. These approaches
were associated with high morbidity rates and failed to gain popularity.[1] Till the 1960s, the ITF was considered surgically inaccessible, and tumors that
extended into the ITF had been considered inoperable. Innovative surgical approaches
were introduced by Conley[2] and Barbosa.[3] Prof. Ugo Fisch has devised various approaches to ITF. These approaches are among
the most commonly used approaches to ITF in current scenario. Various approaches are
named as Fisch types A, B, and C. Preauricular approaches to the skull base are described
by many authors including Sen and Sekhar.[4] Preauricular approaches to skull base access nearly the same area as by Fisch B
and Fisch C approaches from a purely lateral vector of exposure. Skull base surgical
approaches to the ITF have undergone significant changes. The most important among
them is the collaboration among multidisciplinary teams involving otolaryngologists/head
and neck surgeons, neurosurgeons, plastic surgeons, ophthalmologists, radiologists,
and medical and radiation oncologists. Team work improves diagnosis, staging, and
management of the tumor. Preauricular transzygomatic ITF approach helps in mobilization
of the second and third divisions of the trigeminal nerve after drilling of the lateral
loop between the foramina rotundum and ovale. Mobilization of the trigeminal nerve
provides visualization of the auditory tube, tensor veli palatini muscle, and pharyngobasilar
membrane. Removal of pterygoid muscles and plates allows surgical access to the cavernous
sinus, sphenoid, nasopharynx, clivus, PPF and parapharyngeal space.[5] All approaches and modifications of existing technique are to minimize injury to
important neurovascular structures within and adjacent to the ITF. When selecting
the surgical approach, a variety of factors such as histology, biological behavior
of the tumor, the patient’s characteristics, and the surgeon’s experience should be
considered.[6] The approach described here can be modified according to the nature and extensions
of a tumor. However, many do not agree with the same and advocate the use of extensive
approaches regardless of the nature and extensions of the tumor. As the time has eloped
now, more and more endoscopic approaches have evolved to reach ITF, but their success
in large ITF tumors with lateral extension is questionable. In comparison with a lateral
approach, endonasal endoscopic transpterygoid approach provides better visualization
and more direct exposure of median structures such as the nasopharynx, eustachian
tube, sella, and clivus.[7] We studied the association among the characteristics of ITF tumors, and the variables
pertaining to their surgical treatment to demonstrate the effectiveness of the PTZA
according to the characteristics of individual tumors. During surgery a curvilinear
incision was performed starting from in front of the tragus, coursing superiorly and
then anteriorly in the frontal scalp to end superior to the supraorbital notch near
the midline. This can be combined with pterional craniotomy to remove tumors with
intracranial extradural extension.
Materials and Methods
Patients with tumors involving the ITF who underwent surgical treatment via a PTZA,
at our super specialty tertiary care center during the period between January 2012
and June 2014, were included in the study. Total of seven patients were included,
of whom three were malignant and four were benign. Their clinical charts were retrospectively
reviewed, and data were collected regarding patient demographics, radiology and histopathology,
and postoperative extent of excision and associated morbidity ([Table 2]). Clinical and radiological reports were analyzed to establish the origin and extensions
of the tumors. Based on Conley’s classification,[8] tumors were classified as primary tumors, originating primarily from one of the
ITF structures, or as contiguous tumors, originating from the adjacent areas and locally
extending into the ITF. Tumor extensions were grouped according to anatomic sites
([Table 1]).
Table 1
Extension as per anatomic sites
|
Extension
|
Sites
|
|
Abbreviations: ICA, internal carotid artery; IJV, internal jugular vein; PPF, pterygopalatine
fossa.
|
|
Medial
|
Pterygoid plates, PPF, orbit, sinonasal tract, nasopharynx, and clivus
|
|
Lateral
|
Zygoma, mandible, parotid, and masseter
|
|
Superior
|
Greater wing of sphenoid, temporal bone, carotid canal, foramen jugulare, foramen
ovale, maxillary nerve, and mandibular nerve
|
|
Intracranial
|
Gasserian ganglion, cavernous sinus, dura, and brain
|
|
Posterior
|
Vertebrae, ICA, IJV, lower cranial nerves
|
Table 2
Patients’ profile with summary of observation and management
|
Case
|
Age (y)
|
M/F
|
Symptom
|
Extension on imaging
|
Surgical approach
|
Craniotomy
|
HPE
|
Malignant/benign
|
Radiotherapy/chemotherapy
|
|
Abbreviations: AVM, arteriovenous malformation; F, female; HPE, histopathology examination;
M, male.
|
|
1
|
70
|
M
|
Swelling on right cheek
|
Medial, lateral, superior, posterior
|
Preauricular transzygomatic approach with control over carotid
|
No
|
Maxillary artery AVM
|
Benign
|
No
|
|
2
|
18
|
F
|
Pain over face
|
Medial, lateral, superior, intracranial
|
Preauricular transzygomatic approach with pterional craniotomy
|
Yes
|
Clival chordoma
|
Malignant
|
Postoperative radiotherapy
|
|
3
|
28
|
F
|
Progressive loss of vision of right side
|
Medial, lateral, superior, intracranial
|
Preauricular frontotemporal orbitozygomatic approach with pterional craniotomy
|
Yes
|
Chondrosarcoma
|
Malignant
|
Preoperative radiotherapy
|
|
4
|
11
|
M
|
Proptosis with loss of vision on right side
|
Medial, lateral, superior, intracranial, posterior
|
Preauricular frontotemporal orbitozygomatic approach with Pterional craniotomy
|
Yes
|
Clear cell meningioma
|
Malignant
|
Preoperative radiotherapy
|
|
5
|
55
|
F
|
Swelling on left forehead with progressive loss of vision
|
Medial, lateral, superior, posterior
|
Preauricular transzygomatic approach with control over carotid
|
No
|
Pleomorphic adenoma of minor salivary glands
|
Benign
|
No
|
|
6
|
20
|
M
|
Right cheek swelling
|
Medial, lateral, superior, posterior
|
Preauricular transzygomatic approach
|
No
|
Angiofibroma
|
Benign
|
No
|
|
7
|
3
|
M
|
Progressive loss of vision right side
|
Medial, lateral, superior, posterior
|
Preauricular transzygomatic approach
|
No
|
Intraorbital extraconal orbital schwannoma
|
Benign
|
No
|
They were then graded, depending on the number of structures that the tumor involved
in each direction, as minor (single structure involved) and major degrees (multiple
structures involved). Pathological data were reviewed to determine the type and nature
of the tumor, adequacy of the resected margin, and presence of perivascular and perineural
invasion. Treatment data included previous treatment modalities, plan of treatment,
and use of postoperative/preoperative radiotherapy/chemotherapy. Surgical variables
included incision design, osteotomies, craniotomies, and procedures other than the
preauricular approach necessary to complete excision of the tumor. Complications of
treatment, recurrence, need for revision surgery, and postmanagement oncological status
were also noted. In the malignant and benign groups, final outcome was taken as patients
who completed at least 1 year of follow-up.
Results
Malignant Group
Three patients, including one male and two females, had malignant tumors ([Table 2], [Figs 1]
[2]
[3]). Their ages ranged from 10 to 30 years with a mean of 19 years. Two patients were
younger than 19 and one older than 19 years. Tumors originated at the ITF in two patients
(chondrosarcoma, clear cell meningioma), and one (clival chordoma) had tumor that
originated at the adjacent areas and then extended into the ITF. Two patients were
subjected to preoperative radiotherapy (chondrosarcoma and clear cell meningioma).
Near-total excision was done in clival chordoma as it was extending into cavernous
sinus. Surgery was followed by radiotherapy for this patient. Surgical extirpation
involved ITF dissection with pterional craniotomy. Ultimately, all patients received
multimodality treatment, either during their initial treatment or as adjunctive treatment
after the surgery. Reconstruction was not needed in any of the cases. No major surgical
complications were encountered in any patient. Minor cosmetic disfigurement, hematoma,
and infection were seen, which resolved by giving conservative management. Distant
metastases developed in none. Recurrence or persistence of tumor at the local area
occurred in none.
Fig. 1 Case 2. (A) Preoperative axial section of T2 MRI showing clival cordoma having intracranial
extradural extension involving ITF, (B) Preoperative coronal section of T2 MRI showing clival cordoma having intracranial
extradural extension involving ITF, (C) Intraoperative image showing flap with pteryional craniotomy with erosion of zygomatic
root and tumor in ITF, (D) Postoperative CT scan showing complete removal of tumor from ITF and cranium. CT,
computed tomography; ITF, infratemporal fossa; MRI, magnetic resonance imaging.
Fig. 2 Case 3. (A) Preoperative coronal T2 MRI showing chondrosarcoma with intracranial extradural
lesion involving ITF and sphenoid. (B) Intraoperative image showing flap with orbitozygomatic osteotomies. (C) Specimen of orbitozygomatic osteotomy. (D) Postoperative coronal CT scan showing complete removal of tumor. CT, computed tomography;
ITF, infratemporal fossa; MRI, magnetic resonance imaging.
Fig. 3 Case 4. (A) Preoperative axial and T1 MRI images showing clear cell meningioma involving ITF,
rt orbit, sphenoid with intracranial extradural extension. (B) Preoperative axial and T1 MRI images showing clear cell meningioma involving ITF,
rt orbit, sphenoid with intracranial extradural extension. (C) Postoperative coronal CT scan showing complete removal of tumor. (D) Postoperative coronal CT scan showing complete removal of tumor. CT, computed tomography;
ITF, infratemporal fossa; MRI, magnetic resonance imaging.
Benign Group
Four patients (three males, one female) had benign tumors ([Table 2], [Fig 4]). Their ages ranged from 3 to 70 years. Mean age was 37 years. Two patients in this
group were older than 37 years and two were younger than 37 years. Tumors originated
in the ITF in three out of four patients; and in one out of four patients, tumors
originated in the orbit and extended to the ITF. In all patients, tumors had local
extensions into an adjacent area ([Table 2]). Margins of resection were microscopically positive in none.
Fig. 4 Case 5. (A) Preoperative axial section of CT scan showing pleomorphic adenoma of minor salivary
gland involving ITF with orbital extension and erosion of zygomatic bone. (B) Preoperative axial section of CT scan showing pleomorphic adenoma of minor salivary
gland involving ITF with orbital extension and erosion of zygomatic bone. (C) Postoperative axial section CT scan showing complete removal of tumor. (D) Patient image showing postoperative scar of question mark incision. CT, computed
tomography; ITF, infratemporal fossa.
Surgery was the primary treatment for all. No patient was treated for recurrences
that developed after primary surgery. Two patients underwent ITF dissection alone.
ITF dissection was combined with other procedures in two (50%) patients; that is,
in maxillary artery arteriovenous malformation (AVM), control over the common carotid
artery was taken in the neck with modification in incision over the neck. In intraorbital
extraconal orbital schwannoma, orbitozygomatic craniotomy was done. Reconstruction
was needed in none. No major surgical complications were encountered in any of the
patients. Minor complications occurred in patients which resolved by giving conservative
management.
Discussion
ITF lies below middle cranial fossa (MCF), between ramus of the mandible and lateral
wall of the pharynx. Roof is the skull base that is formed by greater wing of the
sphenoid bone and squamous part of the temporal bone. Anteriorly, it is bounded by
the maxilla, IOF, and pterygomaxillary fissure. Posteriorly, it is bounded by carotid
sheath and styloid apparatus, medially by the pterygoids, and laterally by the mandible.
ITF includes the anatomic area below the MCF base, and contains maxillary artery and
vein, V2, V3, fat, and muscles. The ITF is difficult for clinical examination; therefore,
tumors involving this region are difficult to diagnose, and they pose therapeutic
challenges. Some tumors present with insidious and nonspecific signs and symptoms
and are often diagnosed at later stages. A thorough history, physical examination,
high degree of suspicion, and radiological assessment are essential for an early diagnosis.[1] Previously, ITF tumors were considered inoperable. Advances in microsurgery and
skull base surgery lead to multiple surgical approaches to the ITF, aiming for oncologically
safe resections while minimizing the morbidity. Lateral skull base approaches were
mainly made to minimize brain retraction. They include bone removal for exposure and
for identification and preservation of vital neurovascular structures.[10] The preauricular transzygomatic approach to the ITF was developed and modified with
these concepts in mind.[11]
[12]
Various approaches for ITF have been designed, the most used among them are the Fisch
approaches.
Unlike other Fisch approaches, PTZA allows access to ITF, without involving pinna,
middle ear, and mastoid and facial nerve dissection. Incision design can be altered
as per requirement for neck dissection, if needed. PTZA is suitable for the resection
of tumors arising in the ITF with intracranial extradural extension and tumors arising
in the ITF and nearby structures and extending into the ITF. It does not allow safe
resection of any portion of the tympanic bone.[6]
In our patients, the surgical approach began with a question mark incision (coronal
incision with extension over preauricular region), which provided good exposure and
was associated with good cosmetic outcome. Various other approaches such as translocation
approach are also available, but due to cosmetic reasons, standard question mark incision
was chosen ([Fig. 4, case 5)].[13] Craniofacial osteotomies were required in more than 90% of patients in both the
groups to obtain adequate exposure of the tumor and a safe and complete resection.
Our study favors the findings of another study in which cadaveric dissections were
done and showed that surgical exposure of the ITF is superior when orbitozygomatic
osteotomies are used.[14] A pterional craniotomy was required in all malignant cases. No vascularized flaps
were used for reconstruction in all patients. The incision design was decided by the
extension of the tumor. Orbitozygomatic osteotomies were used in patients whose tumors
had medial and intracranial extensions. These associations confirmed that the surgery
could be manipulated as per the nature and extensions of a tumor. The differences
between the two groups could be explained by the need for aggressive and wider tissue
removal for malignant tumors, whereas benign tumors could be removed piecemeal without
compromising outcomes. Surgical treatment provided adequate local control. Moreover,
in both the groups, approximately three-fourths of the cases had no surgical complications.
In the malignant group (i.e., intracranial extension, invasion of the soft tissues
of the orbit), complications were significantly associated with need for a craniotomy,
that is, the degree of morbidity was higher with more advanced surgery. In the malignant
group, disease-free survival was improved by the use of postoperative radiotherapy.
Our study supports evidence-based assumption that the PTZA can be modified as per
the nature and extent of a tumor. Incisions could be designed to provide adequate
exposure of a tumor in all directions while facilitating cosmetic and functional reconstruction.
Osteotomies were needed to enhance the surgical exposure in tumors with medial extensions;
design of the craniotomy reflects the extent of superior or intracranial extensions.
Other surgical procedures may be required to access medial extensions. Attempts should
be made for complete tumor removal, but unnecessary procedures should be avoided to
minimize morbidity rates. Use of adjunctive radiotherapy, chemotherapy, or both should
be considered to improve the outcome of patients with malignant tumors.
Conclusion
In our study, all benign and malignant tumors of the ITF are of major degree (involving
more than one structure). The PTZA to the ITF is versatile and can be used to achieve
complete resection of a variety of tumors restricted to the ITF with intracranial
extradural extension. Incision used in preauricular transzygomatic approach is cosmetically
sounder than other available incisions for access to the ITF. This approach is better
than endoscopic approach as it has wider access to the lateral ITF that is a difficult
area to access through endoscopic approach. This approach can be tailored as per the
nature of disease and its extensions. A detailed study with a larger sample size is
further needed to establish the usefulness of this approach for ITF lesions.
