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| Skull
Base Surgery |
| Infratemporal
Fossa Approach |
| The
infratemporal fossa approach of Fisch encompasses three distinct
variations for use in specific clinical situations. The key point
of the Type-A approach is the anterior transposition of the facial
nerve, which provides optimal access to the infralabyrinthine and
jugular foramen regions as well as the vertical portion of the internal
carotid artery. It is useful for the management of glomus jugulare
tumours, neuromas and meningiomas of the jugular foramen and petrous
bone cholesteatomas.
The Type-B approach allows access from the sigmoid
sinus to the petrous tip, including exposure of the horizontal ICA
and foramen ovale, to reach lesions of the petrous apex and mid
clivus, such as chordomas, meningiomas and extensive petrous apex
cholesteatomas.
The Type-C approach expands this to include the
parasellar region, the cavernous sinus, foramen rotundum, and foramen
lacerum. Removal of the pterygoid plates in this approach also facilitates
access to the nasopharynx. This approach is used in the resection
of small nasopharyngeal carcinomas and angiofibromas. All three
variations of the infratemporal fossa approach involve mastoidectomy,
facial nerve dissection (and transposition), obliteration of the
eustachian tube, middle ear and external auditory canal with resultant
permanent conductive hearing deficit.
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| Case-2
A 40 year old
male was diagnosed to have a malignant (carcinoma Ex-pleomorphic
adenoma) tumour of the right parotid with facial palsy. It was considered
inoperable elsewhere and radiotherapy was given and there was no
improvement. There was a large mass in the parotid region fixed
to the mandible and mastoid. CT showed the tumour surrounding the
ramus of the mandible and carotid shealth and extending to the skull
base superiorly. Since the carotid angiogram showed good cross circulation
after occlusion of ipsilateral internal carotid artery, permanent
balloon occlusion of the internal carotid artery was done at the
junction of the petrous and cavernous portions. The tumour was released
from the skull base by a subtotal petrosectomy and by drilling along
the mid skull base. The vertical part of petrous internal carotid
artery was drilled out, ligated and divided above the tumour. The
whole tumour was then resected en-bloc.
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| CT
shows the parotid tumour surrounding the ramus of mandible
and carotid sheath. Vessels are not seen.
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|
CT
shows tumour reaching the mastoid tip,
lateral compartment of middle skull base. |
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| Balloon
with the contrast material occluding the internal carotid
artery (ICA).
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Latex
balloon used for permanent occlusion of ICA. |
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| Skin
incision.
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Zygomatic
arch and angle of mandible divided. |
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| Subtotal
petrosectomy is done. Middle skull base drilled out. Petrous
portion of ICA (arrow) ligated and divided.
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|
Specimen removed in-toto along with ICA, IJV and lower cranial
nerves. Arrows point at the divided ends of the ICA. |
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| Postoperative
CT shows no residual tumour.
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Postoperative
CT shows the amount of bone resection. |
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Postoperative
photograph.
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