Fisch Approaches to the Infratemporal Fossa

Background: Infratemporal fossa procedures provide wide exposure of the skull base. The main indications for these approaches are glomus jugulare lesions; lesions of the petrous apex and clivus; and nasopharyngeal, sellar, and parasellar lesions—particularly those extending into the infratemporal fossa, orbit, parasellar region, and cavernous sinus. There are three main types of these procedures: A, B, and C. The type A approach is rarely performed today. Types B and C approaches are commonly used, especially by ENT surgeons. Neurosurgical literature lacks detailed anatomical dissection of these three approaches. In this study, we performed cadaver dissection studies of all three approaches and showed the bony, neural, and vascular structures relevant to the approach used.

Materials and Method: Nine formalin-fixed cadaver heads were used to study the Fisch approaches. For the type A approach, a subtotal temporal bone resection was done. External auditory canal, tympanic membrane, and ossicles down to the stapes footplate were removed, and the facial nerve was skeletonized from the stylomastoid foramen to the geniculate ganglion. The upper neck was dissected, and the great vessels and the lower cranial nerves were identified. The bone of the carotid canal was removed. After retraction of the mandibular condyle, a wide exposure of the infratemporal fossa was achieved. For type the B approach, a subtotal temporal bone resection was done. The zygomatic arch and temporalis muscle were reflected inferiorly with the facial nerve. The mandible was reflected inferiorly and the horizontal segment of the carotid artery was dissected. Then the middle fossa skull base structures were seen. For type C, initially a type B approach was performed. This was followed by drilling of the pterygoid process as well as the bone of the skull base. The maxillary branch of the trigeminal nerve was then sectioned, and the carotid canal was decorticated up to the foramen lacerum and the cavernous sinus.

Results: We performed infratemporal approach types A, B, and C, and showed the anatomical structures relevant to these approaches. Retraction of the mandibular condyle was made with limitation in cadavers because of tissue stiffness.

Conclusions: Cadaver studies revealed the pertinent anatomy of the commonly used infratemporal fossa approaches. Although the cadaver specimens have a disadvantage of inherent tissue stiffness, these studies can be used for anatomical training or surgical planning.