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Midsubtemporal ridge as a predictor of the lateral loop formed by the maxillary nerve and mandibular nerve: a
Masahiko Wanibuchi1, Gen Murakami, Taro Yamashita
1Department of Neurosurgery, Sapporo Medical University School of Medicine, Sapporo, Hokkaido, Japan. wanibuti@sapmed.ac.jp
Background:
The lateral loop formed by the maxillary nerve (V2) and the mandibular nerve (V3) consists of a part of the far lateral triangle of the cavernous sinus. Because this triangle becomes a surgical corridor of the preauricular infratemporal fossa approach and a landmark of the extradural approach for the ganglion-type trigeminal schwannomas, identification of the lateral loop has important implications at the early stage of middle cranial base surgery. We realized that a bony ridge usually existed just lateral to the lateral loop.
Objective:
To nominate midsubtemporal ridge (MSR) as the name for this anatomically unnamed bony ridge and to clarify its features.
Methods:
Using 35 cadaver heads, we measured the shape of the MSR on both sides and the distance between the MSR and the adjacent structures.
Results:
The MSR was recognized in 60 of 70 specimens (85.7%). The bony protrusion was 2.9 ± 1.1 mm in height, 6.0 ± 2.1 mm in width, and 9.1 ± 3.2 mm in length. A single peak with anteroposterior length was common in 47 of 60 specimens (78.3%). The MSR was located at the midpoint of the V2 and V3 in 28 specimens (46.7%) and existed 10.7 ± 3.6 mm lateral from the line that bound the foramen rotundum and the foramen ovale.
Conclusion:
We demonstrate morphological characteristics of the MSR. These data on the MSR will assist the surgeon in identifying the lateral loop as a surgical landmark during middle cranial base surgery.
