Microdissection study of CPA for the functional neuprosurgery

Abstract

Objective To study the anatomy relationship among the vessles, nerves and bone landmarks in the region of CPA and provide operation-related anatomy knowledge for microvascular decompression of trigeminal neuralgia and hemifacial spasm. Method 16 cadaver specimens were used. 32 sides of CPA region were dissected with retrosigmoid approach. The optimal bone window center for Ⅶ,Ⅷ cranial nerves was localized and the relationship of nerves and vessels were observed and measured. Results (1)The bone window was 2 cm under the midpoint of superior nuchal line superiorly, 1 cm above superior margin of foramen magnum inferiorly, 3 cm lateral to occipital sinus medially, 0.5 cm medial to mamillary process base laterally. The center of the bone window was properly above the Ⅶ,Ⅷ cranial nerves. (2)The widest distance between the Ⅶ,Ⅷ cranial nerves and trigeminal nerve was 10.20～12.18 mm, mean (11.19±0. 12)mm in the cistern. (3)The distance between Ⅶ,Ⅷ cranial nerve and petrosal vein is 9.10±11.22 mm, mean(10.05±0.11)mm,and this interspace can be used to perform microvascular decompression without cutting off petrosal vein. Conclusions The bone window for microvascular decompression in CPA can be optimized to a special location. The locations of trigeminal nerve and Ⅶ,Ⅷ cranial nerves are relatively constant. Therefore these nerves can be used as intraoperative landmarks. The microvascular decompression operations can be performed in the interspace between nerves and vessles without cutting off petrosal vein. Key words: Cerebellopontine angle; Neuroanatomy; Trigeminal neuralgia