Retrosigmoid intradural suprameatal approach: advantages and disadvantages from an anatomical perspective.
OBJECTIVE
To assess the advantages and disadvantages of the retrosigmoid intradural suprameatal approach by studying the microsurgical anatomy. This study was performed primarily to assess the advantages of the retrosigmoid intradural suprameatal approach by measuring the amount of increased exposure it provides for lesions of the cerebellopontine and petroclival region as well as to identify the disadvantages of the approach.


METHODS
Twenty sides of 10 cadaver heads (embalmed and injected) were dissected under x3 to x40 magnification. A standard retrosigmoid craniotomy was made. The cerebellopontine cistern was entered to expose the neurovascular structures, and the internal auditory canal was opened by drilling the margin of the internal auditory meatus. After this, the suprameatal tubercle was drilled, followed by additional drilling to resect the petrous apex. The trigeminal root was mobilized completely after opening Meckel's cave. During drilling, care was taken to preserve the posterior and superior semicircular canals, petrosal sinus, and the internal carotid artery.


RESULTS
The approach enhanced the exposure of the cerebellopontine cistern and Meckel's cave. There was an additional exposure of 10.7 +/- 1.16 mm length of trigeminal nerve on the right side and an additional 10.7 +/- 1.25 mm on the left. This helped to mobilize and further retract the trigeminal root. Although it facilitated the view of the neurovascular structures medial to the internal acoustic meatus, the depth of exposure did not vary much from a traditional retrosigmoid approach nor did it increase the angle of exposure or the visualization of the clivus and more medially located structures.


CONCLUSIONS
This approach is suitable for lesions mainly in the posterior fossa with some extension into the middle fossa in the anterolateral direction. The key benefits of this approach are the length of trigeminal nerve exposure and the subsequent mobilization that improves visualization of the structures medial to the internal auditory canal, to the petrous apex, Meckel's cave, and the posterior end of the cavernous sinus.
Chanda
Amitabha
A
Department of Neurosurgery, Louisiana State University Health Sciences Center in Shreveport, Shreveport, Louisiana 71130-3932, USA.
Nanda
Anil
A
D001933:Brain Stem / Q000033:anatomy & histology / Q000601:surgery; D002343:Carotid Artery, Internal / Q000033:anatomy & histology / Q000601:surgery; D002426:Cavernous Sinus / Q000033:anatomy & histology / Q000601:surgery; D002530:Cerebellopontine Angle / Q000033:anatomy & histology / Q000601:surgery*; D002531:Cerebellum / Q000033:anatomy & histology / Q000601:surgery; D035301:Cranial Fossa, Middle / Q000033:anatomy & histology / Q000601:surgery*; D003388:Cranial Fossa, Posterior / Q000033:anatomy & histology / Q000601:surgery*; D003392:Cranial Sinuses / Q000033:anatomy & histology / Q000601:surgery; D003399:Craniotomy / Q000295:instrumentation / Q000379:methods*; D004210:Dissection / Q000379:methods; D004388:Dura Mater / Q000033:anatomy & histology / Q000601:surgery; D005154:Facial Nerve / Q000033:anatomy & histology / Q000601:surgery; D006801:Humans; D042282:Microdissection / Q000379:methods; D010579:Petrous Bone / Q000033:anatomy & histology / Q000601:surgery; D014276:Trigeminal Nerve / Q000033:anatomy & histology / Q000601:surgery; D000159:Vestibulocochlear Nerve / Q000033:anatomy & histology / Q000601:surgery