Minimally invasive supracondylar transtubercular (MIST) approach to the lower clivus

Drawbacks of the far-lateral approach to the lower clivus and pontomedullary region include the morbidity of a large incision extending into the cervical musculature and tedious exposure of the vertebral artery (VA), particularly when performing the transcondylar and transtubercular extensions. The authors describe a minimally invasive alternative to the far-lateral approach that has the potential to minimize operative morbidity and decrease the need for VA manipulation.

The minimally invasive supracondylar transtubercular (MIST) and far-lateral supracondylar transtubercular (FLST) approaches were performed in 10 adult cadaveric specimens (20 sides). The microsurgical anatomy of each step and the surgical views were analyzed and compared. In addition, the endoscopic view through the MIST was examined in five fresh cadaveric specimens (10 sides).

The MIST approach provided exposure of the inferior-middle clivus, the anterolateral brainstem, and the premedullary cisterns, including the PICA-VA and vertebrobasilar junctions. The endoscope provided a clear view of cranial nerves III through XII, as well as the vertebrobasilar system. The FLST approach increased visualization of the anterolateral margin of the foramen magnum; otherwise, the surgical view is similar between the MIST and FLST approaches.

The MIST approach could be considered as a potential alternative to the FLST approach in the treatment of lesions involving the inferior and middle clivus, and anterolateral lower brainstem; it does not require a C1 laminectomy, significant disruption of the atlanto-occipital joint, nor extensive exposure of the extracranial VA. Moreover, the MIST approach is an ideal companion to endoscope-assisted neurosurgery.