Simplifying the Surgical Classification and Approach to the Posterolateral Skull Base and Jugular Foramen Using Anatomical Triangles.

Introduction Lesions of the jugular foramen (JF) and postero-lateral skull base are difficult to expose and exhibit complex neurovascular relationships. Given their rarity and the increasing use of radiosurgery, neurosurgeons are becoming less experienced with their surgical management. Anatomical factors are crucial in designing the approach to achieve a maximal safe resection. Methods and methods Six cadaveric heads (12 sides) were dissected via combined post-auricular infralabyrinthine and distal transcervical approach with additional anterior transstyloid and posterior far lateral exposures. Contiguous surgical triangles were measured, and contents were analyzed. Thirty-one patients (32 lesions) were treated surgically between 2000 and 2016 through different variations of the retro-auricular distal cervical transtemporal approaches. Results We anatomically reviewed the carotid, stylodigastric, jugular, condylar, suboccipital, deep condylar, mastoid, suprajugular, suprahypoglossal (infrajugular), and infrahypoglossal triangles. Tumors included glomus jugulare, lower cranial nerve schwannomas or neurofibromas, meningiomas, chondrosarcoma, adenocystic carcinoma, plasmacytoma of the occipitocervical joint, and a sarcoid lesion. We classified tumors into extracranial, intradural, intraosseous, and dumbbell-shaped, and analyzed the approach selection for each. Conclusion Jugular foramen and posterolateral skull base lesions can be safely resected through a retro-auricular distal cervical lateral skull base approach, which is customizable to anatomical location and tumor extension by tailoring the involved osteo-muscular triangles.

The Evolutionary Development of the Brain As It Pertains to Neurosurgery.

Background Neuroanatomists have long been fascinated by the complex topographic organization of the cerebrum. We examined historical and modern phylogenetic theories pertaining to microneurosurgical anatomy and intrinsic brain tumor development. Methods Literature and history related to the study of anatomy, evolution, and tumor predilection of the limbic and paralimbic regions were reviewed. We used vertebrate histological cross-sections, photographs from Albert Rhoton Jr.'s dissections, and original drawings to demonstrate the utility of evolutionary temporal causality in understanding anatomy. Results Phylogenetic neuroanatomy progressed from the substantial works of Alcmaeon, Herophilus, Galen, Vesalius, von Baer, Darwin, Felsenstein, Klingler, MacLean, and many others. We identified two major modern evolutionary theories: "triune brain" and topological phylogenetics. While the concept of "triune brain" is speculative and highly debated, it remains the most popular in the current neurosurgical literature. Phylogenetics inspired by mathematical topology utilizes computational, statistical, and embryological data to analyze the temporal transformations leading to three-dimensional topographic anatomy. These transformations have shaped well-defined surgical planes, which can be exploited by the neurosurgeon to access deep cerebral targets. The microsurgical anatomy of the cerebrum and the limbic system is redescribed by incorporating the dimension of temporal causality. Yasargil's anatomical classification of glial tumors can be revisited in light of modern phylogenetic cortical categorization. Conclusion Historical and modern topological phylogenetic notions provide a deeper understanding of neurosurgical anatomy and approaches to the limbic and paralimbic regions. However, many questions remain unanswered and further research is needed to elucidate the anatomical pathology of intrinsic brain tumors.

Exposure of Dural Venous Sinuses: A Review of Techniques and Description of a Single-piece Troughed Craniotomy.

Intracranial lesions along the falx and tentorium often require exposure of a dural venous sinus. Craniotomies that cross a sinus should maximize exposure while minimizing the risk of sinus injury and provide a cosmetically appealing result with simple reconstruction techniques.  We describe the published techniques for exposing dural venous sinuses, and introduce a new technique for a single-piece craniotomy exposing the superior sagittal sinus or transverse sinus using drilled troughs. A review of the literature was performed to identify articles detailing operative techniques for craniotomies over dural venous sinuses. Our troughed craniotomy for dural sinus exposure is described in detail as well as our experience using this technique in 82 consecutive cases from 2007-2015. Five distinct techniques for exposure of the dural venous sinus were identified in the literature. In our series of patients undergoing a trough craniotomy, there were no sinus injuries despite a range of various locations and pathology along the sagittal and transverse sinuses. Our technique was found to be safe and simple to reconstruct compared to other techniques found in the literature. A variety of different techniques for exposing the dural venous sinuses are available. A single-piece craniotomy using a trough technique is a safe means to achieve venous sinus exposure with minimal reconstruction required. Surgeons should consider this method when removing lesions adjacent to the falx or tentorium.