The standard approach for sectioning of the filum terminale for a tethered spinal cord can be achieved via a limited S₁ exposure. This is performed with the commonly believed idea that the filum fuses with the dura at S₂. We dissected 27 cadavers to exclusively look at the level at which the filum pierces/fuses with the dura and also the level at which the dural sac ends. Most of the fila fused at S₂ with a range from L₅ to S₃. The majority of dural sacs ended at S₂ with a range from S₁ to S₃. However, 15% of the fila (4 of 27) fused above the S₁ level. In addition, 11% of the fila (3 of 27) fused off the midline. We hope that this anatomical information may be useful for neurosurgeons when standard approaches fail to identify the filum at its usual level and location.

AIm: Surgical approaches to Meckel's cave (MC) are often technically difficult and sometimes associated with postoperative morbidity. The relationship of surgical landmarks to relevant anatomy is important. Therefore, we attempted to delineate quantitatively their anatomy and the relationships between MC and surrounding structures. mAteRIAl and methods:With the aid of a surgical microscope, MC and its contents were studied in 15 formalin-fixed cadaver head specimens. Measurements were made and their relationships were observed. Results:The distance from the zygomatic arch and the lateral end of the petrous ridge to MC was 26.5 and 34.4 mm, respectively. The distance from the arcuate eminence, the facial nerve hiatus, and the foramen spinosum to MC was 16.6, 12.8 and 7.46 mm respectively. The TG lay 5.81 mm posterior to the foramen ovale. The distance from the abducens, trochlear and oculomotor nerves to the trigeminal ganglion was 1.87, 5.53 and 6.57 mm respectively. The distance from the posterior and the anterior walls of the sigmoid sinus to the trigeminal porus was 43.6 and 33.1 mm respectively. The trigeminal porus was on average 7.19 mm from the anterior wall of the internal acoustic meatus. ConClusIon:The anatomical landmarks as presented herein regarding MC may be used for a safer skull base approach to the region. BulGulAR: Zigamatik arkusun ve petroz kenarın lateral sonunun Meckel cave'e ortalama uzaklığı sırasıyla 26,5 ve 34,4 mm idi. Arkuat eminens, fasiyal sinir hiatus ve foramen spinosumun Meckel cave'e ortalama uzaklığı sırasıyla 16,6, 12,8 ve 7,46 mm idi. Trigeminal ganglion foramen ovale'nin 5,81 mm arkasında yerleşmiştir. Abdusens, trohlear ve okülomotor sinirlerin trigeminal gangliona ortalama uzaklıkları sırasıyla 1,87, 5,53 ve 6,57 mm idi. Sigmoid sinüsün arka ve ön duvarlarının trigeminal porus'a ortalama uzaklıkları sırasıyla 43,6 ve 33,1 mm idi. Trigeminal porus internal akustik meatusun anterior duvarından ortalama 7,19 mm uzakta idi. sonuÇ: Meckel cave ile ilgili sunulan anatomik belirteçler ve onların anatomik özellikleri ile ilgili bilgiler bu bölgeye güvenli bir yaklaşım için yararlı olabilir.

Object. The authors conducted a study to describe the detailed anatomy of the apical ligament and to acknowledge or refute its historical description as a functionally significant contributor to craniocervical stability. Methods. In 20 adult human cadavers measurements of the apical ligament were obtained, and its detailed anatomy was observed. Ranges of motion were also assessed to discern the function of the apical ligament. Conclusions. Results of the study support the concept that the apical ligament is best described as a vestigial structure that offers no significant added stability to the craniocervical junction. In fact, this ligament was absent in 20% of the specimens examined. These data will aid physicians who frequently view images or manage clinical problems of the craniocervical junction because they may focus on other ligaments of this area and not the apical ligament.

This information will prove useful in planning and executing surgical procedures in and around the free edge of the tentorium cerebelli.

There are multiple anatomical triangles of the skull base. However, to our knowledge, there has been no comprehensive review of these geometric landmarks. To allow for a safe and consistent approach to lesions of the skull base such as those near the internal carotid artery, internal acoustic meatus, and cavernous sinus, a comprehensive review of the variations with illustrations is required. This article provides an overview of the anatomical borders, dimensions, and surgical implications as well as illustrations of the major skull base triangles.