HE falx cerebri is an intracranial midline partition composed of the meningeal layer of the dura mater. This structure has a superior attached portion and an inferior free part housing the superior and inferior sagittal sinuses, respectively. Anecdotally, we have observed ve- nous hemorrhage from the falx cerebri during endoscopic fenestration procedures that were not near the superior or inferior sagittal sinuses. The extant medical literature has scant statements regarding other potential veins within the falx cerebri. Crosby et al. 3 have stated that the inferior sag- ittal sinus “begins in about the middle of the border of the falx with the convergence of the falcial plexus of veins.” The superior sagittal sinus may communicate with the infe- rior sagittal sinus through a venous channel in the falx cere- bri. 8 Rhoton 8 has stated that this connection may rarely be so large that the superior sagittal sinus drains primarily into the inferior sagittal and straight sinuses. This latter config- uration, not to be confused with a falcine venous plexus, most likely represents a persistent falcine sinus to be dis- cussed later. Lastly, Kaplan et al. 4 have stated that freely anastomosing small plexiform channels may be present throughout the falx cerebri. In the present study we sought to further elucidate the anatomy of such falcine veins and to provide landmarks for the neurosurgeon who may need to incise or puncture this midline structure. Materials and Methods We performed dissection in 25 formalin-fixed adult cadavers and two fresh specimens (age range at time of death 60–88 years, mean 81 years). Fifteen specimens were male and 12 were female. No specimen was found to have gross evidence of an intracranial patho- logical entity such as tumor or aneurysm. All specimens underwent isolation and irrigation of the left and right internal jugular veins. Blue or red latex was then manually injected into the internal jugu- lar veins. Following a cure time of 24 hours, the calvaria was re- moved with an oscillating bone saw. The dura mater was incised, and the superior sagittal and straight sinuses were identified. Ten specimens did not have adequate latex perfusion into the small ves- J. Neurosurg. / Volume 107 / July, 2007 J Neurosurg 107:155–157, 2007 Anatomy of the falcine venous plexus R. SHANE TUBBS, M.S., P.A.-C., PH.D., 1,2 MARIOS LOUKAS, M.D., PH.D., 3,4 ROBERT G. LOUIS JR., M.D., 5 MOHAMMADALI M. SHOJA, M.D., 6 LESLIE ACAKPO-SATCHIVI, M.D., PH.D., 2 JEFFREY P. BLOUNT , M.D., 2 E. GEORGE SALTER,PH.D., 1 W. JERRY OAKES, M.D., 2 AND JOHN C. WELLONS III, M.D. 2 1 Department of Cell Biology and 2 Section of Pediatric Neurosurgery, University of Alabama at Birmingham, Alabama; 3 Department of Anatomical Sciences, St. George’s University, Grenada, West Indies; 4 Department of Education and Development, Harvard Medical School, Boston, Massachusetts; 5 Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia; and 6 Department of Anatomy and Neurosurgery, Tabriz Medical University, Tabriz, Iran Object. The superior and inferior sagittal sinuses have been well studied. Interestingly, other venous structures with- in the falx cerebri have received scant attention in the medical literature. The present study was performed to elucidate the presence and anatomy of these midline structures. Methods. The authors examined 27 adult latex- or ink-injected cadaveric specimens to observe the morphological features of the sinuses within the falx cerebri (excluding the inferior and superior sagittal sinuses). Results. All specimens were found to have an extensive network of small tributaries within the falx cerebri that were primarily concentrated in its posterior one third. In this posterior segment, these structures were usually more pro- nounced in the inferior two thirds. The portion of the falx cerebri not containing significant falcine venous sinus was termed a “safe area.” These vascular channels ranged in size from 0.5 mm to 1.1 cm (mean 0.6 mm); 100% of these vessels communicated with the inferior sagittal sinus. Classification of the structures was then performed based on com- munication of the falcine venous sinus with the superior sagittal sinus. Type I falcine sinuses had no communication with the superior sagittal sinus, Type II falcine sinuses had limited communication with the superior sagittal sinus, and Type III falcine sinuses had significant communication with the superior sagittal sinus. Seventeen (63%) of 27 speci- mens communicated with the superior sagittal sinus (Types II and III). Further subdivision revealed 10 Type I, seven Type II, and 10 Type III falcine venous plexuses. Conclusions. There are other venous sinuses in the falx cerebri in addition to the superior and inferior sagittal sinus- es. Neurosurgical procedures that necessitate incising or puncturing the falx cerebri can be done more safely via a de- scribed safe area. Given that the majority of specimens in the authors’ study were found to have a plexiform venous morphology within the falx cerebri, they propose that these channels be referred to as the falcine venous plexus and not sinus. The falcine venous plexus should be taken into consideration by the neurosurgeon. (DOI: 10.3171/JNS-07/07/0155) KEY WORDS • cadaver • cranium • falx cerebri • vein • venous anatomy T 155