The foramen spinosum (FS) and foramen venosum (of Vesalius) (FV) are alisphenoid apertures situated within the hub of the middle cranial fossa in close proximity to foramen ovale (FO). The FS and FV provide a passage to important neurovascular structures. An accurate knowledge of the morphometric details of the FS and FV including their shape, incidence, relation to other foramina and/or presence of any anomalies may represent a reliable anatomical landmark during surgical explorative maneuvers. Therefore, the aim of this study was to investigate the morphologic and morphometric features of the FS and FV. The study was conducted on 100 dry human skulls (n= 200) obtained from the osteological bank at the University of KwaZulu-Natal, to produce a database which may serve as a useful guideline to surgeons and anesthetists. Although single (95%), duplicate (2.5%) and triplicate (0.5%) FS were identified; only single (5%) and duplicate (0.5%) FV were found. Oval (FS: 43.5%; FV: 4.5%) and round (FS: 58%; FV: 0.5%) foramina were observed. In addition, the relationship of the FS and FV to FO was recorded: postero-lateral (FS: 93%; FV: 0%); posterior (FS: 1.9%; FV: 0%); postero-medial (FS: 0.5%; FV: 0%); anterior (FS: 0%; FV: 0.5%); antero-medial (FS: 0%; FV: 4.5%). The mean morphometric parameters of the FS and FV included the internal diameter (FS: 2.53±0.76 mm; FV: 1.93±0.46 mm), external diameter (FS: 2.50±0.74 mm; FV: 2.81±1.53 mm) and distance to the FO (FS: 3.45±1.29 mm; FV: 2.63±1.24 mm). In light of the morphometric and morphological variations of skull-based foramina, the evaluation of the FS and FV in our study may provide a reliable osteometric reference in clinical practice which may be beneficial during interpretation of imaging and surgical intervention.

KEY WORDS: Foramen spinosum; Foramen venosum; Foramen of Vesalius; Middle cranial fossa; Greater wing of sphenoid bone.