“…; occipital type, if the defect lies between foramen magnum and the lambda; parietal type, if the defect lies between the lambda and the bregma; lateral type, if the defect lies along the coronal or lambdoid sutures as far inferiorly as the anterolateral and posterolateral fontanelles; interfrontal type, if the defect lies between the bregma and the nasal bones; temporal, if the defect lies along the superior surface of the petrous pyramid; fronto-ethmoidal type (synonym: sincipital), if the defect lies between the nasal bones and the ethmoid bone; spheno-orbital type, if the ostium for the herniation involves the optic foramen, the superior orbital fissure, or a defect in the orbital wall; sphenomaxillary type, if the ostium for the herniation extends through the superior orbital fissure and the inferior orbital fissure into the pterygopalatine fossa; nasopharyngeal type, if the defect lies within the ethmoid, sphenoid, or basioccipital bones [48]. Martinez-Lage et al [32,33,34] classified AC into two types: Type 1 consisting of arachnoid tissue with clusters of anomalous blood vessels limited to the stalk of the lesion, Type 2 consisting of meningeal tissue intermingled with dermal and fibrous tissue, as well as clusters of anomalous blood vessels, extending as a net, and ectopic neural or glial elements. In according to classification of Martinez-Lage et al [32,33,34], our case can be evaluated as type 1.…”