RESUMEN
BACKGROUND: The occipital sinus (OS) lies in the attached margin of the faix cerebelli in the internal occipital crest of the occipital bone. The OS extends from the foramen magnum to the confluence of sinuses. Standard textbooks and research reports do not describe in detail any variation in the groove for the occipital sinus. METHODS: In the present study, we examined a total of 50 human dried skulls for the groove of OS and its possible variations. We also performed an osteological study supplemented with digital X ray and CT scan. RESULTS: Out of 50 skull specimens, a single case with two grooves for OS was observed (2%). The two grooves for OS traversed as two limbs from the foramen magnum to join the other at the internal occipital protuberance. An accessory faint groove was also found at the lateral aspect of the left limb. Interestingly, in the same specimen, the superior sagittal sinus instead of continuing as right transverse sinus, continued as left transverse sinus. The X ray and CT scan of the anomalous bone specimen were compared to those of the normal bone specimen. DISCUSSION: To the best of our knowledge, this is the first anatomico-radiological study of multiple OS groove with associated anomalies. Surgeons should be aware of the variations of the OS in order to check any inadvertent injury during skull surgeries. Presence of such variations may also result in erroneous interpretation of radiological findings (Tab. 1, Fig. 7, Ref. 17).