Cerebrospinal fluid spaces between intracranial venous sinuses and overlying dura mater: magnetic resonance imaging.

Purpose The intracranial venous sinuses are thought to lie interdurally, circumferentially contacting the dura maters. There has been no report documenting the cerebrospinal fluid spaces intervening between the venous sinuses and overlying dura mater. Here, we explored such structures using magnetic resonance imaging. Methods A total of 206 patients underwent magnetic resonance imaging with a T2-weighted or constructive interference steady-state sequence. Imaging data were analysed on a workstation. Results The peri-superior sagittal sinus cerebrospinal fluid spaces were identified in 100% of 133 patients who underwent coronal and sagittal T2-weighted imaging and in 98.6% of 73 with a constructive interference steady-state sequence. Among the 205 patients, the cerebrospinal fluid spaces were distributed over the frontoparietal region in 84% and the parietal region in 16%. On sagittal sections performed for 58 patients, the cerebrospinal fluid spaces were identified between the superior sagittal sinus and overlying dura mater. The peri-sinus spaces were found in 91% of the identified transverse sinuses, 29% of the straight and 70% of the occipital sinuses. The peri-superior sagittal sinus cerebrospinal fluid spaces were classified into five distinct appearances. The circumferential type was the most predominant and was found in 68.7%, followed by lateral in 10.2%, lateral plus inferior in 7.5%, lateral plus superior in 6.8% and superior in 6.8%. Conclusions The intracranial venous sinuses do not circumferentially contact with the dura maters. Instead, they are adjacent to the cerebrospinal fluid spaces intervening between the walls and overlying dura maters. These spaces are critical when considering tumour extensions contralateral to the superior sagittal sinus and safe surgical manoeuvres around it.