ANATOMIC DETAILS OF INTRADURAL CHANNELS IN THE PARASAGITTAL DURA - A POSSIBLE PATHWAY FOR FLOW OF CEREBROSPINAL-FLUID

OBJECTIVE: The absorption of cerebrospinal fluid occurs primarily by m eans of arachnoid granulations (AG) in the superior sagittal sinus (SS S) and the lacunae laterales (LL) in the parasagittal dura. Previous d escriptions of this region suggest a network of intradural channels, b ut finer details of extent and relationship between channels and AC we re not addressed. Therefore, we undertook an anatomic study of cadaver ic parasagittal dura. METHODS: The SSS and parasagittal dura of 20 for malin-fixed adult cadavers and 15 autopsy specimens from patients rang ing in age from 18 weeks of gestation to 80 years were studied by use of a light microscope, a scanning electron microscope, and corrosion c asting. Intradural injections into the parasagittal region were perfor med in two formalin-fixed and four autopsy specimens from adults by us e of normal saline and corrosion casting. RESULTS: Extensive networks of intradural channels from 0.02 to 2.0 mm in diameter were noted in a ll of the specimens. Channels either were connected to the SSS at inte rvals along the side wall or drained directly into the LL, which exten ded up to 3 cm from midline. Channels lined with endothelium stained p ositive for Factor VIII, as did the endothelium of the LL and SSS. In some places, the network of channels seemed to coalesce to form LL. Th e underside of the dura was coarse and trabeculated where the channels were abundant, and AG were interdigitated between these trabeculae. I n regions of the dura where channels were sparse or absent, the dural underside was smooth and lacked AG. Underlying cortical veins opened d irectly into the SSS and were unrelated to intradural channels. Intrad ural parasagittal injections from the epidural side accessed the SSS b y way of channels using pressures between 0 and 20 cm H2O at 1.5 ml/mi n. CONCLUSION: These channels may represent a pathway for the flow of cerebrospinal fluid from AG to the SSS.