Are gait changes linked to CSF flow changes in the sagittal sinus?

Purpose To identify if specific findings on magnetic resonance imaging (MRI) cerebrospinal fluid (CSF) flow studies can be utilised to identify which patients with idiopathic normal pressure hydrocephalus (iNPH) will have improved gait following a CSF tap test (TT). Methods Prospective study of patients undergoing a CSF TT for iNPH. Functional gait was assessed using the timed up and go (TUG) test before and after the CSF TT. MRI CSF flow studies accompanied the CSF TT. The minimum clinically important difference for the TUG (3.63 s) was used as a cutoff value to categorise patients as responders to the CSF TT. Results Fifty-three patients underwent CSF TT and MRI CSF flow studies. Significant differences were identified between groups for (non-responder vs responder) superior sagittal sinus flow (47.10% vs 40.41%), sagittal sinus stroke volume (274 vs 176.5 μl), sagittal sinus to arterial stroke volume ratio (0.203 vs 0.164), sagittal sinus area (42.2 mm 2 vs 36.2 mm 2 ) and circumference (27.7 mm vs 24.95 mm). No differences were present for aqueduct stroke volume, arterial stroke volume or aqueduct net flow. Conclusion A link between gait improvement resulting from CSF drainage and sagittal sinus measurements indicates that the sagittal sinus may play a role in the manifestation of symptoms in iNPH. This may have implications for the diagnosis of iNPH and potentially inform clinical decision making regarding surgical intervention.