Introduction Venous outflow obstruction is recognized as a contributing factor in a subset of patients with idiopathic intracranial hypertension (IIH). Little is known about venous sinus waveform morphology or how it changes after stenting.

Methods Fifteen patients with IIH underwent waveform recording during catheter venography and manometry. Ten patients (Group A) with venous sinus stenosis and pressure gradient ≥7 mm Hg underwent waveform recording during awake venography and during stenting under general anesthesia. Five control IIH patients (Group B) without a gradient underwent awake recording only.

Results Group A patients underwent successful stenting with reduction of their gradient from 15.1±6.19 mm Hg to 1.2±0.60 mm Hg. This resulted in an amplitude reduction from 8.3 mm Hg to 2.8 mm Hg (P=0.02). Qualitative evaluation of the waveform yielded a number of novel findings. In Group A before stenting, the observed waveform progressed from an intracranial pressure (ICP)-dominated to central venous pressure (CVP)-dominated waveform. Stenting abolished the high amplitude waveform and smoothed the transition from the intracranial to central venous measurement points. Group B displayed primarily CVP-influenced waveforms distal and proximal to the transverse-sigmoid junction along with respiratory variability of the waveform, absent in 8/10 Group A patients. General anesthesia appeared to blunt the waveform in 5/10 Group A patients.

Conclusion The cerebral venous waveform appears to be influenced by both the ICP and CVP waveforms. As measurement moves proximally, the waveform progressively changes to mirror the CVP waveform. Venous sinus stenosis results in a high amplitude waveform which improves with treatment of the stenosis.