Decreases in Ventricular Volume Correlate with Decreases in Ventricular Pressure in Idiopathic Normal Pressure Hydrocephalus Patients Who Experienced Clinical Improvement after Implantation with Adjustable Valve Shunts

Abstract

OBJECTIVE:This retrospective study examined whether changes in ventricular volume correspond with changes in adjustable valve pressure settings in a cohort of patients who received shunts to treat idiopathic normal pressure hydrocephalus. We also examined whether these pressure -volume curves and other patient variables would co-occur with a positive clinical response to shunting. METHODS:We selected 51 patients diagnosed with idiopathic normal pressure hydrocephalus who had undergone implantation of a Codman Hakim programmable valve (Medos S.A., Le Locle, Switzerland). Clinical data were gathered from the patients' records and clinical notes by an investigator blinded to patients' ventricular volumes. Ventricular volume was measured using 3D Slicer, an image analysis and interactive visualization software package developed and maintained at the Surgical Planning Laboratory at Brigham and Women's Hospital. RESULTS:Eighty-six percent of patients with gait disturbance at presentation showed improvement of this symptom, 70% experienced improvement in incontinence, and 69% experienced improvement in dementia. For the group showing 100% clinical improvement, the correlation coefficient of average changes in valve pressure over time (ΔP/ΔT) and average changes in ventricular volume over time (ΔV/ΔT) were high at 0.843 (P < 0.05). For the group experiencing no or only partial improvement, the correlation coefficient was 0.257 (P = 0.32), indicating no correlation between average ΔV/ΔT and average ΔP/ΔT for each patient. CONCLUSION:This was a carefully analyzed modeling study of idiopathic normal pressure hydrocephalus treatment made possible only by adjustable valve technology. With careful volumetric analysis, we found that changes in ventricular volume correlated with adjustments in valve pressure settings for those patients who improved clinically after shunting. This suggests that positive clinical responders retained parenchymal elasticity, emphasizing the importance of dynamic changes in this cohort. NIH Public Access Author ManuscriptNeurosurgery. Author manuscript; available in PMC 2006 January 25. (5,6,14,17,19,21,23,26). These previous studies had only twodimensional measures, namely the Evans ratio, with which to follow any changes in ventricular size after shunting; such linear measures have been shown to be inadequately sensitive to the minimal changes in ventricular size typically sought for the treatment of INPH. The dynamic relationship between valve pressure setting and ventricular volume in the setting of INPH also is poorly understood.Anderson et al.(1) recently used a three-dimensional analysis to measure ventricular volume changes after shunting for INPH. They observed a decrease in ventricular volume after shunting in 10 of 11 patients. In their study, a traditional two-dimensional analysis by an independent radiologist found decreases in ventricular size in only 2 of the 11 patients. Anderson et al., however, were unable to examine any relationship between decreasing ventricular volume...

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus: Second Edition

“…The efficacy of shunt procedures maintained for the short term ranged from 3-6 months in 64-96% of patients, 2,5,15,21,22,24,32,35,36,48) and at 1 year in 41-95% 10,12,18,25,33,40,49,50,62,66) ; while the efficacy of shunt procedures maintained for the long term ranged from 3-5 years in 28-91% of patients. 2,9,21,32,36,38,46,49,50,52) The best improvement rate was for gait disturbance, between 58-90%.…”

“…In contrast, large volume removal of CSF (300-500 ml) is carried out via an external lumbar drain over several days (external lumbar drainage test). 35,39,40,82,83,88,89,94,107,122,139,140,141) Complications such as disconnection or fracture of the indwelling catheter, radicular pain, or meningitis were reported in 2-8% of patients. 39,89,94,139,141) Since patients with iNPH are elderly, attention should be given to spinal canal stenosis or obstruction of the CSF pathway.…”

“…18,57,68,108,110) Lumbar subarachnoid pressure is the most frequently measured 8,10,18,25,31,57,68,96,108,141) ; however, there are also studies measuring parenchymal pressure, 34,35) intraventricular pressure, 110) and epidural pressure. 109,113,127,131) The following 3 items are examined during the measurement.…”

“…Conversely, some studies report that there is no correlation between the baseline ICP and the efficacy of shunting. 31,34,35,109) 2) Pressure wave: The incidence of B-waves is high during sleep, especially during rapid eye movement sleep. 68) The higher their incidence becomes (more than 15% of all records), the more effective is the shunt procedure.…”

“…31,108,109,141) 3) CSF pulse pressure: Increased amplitude together with decreased latency of the ICP pulse wave are noted in most of shunt-effective cases. 9,10,22,33,35,110) A high proportion of high amplitude waves of À9 mmHg predicts postsurgical improvement (positive predictive value 96%) 110) (Recommendation grade C1).…”