External lumbar drainage (ELD) is known as a good predictor of favourable outcome in shunting patients suffering from idiopathic normal pressure hydrocephalus (iNPH). To date there has been no study to investigate the changes occurring in the CSF composition of patients undergoing (ELD).
Methods: Eleven patients suffering from iNPH participated in a research study to quantify any improvement in their clinical symptoms, for which a lumbar drain (LD) was inserted for 72 hours. CSF samples were collected during the LD insertion, and also at 48 and 72 hours post-insertion. The lumbar CSF levels of lactate, 8-isoprostane, vascular endothelial growth factor (VEGF), glial fibrillary acidic protein (GFAP), neurofilament (heavy chain) protein (NfH), Aβ1-42 (β- amyloid) and total tau were assayed samples from all three time points.
Results: The concentrations of lactate, VEGF, GFAP and tau increased significantly during the 72 hours of drainage. There were also increases in 8-isoprostane and Aβ1-42 (non significant). The concentration of NfH was reduced significantly following 72 hours of drainage. There was a significant positive correlation between Aβ1-42 and total tau in the first sample which did not continue in the next 48 hours. GFAP was negatively correlated in a significant fashion with both Aβ1-42 and total tau in the first sample. NfH was negatively correlated with VEGF in the first sample.
Conclusion: We provided evidence that ELD is producing measurable changes in the CSF composition of patients with iNPH. We discuss how such changes may be implicated in the pathophysiology of the condition.