A neuropsychological examination is often used in tandem with other measures to confirm the diagnosis of idiopathic Normal Pressure Hydrocephalus (iNPH) and to assess improvement in cognitive functioning after a lumbar puncture test. Improvement in symptoms is thought to predict benefit from installation of a ventriculoperitoneal shunt that redirects CSF from the brain. Although the 72-hour external lumbar drain (ELD) has long been the gold-standard drainage procedure, hospitals are increasingly opting for the high-volume lumbar puncture, during which 50ml of CSF is released over an hour before the patient is tested for improvement in symptoms. The primary aims of this study were to evaluate the changes in cognitive performance produced by the two LP procedures and to compare the results produced by each procedure. In a review of medical records, 40 patients met criteria for inclusion. Cognitive functioning in the 72-hour ELD (n = 10) group was compared to changes in patients in the HVLP group, in terms of baseline level of functioning and post-drain changes. Statistical methods used to determine change included ANOVA and Reliable Change Indices. Dominant-hand Grooved Pegboard Test showed significant change after lumbar puncture, with higher mean change in the 72-hour ELD group. 72-hour ELD patients had a slightly higher rate of Reliable Change than HVLP patients. Cognitive changes were bi-directional in both groups. Results suggest that changes in cognitive functioning after lumbar puncture occur in a minority of patients, regardless of procedure type, and may have low predictive value for VPS benefit.