REVIEW Natural history of idiopathic normal-pressure hydrocephalus Ahmed K. Toma & Simon Stapleton & Marios C. Papadopoulos & Neil D. Kitchen & Laurence D. Watkins Received: 29 June 2010 / Revised: 15 January 2011 / Accepted: 28 January 2011 # Springer-Verlag 2011 Abstract Natural history of idiopathic normal-pressure hydrocephalus (INPH) is not clear. We performed a literature search for studies that looked into the outcome of unshunted INPH patients trying to answer the following questions: Do all INPH patients deteriorate without shunt? If yes, at what rate? Do some NPH patients improve without shunt? If yes, to what extent? Six studies objectively described the outcome of 102 INPH patients. Result shows that without surgery, most INPH patients had measurable deterioration as early as 3 months following initial assessment. A small number of patients might improve without shunt, however the extent of improvement is not clear. The homogeneity of the findings of the cohort studies provided high evidence supporting the rule of shunt surgery in INPH patients. Keywords Normal-pressure hydrocephalus . Chronic adult hydrocephalus . Natural history Introduction Cerebrospinal fluid shunt insertion is the most widely practiced method of treatment of idiopathic normal-pressure hydrocephalus (INPH) [2, 3] since its description by Hakim and Adams in 1965 [1, 6]. However, no study has compared surgical versus conservative treatment in this population, hence the natural history of this condition is not clear and the evidence supporting shunt insertion is not of high quality [3]. INPH diagnosis is difficult since the presenting symp- toms are often attributed to aging or more common differential diagnosis. Furthermore associated comorbidities can affect shunt response negatively [13, 16]. There is no gold standard test for diagnosis and many think that the sole practical test for definitive NPH is the patient’ s response to shunt insertion [9, 19]. If shunt placement was offered solely on the basis of patient history, examination and presence of ventriculome- galy on neuroimaging, only 46–61% of patients would benefit from surgery [2]. Early surgical series of shunt insertion in idiopathic normal-pressure hydrocephalus have shown low improvement and high complication rates [3, 7]; subsequently, shunt insertion has been advised to be reserved for patients in whom there is a favourable risk- to-benefit ratio [3]. Additional selection criteria based on physiological or functional testing are used in different centres to predict shunt responsiveness, with variable outcome results [2, 13]. The purpose of this review is to try to provide clearer understanding of the outcome of INPH patients without shunt surgery. Methods The following research questions were formulated: Do all INPH patients deteriorate without shunt? If yes, at what rate? A. K. Toma (*) : N. D. Kitchen : L. D. Watkins Victor Horsley Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK e-mail: ahmedktoma@yahoo.com S. Stapleton : M. C. Papadopoulos Academic Neurosurgery Unit, St George’ s University of London, London, UK Neurosurg Rev DOI 10.1007/s10143-011-0316-7