ORIGINAL ARTICLE The Neuropsychology of Normal Pressure Hydrocephalus (NPH) E. E. DEVITO 1,2 , J. D. PICKARD 1,3 , C. H. SALMOND 2,3 , J. L. IDDON 1 , C. LOVEDAY 1,4 & B. J. SAHAKIAN 2 Departments of 1 Neurosurgery and 2 Psychiatry, and the 3 Wolfson Brain Imaging Centre, University of Cambridge School of Clinical Medicine, Addenbrooke’s Hospital, Cambridge CB2 2QQ, UK and 4 Cognitive Science Research Unit, University of Westminster, Watford Road, Middlesex HA1 3TP, UK Abstract Normal pressure hydrocephalus (NPH) accounts for one of the few known forms of reversible dementia. Varied aetiology and clinical presentation contribute to difficulties with early or differential diagnoses, and delayed surgical treatment may be less efficacious. Clinical neuropsychology provides a means of determining a cognitive profile for NPH, assisting in differential diagnosis, tracking the disorder’s progression and assessing the efficacy of treatment. This article will review possible applications of clinical neuropsychology and propose a clinical assessment protocol for NPH. Key words: Clinical assessment, normal pressure, hydrocephalus, neuropsychology, NPH, cognition, dementia, CANTAB. The diagnosis of NPH Normal pressure hydrocephalus (NPH) is a condition of cerebrospinal fluid (CSF) dysregulation, which arises idiopathically or secondary to an insult to the brain. Hakim & Adams 1 first characterised the ‘clinical triad’ of NPH symptoms as a progressive gait disturbance, followed by ‘dementia’, then often compounded by urinary incontinence. A CSF diver- sion procedure more often than not helps the gait disturbance and incontinence, reduces somnolence and may help reverse some components of the dementia, particularly in the earlier stages. 2,3 Owing to the invasive nature of the surgical treatment, accurate diagnosis and attempts to characterise a subset of NPH patients who show marked improve- ment with shunt surgery are of paramount importance. However, NPH has proven challenging to characterize because of its mixed aetiology, rarity and symptom overlap with other conditions involving ventriculome- galy. Differential diagnosis of NPH is complicated by cognitive decline, which may be qualitatively similar to normal aging, 4 or progressive dementia with gait disturbance, which may appear clinically similar to Alzheimer’s or Parkinson’s disease, for instance. Much debate surrounds the specificity and sensitivity of ancillary investigations, such as ICP monitoring, CSF infusion studies, dynamic MR scanning, RISA cisternography and cerebral blood flow, and their potential contribution to early diagnosis or prediction of treatment outcome in NPH. Clinical neuropsychol- ogy has assisted in the understanding of the cognitive deficits and carries the potential to contribute greatly to the future management of NPH. What is clinical neuropsychology? Clinical neuropsychology studies the effects of brain dysfunction on cognition by observing its expression through measurable behaviour. 5 The neuropsycholo- gical approach assumes that behaviour, as measured by task performance, represents the underlying mental processes that are reflective of brain function. The broad aim of the discipline is to clarify which aspects of cognition are affected in an individual or group, and quantify the degree to which they vary from the norm. A number of contexts lend themselves to the application of clinical neuropsychology. Neuropsy- chological investigations have begun to uncover a cognitive profile for NPH, which could contribute to diagnosis, clinical management and rehabilitation. Repeated testing of an individual provides a means for measuring cognitive changes that may result from disease progression, surgery, valve pressure resetting or pharmacotherapy. Neuropsychology applies tests to investigate estab- lished psychological processes (e.g. memory, attention) via their fractionation into sub-processes Correspondence: Professor Barbara Sahakian, University of Cambridge School of Medicine, Department of Psychiatry, Addenbrooke’s Hospital, Cambridge, CB2 2QQ, UK. Tel: + 44 1223 331 209. Fax: + 44 1223 336 968. E-mail: eed24@medschl.cam.ac.uk Received for publication 21 February 2005. Accepted 31 May 2005. British Journal of Neurosurgery, June 2005; 19(3): 217 – 224 ISSN 0268-8697 print/ISSN 1360-046X online ª The Neurosurgical Foundation DOI: 10.1080/02688690500201838 Br J Neurosurg Downloaded from informahealthcare.com by Yale Dermatologic Surgery on 02/03/15 For personal use only.