Diagnosis, treatment, and analysis of long-term outcomes in idiopathic normal-pressure hydrocephalus.

To the Editor:We read with interest the article by McGirt et al. (9) entitled“Diagnosis, Treatment, and Analysis of Long-term Outcomes inIdiopathic Normal Pressure Hydrocephalus.” The authors con-clude that gait impairment is the primary symptom that inde-pendently predicted improvement after shunting. The studyincluded 132 patients, 129 (98%) of whom had gait impairmentas a feature. We would like to comment on this particular selec-tion criterion, as well as improvements in the Mini Mental StateExamination (MMSE) as the sole measure of postoperative cog-nitive improvement.One of the inclusion criteria for this study was presentationwith two or more features of the classic triad. Thus, the analy-sis inevitably includes patients presenting with dementia andurinary incontinence symptoms but not gait ataxia. Althoughdementia was originally thought to be the main feature of thissyndrome, we have now come to understand that gait distur-bance is an essential selection feature for any study with nor-mal pressure hydrocephalus (NPH) patients (4, 6). In a prospec-tive study of 151 patients, Marmarou et al. (8) recently advisedthat gait improvement immediately after external lumbardrainage is the best prognostic indicator of a positive shuntoutcome with greater than 90% accuracy for prediction.Although the two extra inclusion criteria, namely either A- orB-waves, present during continuous pressure monitoring andclinical improvement in symptoms during a 3-day trial of con-trolled cerebrospinal fluid (CSF) drainage should safeguardagainst any false positive cases, we still think that the presenceof gait ataxia should have been an essential inclusion criterionin the above study. Recent guidelines published in