The phenotype of idiopathic normal pressure hydrocephalus-a single center study of 429 patients.

INTRODUCTION

Idiopathic Normal Pressure Hydrocephlaus (iNPH) is, despite a vastly improved knowledge of the disorder since its first description still underdiagnosed and undertreated. Because of this, there is a need for further large studies describing the typical symptomatology and reversibility of symptoms in iNPH, which was the aim of this study.

METHODS

In all, 429 patients (mean age 71 years) were included. Detailed pre- and postoperative examinations of symptoms and signs were analyzed. A composite outcome measure was constructed.

RESULTS

Sixty-eight % improved after surgery. Preoperatively, 72% exhibited symptoms from three or four of the assessed domains (gait, balance, neuropsychology and continence) while 41% had symptoms from all four domains. Ninety % had gait disturbances, of which 75% had broad-based gait, 65% shuffling gait and 30% freezing of gait. These disturbances coexisted in most patients preoperatively, but were more likely to appear as isolated findings after surgery. Impaired balance was seen in 53% and retropulsion in 46%. MMSE <25 was seen in 53% and impaired continence in 86%. Improvements were seen in all symptom domains postoperatively.

CONCLUSIONS

The iNPH phenotype is characterized by a disturbance in at least 3/4 symptom domains in most patients, with improvements in all domains after shunt surgery. Most patients present with a broad-based and shuffling gait as well as paratonia. Present symptoms in all domains and a shuffling gait at the time of diagnosis seem to predict a favorable postoperative outcome, whereas symptom severity does not.