Objective: The diagnosis and management of idiopathic normal-pressure hydrocephalus (iNPH) remains controversial, particularly in selecting patients for shunt insertion. Diagnostic criteria target the pathological features of the dynamics of the cerebrospinal fluid (CSF); however, the effectiveness in predicting the shunt success has room for improvement. The aim of our study was to systematically assess the influence of the co-morbidity determining the benefit from shunt surgery.
Methods: Between 1997 and 2006 134 patients suffering from iNPH were treated with a ventriculo-peritoneal shunt with a gravity-controlled valve. The coincident disease processes were recorded. Shunt outcome was assessed at 2 years postsurgery in 116 patients (follow up rate 87%). The results of this follow-up examination (Kiefer score, NPH recovery rate) were compared using the preoperative co-morbidity index (CMI).
Results: Of the 134 patients 76 (56.7%) had a CMI of 0-3 and 58 patients (43.3%) had a CMI of 4-8. Two years after surgery 65 out of 70 shunt responders (93%) could be identified in the patients group with a CMI of 0-3 and only 29 of 46 (63%) in group with a CMI of 4-8. This difference was significant (p < 0.0001). Remarkably few patients scoring between 6 and 8 on the CMI scale experienced a favourable outcome. The patients in this latter group showed excellent outcomes in only 1% and poor outcomes in 33%.
Conclusion: Data in this report affirm that co-morbidity is a statistically significant predictor of the quality of the clinical outcome for patients with iNPH undergoing shunt therapy. A CMI of more than 3 significantly decreases the chance of a favourable outcome and this should form part of the assessment when the risks and benefits of surgery are considered. According to these data, a successful outcome in patients with a CMI of 6 or more is not to be expected.