The influence of co-morbidity on the postoperative outcomes of patients with idiopathic normal pressure hydrocephalus (iNPH)

Background A critical question in the diagnosis and treatment of idiopathic normal pressure hydrocephalus (iNPH) is that of which preoperative factors can most reliably predict outcomes following shunt insertion. The number and type of co-morbidities are increasingly being viewed as important predictive indicators.

Methods Between 1997 and 2004, 95 patients were implanted with a gravitational ventriculo-peritoneal shunt as treatment for iNPH. All coincident disease processes were recorded. Eighty-two of these patients underwent follow-up 2 years postoperatively. The results of this prospective follow-up examination (Kiefer Score, NPH Recovery Rate) were compared with the preoperative Co-Morbidity Index (CMI).

Findings Of the patients with a CMI score of 0–1 (n=18), 67% experienced an excellent outcome, 28% a good outcome and 5% and 0% a fair and poor outcome respectively. A CMI score of 2–3 was associated with markedly poorer outcomes (n=33); 42% excellent, 30% good, 18% fair and 10% poor. A score of 4–5 was related to 14% excellent, 27% good, 23% fair and 36% poor outcomes (n=22). Remarkably few patients scoring between 6 and 8 on the CMI scale experienced a favourable outcome. The outcomes for this latter group were 0% excellent, 10% good, 45% fair and 45% poor (n=9).

Conclusions Co-morbidity is a statistically significant predictor of the quality of clinical outcome for patients with iNPH undergoing shunt therapy.