Regional cerebral blood flow and metabolism in hydrocephalus; from misery to luxury

In the decision of when to treat hydrocephalus, ventricular size alone is of limited value. Since decreased cerebral blood flow and metabolism may play an important role in hydrocephalus, we used tc-99 ECD-SPECT and F-FDG-PET imaging of regional cerebral blood flow and glucose metabo lism respectively to identify regions of neural tissue at risk. First, blood flow studies were performed alone, before and after lumbar puncture, in an attempt to determine who may benefit from CSF diversion. Subsequently, combined blood flow and glucose metabolism imaging was analysed to find regional mismatches before and after surgical CSF diversion. Results In 18 patients with adult chronic hydrocephalus, blood flow imaging alone and with lumbar puncture was not sensitive in identifying patients who would benefit from shunting. In 5 patients where both blood flow and metabolic studies were performed before and after surgery, regions of both misery perfusion and luxury perfusion were seen, often in the same patient pre-operatively. Post-operatively, both areas of misery and luxury perfusion tended to normalise. This was correlated with clinical improvement. Conclusion Hydrocéphalie patients have an abnormal mismatch between cerebral blood flow and metabolism with both misery and luxury patterns. Since clinical improvement is correlated with normalisation of these areas, both types of flow-metabolism mismatch may reflect dysfunctional, but resuscitable neural tissue. This imaging analysis may aid in our clinic evaluation of hydrocephalus and improve our understanding of the pathophysiology of associated neural dysfunction.