Correlates of local cerebral blood flow (CBF) in normal pressure hydrocephalus patients before and after shunting—A retrospective analysis of [¹⁵O]H₂O PET-CBF studies in 65 patients

Objectives:

Findings in local cerebral blood flow (rCBF) in Normal pressure hydrocephalus (NPH) have always been challenged by the variable and inconsistent relation to clinical symptoms before and after shunt treatment. [15O]H2O PET data from a consecutive cohort of 65 idiopathic NPH patients were retrospectively analyzed questioning whether the functional status before and after shunt treatment might correlate with local blood flow.

Patients and methods
Using statistical parametric mapping (SPM99, Wellcome Department of Cognitive Neurology, London), the [15O]H2O uptake was correlated with the preoperative clinical scores, graded according to a modified Stein and Langfitt score. Furthermore, differences in the uptake in the pre-and post-shunt treatment study after seven to 10 days in patients with and without clinical improvement were studied.

Results
A higher clinical score significantly correlated with a reduced tracer uptake in mesial frontal (k = 1239 voxel, Z = 4.41) and anterior temporal (k = 469, Z = 4.07) areas. In the mesial frontal areas, tracer uptake showed significant reciprocal changes in the clinically improved vs. the unimproved patients.

Conclusion
Matched with the existing literature, the regional blood flow alterations are suggested relevant to the NPH syndrome and to post-treatment functional changes. The present rCBF findings warrant prospective studies on the accuracy of neuroimaging studies as they may provide a more specific insight into disease mechanisms.