Is a combination of Tc-SPECT or perfusion weighted magnetic resonance imaging with spinal tap test helpful in the diagnosis of normal pressure hydrocephalus?

OBJECTIVE: The aim of this study was to evaluate the combination of spinal tap test (STT) with cerebral perfusion measurement assessed either by Tc-bicisate-SPECT (Tc-SPECT) or perfusion weighted MRI (pwMRI), or both, for a better preoperative selection of promising candidates for shunt operations in suspected idiopathic normal pressure hydrocephalus.
METHODS: 27 consecutive patients were examined with a standard clinical protocol (assessed by the Homburg Hydrocephalus Scale (HHS)) as well as with 99m Tc-bicisate-SPECT (n=27) or additionally by pwMRI (n=12) before and after STT. The results of these examinations were compared preoperatively for each patient and correlated with postoperative clinical outcome after shunt surgery.
RESULTS: Nine patients showed both, a clinical improvement, and increased cerebral perfusion after STT. They underwent shunt surgery with good to excellent results. In another nine patients increasing cerebral perfusion was detected although they did not show a clear clinical improvement after STT. Six of them also received a shunt operation with good to excellent outcome. Three patients of the last group could have an operation. Nine patients did not show any clinical improvement or any kind of increasing cerebral perfusion after STT. Therefore, they did not undergo surgery. The results of SPECT and pwMRI correlated in 92 % of the patients (11 of 12).
CONCLUSION: It is concluded that a combination of clinical assessment with SPECT or pwMRI is helpful in the preoperative selection of patients for shunting procedures with suspected NPH syndrome. This combination is a minimal invasive and objective test modality that is superior to STT alone. Further studies are necessary for a comparison of the described imaging techniques with different diagnostic tests in this difficult field of cerebral disease.