Good outcome of shunt surgery for idiopathic normal pressure hydrocephalus (iNPH) patients are highly dependent on accurate preoperative assessments. Acetazolamide ethylcysteinate-dimer–single photon emission computer tomography (SPECT) was applied to iNPH patients for more exact preoperative evaluation.
Sixty-five patients were categorized into 3 groups: group I (normals, n = 30), group II (with ventriculomegaly due to age-relating changes, n = 10), and group III (who underwent shunt surgery based on the diagnosis of iNPH, n = 25). Acetazolamide SPECT was performed in all patients, and mini-mental state examination (MMSE) was performed before and 1 month after the surgery in group III.
Acetazolamide SPECT study demonstrated normal increase of cerebral blood flow (CBF, more than 40%) in groups I and II. Group III was classified into 2 subgroups on the examination; a mean increasing percentage (%increase) of CBF was less than 20% in group IIIa and more than 40% in group IIIb. One month after the surgery, acetazolamide SPECT showed normal %increase of CBF in IIIa, and the increase in postoperative MMSE score was significantly greater in group IIIa than IIIb (P < 0.05). In iNPH patients, less than 20% increase in preoperative acetazolamide SPECT predicted improvement of MMSE score with 100% sensitivity and 60% specificity.
Poor %increase of CBF by acetazolamide implies a low capacity for vasodilation in the brain due to compression and stretching by ventriculomegaly. Acetazolamide SPECT study is not an absolute examination but one of the valuable supplementary objective examinations to determine the surgical indication in iNPH-suspected patients.
From the *Department of Neurosurgery, Rissho Kosei-kai Hospital, Tokyo; and †Department of Neurosurgery, Kochi University, Kochi Medical School, Nankoku, Japan.
Received for publication October 24, 2012; and revision accepted April 7, 2013.
Conflicts of interest and sources of funding: none declared.
Reprints: Shoko M. Yamada, MD, Department of Neurosurgery, Teikyo University Chiba Medical Center, 3426-3 Anesaki, Ichihara-city, Chiba-prefecture, 299-0111, Japan. E-mail: firstname.lastname@example.org.
SMY: study concepts, guarantor of the integrity of the study, manuscript preparation, and revision of the article.
NM: clinical studies and data analysis.
YK: clinical studies, data acquisition, and literature research.
YF: data and statistical analysis.
KS: study concepts and manuscript review.