Chronic rhinosinusitis and posterior cingulate hypoperfusion on SPECT in dementia diagnosis

Introduction Single-photon emission computed tomography (SPECT) is widely used in dementia clinics to evaluate regional cerebral blood flow (rCBF). Posterior cingulate cortex (PCC) hypoperfusion is a supportive, though not definitive, marker for Alzheimer’s disease (AD). Magnetic resonance imaging (MRI)-defined sinus inflammation has been associated with systemic inflammation and altered brain connectivity; therefore, we aimed to determine whether MRI-defined chronic rhinosinusitis (CRS) is associated with differences in PCC perfusion patterns on SPECT among patients with cognitive impairment. Methods We retrospectively reviewed 54 patients with cognitive impairment who had undergone brain MRI and SPECT. CRS was defined using MRI-based modified Lund–Mackay scores. SPECT findings were analyzed using the easy Z-score Imaging System (eZIS), focusing on PCC severity, extent, and ratio. Comparisons were performed between patients with and without CRS. Results Ten patients (18.5%) had CRS. The frequency of AD was higher in patients with CRS than in patients without CRS ( p = 0.028). Compared with patients without CRS (n = 44), those with CRS showed significantly greater PCC hypoperfusion: eZIS severity (1.7 ± 0.5 vs. 1.2 ± 0.4, p = 0.026), extent (26.1 ± 13.4% vs. 15.1 ± 14.3%, p = 0.196), and ratio (5.0 ± 2.8 vs. 2.0 ± 1.7, p = 0.013). No differences were observed in the cingulate island sign score (CIScore; p = 0.215). Moreover, in the subgroup of patients clinically diagnosed with AD, those with CRS showed significantly greater PCC hypoperfusion than those without CRS (1.8 ± 0.3 vs. 1.4 ± 0.5; p = 0.023). PCC hypoperfusion in CRS overlapped with canonical AD patterns but was not observed in non-AD dementias. Conclusion Our exploratory findings suggest that MRI-defined CRS may be associated with differences in SPECT-derived PCC perfusion patterns in patients with cognitive impairment. Awareness of CRS as a common incidental MRI finding may help neurologists interpret SPECT results more cautiously in memory clinic settings.