Cerebral iron deposition in the Globus pallidus and Substantia nigra of aging dogs and cats presenting as bilateral hypointensity on T2w and iron-sensitive MRI sequences (SWI, T2*)

Abstract

Introduction: With aging, dysregulation of brain iron homeostasis can lead to cerebral iron accumulation, a process associated with the pathogenesis of neurodegenerative diseases and recognized as an imaging marker in humans. Similarly, MRI-detected cerebral iron accumulation has been reported in aging beagles, suggesting parallels with human findings. Methods: Single-center, observational study that retrospectively and prospectively evaluated 236 client-owned animals (198 dogs, 38 cats) undergoing brain MRI between 2014 and 2024. Patients represented various breeds and ages; scans were performed at different field strengths, 1-3 Tesla (T), with each animal examined once at a single field strength. MRIs were evaluated for bilateral hypointensities in T2-weighted (T2w) and iron-sensitive imaging (SWI, T2*) in the Globus pallidus and Substantia nigra. In selected cases, iron deposition was validated via post-mortem iron-sensitive Perl’s staining of fixed brain tissues. Results: Logistic regression analysis identified age as a significant predictor of improved visibility (OR = 1.21, p < 0.0001). Compared with 1T, 1.5T increased the odds of visibility by 2.78-fold (p = 0.0366), and 3T by 4.82-fold (p < 0.001). Species-specific analysis showed that, in cats, field strength had no significant effect (p = 0.1575), whereas age remained a significant predictor (p = 0.0192). Iron-sensitive sequences (SWI, T2*) provided superior visibility of iron deposits compared to T2w, particularly in dogs. No significant difference in hypointensity detection was observed between the two brain regions. Discussion: In summary, age and MRI field strength significantly affect the visibility of cerebral iron deposits in dogs, whereas feline results require further investigation due to the limited sample size. SWI and T2* enhance iron detection compared to T2w, particularly in canines.