A Review on Radiologic Hot Cross Bun Sign and Related Clinical Conditions

The hot cross bun (HCB) sign is a cruciform-shaped hyperintensity on axial T2 weighted-image magnetic resonance imaging (MRI), mostly reported with multiple system atrophy (MSA). However, several other diagnoses were reported with this radiologic manifestation as well. This review investigates the wide spectrum of disorders in which the HCB sign has been reported as a positive radiologic manifestation. This narrative review was conducted using the PubMed database. Studies reporting the HCB sign in their manuscript are included in this manuscript. 83 studies with available full text met the inclusion criteria for this review. The total number of reported patients with HCB sign is addressed in the manuscript. In addition to MSA, the HCB sign has been reported in various other disorders, including spinocerebellar ataxia, malignancies, infections, autoimmune disorders, and some vascular and ischemic changes. Any disorder involving the pontocerebellar fibers can manifest the HCB sign following the gliosis changes or infarction-mediated damage to the region, whether due to gliosis changes. The range of diseases linked to the HCB sign is broader than previously recognized, as numerous disorders affect the transverse pontocerebellar fibers and cause radiologic HCB manifestation. MSA remains the most common condition; however, clinicians should consider alternate differential diagnoses in patients displaying the HCB sign in whom clinical presentation is not typical of MSA.