Venous sinus volume in the caudal cranial fossa in Cavalier King Charles spaniels with syringomyelia

Syringomyelia (SM) in Cavalier King Charles spaniels (CKCS) has a complex pathophysiology. Recent studies support a relationship between altered venous drainage and cerebrospinal fluid flow dynamics. The aim of this study was to evaluate the relationship between venous sinus and parenchymal volume within the caudal cranial fossa (CCF) in CKCS with SM (n = 22) and without SM (n = 12) using magnetic resonance venography (MRV). MRI and MRV images were used to obtain volumetric calculations of CCF volume, as well as the percentage of this volume occupied by parenchyma (CCFP%) and venous sinuses (CCFV%). In CKCS with SM, CCFP% was significantly higher (P < 0.001), whilst CCFV% was significantly lower (P = 0.001) than in CKCS without SM. These results support a role for reduced venous drainage and parenchymal ‘overcrowding’ of the CCF in the pathophysiology of SM.