Associations between cardiopulmonary variables and the cerebrospinal fluid signal-void sign in small-breed dogs

The cerebrospinal fluid (CSF) signal-void sign is a CSF signal loss, especially on T2-weighted magnetic resonance (MR) images. The CSF signal-void sign is often seen in small dogs with hydrocephalus and syringomyelia. In people, this sign is attributed to high velocity or turbulent CSF flow resulting from normal arterial pulsations, but is more pronounced in hydrocephalic patients with reduced intracranial compliance. If dogs are similar, then detection of this sign might be influenced by cardiovascular variables affected by anesthesia or related to intracranial compliance (e.g., blood pressure) or that affect CSF flow (e.g., heart rate). Therefore, the purpose of this study was to investigate whether the CSF signal-void sign is associated with these cardiovascular variables. The sample population consisted of 53 small-breed (< 15kg) anesthetized dogs undergoing spin echo, T2-weighted MR imaging of the neurocranium. Heart rate, blood pressure (systolic, mean, diastolic, pulse), and end-tidal CO2 were recorded and dogs were grouped as having a CSF signal-void sign in the mesencephalic aqueduct (19/53) or not (34/53). Normality was confirmed and t-tests used. No statistical difference was detected between groups for any of the cardiovascular variables. However, the sample size was too small to accept the null hypothesis that no difference existed between groups for any of the variables assessed. Therefore, although it is uncertain whether the investigated variables alter the frequency of detecting a CSF signal-void sign, any possible relationship does not appear strong.