ASL Perfusion Lightbulb Sign: An Imaging Biomarker of Pediatric Posterior Fossa Hemangioblastoma.

Abstract

Hemangioblastoma is a rare vascular tumor that occurs within the central nervous system in children. Differentiating hemangioblastoma from other posterior fossa tumors can be challenging on imaging, and preoperative diagnosis can change the neurosurgical approach. We hypothesize that a 'lightbulb sign' on the ASL sequence (diffuse homogenous intense hyperperfusion within the solid component of the tumor) will provide additional imaging finding to differentiate hemangioblastoma from other posterior fossa tumors. In this retrospective comparative observational study, we only included pathology-proven cases of hemangioblastoma, while the control group consisted of other randomly selected pathology-proven posterior fossa tumors from January 2022 to January 2024. Two blinded neuroradiologists analyzed all applicable MRI sequences, including ASL sequence if available. ASL was analyzed for the 'lightbulb sign'. Disagreements between the radiologists were resolved by a third pediatric neuroradiologist. Chi-square and Fisher's exact test were used to analyze the data. 95 patients were enrolled in the study; 57 (60%) were male. The median age at diagnosis was 8 years old (IQR: 3-14). Out of the enrolled patients, 8 had hemangioblastoma, and 87 had other posterior fossa tumors, including medulloblastoma (n=31), pilocytic astrocytoma (n=23), posterior fossa ependymoma type A (n=16), and other tumors (n=17). The comparison of hemangioblastoma vs non-hemangioblastoma showed that peripheral edema (p=0.02) and T2 flow void (p=0.02) favors hemangioblastoma, whereas reduced diffusion (low ADC) (p=0.002) and ventricular system extension (p=0.001) favors nonhemangioblastoma tumors.Forty-two cases also had ASL perfusion sequences. While high perfusion favors hemangioblastoma (p=0.03), the lightbulb sign shows a complete distinction since all the ASL series of hemangioblastoma cases (n=4) showed the lightbulb sign, whereas none of the nonhemangioblastoma cases (n=38) showed the sign (p<0.001). Lightbulb-like intense and homogenous hyperperfusion patterns on ASL are helpful in diagnosing posterior fossa hemangioblastoma in children.ABBREVIATIONS ASL = Arterial spin labelling; pASL = Pulsed arterial spin labelling; pCASL = Pseudocontinuous arterial spin labelling; DCE = Dynamic contrast-enhanced; DSC = Dynamic susceptibility contrast; VHL = Von Hippel Lindau.