The yield of initial conventional MRI in 115 cases of angiographically confirmed spinal vascular malformations

MRI is the primary screening tool for patients with myelopathy. The decision to obtain additional imaging, notably spinal angiography, is generally based on initial MRI findings. This study retrospectively analyzed the yield of initial MRI in a cohort of patients with angiographically confirmed vascular malformations. MRI obtained at symptom onset was available in 115 patients with either high-flow (29 cases) or low-flow (86 cases) vascular malformations. MRI was classified as "positive" when the report mentioned a vascular malformation or "negative" when considered normal or when another diagnosis was suggested. Initial MRI was positive in 61 patients (53.0%), correctly identifying 28 high-flow (96.6%) but only 33 low-flow (38.4%) lesions. Flow voids were noted in 96.6% of the high-flow lesions and 38.4% of the low-flow ones. T2-signal anomalies (77.4%) and parenchymal enhancement (54.5%) were also common in low-flow anomalies. Patients with negative MRI had an average delay of 111 days before angiography and 239 days before therapy; these intervals were 27 and 76 days for those with positive MRIs. In summary, MRI shows a high yield for high-flow vascular malformations, i.e., characterized by prominent flow voids on T2-weighted images, but misdiagnosed over 60% of low-flow lesions. The percentage of correctly identified anomalies matched the percentage of observed flow voids in both groups, indicating over-reliance on this sign for the diagnosis of slow-flow lesions. MRI findings in slow-flow vascular malformation overlap with other conditions, notably transverse myelitis, which was initially misattributed to 40% of the slow-flow lesions in our cohort.