Isolated CSF Facet Effusions as a Predictor of Lateral Dural Tear Location in Spontaneous Intracranial Hypotension: A Multi-Institutional Study

BACKGROUND AND PURPOSE: Ventral and lateral spinal dural tears are common causes of spontaneous intracranial hypotension, each requiring different myelographic approaches for leak localization. Spine MRI can infer the presence of a dural tear but has limited utility in localizing leaks. One recent case series described several patients with isolated facet effusions at the site of lateral dural tears. We investigated whether the presence of an isolated facet joint effusion on spine MRI could predict the type and location of a dural tear in patients with spontaneous intracranial hypotension. MATERIALS AND METHODS: We identified consecutive patients with precisely localized ventral or lateral dural tears on advanced myelography at three centers. A single neuroradiologist at each center assessed for isolated facet effusions on pre-myelographic spine MRIs, defined as fluid accumulation in a single facet joint that was visually greater than any other joint in the spine. Myelographic studies were reviewed to confirm leak type/location. The frequency of isolated facet effusions was compared between patients with lateral and ventral dural tears using Fisher's exact test. The proximity of facet effusions to leak level/side was assessed. RESULTS: Sixty-four patients (32 ventral and 32 lateral dural tears) were included. All patients had epidural CSF on MRI. Isolated facet effusions were more common in patients with lateral dural tears (21/32, 66%) compared with ventral dural tears (0/32, 0%) (p < .001). The effusion was at the same level and side as the leak in 11/21 (52%) patients and within one ipsilateral spinal level of the leak in 7/21 (33%) patients. Contrast filling of a facet joint was seen in 9/21 (43%) cases and corresponded to the site of MRI effusion in 8/9 (89%). CONCLUSIONS: Isolated facet joint effusions on spine MRI were seen exclusively in patients with lateral dural tears and were usually located at or within one ipsilateral spinal level of the leak. This finding may provide a useful imaging clue that there is an underlying lateral dural tear, which is helpful to plan optimal myelographic positioning and technique.