Preoperative and postoperative magnetic resonance imaging (MRI) findings of radiculomeningeal arteriovenous malformations: important role of gravity in the symptoms and MRI.

Background: The symptoms of radiculomeningeal arteriovenous malformations (AVMs) are reported to be uniform, which suggests it to be a conus medullaris syndrome, and in fact, the lesions on magnetic resonance imaging (MRI) images usually include the conus medullaris. However, the reason why the conus medullaris is always involved in the lesion has not been discussed.

Methods: We encountered seven patients with spinal radiculomeningeal AVMs and operated on all of them. We evaluated the preoperative and postoperative MRI findings in these patients. Postoperative MRI was followed ranging from 6-32 months (mean: 21 months) after surgery.

Results: All of our patients showed swelling of the spinal cord, including the conus medullaris, on the preoperative magnetic resonance image. Postoperatively, MRI showed that the swelling of the spinal cord had resolved but that it had finally deteriorated into an atrophic condition. In all of five patients who could be followed up using multiple postoperative MRI scans, sequential T2-weighted images showed that the most rostral level of areas with increased signal in the spinal cord moved in a caudal direction with time.

Conclusions: This and the fact that the conus medullaris was included in the swelling of the spinal cord regardless of the level of the nidus in all our patients, suggested that gravity played an important role in the etiology of radiculomen-ingeal AVM in these patients.