Subacute hemorrhagic cyst of the ligamentum flavum occurred in the lumbosacral transitional vertebra presenting as progressive lumbar nerve root compression: a case report.

The lumbosacral transitional vertebrae (LSVT) has been reported to be a cause of lumbar disc herniation as a result of mechanical stress, however there were no reports about relationship between LSTV and hemorrhagic intervertebral cystic lesion. We report a rare case of a hemorrhagic intravertebral cystic lesion that occurred in the LSVT of a 42-year-old man and had a subacute course of lumbar nerve root compression. He presented our hospital with complain of increasing left leg pain for one week. Contrast-enhanced MRI (Gd-T1WI) showed a heterogenous contrast-enhanced effect on the nodule at the entrance of the left pedicle root of L6. The LSTV was classified as Type IIIA using the Castellvi's classification, and the nodule was found on the ipsilateral of the lumbarization. From the imaging findings, disc cysts, ganglion cysts, synovial cysts, disc sequestration and Schwannomas were differentials of the intravertebral canal cystic lesions; however, it was suspected to be a hemorrhagic cystic lesion because of their acute progression of his symptoms, his relatively young age and imaging findings. His symptoms improved shortly after the resection of the cyst and he was diagnosed as intracystic hemorrhage of a ganglion in the ligamentum flavum. There were no features suggestive of recurrence of the cystic lesion in the follow-up MRI on 6 months after the surgery. It was speculated that in the LSTV, twisting movements act on the upper part adjacent to the transitional vertebra, causing microtrauma around the facet joint that leads to the forming a hemorrhagic cyst following damage around the joint capsule. It is difficult to make a diagnosis of hemorrhagic cyst from imaging alone. It must be suspected from the aspect of age (relatively young), gender (male), clinical course (acute to subacute) and MR imaging (various signal intensity patterns on T2WI and contrast effect on Gd enhancement). 2021 Journal of Spine Surgery. All rights reserved.