A Case of Intraspinal Cystic Mass Formation with Involvement of the Pseudoarthrosis of an Osteoporotic Vertebral Compression Fracture after Selective Nerve Root Block

<p>  An 85-year-old woman was admitted to our hospital for back pain and severe bilateral anterior thigh pain. She was radiographically diagnosed with an L2 osteoporotic vertebral compressed fracture accompanied by an intervertebral cleft with consequent bilateral L2/3 foraminal stenosis. We first performed a bilateral L2 root block since she had severe congestive heart failure. Her anterior thigh pain subsided thereafter, but she complained of left leg dominant paraparesis 8 weeks later. Magnetic resonance imaging (MRI) revealed a large cystic mass posterolaterally in the spinal canal, compressing the cauda equina at the T11-L1 level, with an intensity identical to that of fluid in the L2 vertebral cleft and cerebrospinal fluid (CSF). The wall of the cyst was enhanced by gadolinium-diethylenetriamine pentaacetic acid (GD-DTPA). Because of her severe paresis, the patient underwent T11-L1 left-side hemilaminectomy and removal of the cyst wall. The cyst wall was very thin and could not be dissected from the dura ; therefore, only the outer wall of the cyst was removed. The fluid in the cyst was serous and slightly yellowish. The resected cyst wall and fluid were culture-negative. Microscopic inspection showed granulation tissue mainly consisting of collagen fibers with bone and cartilage fragments. Although the patient showed marked recovery from paraparesis after the operation, the paraparesis deteriorated after extradural drain removal. MRI showed a recurrent large cystic mass and subcutaneous fluid collection. A computed tomography myelogram performed 6 hours after contrast medium (CM) injection showed relatively dense CM in the vicinity of the right L2 root and L2 vertebral cleft. However, CM in the cyst and subcutaneous space was thinner than that in the cleft. We speculated that the pseudoarthrosis of the L2 cleft drew CSF from the hole in the L2 root made by the root block into the L2 cleft with lumbar extension and excreted the pooled CSF into the extradural space with lumbar flexion. Histological findings suggested that the excreted CSF in the extradural space was converted to granulation tissue. Thereafter, the patient was treated successfully with spinal drainage and subsequent spinal column reconstruction surgery.</p><p>  Intraspinal cystic masses causing neurological deficits, which are considered to be derived from fluid in the intervertebral cleft, are extremely rare. To our knowledge, only three cases have been reported. We present a case with paraparesis caused by an intraspinal cystic mass derived from the intervertebral cleft in conjunction with an L2 root block.</p>