Staff Physician Cleveland Clinic Foundation Cleveland, Ohio, United States
Case Diagnosis: Thoracic Spinal Arachnoid Web
Case Description: 74 y/o M presented for evaluation of progressive low back pain over the past year. He reported worsening stiffness of his low back and patchy, intermittent numbness distal to his waste. Additionally, he noted altered balance and difficulty with ambulation. Exam revealed limited lumbar range of motion but normal strength in extremities. Upper extremity reflexes were normal but increased in bilateral patellar and achilles with bilateral ankle clonus. There was patchy sensory loss of bilateral lower extremities and was unable to perform tandem gait. Prior lumbar radiography revealed bridging anterior endplate osteophytes. MRI of cervical, thoracic, and lumbar spine revealed a focal thoracic cord contour abnormality at T7 consistent with a spinal arachnoid web (SAW), with associated cord edema and syrinx at T8. At the time of submission, he is pending surgical evaluation.
Discussions: SAW are a rare pathology caused by abnormal thickening of arachnoid tissue that can result in dorsal spinal cord compression and impaired CSF flow, most seen within the thoracic spine. Associated syringomyelia is commonly found and thought to result from SAW mass effect or obstruction of CSF flow. The pathophysiology is unknown but thought to share similar etiology as arachnoid cyst formation. Presenting symptoms include back pain, weakness, sensory disturbance, and hyperreflexia. MRI can reveal the “scalpel sign” of a focal, dorsal indentation of the spinal cord. However, the findings can be subtle and only confirmed on surgical evaluation. Definitive treatment is surgical resection and repair of CSF flow. Favorable outcomes have been seen with prompt surgical intervention.
Conclusions: SAW are a rare cause of myelopathy that can be overlooked on MRI. Careful examination and evaluation of imaging allow for accurate diagnosis and prompt surgical resection for favorable outcomes.
