Idiopathic Spinal Cord Herniation With Severe Adhesions Treated Using the Hammock Method: A Case Report

Idiopathic spinal cord herniation has traditionally been considered a relatively rare disease. It presents as a slowly progressive myelopathy and necessitates surgical treatment. Herein, we describe a case of idiopathic spinal cord herniation treated with the hammock method. The patient was a 63-year-old male who became aware of numbness in his left toe twelve months prior to his initial visit. At that time, he had difficulty standing on his right leg. Sensation for pain and temperature was decreased in the left half of his body below the navel. Bilateral lower extremity tendon reflexes were hyperactive, and the bilateral Babinski reflex was positive. He also reported a weak urine stream. The Japanese Orthopedic Association (JOA) score for the thoracic spine was 5 out of 11. Magnetic resonance imaging (MRI) revealed a dural defect at the T4 level, with spinal cord extramedullary prolapse and anterior deviation. Computed tomography (CT) myelography revealed a dural defect in the same area. The patient presented with Frankel classification grade C paraplegia and a slowly progressive Brown-Séquard syndrome. He was diagnosed with idiopathic spinal cord herniation. We performed dural patch closure using the hammock method. Transcranial electrically stimulated muscle evoked potentials and somatosensory evoked potentials were used for monitoring during surgery. After a laminectomy from T3 to T6, a mid-longitudinal incision was made through the dura and arachnoid to expose the spinal cord. The denticulate ligaments were dissected bilaterally, and the nerve roots were preserved. Due to severe adhesions, we expanded the cephalic defect. Next, we passed a non-powdered nitrile sheet anteriorly under the spinal cord, suspending it. The adhesions around the defect and the spinal cord were completely removed, and the spinal cord emerged. An expanded polytetrafluoroethylene (ePTFE) sheet was then inserted to replace the nitrile sheet and sutured to the dura mater as a full-perimeter patch to cover the defect. Postoperatively, there was no progression of paralysis, the anterior deviation of the spinal cord disappeared, and no recurrence was observed two years after surgery. Although he still needed a walking stick, his walking speed improved, and his sensory impairment improved. Final JOA score for the thoracic spine was 8 out of 11.