A 48-year-old female presented with two year history of back pain and progressive difficultly walking. She gradually developed increasing numbness in both lower limbs over one year. She also developed increasing urinary retention. There was no history of trauma/fever or any other systemic disease. She was evaluated by an orthopedic spine surgeon and was referred to a physician following a negative lumbar magnetic resonance imaging (MRI). Neurological examination revealed presence of weakness in bilateral lower extremities (4-/5, Medical Research Council [MRC] grade) and asymmetrical sensory loss from T8 below consistent with a diagnosis of thoracic myelopathy (Nurick grade 4). Persistent symptoms with worsening gait imbalance led us to perform of thoracic spine MRI which surprisingly revealed presence of a focal anterior kink of the thoracic cord at the T7-T8 level (). The spinal cord at T7/8 level was narrow and deformed without any definite T2 signal abnormality with prominence of the dorsal subarachnoid space. The MRI imaging was suspicious of a diagnosis of anterior transdural spinal cord herniation (). Surgical management was planned and a unilateral right paramedian incision was used to perform a transpedicular exposure due to slight eccentric location of the spinal cord herniation to the right (). Intraoperative neuromonitoring was performed recording somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs). T7/T8 pediculotomy was performed with partial costotransversectomy to provide the optimal anterolateral trajectory. A paramedian right dura incision was made, providing exquisite visualization of the anterior dural defect with the herniated spinal cord (). Using a Woodson dissector, the spinal cord was reduced back into the thoracic dura. The SSEP's were normal throughout the procedure. There was transient reduction in MEP amplitude during mobilization of the spinal cord to reduce the herniation. The MEP amplitude returned to baseline status an hour later. A Duragen (Integra Life Sciences Corp., Plainsboro, NJ, USA) patch was used as graft to seal the defect which was reinforced with Tisseel fibrin glue. (Baxter Healthcare Corp., Deerfield, IL, USA) No fusion or instrumentation was performed. Patient experienced improvement in sensory symptoms right after the surgery and had improvement in her pain, motor strength (4+/5, MRC grade) and gait at three months follow-up with improvement in her Nurick myelopathy grade to 2. Postoperative MRI revealed reduction of the spinal cord with no evidence of herniation ().
This 58-year-old female complained about temperature changes and hyperpathy in her left leg for the past 12 months. On the right side, the sensibility was different but not normal. The strength in her left leg was diminished. These complaints ascended over time, initially starting at the foot and developing further to the groin at the time of presentation.\nNeurological examination revealed only a paretic quadriceps femoris muscle on the left side. Vital sensibility was disturbed on the left side below T10. The plantar reflexes on both sides were indifferent.\nAn MRI revealed a herniation of the SC at T8 (Figure ).\nDuring surgery, a laminectomy on T8 and T7 was performed. The dentate ligaments were transected. While gently mobilizing the SC from the left to the right, a large defect in the ventral dura was observed. The same maneuver at the right side revealed a fixed SC with the defect. After transection of some adhesions, a tumor-like extension of the SC was seen (Figure ) and was finally mobilized completely intradurally. To prevent re-herniation, an artificial graft was gently placed in front of the SC covering the defect and fixated laterally to the dural sleeve. Throughout the entire surgery, MEPs, SSEPs, and D-waves were monitored. Changes were not noticed. Post-operatively, the patient did not notice any new complaints.