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 ().
A 52-year-old male fell 10 years before presentation from a scaffolding. Immediately after this fall, he noticed a diffuse sensibility loss in his right leg, which did not improve. Remarkably, he did not notice temperature changes or pain in that leg. Gradually, the strength in his left leg diminished. In recent years, this has clearly been progressive. In his lower left leg, he noticed paresthesias. He had a normal erectile function, but was unable to ejaculate.\nOn neurological examination, his left leg was slightly paretic. Vital and gnostic sensibility loss were present on the right side below T8. Within the L4 dermatoma on the left side, the vital sensibility was lost. The reflexes of both legs were pathologically increased with a Babinski’s sign on both sides. Radiological examination revealed a herniation of the SC at T4–T5 (Figure ).\nDuring surgery, the dura was opened after a midline approach with laminectomy T4 and T5. The dentate ligaments were transected on both sides, allowing some manipulation of the SC. On the ventral side, a defect of the dura was seen, along with many adhesions from the dura to the SC. These were sharply transected from both sides. Finally, the SC was freed from the dural defect and a mass originating from the ventral part of the SC was developed from the dural defect (Figure ). To prevent re-herniation, an artificial graft was gently placed in front of the SC covering the defect and was fixated laterally to the dural sleeve. Throughout the entire surgery, MEPs, SSEPs, and D-waves were monitored. During manipulation, the signals diminished twice. After waiting for several minutes, the signals returned to a normal level. Post-operatively, the patient did not notice any new complaints. The neurology is his right leg remained unaltered three months after surgery, whereas the symptoms in his left leg had improved.