A 66-year-old previously well man presented with an 18-year history of upper thoracic spine pain. The pain was initially intermittent and mild, but in the 14 months prior to presentation, it had gradually increased in severity and persistence. The pain radiated to the left side of the neck, and when severe, spread around both sides of the chest. The patient reported two episodes of left arm weakness lasting a few hours with spontaneous resolution, but denied paresthesia, sensory loss, or sphincter disturbance. There was no history of spinal surgery, trauma, or spinal disorders. Clinical examination demonstrated an upper thoracic spine gentle kyphosis. There were no abnormal findings on neurological motor, sensory, and reflex examination. A suboptimal quality MRI of the thoracic spine performed at a different institution was interpreted as an intradural mid-thoracic lesion, with a described intradural extramedullary mass indenting the dorsal aspect of the spinal cord. These findings were initially thought to be a dorsal arachnoid cyst. Repeat MRI at our institution demonstrated findings consistent with the characteristic features of ISCH. T2-weighted images showed anterior kinking and mild flattening of the spinal cord at T5, with widening of the subarachnoid space posterior to the cord and pulsation artifact within the CSF space []. The patient was treated with conservative management, with clinical and radiological surveillance. The patient remained neurologically stable at 4 months after presentation.
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 ().