A 37-year-old female presented with the sudden onset of abdominal pain rapidly accompanied by numbness and weakness in both lower extremities. On examination, she was paraparetic (right 3/5 and left 4/5 proximally/distally) and exhibited decreased pin, temperature, vibration, and position perception below the T8 level.
The thoracic magnetic resonance image (MRI) revealed a dorsal intradural extramedullary cyst at the T7 level, compressing, and displacing the cord anteriorly. The T2-weighted image is showed a high-intensity uniform cyst (filled with cerebral spinal) [Figure 1]. The myelogram further demonstrated a near complete block at the T7 level (e.g., intrathecal contrast only slowly passed the T7 level extending cephalad). The thoracic computed tomography myelography confirmed the presence of a uniformly filling arachnoid cyst [Figure 2a-c].
Initially, the patient was treated conservatively with steroid therapy; indeed, she exhibited some gradual spontaneous improvement (e.g., able to walk without any support within 1 day). However, her ataxia and proprioceptive deficits in both legs persisted, and the spinal arachnoid cyst did not regress on the follow-up MRI. Surgery consisting of a T6-T8 hemilaminectomy, therefore, was performed 2 weeks after the onset of symptoms. Upon opening the dura mater, we found an arachnoid cyst with a thick whitened wall compressing the spinal cord. Notably, the cyst pulsated with each heartbeat and contained clear CSF fluid. There was, however, no documented communication between the cyst and the subarachnoid space. After removing the cyst, the histological examination confirmed the diagnosis of an arachnoid cyst. Two weeks postoperatively, the patient fully recovered.