PLE-273

A patient had been in a car accident, wherein he suffered superficial lacerations, but the neurologic exam was normal. Six months later, he complains of loss of pain and temperature sensations in the hands and forearm. This progressed to include mild weakness of hand grip and extension of the sensory loss to the arm and shoulders. An MRI of the spinal cord shows a cyst in a segment of the spinal cord. What pathology is consistent with this?