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Kinematic Magnetic Resonance Imaging of a Thoracic Spinal Extradural Arachnoid Cyst: An Alternative Suggestion for Exacerbation of Symptoms During Straining

Study Design. A case study of an extradural arachnoid cyst using kinematic magnetic resonance imaging. Objectives. To access the dynamic and pathologic changes of an extradural subarachnoid cyst during straining by kinematic magnetic resonance imaging and to clarify the pathomechanism of a fluctuation in symptoms. Summary of Background Data. Extradural arachnoid cysts of the spine are an uncommon cause of myelopathy secondary to spinal cord compression; however, the precise mechanism of cord compression and subsequent symptoms remain unclear. Methods. A 31-year-old female presented with severe left lower thoracic back pain and leg stiffness, which were exacerbated by coughing and straining. She was diagnosed with an extradural subarachnoid cyst by magnetic resonance imaging. Kinematic magnetic resonance imaging was carried out to assess the dynamic change of the extradural cyst and to demonstrate the mechanism causing her chest pain and leg stiffness during straining. Results. Kinematic magnetic resonance imaging demonstrated that the cyst wall was compressed, and the size of extradural cyst was decreased for several seconds during straining. Furthermore, the ring of cerebrospinal fluid was gradually compressed circumferentially. After surgery, the patient experienced complete relief of symptoms. Postoperative kinematic magnetic resonance imaging revealed good decompressive results had been obtained, and the ring of cerebrospinal fluid was preserved even when the patient strained for a few minutes. Conclusions. Kinematic magnetic resonance imaging study demonstrated that pressure changes which occur in the extradural space as well as in the arachnoid cyst might cause spinal cord compression and result in intermittent exacerbation of symptoms.