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Hisato Tanaka, Kensei Nagata, Akio Inoue, and Mitsuaki Yoshizuka

The authors conducted a study in which they applied the spinal cord compression-decompression model in rabbits to investigate the morphological changes and histopathological findings in the deformed spinal cord over a long-term period after performing decompressive surgery.

Throughout the experimental period, mangnetic resonance (MR) images were obtained frequently; after obtaining a final MR image, the spinal cord was dissected and underwent histological examination.

Immediately after decompressive surgery, axial T1-wieighted MR imaging revealed an increase in the cross-sectional area of the spinal cord during the 1st and 2nd weeks. The spinal cord area achieved a peak at an average of 5.9 weeks after decompressive surgery, when it displayed isointensity on T1- and high-intensity on T2-weighted images. The main histological findings were spongy changes in the white matter, which persisted for 4 months postsurgery. There was a significant correlation between the presurgical spinal cord area and the postsurgical decreased number of motor neuron cells.

Based on the MR imaging and histopathological studies, although the deformed spinal cord that underwent compression for 3 months was immediately restored morphologically after decompressive surgery, the change in quality in the spinal cord persisted at least 4 months.

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Kimiaki Sato, Kensei Nagata, and Yasuo Sugita

Object

Spinal extradural meningeal cysts are uncommon and rarely cause neural compression. The clinical, radiological, and histopathological characteristics of the lesions are discussed and previous reports reviewed.

Methods

The authors describe five cases of a spinal extradural meningeal cyst (three female and two male patients, with a mean age of 47 years (range 14–75 years). Four of the cysts were located at the thoracolumbar level, the fifth at the sacral level. Radiological and neuroimaging-based diagnosis was made using a combination of magnetic resonance imaging, myelography, and/or computerized tomography (CT) myelography.

A connection between the spinal subarachnoid space and the cyst cavity was demonstrated on myelography and/or CT myelography in all cases, and dural defects were confirmed visually intraoperatively. In all cases histopathological examination confirmed that the cyst wall was formed by nonspecific fibrous connective tissue without a single-cell layer of inner arachnoid lining.

Conclusions

A diagnosis of spinal extradural meningeal cyst is difficult to make based solely on histopathological examination. It is essential that the final characterization and diagnosis be based on intraoperative inspection combined with radiological and histopathological findings.