• Atsushi Seichi, Katsushi Takeshita, Hiroshi Kawaguchi, Susumu Nakajima, Toru Akune, and Kozo Nakamura.
• Department of Orthopaedic Surgery, Faculty of Medicine, University of Tokyo, Tokyo, Japan. seichi-ort@h.u-tokyo.ac.jp
• Spine. 2004 Jul 1;29(13):1478-82; discussion 1482.

Study DesignA cohort study.ObjectiveTo determine the frequency of swelling of the spinal cord with an intramedullary lesion occurring after laminoplasty for nontraumatic cervical myelopathy and the possible mechanism of postoperative motor paresis of the upper extremity.Summary Of Background DataPostoperative enlargement of the spinal cord with an intramedullary lesion after decompression surgery for cervical stenotic myelopathy has been reported. But the frequency of the incidence remains unknown. Postoperative motor paresis occurring mainly in the C5 and C6 segments is known but various theories on its etiology exist, including the root involvement hypothesis and the spinal cord impairment hypothesis. Thus, the etiology is controversial.MethodsOne hundred fourteen patients with cervical stenotic myelopathy were included in this study. All of them underwent preoperative magnetic resonance imaging and postoperative magnetic resonance imaging 3 weeks after surgery. We watched for the occurrence of postoperative neurologic deterioration including paralysis of the upper extremities. We also observed the presence or absence of postoperative abnormal expansion of T2 high-signal intensity areas on magnetic resonance imaging in the spinal cord.ResultsSeven patients (6.1%) showed postoperative abnormal expansion of the T2 high-signal intensity area; 3 of the 7 were asymptomatic. A total of 9 patients (7.9%) experienced unilateral upper motor paresis after surgery. In 4 of the 9 cases, paresis of the unilateral deltoid, biceps and brachialis muscles (proximal paresis) occurred between 4 and 6 days after surgery. None of the 4 showed postoperative abnormal expansion of the T2 high-signal intensity area. In 3 other of the 9 patients, distal paresis occurred just after surgical intervention. Two of the 3 showed postoperative abnormal expansion of the T2 high-signal intensity area and 1 showed slight expansion of the area. In the other 2 cases, diffuse paresis occurred, and their postoperative magnetic resonance imaging showed abnormal expansion of the T2 high-signal intensity area.ConclusionsSpinal cord enlargement with abnormal expansion of the T2 high-signal intensity area, although not common, is an unpreventable complication after laminoplasty. This was strongly related with distal and diffuse type of postoperative paresis of the upper extremity without deterioration of lower motor function, but was little associated with a proximal type of paresis, so-called C5 and C6 palsies.

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