Yoshihiro Mikawa

Spinal deformity and instability after multilevel cervical laminectomy.

Sixty-four patients who had undergone multilevel cervical laminectomy were studied for postoperative spinal deformity and instability. Special attention was given to patients with cervical spondylosis (CS), ossification of the posterior longitudinal ligament (OPLL), and spinal cord tumors. Twenty-three (36%) of 64 patients showed postoperative changes in curvature type and 9 (14%) had developed spinal deformity (kyphotic or meandering-type curvature). In two juvenile patients, the deformity developed soon after operation and spinal fusion was required to prevent neurologic complications. In the adult cases, contrary to the hitherto accepted concept, long-term follow-up revealed the tendency of the deformity to develop more frequently in OPLL cases than in CS cases. Mobility of the cervical spine was reduced considerably after laminectomy, both in CS and OPLL cases. There was no adult patient who required further operation for severe deformity or instability after laminectomy. Extensive laminectomy, even including the C2 lamina, seemed to have no adverse effect on the stability of the cervical spine.

morphometric Analysis of the Lumbosacral Nerve Roots and Dorsal Root Ganglia by Magnetic Resonance Imaging

Study Design Lumbosacral nerve roots and dorsal root ganglia in relation to surrounding bony structures in normal subjects were investigated using magnetic resonance imaging. Objectives This study determined the normal anatomic parameters of the lumbosacral nerve root and dorsal root ganglion, to which degenerative or pathologic changes may be compared. Summary of Background Data In the previous literature, most authors have used various modalities in either cadavers or symptomatic patients to study the anatomic details of the lumbar nerve roots and dorsal root ganglia. The data in the literature are conflicting, mainly because of individual variations and different degrees of degenerative change in the spine. Methods Twenty male volunteers who had no back pain or radiculopathy underwent magnetic resonance imaging. Ages ranged from 22 to 38 years, with a mean of 30.4 years. T1‐weighted coronal magnetic resonance images were taken from L1 to S1. Two hundred thirty‐three nerve roots were examined, including 36 L1, 40 L2, 40, L3, 39 L4, 40 L5, and 38 S1 nerve roots. Measurements were determined using a computer digitizer. Results The nerve root origin was at a more cephalad level for the caudad nerve roots, particularly the S1. The take‐off angles acutely changed at L1 and S1. The length of the nerve roots increased progressively to a maximum at L5, and decreased at S1. The center of the dorsal root ganglion was positioned more cephalad at S1. The average dimension of the dorsal root ganglion gradually increased from L1 to S1. The most striking difference was in the S1 root, which takes off more cephalad, at a more vertical angle, and has the shortest length of any of the nerve roots. The S1 dorsal root ganglion was also unique in that it was the largest and more frequently located intraspinally. Conclusions The anatomy of the lumbar nerve roots and dorsal root ganglia and their relations to bony structures have been better defined in this study. Because of its more medial location, S1 radiculopathy may involve both the nerve root and dorsal root ganglion as a result of either disc herniation or degenerative L5‐S1 facet changes. The relatively larger dorsal root ganglia and the greater dorsal root ganglion/foramen height ratios in the lower lumbar region may explain the higher incidence of L5 or S1 radiculopathy, particularly given the propensity to disc degeneration and intervertebral foraminal narrowing in the lower lumbar region.

Hypertrophic Spinal Pachymeningitis

A patient with idiopathic hypertrophic spinal pachymeningitis (HSP) with predominant involvement of the cervical and thoracic dura is reported. Serial magnetic resonance (MR) images detected isolated thickening and ridges of the dura mater. There has been no report describing the serial changes of MR images in idiopathic HSP. According to a review of the English and Japanese literature on idiopathic HSP, the prognosis of patients with positive inflammatory signs is worse than that of those with no inflammatory signs. Idiopathic HSP is a rarely reported disease that can resemble other disorders associated with dural compression. MR imaging can help to differentiate it from other disorders, and enables the diagnosis of the disease in its early stage. The prognosis of idiopathic HSP with positive inflammatory signs may be worse; the authors stress the significance of early surgical treatment.

Cerebellar hemorrhage complicating cervical durotomy and revision C1-C2 fusion

Study Design A case of cerebellar hemorrhage complicating cervical durotomy and revision C1-C2 fusion is reported. There has been only one report on cerebellar hemorrhage after cervical durotomy. Summary of Background Data The patient became comatose approximately 16 hours after surgery. According to a review of the recovery room records, the patients cerebellar hemorrhage probably occurred some time within the first 10 hours after the procedure and not during the operation. Methods The authors reviewed reports on complicated cerebellar hemorrhage, and the causative factors were studied. Conclusion Postoperative drainage of cerebrospinal fluid, especially when negative pressure is applied, may play a role in the occurrence of cerebellar hemorrhage.

Elastin in the human posterior longitudinal ligament and spinal dura. A histologic and biochemical study.

Study Design A histologic and biochemical study of elastin in the posterior longitudinal ligament and spinal dura was performed using autopsy cadavers. Objective To provide a rationale for resiliency of the PLL and the spinal dura. Summary of Background Data Among the spinal ligaments, the nuchal ligament and the ligmentum fiavum have a very high elastin content, and some biochemical and morphologic studies of these ligaments have been published. No reports on the elastin content have been published. No reports on the elastin content in the posterior longitudianl ligarnent or spinal dura have been published. Methods Specimens of the posterior longitudinal ligament and the dura collected from three cadavers were studied histologically. For quantitative analysis of elastin and collagen, the posterior longitudinal ligament specimens were collected from 22 cadavers and the dura specimens from 20 cadavers. Elastin was extracted using the hot alkali method of Lansing et al. Results The elastic fibers in the posterior longitudinal ligament generally were arranged parallel in the cephalocaudal direction, wheras the fibers in the spinal dura had a more multidirectional arrangement. The elastin content of the posterior longitudinal ligament averaged 7.3% of the total dry weight and that of the spinal dura was 7.1% for the ventral aspect and 13.8% for the dorsal aspect, The elastin content of the spinal dura was about two times higher in all dorsal specimens than in the corresponding ventral specimens. The elastin content of the lower thoracic region was higher than that of any other region. The amino acid composition of the elastin in the posterior longitudinal ligament and spinal dura was similar to that previously determined in other spinal ligaments.

The effect of age on inflammatory responses and nerve root injuries after lumbar disc herniation: an experimental study in a canine model.

Study Design. An experimental investigation on the effect of age on pathologic events surrounding the herniated disc and at the adjacent nerve root. Objectives. To investigate the role of age on the inflammatory responses and nerve root damage surrounding a sequestered lumbar disc fragment using a dog model. Summary of Background Data. Lumbar disc herniation is manifested in patients by variable clinical findings, natural history, and resorption phenomena in which the variability is particularly noted among patients with different ages. There are no previous reports on the effect of age on pathologic events induced by the herniated disc. Methods. Six beagle dogs, including two animals of each age group of 6, 12, and 24 months (human equivalent ages of 10, 15, and 24 years), were used in this study. The dogs underwent L4–L5, L5–L6, and L6–L7 laminotomy and discectomy under general anesthesia. An autologous intervertebral disc from the tail was divided into anulus fibrosus and nucleus pulposus fragments. The anulus fibrosus and nucleus pulposus fragments were placed in the anterolateral epidural space of L5–L6 and L6–L7, respectively. The L4–L5 discectomy site served as a control. Dogs were killed at 12 weeks after surgery. The lumbar spine was removed en bloc, and histologic sections were prepared consecutively and examined. Results. In the nucleus pulposus group at L6–L7, neovascularity, and intensive infiltration of lymphocytes, macrophages, and fibroblasts were observed surrounding the nucleus pulposus fragment in the 24-month-old group only. Degenerative changes of the nerve root fibers were observed in the 24-month-old group only. In the control and anulus fibrosus groups at L4–L5 and L5–L6, there were no marked inflammatory reactions in all age groups. The nerve root fibers around the anulus fibrosus were normal in all age groups. Conclusions. There is an effect of age on the inflammatory response and nerve root injury caused by the herniated disc. The apparent neuroprotective mechanism in the young animal, and the apparent inflammatory and resorption changes of the nucleus pulposus fragment in the older animal are quite intriguing.

Stress fracture of the first rib in a weightlifter

SummaryAn isolated fracture of the first rib is rare. Stress fractures of the first rib have previously been reported in various sports [6, 10, 15, 16] and the mechanism of fractures of the first rib has been well documented [3, 6, 11, 15]. Stress fractures of the first rib have also been reported in laborers involved in heavy lifting [4]. The course is insidious, and identification of the lesion is usually made on the basis of an incidental roentgenogram. No reported case of stress fracture of the first rib in a weightlifter has hitherto been available. This paper describes such a case for the first time.

Solitary fibrous tumor of the spinal cord : Report of a case with scrape cytology

BACKGROUND Solitary fibrous tumor is a rare spindle cell tumor and has been forced at a variety of sites. To the best of our knowledge, only two cases of solitary fibrous tumor arising in the spinal cord have been reported; no cytologic findings were documented. CASE A 62-year-old male presented with a spinal cord tumor. A scrape smear of the resected tumor revealed naked, spindle-shaped nuclei. Some nuclei were twisted or had long spindles. In the background, abundant, thin and thick collagen fibers were present. Immunohistochemically, the spindle cells were positive for CD34 and negative for S-100 protein and alpha-smooth muscle actin. Histologic diagnosis of the tumor was benign solitary fibrous tumor. CONCLUSION Our case indicates that solitary fibrous tumor can occur in the spinal cord and should be differentiated from other benign spindle cell tumors, such as meningioma and schwannoma. The key cytologic features of solitary fibrous tumor may be the presence of abundant thin and thick collagen fibers in scrape specimens.

Fracture through a synchondrosis of the anterior arch of the atlas

A four-year-old boy was playing on a slide when he fell, striking his head on the ground and hurting his neck. He held his head in the “cock-robin” position and examination revealed limited movement of the neck and paravertebral muscle spasm. A lateral radiograph showed subluxation of Cl on C2 (Fig. 1). Halter traction was applied, and after a few days there was a normal range of flexion and rotation, but a further radiograph showed that the subluxation was unchanged. A CT scan revealed a fracture-separation through the synchondrosis on the left side of the anterior arch of the atlas, with widening of the atlanto-axial interval (Fig. 2). After three weeks ofcervical traction, a cervicothoracic brace was applied and retained for two

An experimental study on prevention of postlaminectomy scar formation by the use of new materials

An experimental study was performed to investigate the prevention of scar formation after lumbar laminectomy, using Elastase and the new polylactic acid (PLA) membrane containing Elastase. The experimental animals consisted of four groups: 1) control group, 2) E group (using intravenous administration of Elastase), 3) P group (covering the laminectomy defect with PLA membrane), and 4) P - E group (covering the laminectomy defect with “PLA” + Elastase” membrane). The animals were killed at varying intervals (2-12 weeks) and changes in the lumbar spines were evaluated histologically. Scar formation was suppressed most significantly in the P-E group, followed in order by the E group, the P group, and the controls.