Split cord malformation: Part I: A unified theory of embryogenesis for double spinal cord malformations.

Much confusion still exists concerning the pathological definitions and clinical significance of double spinal cord malformations. Traditional terms used to describe the two main forms of these rare malformations, diastematomyelia and diplomyelia, add to the confusion by their inconsistent usage, ambiguities, and implications of their dissimilar embryogenesis. Based on the detailed radiographic and surgical findings of 39 cases of double cord malformations and the autopsy data on two other cases, this study endorses a new classification for double cord malformations and proposes a unified theory of embryogenesis for all their variant forms and features. The new classification recommends the term split cord malformation (SCM) for all double spinal cords. A Type I SCM consists of two hemicords, each contained within its own dural tube and separated by a dura-sheathed rigid osseocartilaginous median septum. A Type II SCM consists of two hemicords housed in a single dural tube separated by a nonrigid, fibrous median septum. These two essential features necessary for typing, the state of the dural tube and the nature of the median septum, do not ever overlap between the two main forms and can always be demonstrated by imaging studies so that accurate preoperative typing is always possible. All other associated structures in SCM such as paramedian nerve roots, myelomeningoceles manqué, and centromedian vascular structures frequently do overlap between types and are not reliable typing criteria. The unified theory of embryogenesis proposes that all variant types of SCMs have a common embryogenetic mechanism. Basic to this mechanism is the formation of adhesions between ecto- and endoderm, leading to an accessory neurenteric canal around which condenses an endomesenchymal tract that bisects the developing notochord and causes formation of two hemineural plates. The altered state of the emerging split neural tube and the subsequent ontogenetic fates of the constituent components of the endomesenchymal tract ultimately determine the configuration and orientation of the hemicords, the nature of the median septum, the coexistence of various vascular, lipomatous, neural, and fibrous oddities within the median cleft, the high association with open myelodysplastic and cutaneous lesions, and the seemingly unlikely relationship with fore and midgut anomalies. The multiple facets of this theory are presented in increasing complexity against the background of known embryological facts and theories; the validity of each facet is tested by comparing structures and phenomena predicted by the facet with actual radiographic, surgical, and histopathological findings of these 41 cases of SCM.     

Shoulder pain in chronic spinal cord injury, Part I: Epidemiology, etiology, and pathomechanics

STUDY DESIGN: Review of the literature. BACKGROUND/OBJECTIVE: Shoulder pain is extremely common in individuals with chronic spinal cord injury (SCI) and is a source of morbidity and functional loss. The purpose of this review is to outline the present knowledge of the epidemiology, etiology, and pathomechanics of musculoskeletal shoulder pain in individuals with chronic SCI. METHODS: Review of the literature using PubMed/MEDLINE, EMBASE, and bibliographies of selected articles. RESULTS: Shoulder pain is more common in individuals with tetraplegia and complete injuries and may occur more frequently in women. Musculoskeletal conditions, primarily injuries to the rotator cuff, are most common. Risk factors include the duration of injury, older age, higher body mass index, the use of a manual wheelchair, poor seated posture, decreased flexibility, and muscle imbalances in the rotator cuff and scapular stabilizing muscles. CONCLUSION: With a better understanding of the epidemiology, etiology, and basic pathomechanics of shoulder pain in SCI, physicians are in a better position to evaluate, treat, and prevent these disorders.     

Multiple neurinoma of the spinal cord: case report

The patient, a 72-year-old female, was admitted with an 11-year history of progressive dysesthesia in the left leg. Neurological findings on admission revealed weakness in the bilateral legs, hyperreflexia of left leg, hypalgesia and hypesthesia under the Th 8 level, and urinary incontinence. Plain lumber X-ray showed enlargement of the intervertebral foramen of L 1/2. Myelography disclosed block age at the level of Th 9 and filling defect at the level of Th 10/11 and L1/2. CT myelography revealed a cord swelling and partially exophytic tumor from Th 8 to Th 9, another tumor located posterior-laterally at the level of Th 11, and another tumor located extra and intradural at the level of L1/2. Laminectomy was performed from Th 8 to L 3. A tumor of the Th 9 was located intramedullary, another tumor of the Th 11 was located intradural extramedullary, and another tumor of the L1/2 was located in the epidural space (so-called dumb-bell type tumor). These tumors were removed completely except the extra-canal part of L1/2 tumor. Histopathological examination revealed typical Antoni type A schwannoma in all tumors. This case was considered multiple neurinomas of the spine in which tumors were located in three separate anatomical sites, intramedullary, intradural extramedullary, and epidural sites. This patient did not show café-au-lait spot, and neurofibroma in her body. The authors considered the patient might be a case of central neurofibromatosis. The authors stressed that multiple neurinomas of the spine is not rare, so careful study of the whole spine is necessary including its intramedullar space.     

Monitoring of the brain and spinal cord

IOM has become commonly used by many surgeons to enhance their intraoperative decision making and reduce the morbidity and mortality of selected procedures. The ability to perform these tests rests on the anesthesiologist's ability to provide the patient with an anesthetic plan that provides comfort and monitoring. When events occur, the anesthesiologist's knowledge and ability to manipulate the patient's physiologic condition become integral to the decision making. A good understanding of the neural anatomy, impact of physiology, and anesthetic medications can allow effective IOM and good team decision making when changes in IOM occur.     

Multicentric gliomas of brain and spinal cord

The clinical and histopathological findings in a child suffering from both cerebral and spinal gliomas of differing histological types are described. There was a family history of von Recklinghausen's neurofibromatosis. The possibility of overlooking the symptoms and signs pointing to a spinal cord lesion in the presence of a known intracranial tumour is stressed.     

Antinociceptive actions of intrathecal xylazine: interactions with spinal cord opioid pathways

We have studied rats with chronically implanted subarachnoid catheters. Xylazine, an alpha 2 adrenoceptor agonist, was injected intrathecally and nociceptive thresholds measured at two skin sites: the tail and the neck. Intrathecal xylazine (dose range 24.3-389 nmol) produced increases in electrical thresholds for nociception in the tail without any change in the neck; this observation suggested that the antinociceptive action of this drug was confined to the caudal part of the spinal cord responsible for tail innervation. The magnitude of this effect was dose-dependent. Tail flick latency also increased in these rats and the antinociceptive effects were antagonized in a dose- dependent manner by the selective alpha 2 adrenoceptor antagonist idazoxan (dose range 6.7-540 nmol). Intrathecal idazoxan also suppressed the increase in tail flick latency caused by the mu opioid agonist fentanyl (0.74 nmol) given intrathecally. This effect was also dose-dependent. The idazoxan dose-response curve for this suppression of fentanyl antinociception assessed with tail flick latency was the same as that for suppression of xylazine. In contrast, the antinociceptive effects of intrathecal xylazine were not affected by concurrent administration of opioid or GABAA antagonists. We conclude that intrathecal xylazine produced spinally mediated antinociceptive effects by combination with spinal cord alpha 2 adrenoceptors and that neither opioid nor GABA-containing propriospinal neurones were involved in the mediation of this effect. However, alpha 2 adrenoceptors in the spinal cord appear to be involved with antinociception produced by intrathecal fentanyl.      

Editorial note: Trauma of the brain and spinal cord

The predictive values of certain features of computerized tomographic (CT) scans in estimating intracranial pressure (ICP) were investigated in 40 patients following closed head injuries. The various features of CT scans selected for study included ventricular compression, the size of the parenchymal mass lesion, midline shift, and an intraventricular clot. All patients with intraventricular clot exhibited severe elevation of pressure. Ventricular compression correlated well with the level of intracranial pressure. Size of the mass was found to be suggestive of pressure elevation but did not reach statistical significance. Midline shift showed no correlation with the intracranial pressure.     

Steroid receptors in human brain and spinal cord tumors

Previous investigators have shown evidence of hormonal receptor protein in human brain tumors. In spite of conflicting results, antiestrogen agents (e.g., tamoxifen) have been used in clinical trials of recurrent unresectable meningiomas. In an effort to accrue further comprehensive in vitro data on this subject, we have evaluated 50 human brain and spinal tumors for estrogen, progesterone, and androgen receptor markers. Twenty-nine of the 50 tumors were meningiomas. The other 21 included 11 gliomas of various grades, 5 schwannomas, 3 metastatic carcinomas, 1 angiofibroma, and 1 craniopharyngioma. Only 8 tumors, all meningiomas, were positive for both progesterone and androgen receptors. The 8th tumor was positive for all three receptor proteins. Our study did not find a significant relationship between meningiomas and the presence of steroid receptor protein. We conclude that the use of antiestrogen agents is not indicated in the treatment of meningioma. No significant relationship to sex, menopausal status, tumor type, or tumor location was observed.     

鞘内注射吗啡对大鼠中脑导水管周围灰质、海马和脊髓μ阿片受体mRNA表达的影响

目的研究鞘内注射吗啡对大鼠中脑导水管周围灰质（PAG）、海马和脊髓μ阿片受体（MOR）mRNA表达的影响,探讨大鼠鞘内注射吗啡免疫功能抑制的机制。方法清洁级成年雄性SD大鼠,鞘内置管成功的16只大鼠随机分为2组（n=8）：生理盐水组（NS组）和吗啡组（M组）。M组鞘内持续输注吗啡10μg/h 7 d（生理盐水稀释）,NS组给予等体积的生理盐水。输注7 d后断头处死大鼠,取出大鼠PAG、海马和脊髓标本,采用巢式RT-PCR测定MOR mRNA的表达。结果与NS组比较,M组PAG和海马MOR mRNA表达下调（P〈0.05或0.01）,脊髓MOR mRNA表达无统计学意义（P〉0.05）。结论大鼠PAG和海马MOR表达下调可能是鞘内注射吗啡导致免疫功能抑制的机制之一。     

The optimal radiologic method for assessing spinal canal compromise and cord compression in patients with cervical spinal cord injury. Part I: An evidence-based analysis of the published literature

STUDY DESIGN: An evidence-based analysis of published radiologic criteria for assessing spinal canal compromise and cord compression in patients with acute cervical spinal cord injury. OBJECTIVES: This study was conducted to determine whether literature-based guidelines could be established for accurate and objective assessment of spinal canal compromise and spinal cord compression after cervical spinal cord injury. SUMMARY OF BACKGROUND DATA: Before conducting multicenter trials to determine the efficacy of surgical decompression in cervical spinal cord injury, reliable and objective radiographic criteria to define and quantify spinal cord compression must be established. METHODS: A computer-based search of the published English, German, and French language literature from 1966 through 1997 was performed using MEDLINE (U.S. National Library of Medicine database) to identify studies in which cervical spinal canal and cord size were radiographically assessed in a quantitative manner. Thirty-seven references were included for critical analysis. RESULTS: Most studies dealt with degenerative disease, spondylosis, and stenosis; only 13 included patients with acute cervical spinal cord injury. Standard lateral radiographs were the most frequent imaging method used (23 studies). T1- and T2-weighted magnetic resonance imaging were used to assess spinal cord compression in only 7 and 4 studies, respectively. Spinal cord size or compression were not precisely measured in any of the cervical trauma studies. Interobserver or intraobserver reliability of the radiologic measurements was assessed in only 7 (19%) of the 37 studies. CONCLUSIONS: To date, there are few quantitative, reliable radiologic outcome measures for assessing spinal canal compromise or cord compression in patients with acute cervical spinal cord injury.