Diagnosis and treatment of ossification of the posterior longitudinal ligament of the spine: report of eight cases and literature review

Mechanical response of human thoracic spine ligaments under quasi-static loading: An experimental study

PURPOSE

This study aimed to investigate the geometrical and mechanical properties of human thoracic spine ligaments subjected to uniaxial quasi-static tensile test.

METHODS

Four human thoracic spines, obtained through a body donation program, were utilized for the study. The anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL), capsular ligament (CL), ligamenta flava (LF), and the interspinous ligament and supraspinous ligament complex (ISL + SSL), were investigated. The samples underwent specimen preparation, including dissection, cleaning, and reinforcement, before being immersed in epoxy resin. Uniaxial tensile tests were performed using a custom-designed mechanical testing machine equipped with an environmental chamber (T = 36.6 °C; humidity 95%). Then, the obtained tensile curves were averaged preserving the characteristic regions of typical ligaments response.

RESULTS

Geometrical and mechanical properties, such as initial length and width, failure load, and failure elongation, were measured. Analysis of variance (ANOVA) revealed significant differences among the ligaments for all investigated parameters. Pairwise comparisons using Tukey's post-hoc test indicated differences in initial length and width. ALL and PLL exhibited higher failure forces compared to CL and LF. ALL and ISL + SSL demonstrated biggest failure elongation. Comparisons with other studies showed variations in initial length, failure force, and failure elongation across different ligaments. The subsystem (Th1 - Th6 and Th7 - Th12) analysis revealed increases in initial length, width, failure force, and elongation for certain ligaments.

CONCLUSIONS

Variations of both the geometric and mechanical properties of the ligaments were noticed, highlighting their unique characteristics and response to tensile force. Presented results extend very limited experimental data base of thoracic spine ligaments existing in the literature. The obtained geometrical and mechanical properties can help in the development of more precise human body models (HBMs).

Multilevel ossification of the posterior longitudinal ligament causing cervical myelopathy: An observational series of North American patients

Background

Few studies regarding ossification of the posterior longitudinal ligament (OPLL) outside of Asia currently exist in the literature. A set of patients with multilevel cervical OPLL causing symptomatic myelopathy or radiculopathy from a North American sample is analyzed.

Objective

The objective of this study was to describe the demographics, radiographic findings, and surgical outcomes of a cohort of North American patients with degenerative spondylosis presenting for operative management of multilevel (>3 segments) cervical OPLL.

Materials and Methods

Forty-three patients diagnosed with multilevel cervical OPLL and degenerative spondylosis presenting with symptomatic cervical myelopathy or radiculopathy were surgically treated over a 9-year period at a single tertiary care academic medical center. Radiographic measurements were performed on preoperative computed tomography and magnetic resonance imaging images of the cervical spine. Clinical outcomes included pre- and postoperative Nurick scores, 90-day readmission, complication, and revision surgery rates.

Results

The mean age was 66.1 ± 10.9 years with a mean latest follow-up time of 32.7 ± 16.4 months. Most patients had previous diagnoses of obesity (70.7%) and hypertension (55.8%). At least one-quarter of patients were diagnosed with type 2 diabetes (34.9%), hyperlipidemia (41.9%), cardiovascular disease (25.6%), or chronic kidney disease (25.3%). The most common OPLL subtype was segmental (39.5%) and spanned a mean of 3.54 ± 1.48 segments. Myelopathic symptoms were present in 88.4% of patients. All patients experienced significant neurologic improvement at 3-week and latest follow-up (P < 0.001 for both).

Conclusions

Obesity, diabetes, and other metabolic derangements in patients with existing cervical spondylosis may be risk factors for a particularly aggressive form of multilevel OPLL. Various operative approaches may be employed to achieve adequate neurologic recovery. Further workup for OPLL in patients with these risk factors may prove beneficial to ensure appropriate operative management.

Sacroiliac Joint Variation in Patients With Ossification of the Posterior Longitudinal Ligament

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVES

Ossification of the posterior longitudinal ligament (OPLL) reveals heterotopic ossification in the spinal ligament. OPLL also tends to ossify ligaments and entheses throughout the body. However, hallmarks of sacroiliac (SI) joint ossification and its variation in OPLL have not been clarified. Here, we investigated the morphological changes in SI joints in individuals with and without OPLL.

METHODS

We included 240 age- and sex-matched patients (OPLL+, 120; OPLL-, 120) in the study. SI joint variations were classified into 4 types: Type 1, normal or small peripheral bone irregularity; Type 2, subchondral bone sclerosis and osteophyte formation; Type 3, vacuum phenomenon; and Type 4, bridging osteophyte and bony fusion. Type 4 was further divided into 3 subgroups as previously described. Interactions between the ossified spinal region in OPLL and morphological changes in the SI joint were evaluated.

RESULTS

SI joint ankylosis occurs more frequently in patients with OPLL (51.7%) than in those without (non-OPLL) (33.3%). The SI joint vacuum phenomenon (49.2%) was the main finding in non-OPLL. SI joint ankylosis in OPLL was characterized by anterior bridging and intra-articular fusion. OPLL patients with multilevel ossification tend to develop degeneration and ankylosis of the SI joints.

CONCLUSIONS

OPLL conferred a high risk of SI joint ossification compared with non-OPLL, and patients with extensive ossification had a higher rate of SI joint ankylosis. Understanding SI joint variation could help elucidate OPLL etiology and clarify the phenotypic differences in the SI joint between OPLL and other spinal disorders.

How Does Ossification of Posterior Longitudinal Ligament Progress in Conservatively Managed Patients?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to elucidate the progression of ossification of the posterior longitudinal ligament (OPLL) in conservatively managed patients and determine its risk factors SUMMARY OF BACKGROUND DATA.: Although several studies have demonstrated how OPLL progresses after laminoplasty or fusion, its progression in conservatively managed patients remains unclear.

METHODS

The vertical length of the ossified mass and its thickness at each segment were evaluated on sagittal computed tomography images. Patients with vertical growth >2 mm were included in the vertical progression group. Segments with a thickness progression >1 mm were classified as thickness progressed segments, and patients who had at least one progressed segment were included in the thickness progression group. Based on the characteristics at each disc level, the ossified mass at each segment was classified into four types: type 1, no disc space involvement; type 2, involving the disc space, but not crossing; type 3, crossing the disc space, but not fused; and type 4, completely fused.

RESULTS

The progression of ossified mass was observed in younger patients (P < 0.01) and in C2-C3 involvement (P < 0.01) cases. Moreover, progression in both directions was observed more frequently in the mixed-type OPLL (P < 0.01). Progression occurred most often in type 3 segments (72.0%, P < 0.01). In type 3 segments, thickness progression was found more frequently in segments with segmental range of motion (ROM) ≥5° (55.6% vs. 27.8%, P = 0.04). The proportion of segments whose initial thickness was >5 mm was significantly higher among progressed segments (60.0% vs. 35.2%, P = 0.03).

CONCLUSION

Young age, C2-C3 involvement, and mixed-type OPLL are risk factors for OPLL progression. Segments with morphology of crossing the segment, but without fusion (type 3), segmental ROM ≥5°, and initial thickness >5 mm need special attention.

LEVEL OF EVIDENCE

3.

Spinal cord infarction at the level of ossification of the posterior longitudinal ligament

INTRODUCTION

We report a case of acute tetraplegia, without any trauma or symptoms prior to onset, who presented with ossification of the posterior longitudinal ligament (OPLL) in the cervical spine with concomitant spinal cord infarction.

CASE PRESENTATION

A 64-year-old man with a number of risk factors for vascular disease was admitted to our hospital with progressive motor weakness in the bilateral upper and lower extremities. He had initially felt numbness in his left upper extremity and had no previous neurological symptoms or trauma. The night after the initial symptoms, he developed spastic tetraplegia requiring respiratory support. Computed tomography images of the cervical spine demonstrated the segmental type of OPLL. Spinal cord compression and signal intensity changes were identified at the level of C3/4 on magnetic resonance imaging (MRI). He underwent emergency surgery consisting of posterior decompression with laminoplasty of C3-6. Despite the surgery, the patient's tetraplegia did not improve and he continued to require respirator support. There was still no improvement in his neurological status at 10 days postoperatively, and MRI demonstrated evidence of marked spinal cord infarction.

DISCUSSION

Mechanical compression of spinal arteries by OPLL and pre-existing vascular compromise had a role in the pathogenesis of spinal cord infarction. Chronic spinal compression may be characterized by 3 important factors, namely an uncommonly devastating clinical course, vascular risk factors and persistent findings on MRI, and these might lead to early diagnosis of spinal cord infarction.

A global perspective on the outcomes of surgical decompression in patients with cervical spondylotic myelopathy: results from the prospective multicenter AOSpine international study on 479 patients

STUDY DESIGN

Prospective, multicenter international cohort.

OBJECTIVE

To evaluate outcomes of surgical decompression for cervical spondylotic myelopathy (CSM) at a global level.

SUMMARY OF BACKGROUND DATA

CSM is a degenerative spine disease and the most common cause of spinal cord dysfunction worldwide. Surgery is increasingly recommended as the preferred treatment strategy for CSM to improve neurological and functional status and quality of life. The outcomes of surgical intervention for CSM have never been evaluated at an international level.

METHODS

Between October 2007 and January 2011, 479 symptomatic patients with image evidence of CSM were enrolled in the prospective, multicenter AOSpine CSM-International study from 16 global sites. Preoperative and postoperative clinical status, functional impairment, and quality of life were evaluated using the modified Japanese Orthopaedic Assessment Scale, Nurick Scale, Neck Disability Index, and Short-Form-36v2. Preoperative and 12- and 24-month postoperative outcomes were compared using mixed-model analysis of covariance for repeated measurements.

RESULTS

The study cohort consisted of 310 males and 169 females, with a mean age of 56.37 ± 11.91 years. There were significant differences in age, etiology, and surgical approaches between the regions. At 24 months postoperatively, the mean modified Japanese Orthopaedic Assessment Scale score improved from 12.50 (95% confidence interval [CI], 12.24-12.76) to 14.90 (95% CI, 14.64-15.16); the Neck Disability Index improved from 36.38 (95% CI, 34.33-38.43) to 23.20 (95% CI, 21.24-25.15); and the SF36v2 Physical Component Score and Mental Composite Score improved from 34.28 (95% CI, 33.46-35.10) to 40.76 (95% CI, 39.71-41.81) and 39.45 (95% CI, 38.25-40.64) to 46.24 (95% CI, 44.94-47.55), respectively. The rate of neurological complications was 3.13%.

CONCLUSION

Surgical decompression for CSM is safe and results in improved functional status and quality of life in patients around the world, irrespective of differences in medical systems and sociocultural determinants of health.

LEVEL OF EVIDENCE

3.

Degenerative Cervical Myelopathy: Epidemiology, Genetics, and Pathogenesis

STUDY DESIGN

Review.

OBJECTIVE

To formally introduce "degenerative cervical myelopathy" (DCM) as the overarching term to describe the various degenerative conditions of the cervical spine that cause myelopathy. Herein, the epidemiology, pathogenesis, and genetics of conditions falling under this hypernym are carefully described.

SUMMARY OF BACKGROUND DATA

Nontraumatic, degenerative forms of cervical myelopathy represent the commonest cause of spinal cord impairment in adults and include cervical spondylotic myelopathy, ossification of the posterior longitudinal ligament, ossification of the ligamentum flavum, and degenerative disc disease. Unfortunately, there is neither a specific term nor a specific diagnostic International Classification of Diseases, Tenth Revision code to describe this collection of clinical entities. This has resulted in the inconsistent use of diagnostic terms when referring to patients with myelopathy due to degenerative disease of the cervical spine.

METHODS

Narrative review.

RESULTS

The incidence and prevalence of myelopathy due to degeneration of the spine are estimated at a minimum of 41 and 605 per million in North America, respectively. Incidence of cervical spondylotic myelopathy-related hospitalizations has been estimated at 4.04/100,000 person-years, and surgical rates seem to be rising. Pathophysiologically, myelopathy results from static compression, spinal malalignment leading to altered cord tension and vascular supply, and dynamic injury mechanisms. Occupational hazards, including transportation of goods by weight bearing on top of the head, and other risk factors may accelerate DCM development. Potential genetic factors include those related to MMP-2 and collagen IX for degenerative disc disease, and collagen VI and XI for ossification of the posterior longitudinal ligament. In addition, congenital anomalies including spinal stenosis, Down syndrome, and Klippel-Feil syndrome may predispose to the development of DCM.

CONCLUSION

Although DCMs can present as separate diagnostic entities, they are highly interrelated, frequently manifest concomitantly, present similarly from a clinical standpoint, and seem to be in part a response to compensate and improve stability due to progressive age and wear of the cervical spine. The use of the term "degenerative cervical myelopathy" is advocated.

LEVEL OF EVIDENCE

5.

Surgical outcome in patients with cervical ossified posterior longitudinal ligament: A single institutional experience

OBJECTIVE

Ossification of the posterior longitudinal ligament (OPLL) is a complex multi-factorial disease process having both metabolic and biomechanical factors. The role of surgical intervention as well as the choice of approach weather anterior or posterior is ambiguous. The objective of this study was to assess the surgical out come and post operative functional improvement in patients with cervical OPLL at a tertiary care centre.

PATIENTS AND METHODS

This prospective study included 63 patients of cervical OPLL who underwent either anterior and/or posterior surgeries in Department of Neurosurgery, Nizam's Institute of Medical Sciences, Hyderabad between June 2009 to May 2011. Patient's data including age, sex, pre and post operative functional status, radiographic findings and OPLL subtypes were recorded and analyzed over a follow up ranging up to minimum two years.

RESULTS

The mean age of the patients was 51.1 (range 30-80 years) involving 14 women and 49 men. Out of 63 patients, 14 patients underwent surgery by anterior approach (corpectomy and fusion) and all of them improved (P = 0.52). 49 patients underwent surgery by posterior approach where decompressive laminectomy was performed in 40, laminectomy with instrumentation was done in 5, laminoplasty was done in 3 and 1 patient underwent both anterior and posterior surgeries. Of those who underwent posterior surgery, 40 patients improved, 7 remained the same as their preoperative status (who were having signal intensity changes on T2W MRI) and 2 patients deteriorated in the immediate post operative period and then showed gradual improvement. All the patients were followed up for 24 months. The mean pre-operative Nurick grade was 2.82 which later on improved to 2.03 post surgery (P < 0.05). Minor complications included wound infections in two patients (1.26%).

CONCLUSIONS

Anterior cervical decompression and reconstruction is a safe and appropriate treatment for cervical spondylitic myelopathy in the setting of single or two level OPLL. Laminectomy or laminoplasty is indicated in patients with preserved cervical lordosis having three or more levels of involvement. Younger patients with good pre operative functional status and less than 2 levels of involvement have better outcome following anterior surgery.

Does ossification of the posterior longitudinal ligament progress after laminoplasty? Radiographic and clinical evidence of ossification of the posterior longitudinal ligament lesion growth and the risk factors for late neurologic deterioration

Ossification of the posterior longitudinal ligament (OPLL) is a disease process characterized by progressive growth and calcification resulting in spinal canal compromise and serious neurological sequelae in advanced cases. Historically, OPLL has most commonly been treated with posterior surgical decompression. Although this procedure indirectly decompresses the spinal cord, it does not address the offending pathological entity, and further growth of the lesion may result in delayed neurological deterioration. This fact is particularly relevant because a number of long-term studies have revealed both longitudinal and transverse disease progression in individuals treated both surgically and conservatively. Despite these high rates of radiographically documented progression, however, the rate of neurological decline in patients undergoing posterior surgery with laminoplasty is low. In this article, the authors review the pathophysiology of OPLL, evidence of disease progression, and outcome data addressing conservative and surgical treatments.

Conservative management of ossification of the posterior longitudinal ligament. A review

OBJECT

Ossification of the posterior longitudinal ligament (OPLL) can result in significant myelopathy. Surgical treatment for OPLL has been extensively documented in the literature, but less data exist on conservative management of this condition.

METHODS

The authors conducted a systematic review to identify all reported cases of OPLL that were conservatively managed without surgery.

RESULTS

The review yielded 11 published studies reporting on a total of 480 patients (range per study 1-359 patients) over a mean follow-up period of 14.6 years (range 0.4-26 years). Of these 480 patients, 348 (72.5%) were without myelopathy on initial presentation, whereas 76 patients (15.8%) had signs of myelopathy; in 56 cases (15.8%), the presence of myelopathy was not specified. The mean aggregate Japanese Orthopaedic Association score on presentation for 111 patients was 15.3. Data available for 330 patients who initially presented without myelopathy showed progression to myelopathy in 55 (16.7%), whereas the other 275 (83.3%) remained progression free. In the 76 patients presenting with myelopathy, 37 (48.7%) showed clinical progression, whereas 39 (51.5%) remained clinically unchanged or improved.

CONCLUSIONS

Patients who present without myelopathy have a high chance of remaining progression free. Those who already have signs of myelopathy at presentation may benefit from surgery due to a higher rate of progression over continued follow-up.

Diffuse Idiopathic Skeletal Hyperostosis (DISH)-A Rare Etiology of Dysphagia

A 72-year-old gentleman presented to the hospital with progressively worsening dysphagia to soft foods and liquids. He was diagnosed with severe pharyngeal dysphagia by modified barium swallow. A CT scan of the neck with IV contrast showed anterior flowing of bridging osteophytes from C3–C6, indicative of DISH, resulting in esophageal impingement. He underwent resection of the DISH segments. Following the surgery, a PEG tube for nutrition supplementation was placed. However, the PEG tube was removed after five months when the speech and swallow evaluation showed no residual dysphagia. DISH is a rare non-inflammatory condition that results in pathological ossification and calcification of the anterolateral spinal ligaments.

Advanced Ossification of the Posterior Longitudinal Ligament in a Mildly Symptomatic Patient

We describe the imaging findings of a man who developed neurologic symptoms due to ossification of the posterior longitudinal ligament with narrowing of the spinal canal and compression of the spinal cord. CT study allowed a detailed evaluation of the stenosis and the extension of the ossification while MRI gave an excellent visualization of the spinal lesions caused by spinal cord compression by the mass. The neurological status of patients with ossification of the posterior longitudinal ligament depends on many factors such as the degree of spinal canal stenosis, life style, accidental mechanical stress and trauma.

Ossification of the posterior longitudinal ligament in a Nigerian woman

Ossification of the posterior longitudinal ligament (OPLL), though commonly reported among the Japanese population, has however been infrequently reported among other racial groups. It has not been reported among black Africans. A case of OPLL of the cervical spine seen in a 62-year-old Nigerian woman is hereby reported.

P2Y1 transient overexpression induced mineralization in spinal ligament cells derived from patients with ossification of the posterior longitudinal ligament of the cervical spine

Ossification of the posterior longitudinal ligament of the spine (OPLL) is characterized by ectopic bone formation in the spinal ligaments. We previously reported that P2 purinoceptor Y1 (P2Y1) expression is elevated in the spinal ligament cells of OPLL patients, but the role of P2Y1 in the spinal ligament calcification process is unknown. To verify the hypothesis that P2Y1 expression causes ossification of the spinal ligaments, we forced expression of P2Y1 in spinal ligament cells obtained from OPLL and non-OPLL patients using a cytomegaloviral vector. The expression of mRNA and protein was investigated by quantitative real-time polymerase chain reaction and immunofluorescence staining, respectively. After transfection, bone morphogenetic protein-2 (BMP-2) and Sox9 mRNA expression was significantly increased in spinal ligament cells derived from OPLL patients (4.36- and 6.44-fold, respectively) compared with cells from non-OPLL patients (0.57- and 3.64-fold, respectively) 2 days after P2Y1 transient transfection. Furthermore, a statistically significant correlation was observed between BMP-2 and P2Y1 mRNA expression levels in cells obtained from OPLL patients but not from non-OPLL patients. Immunofluorescence analysis showed that BMP-2 and P2Y1 expression was increased in OPLL patients only, while Sox9 expression was increased in OPLL and non-OPLL patients. MRS2279, a selective P2Y1 antagonist, blocked the upregulation of Sox9 and BMP-2 after forced expression of P2Y1. Furthermore, 4 days after transient transfection of P2Y1, mineralization was observed only in spinal ligament cells from OPLL patients. These results suggest that P2Y1 expression plays an important role in ectopic bone formation in the spinal ligaments of OPLL patients.

Ossification of the posterior longitudinal ligament in non-Asians: demographic, clinical, and radiographic findings in 43 patients

Object

Ossification of the posterior longitudinal ligament (OPLL) is a disorder afflicting as many as 2% of East Asians. However, reports of OPLL in non-Asians have been sporadic in the medical literature. This study describes clinical and radiographic findings with OPLL in non-Asians at a tertiary care center treating a diverse multiethnic population.

Methods

Over a 6-year period, 43 patients not of East Asian descent presented to an urban tertiary medical center with OPLL. Patient data, including ethnicity, spinal cord function, Nurick grade, radiographic findings, OPLL subtype, and degree of cervical stenosis, were recorded.

Results

The average patient age was 59 years (range 32–92 years) with 18 women and 25 men. There were 22 Caucasian patients, 17 Hispanic patients, and 4 Black patients. With respect to the radiographic findings, OPLL morphology was continuous in 19, segmental in 17, mixed in 6, and other in 1. Average canal diameter was 7.6 mm (range 4.2–9.0 mm) at the most stenotic points. The mean Nurick grade was 2.95 at presentation, but 7 of the patients had OPLL identified incidentally and with early or minimal symptoms and signs of myelopathy.

Conclusions

Ossification of the posterior longitudinal ligament in non-Asians demonstrates similar demographic and radiographic characteristics as in East Asians. The representation of different ethnic groups mirrors the demographics of the medical center population in general, showing no specific predilection for particular ethnic groups. Surgical decompression in appropriately selected patients results in similar rates of improvement when compared with the Japanese literature.

Association of toll-like receptor 5 gene polymorphism with susceptibility to ossification of the posterior longitudinal ligament of the spine in korean population

OBJECTIVE

Ossification of the posterior longitudinal ligament (OPLL) has a strong genetic component. Specific gene polymorphisms may be associated with OPLL in several genes which regulate calcification in chondrocytes, change of extracellular collagen matrix and secretions of many growth factors and cytokines controlling bone morphogenesis. Toll-like receptor 5 (TLR5) may play a role in the pathogenesis of OPLL by intermediate nuclear factor-kappa B (NF-κB). The current study focused on coding single nucleotide polymorphisms (SNPs) of TLR5 for a case-control study investigating the relationship between TLR5 and OPLL in a Korean population.

METHODS

A total of 166 patients with OPLL and 231 controls were recruited for a case-control association study investigating the relationship between SNPs of TLR5 gene and OPLL. Four SNPs were genotyped by direct sequencing (rs5744168, rs5744169, rs2072493, and rs5744174). SNP data were analyzed using the SNPStats, SNPAnalyzer, Haploview, and Helixtree programs. Multiple logistic regression analysis with adjustment for age and gender was performed to calculate an odds ratio (OR).

RESULTS

None of SNPs were associated with OPLL in three alternative models (codominant, dominant, and recessive models; p > 0.05). A strong linkage disequilibrium block, including all 4 SNPs, was constructed using the Gabriel method. No haplotype was significantly associated with OPLL in three alternative models.

CONCLUSION

These results suggest that Toll-like receptor 5 gene may not be associated with ossification of the posterior longitudinal ligament risk in Korean population.

Ossification of the posterior longitudinal ligament of the cervical spine

Although ossification of the posterior longitudinal ligament (OPLL) of the cervical spine is an uncommon condition, its strong prevalence among the Japanese and non-Japanese Asians is well known. Genetic predisposition coupled with ageing and an imbalance in bone-seeking hormones are some actiological factors postulated in recent years. Imaging is directed at showing the calcified mass, cord compression and any attendant damage, as the latter are important prognostic factors. We describe 6 cases of OPLL of the cervical spine seen at Westmead Hospital between 1979 and 1994. Of the 4 patients presenting with disabling compressive myelopathy, 3 made significant recovery following surgical decompression. Characteristic plain film features manifesting as a dense calcified linear structure along the course of the posterior longitudinal ligament (PLL) were present in 5 patients, including 1 who was asymptomatic. Computed tomography (CT) was invaluable in demonstrating the full extent of the disease in all 5 symptomatic patients. Magnetic resonance imaging (MRI) was helpful in excluding myelomalacia in 2 patients prior to successful surgery. The myelopathy caused by cervical OPLL remains rare, affecting mainly middle aged males of Asiatic and European extraction.

Cervical myelopathy by C1 posterior tubercle impingement in a patient with DISH

STUDY DESIGN

A unique case of a patient with diffuse idiopathic skeletal hyperostosis (DISH) associated with C1 posterior tubercle impingement resulting in spinal canal stenosis and cervical myelopathy.

OBJECTIVE

To describe an uncommon mechanism of spinal cord compression in patient with DISH.

SUMMARY OF BACKGROUND DATA

The neurologic deficits due to cervical DISH are relatively rare and a few cases of cervical spinal cord compression due to atlantoaxial subluxation, odontoid fracture, pseudotumor, ligamentous hypertrophy, and basilar impression have been reported. To the best of our knowledge, there has been no other report of a patient with DISH causing C1 posterior tubercle impingement and cervical myelopathy.

METHODS

A 75-year-old Japanese man, first diagnosed as hyperostosis of anterior and posterior longitudinal ligament 25 years ago, presented with gradual progression of numbness in both lower extremities, disturbed precise hand motion and urinary function. DISH, OPLL, and C1 posterior tubercle impingement was diagnosed by radiograph, CT, and MRI. Hyperintense signal in the C1 spinal cord on T2 weighted sequence was observed.

RESULT

Laminectomy from C1-C3 was performed. Myelocompression and myelopathy improved after the surgical intervention. Multilevel fusion of the subaxial cervical spine and increase of the mechanical stress on the craniocervical segment may leads to partial damage of the ligaments and resulted in C1 posterior arch impingement.

CONCLUSION

This is the first report of unique C1 posterior tubercle impingement and myelopathy caused by DISH. We should keep it in mind that DISH can cause serious problems in the upper cervical spine even after 25 years of interval.

FokI variant of vitamin D receptor gene and factors related to atherosclerosis associated with ossification of the posterior longitudinal ligament of the spine: a multi-hospital case-control study

STUDY DESIGN

A sex- and age-matched case-control study with genotyping of the FokI variant of the vitamin D receptor gene (VDR) was carried out.

OBJECTIVES

To facilitate the early prediction, prevention, and treatment of ossification of the posterior longitudinal ligament (OPLL) of the spine, we analyzed the FokI variant of VDR and past body mass indexes, histories of past illness, family history, and body pliability along with lifestyle factors.

SUMMARY OF BACKGROUND DATA

Many possible genetic and environmental risk factors for OPLL have been suggested, including male sex, high body mass index, diabetes mellitus, trauma, hormonal imbalance, and dietary and sleeping habits and genetic variants.

METHODS

Both a self-administered questionnaire and whole blood samples were obtained from 63 patients with OPLL and 126 sex-, age-, and hospital-matched controls free of backbone diseases were randomly selected from hospital patients. VDR genotyping was carried out using PCR-RFLP methods. After univariate analysis, multivariate and subgroup analyses according to the VDR genotype was applied to clarify the confounding relationship between VDR genotype and other possible risk factors.

RESULTS

A multivariate analysis revealed that the VDR FF genotype, family history of myocardial infarction, high body mass index at age 40, long working hours, and working with night shift to be independent potent risk factors for OPLL.

CONCLUSION

The risk of developing OPLL may possibly be reduced gradually and effectively by removing or minimizing the effect of such lifestyle factors one at a time through targeted preventive intervention.

Open-door Laminoplasty With Suture Anchor Fixation for Cervical Myelopathy in Ossification of the Posterior Longitudinal Ligament

Expansive laminoplasty was developed to achieve posterior spinal cord decompression while preserving cervical spine stability. In the classic Hirabayashi procedure, the lamina door is tethered open by sutures between the spinous process and facet capsule or paravertebral muscle. The authors present a modified technique, which enhances secure fixation and prevents restenosis owing to hinge closure. Twenty-seven patients (7 females, 20 males) with cervical myelopathy secondary to ossification of the posterior longitudinal ligament were enrolled. Each patient underwent unilateral open-door laminoplasty with suture anchor fixation. Tying and fixation of the sutures onto the holed lateral mass screws was used instead of the conventional method. Radiography, magnetic resonance imaging, and computed tomography scanning were used for imaging studies. The Nurick score was used to assess myelopathy severity, whereas the Japanese Orthopedic Association score was adopted to compare clinical outcome before and after surgery. Mean follow-up period was 38 months (range, 18 to 60). Ten patients had 5 levels of decompression (C3-7), and 17 patients had 4 (C3-6, 12 patients; C4-7, 5 patients). All patients experienced functional improvement of at least 1 Nurick score after surgery. The Japanese Orthopedic Association score increased significantly from 7.5+/-3.2 before surgery to 13.2+/-1.6 at final follow-up. Postoperative radiography and computed tomography scan demonstrated significantly increased sagittal diameter and canal expansion. No neurologic deterioration owing to hinge reclosure or major surgery-related complications were observed. In conclusion, unilateral open-door laminoplasty with suture anchor fixation effectively maintains expansion of the spinal canal and resists closure while preserving alignment and stability. This modified technique has a low complication rate and provides marked functional improvement in patients with cervical myelopathy owing to ossification of the posterior longitudinal ligament.

Pathophysiology of cervical myelopathy

BACKGROUND CONTENT

Cervical myelopathy is a group of closely related disorders usually caused by spondylosis or by ossification of the posterior longitudinal ligament and is characterized by compression of the cervical spinal cord or nerve roots by varying degrees and number of levels. The decrease in diameter of the vertebral canal secondary to disc degeneration and osteophytic spurs compresses the spinal cord and nerve roots at one or several levels, producing direct damage and often secondary ischemic changes.

PURPOSE

Clinicians who treat cervical myelopathy cord injuries should have a basic understanding of the pathophysiology and the processes that are initiated after the spinal cord has been injured.

STUDY DESIGN/SETTING

Literature review.

METHODS

Literature review of human cervical myelopathy and clinically relevant animal models to further our understanding of the pathological mechanisms involved.

RESULTS

The pathophysiology of cervical myelopathy involves static factors, which result in acquired or developmental stenosis of the cervical canal and dynamic factors, which involve repetitive injury to the cervical cord. These mechanical factors in turn result in direct injury to neurons and glia as well as a secondary cascade of events including ischemia, excitotoxicity, and apoptosis; a pathobiology similar to that occurring in traumatic spinal cord injury.

CONCLUSIONS

This review summarizes some of the significant pathophysiological processes involved in cervical myelopathy.

Current Topics in Pharmacological Research on Bone Metabolism: Molecular Basis of Ectopic Bone Formation Induced by Mechanical Stress

Ectopic bone formation (EBF) is frequently found in various tissues and affects the prognosis of diseases accompanied by EBF. Although the mechanism of EBF remains unclear, several local factors that influence the progression of EBF have been proposed. We have been focusing on the role of mechanical stress as a local factor in EBF in spinal ligament tissues, that is, ossification of the posterior longitudinal ligament (OPLL), which causes serious neurological deficiencies. Transcriptome analyses revealed that the expressions of several marker genes related to bone remodeling were enhanced after exposure of ligament cells derived from OPLL patients (OPLL cells) to cyclic stretching as a type of mechanical stress. However, no significant alterations in gene expressions were detected after cyclic stretching of ligament cells derived from non-OPLL patients. OPLL cells exposed to cyclic stretching released several autocrine/paracrine factors that are known to mediate bone remodeling. These results suggest that OPLL cells have been transformed into cells that are highly sensitive to mechanical stress, which may induce the progression of OPLL. These observations provide information regarding the role of mechanical stress in the process of EBF.

Cervical cord compression secondary to ossification of the posterior longitudinal ligament

STUDY DESIGN

Resident's case problem.

BACKGROUND

A 52-year-old Chinese male with a 10-year history of gradually worsening right hip stiffness, weakness, and pain was referred to physical therapy by his orthopedist, who made a diagnosis of developmental dysplasia of the right hip, with possible Legg-Calve-Perthes disease. The patient reported multiple falls over the last several years and a gradual onset of low back pain with an onset of "electricity" down both legs. The patient also reported mild numbness in both forearms and the right hand over the previous several months. This resident's case problem illustrates how a physical therapist recognized the presence of an atypical musculoskeletal pathology through the use of hypothesis-driven clinical reasoning and detailed physical examination.

DIAGNOSIS

Examination of the patient's lumbar and cervical spine and hips revealed joint dysfunctions. Neurological testing revealed hyperreflexia. Special testing revealed lower extremity clonus with a positive Babinski sign with gait disturbances. The patient was referred back to his primary physician and then to a neurologist and neurosurgeon. An MRI revealed cervical myelopathy due to ossification of the posterior longitudinal ligament from C3/C4 to C5/C6. The patient then underwent a C3 through C7 laminectomy.

DISCUSSION

It is always imperative that sound clinical reasoning be used when performing physical therapy evaluations, regardless of the referral status of the patient. Patients with nonmusculoskeletal pathology may seek physical therapy services and it is the physical therapist's responsibility to complete a thorough examination and refer to specialists when appropriate.

COL6A1, the candidate gene for ossification of the posterior longitudinal ligament, is associated with diffuse idiopathic skeletal hyperostosis in Japanese

STUDY DESIGN

Genetic screening of collagen 6A1 gene (COL6A1) in patients with diffuse idiopathic skeletal hyperostosis (DISH) recruited in Japan and the Czech Republic.

OBJECTIVE

To investigate allelic associations between DISH and nucleotide variants of COL6A1.

SUMMARY OF BACKGROUND DATA

DISH is a skeletal hyperostotic disease characterized by ligamentous ossification of the anterolateral side of the spine. Ossification of the posterior longitudinal ligament (OPLL) is a related disorder with DISH, and COL6A1 was identified as a susceptibility gene to OPLL. COL6A1 was examined for susceptibility in DISH patients from Japan and the Czech Republic.

METHODS

Seven single nucleotide polymorphisms of COL6A1 were genotyped by direct sequencing. The allele frequencies were compared between 97 Japanese DISH patients and 298 Japanese controls, and between 96 Czech DISH patients and 96 Czech controls by chi2 test.

RESULTS

The intron 32 (-29) single nucleotide polymorphisms of COL6A1 was significantly associated with the Japanese DISH patients (chi2 = 9.33; P = 0.0022), but not with the Czech DISH patients.

CONCLUSIONS

Because COL6A1 could be a susceptibility to the occurrence of DISH and OPLL in the Japanese population, we consider that COL6A1 could be responsible for the hyperostotic state, leading to ectopic bone formation in the spinal ligament.

Choking, sore throat with referred otalgia and dysphagia in a patient with diffuse idiopathic skeletal hyperostosis (DISH)

A patient with a progressively increasing immobilisation of the cervical spine, severe impaired swallowing (choking), sore throat with referred right-sided otalgia, mild voice disorder and dysphagia due to extrinsic bone compression of the posterior hypopharyngeal wall and oesophagus is presented. Radiographic investigation demonstrated the underlying condition to be a diffuse idiopathic skeletal hyperostosis with prominent and bumpy alteration of the anterior longitudinal ligament impinging the hypopharynx. Via an anterolateral approach towards the cervical spine the anterior irregular part of the ossification was removed and the surface of the spine flattened. The postoperative evolution was uneventful.

Genomewide linkage and linkage disequilibrium analyses identify COL6A1, on chromosome 21, as the locus for ossification of the posterior longitudinal ligament of the spine

Ossification of the posterior longitudinal ligament (OPLL) of the spine is a subset of "bone-forming" diseases, characterized by ectopic ossification in the spinal ligaments. OPLL is a common disorder among elderly populations in eastern Asia and is the leading cause of spinal myelopathy in Japan. We performed a genomewide linkage study with 142 affected sib pairs, to identify genetic loci related to OPLL. In multipoint linkage analysis using GENEHUNTER-PLUS, evidence of linkage to OPLL was detected on chromosomes 1p, 6p, 11q, 14q, 16q, and 21q. The best evidence of linkage was detected near D21S1903 on chromosome 21q22.3 (maximum Zlr=3.97); therefore, the linkage region was extensively investigated for linkage disequilibrium with single-nucleotide polymorphisms (SNPs) covering 20 Mb. One hundred fifty positional candidate genes lie in the region, and 600 gene-based SNPs were genotyped. There were positive allelic associations with seven genes (P<.01) in 280 patients and 210 controls, and four of the seven genes were clustered within a region of 750 kb, approximately 1.2 Mb telomeric to D21S1903. Extensive linkage disequilibrium and association studies of the four genes indicated that SNPs in the collagen 6A1 gene (COL6A1) were strongly associated with OPLL (P=.000003 for the SNP in intron 32 [-29]). Haplotype analysis with three SNPs in COL6A1 gave a single-point P value of.0000007. Identification of the locus of susceptibility to OPLL by genomewide linkage and linkage disequilibrium studies permits us to investigate the pathogenesis of the disease, which may lead to the development of novel therapeutic tools.

Clinical manifestations of diffuse idiopathic skeletal hyperostosis of the cervical spine

OBJECTIVES

To describe the clinical manifestations and the complications of cervical spine (C-spine) involvement in diffuse idiopathic skeletal hyperostosis (DISH).

METHODS

Two patients, who presented with dysphagia resulting from large anterior osteophytes of the C-spine, were diagnosed as having DISH. A Medline search from 1964 to present, using the terms "diffuse idiopathic skeletal hyperostosis" and "cervical spine," identified several clinical manifestations associated with DISH.

RESULTS

Two groups of conditions associated with DISH were found. 1. Spontaneous complications such as: dysphagia, being the commonest, dyspnea, stridor, myelopathy associated with ossification of the posterior longitudinal ligament (OPLL) or with atlanto-axial pseudoarthrosis or subluxation. Other rare events were aspiration pneumonia, sleep apnea and thoracic outlet syndrome. 2. Provoked complications such as endoscopic and intubation difficulties and fractures of the C-spine with frequent transverse shift of the fractured segment and resultant myelopathy.

CONCLUSIONS

C-spine involvement in DISH is a recognized cause of various clinical manifestations involving the pharynx, larynx and the esophagus. Prior knowledge of the existence of cervical DISH should alert the clinicians for possible complications, at times severe, during invasive procedures in the neck region and as a consequence of trauma.

Anterior decompression for cervical spondylosis associated with an early form of cervical ossification of the posterior longitudinal ligament

Object

The goal of this study was to determine the appropriate surgical strategy for cervical spondylosis associated with an early form of ossification of the posterior longitudinal ligament (EOPLL) of the cervical spine.

Methods

Patients with EOPLL-associated cervical spondyosis were selected for treatment. Medical records and radiographs were retrospectively reviewed. Specimens taken at the time of operation were histologically examined. There were 24 men and six women ranging in age from 39 to 74 years (mean 57.6 years). Symptoms consisted of myelopathy in 28 cases and radiculopathy in two cases. Anterior decompressive surgery was performed. The EOPLL, hypertrophy of the posterior longitudinal ligament (HPLL), and the disc–PLL complex were directly resected. The mean preoperative Japan Orthopaedic Association score was 12.6, and the mean postoperative score was 14.4. Histologically, EOPLL was consistent with foci of compact lamellar bone in the degenerative thickening of the PLL.

Conclusions

Appropriate corpectomy should follow direct removal of EOPLL associated with HPLL compressing the spinal cord to achieve good outcomes.

Functional impact of human collagen alpha2(XI) gene polymorphism in pathogenesis of ossification of the posterior longitudinal ligament of the spine

Ossification of the posterior longitudinal ligament (OPLL) of the spine is the leading cause of myelopathy in Japan. In earlier studies, we provided genetic linkage and allelic association evidence of distinct differences in the human collagen alpha2(XI) gene (COL11A2) that might constitute inherited predisposition to OPLL. In the present study, a strong allelic association with non-OPLL (p = 0.0003) was observed with an intron 6 polymorphism [intron 6 (-4A)], in which the intron 6 (-4A) allele is more frequently observed in non-OPLL subjects than in OPLL patients. In addition, a newly identified polymorphism in exon 6 [exon 6 (+28A)] was in linkage disequilibrium with the intron 6 (-4A). The functional impact of the polymorphisms was analyzed by comparing the differences in messenger RNA (mRNA) splicing by reverse-transcription polymerase chain reaction (RT-PCR) analysis in cultured cells from the interspinous ligament and an in vitro exon trapping study. The intron 6 (-4A) allele resulted in skipping exon 6 and retaining exon 7, while the exon 6 (+28A) allele was not associated with alteration in mRNA splicing. Similar mRNA species were observed in undifferentiated osteoblast (Ob) cells and in cells from posterior longitudinal ligament of non-OPLL subjects. The region containing exons 6-8 is an acidic subdomain presumably exposed to the surface that could interact with molecules of the extracellular matrix. Accordingly, retaining exon 7 together with removal of exon 6 observed in intron 6 (-4A) could play a protective role in the ectopic ossification process because the same pattern was observed in undifferentiated Ob cells and nonossified posterior longitudinal ligament cells.

Geometric and mechanical properties of human cervical spine ligaments

This study characterized the geometry and mechanical properties of the cervical ligaments from C2-T1 levels. The lengths and cross-sectional areas of the anterior longitudinal ligament, posterior longitudinal ligament, joint capsules, ligamentum flavum, and interspinous ligament were determined from eight human cadavers using cryomicrotomy images. The geometry was defined based on spinal anatomy and its potential use in complex mathematical models. The biomechanical force-deflection, stiffness, energy, stress, and strain data were obtained from 25 cadavers using in situ axial tensile tests. Data were grouped into middle (C2-C5) and lower (C5-T1) cervical levels. Both the geometric length and area of cross section, and the biomechanical properties including the stiffness, stress, strain, energy, and Young's modulus, were presented for each of the five ligaments. In both groups, joint capsules and ligamentum flavum exhibited the highest cross-sectional area (p < 0.005), while the longitudinal ligaments had the highest length measurements. Although not reaching statistical significance, for all ligaments, cross-sectional areas were higher in the C5-T1 than in the C2-C5 group; and lengths were higher in the C2-C5 than in the C5-T1 group with the exception of the flavum (Table 1 in the main text). Force-deflection characteristics (plots) are provided for all ligaments in both groups. Failure strains were higher for the ligaments of the posterior (interspinous ligament, joint capsules, and ligamentum flavum) than the anterior complex (anterior and posterior longitudinal ligaments) in both groups. In contrast, the failure stress and Young's modulus were higher for the anterior and posterior longitudinal ligaments compared to the ligaments of the posterior complex in the two groups. However, similar tendencies in the structural responses (stiffness, energy) were not found in both groups. Researchers attempting to incorporate these data into stress-analysis models can choose the specific parameter(s) based on the complexity of the model used to study the biomechanical behavior of the human cervical spine.

Symptomatic ossification of the posterior longitudinal ligament of the lumbar spine. Case report

The authors report a case of focal ossification of the posterior longitudinal ligament (OPLL) behind the L-3 vertebral body. This is relatively rare among previously reported cases in the literature. Magnetic resonance (MR) imaging revealed that the ossifying portion of the PLL was impinging on the left L-3 nerve root. Contrast enhancing hypertrophic PLL was also demonstrated around the ossification and along the lumbosacral PLL. Via a laminectomy and wide excision of the PLL the lesion was removed. Pathological examination revealed a nodule composed of fibrous cartilage, lamina bone, and mature fat marrow. Enchondral ossification could be identified under a microscope. The authors believe that preoperative MR imaging evaluation is important for the detection of the relationship between an OPLL and the neural structure. Excision of the symptomatic OPLL should be performed when needed to obtain adequate nerve root decompression.

[Ossification of the posterior longitudinal ligament in the cervical spine: case report]

Ossification of the posterior longitudinal ligament (OPLL) is an uncommon cause of compressive myelopathy in the Caucasian population. A case of spastic paraparesis in a Caucasian man whose radiological investigation showed OPLL is presented. The radiographs of the cervical spine showed a strip of bony density posterior to the vertebral bodies, extending from C2 to T1. Computerized tomography (CT) and CT myelography showed OPLL at the same level. Magnetic resonance showed an area of increased signal on T2-weighted sequences at C7-T1 level suggestive of myelomalacia. The patient underwent an open-door laminoplasty (C2 to C7) with improvement of the paraparesis. OPLL should be included in the differential diagnosis of cervical myelopathy. It can be easily detected by plain radiographs and CT of the cervical spine. A review of the clinical and radiological features and the treatment of OPLL is presented.

Ossification of the posterior longitudinal ligament in three geographically and genetically different populations of ankylosing spondylitis and other spondyloarthropathies

STUDY DESIGN

Cross sectional.

RESEARCH QUESTIONS

(a) Is any clinical variable of ankylosing spondylitis (AS) associated with the presence of ossification of the posterior longitudinal ligament (OPLL)? and (b) Is OPLL present in patients with AS from different geographical or genetic backgrounds?

METHODS

Three groups were assembled: (1) a prospective group of 103 consecutive AS patients from two community based rheumatology clinics from Guadalajara, who were evaluated using: a questionnaire with disease characteristics variables; clinical assessment by a neurologist; lateral radiographic views of the cervical spine and somatosensory evoked potentials (SSEP). (2) Fifty one spondyloarthropathies (SpA) patients from Mexico city whose cervical spine films were retrospectively reviewed. (3) Thirty nine AS patients from Edmonton, Canada whose cervical spine films were retrospectively reviewed and compared with 72 controls.

RESULTS

Group 1: 74% of the 103 patients were men and 86% were HLA-B27 positive. The mean age was 35 years, and mean (SD) disease duration 10 (8) years. OPLL was reported in 16 patients (15.5%; 95% CI 9, 22). OPLL was statistically associated with older age (p = 0.001), longer disease duration (p = 0.001), clinical myelopathy (p = 0.03), worst functional index (p = 0.042), restricted axial movement measurements (all p < 0.001), radiological sacroilitis (p < 0.001 for linear association), osteitis pubis (p = 0.009), hip involvement (p = 0.006 for linear association), and abnormal SSEP (p = 0.008). Group 2: 92% of 51 patients were men; the mean age was 30 years and the mean (SD) disease duration 11 (7) years. OPLL was reported in 15 (29%, 95% CI 17, 41) patients (nine AS, two psoriatic arthritis, three juvenile AS, and one Reiter's syndrome). Group 3: 95% of the 39 patients were men; the mean of age was 46 years and disease duration of 18 (10) years. OPLL was reported in nine (23%; 95% CI 10, 36) patients, including one with psoriatic arthritis, and two with Crohn's disease. OPLL was observed in two of the control group.

CONCLUSIONS

The prevalence of OPLL in AS and SpA is higher than previously recognised and seems to be associated with variables identifying more severe axial disease.

Genetic mapping of ossification of the posterior longitudinal ligament of the spine

Ossification of the posterior longitudinal ligament of the spine (OPLL) is recognized as a common disorder among Japanese and throughout Asia. Estimates of its prevalence are in the range of 1. 9%-4.3%. Although its etiology is thought to involve a multiplicity of factors, epidemiological and family studies strongly implicate genetic susceptibility in the pathogenesis of OPLL. In this study we report an identification of a predisposing locus for OPLL, on chromosome 6p, close to the HLA complex. The evidence for this localization is provided by a genetic-linkage study of 91 affected sib pairs from 53 Japanese families. In this sib-pair study, D6S276, a marker lying close to the HLA complex, gives evidence for strongly significant linkage (P = .000006) to the OPLL locus. A candidate gene in the region, that for collagen 11A2, was analyzed for the presence of molecular variants in affected probands. Of 19 distinct variants identified, 4 showed strong statistical associations with OPLL (highest P = .0004). These observations of linkage and association, taken together, show that a genetic locus for OPLL lies close to the HLA region, on chromosome 6p.

Magnetic resonance imaging findings in ossification of the posterior longitudinal ligament of the cervical spine

OBJECT

Because of the lack of magnetic resonance (MR) signal from cortical bones, MR imaging is inadequate for diagnosing ossified lesions in the spinal canal. However, MR imaging provides important information on spinal cord morphology and associated soft-tissue abnormality. The purpose of this study is to determine the role of MR imaging in the diagnosis and treatment of patients with ossification of the posterior longitudinal ligament (OPLL) of the cervical spine.

METHODS

The authors reviewed MR imaging findings in 42 patients with cervical OPLL who were examined with a superconducting MR imaging system. The types of OPLL reviewed included eight cases of continuous, 21 cases of segmental, and 13 cases of the mixed type. All patients were treated surgically either by anterior (26 cases) or posterior decompression (16 cases).

CONCLUSIONS

The T1-weighted images clearly demonstrated the spinal cord deformity caused by OPLL. Associated disc protrusion was found to be present at the maximum compression level in 60% of the patients in this series. The highest incidence of disc protrusion (81%) was found in patients with segmental OPLL. Intramedullary hyperintensity on T2*-weighted imaging was noted in 18 patients (43%). The neurological deficits observed in these 18 patients were significantly more severe than those observed in the other 24 patients. Postoperative MR imaging revealed improvement in the spinal cord deformity, although the intramedullary hyperintensity was still observed in most cases. The present study demonstrates the importance of associated disc protrusion in the development of myelopathy in patients with cervical OPLL. Magnetic resonance imaging findings may be used to help determine the actual levels of spinal cord compression and to suggest the method of surgical treatment.

A controlled study of diffuse idiopathic skeletal hyperostosis. Clinical features and functional status

Diffuse idiopathic skeletal hyperostosis (DISH) is a common but little-studied disorder in the elderly that is infrequently recognized by physicians. Its prevalence in adults over 40 years of age is estimated at 3.8% for men and 2.6% for women. The present case-control study evaluated the history of pain and stiffness, radicular pain and enthesitis, physical findings on the musculoskeletal examination, and level of physical and psychologic disability in 130 persons: 56 patients with DISH, 43 control patients with spondylosis of the lumbar spine, and 31 healthy control patients. DISH patients were more likely to report a past history of upper extremity pain, medial epicondylitis of the elbow, enthesitis of the patella or heel, or dysphagia than spondylosis patients. They had more extremity and spinal stiffness and pain than healthy controls. DISH patients weighed more at a young age and their body mass index was greater at the time of the clinical evaluation than either spondylosis or healthy control patients. On musculoskeletal examination, DISH patients had a greater reduction in neck rotation and thoracic movements than either spondylosis patients or healthy controls, and had a greater reduction in lumbar movement than healthy controls. DISH patients had similar levels of spinal disability and physical disability overall, as measured by standardized indices, as spondylosis patients. No differences were found among the 3 groups of patients for the laboratory tests evaluated. DISH is clearly a distinct disorder with signs and symptoms that distinguish it from other causes of spinal complaint and from healthy individuals. It has the potential to cause major disability. Future studies need to address the natural history of DISH, pursue pathogenic mechanisms, and evaluate treatment modalities.

Neurosurgery at the Montreal Neurological Institute and McGill University Hospitals

For the past 60 years, the Montreal Neurological Institute and Hospital and three associated McGill University teaching hospitals have provided a broad course of instruction in neurosurgery and the related neurosciences. This integrated program offers a wealth of experience in adult and pediatric neurosurgery, based on a total of 140 beds, covering a full range of general and subspecialty neurosurgery. The institute, recognized for many years as a world center for epilepsy surgery, has traditional strengths in the treatment of brain tumors and cerebrovascular and spinal disorders; it has been at the cutting edge of brain imaging in all modalities applied to neurosurgical diagnosis and cerebral localization, including three-dimensional monitoring in the operating room. New approaches to stereotactic procedures have been developed in conjunction with imaging technology, including functional neurosurgery and the versatile McGill double rotation method for radiosurgery with a linear accelerator. Experience in managing trauma, pediatric cases, and general neurosurgical problems is gained at the Montreal General Hospital, the Montreal Children's Hospital, and the Jewish General Hospital. Well-established research units, including burgeoning groups in neurogenetics, molecular neurobiology, and neural regeneration, provide a wide variety of academic opportunities to provide trainees with a sound basis for coping with the rapidly advancing field of neurosurgery.

Ossification of the posterior longitudinal ligament in one of a pair of identical twins concordant for ankylosing spondylitis

A pair of identical twins suffering from ankylosing spondylitis is reported. One brother developed an earlier-onset disease and showed ossification of the posterior longitudinal ligament and the flavum ligament in his cervical spine.