Osteogenesis Imperfecta

Specific entities affecting the craniocervical region: osteogenesis imperfecta and related osteochondrodysplasias: medical and surgical management of basilar impression

INTRODUCTION

Osteogenesis imperfecta (OI) is an inheritable disorder of bone development caused by defective collagen synthesis. The attendant basilar impression or secondary basilar invagination is uncommon but can be devastating.

CLINICAL MATERIALS AND METHODS

Fifty-two patients with osteochondrodysplasia (28 with OI, six with Hajdu-Cheney syndrome, six with Paget's disease, and 12 with spondyloepiphyseal dysplasia) with basilar impression were evaluated between 1985 and 2005. The male/female ratio in this cohort was 1:1. The mean age at presentation was 12.2 years.

SYMPTOMS

Symptoms and signs included headache, lower cranial nerve dysfunction, dysphagia, respiratory embarrassment, weakness, and ataxia.

TREATMENT

In the earlier part of the series (1985-1995), all patients with hydrocephalus were shunted and a ventral transoral decompression made for ventral compression of the pontomedullary junction followed by a dorsal occipitocervical fusion. As a result of this evaluation, it was felt that most patients would benefit by early bracing after the hydrocephalus was shunted if it existed. However, 20% of patients still required an anterior ventral decompression and the occipitocervical fusion.

RESULTS

The results showed that the fusions were stable but over a period of time, there was progressive forward bending with osteogenesis imperfecta as well as with the Hajdu-Cheney syndrome. All patients with spondyloepiphyseal dysplasia had a good strong stable fusion which stood the test of time.

CONCLUSION

In conclusion, we feel that early intervention with occipitocervical bracing can prevent the progressive march of significant basilar impression which leads to mortality.

Syndromes with congenital brittle bones

Background

There is no clear definition of osteogenesis imperfecta (OI). The most widely used classification of OI divides the disease in four types, although it has been suggested that there may be at least 12 forms of OI. These forms have been named with numbers, eponyms or descriptive names. Some of these syndromes can actually be considered congenital forms of brittle bones resembling OI (SROI).

Discussion

A review of different syndromes with congenital brittle bones published in the literature is presented. Syndromes are classified in "OI" (those secondary to mutations in the type I pro-collagen genes), and "syndromes resembling OI" (those secondary to mutations other that the type I pro-collagen genes, identified or not). A definition for OI is proposed as a syndrome of congenital brittle bones secondary to mutations in the genes codifying for pro-collagen genes (COL1A1 and COL1A2).

Summary

A debate about the definition of OI and a possible clinical and prognostic classification are warranted.

Bone turnover markers in patients with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a heterologous group of rare inherited bone disorders resulting from defect in collagen synthesis or function. In previous studies, bone turnover has been found either increased or low-normal. These contradictory results might result from the study population made of children with prior recent fractures. We measured serum total and bone alkaline phosphatase (total and bone AP) serum osteocalcin (sOC), serum type I collagen C-telopeptide breakdown products (sCTX), urinary free-deoxypyridinoline (ufDPD), and urinary cross-linked N-telopeptides of type I collagen (uNTX) in 39 male and 38 premenopausal patients with different types of OI aged between 18 and 51 years who had not experienced new clinical fracture during 12 months preceding the laboratory assessment. The study also includes a control group of 29 men and 26 women matched for age and gender. Most bone markers were 50-200% higher in patients than in controls. Only sCTX was comparable to that found in controls. From a sub-analysis of the data, a trend for higher bone resorption markers was observed for any OI type, but patients with OI type III and IV had significantly higher values in ufDPD and uNTX than patients with type I OI, and their sOC levels were not significantly higher than in controls. These results provide a strong rational for the use of anti-resorbing agent in OI.

Intravenous neridronate in adults with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a heritable disease of connective tissue, characterized by increased bone fragility. Bisphosphonates currently seems to be the most promising therapy, at least in children. We tested IV neridronate, an amino-bisphosphonate structurally similar to alendronate and pamidronate in adults with OI. Twenty-three men and 23 premenopausal women with OI were randomized to either iv neridronate (100 mg infused intravenously for 30 minutes every 3 months) or no treatment with a ratio of 2 to 1. Control patients were given the same bisphosphonate therapy at the end of the first year. Clinical evaluation included bone densitometry measurements using dual energy X-ray absorptiometry (DXA), fasting serum and urinary biochemistry every 6 months, and radiographs of the spine taken at baseline and after 12 and 24 months of follow-up. Spine and hip bone mineral density rose by 3.0 +/- 4.6% (SD) and by 4.3 +/- 3.9%, respectively, within the first 12 months of treatment, whereas small insignificant changes were observed in the control group. During the second year of follow-up, additional 3.91% and 1.49% increases were observed at the spine and hip, respectively. Markers of skeletal turnover significantly fell during neridronate treatment. Fracture incidence during neridronate treatment was significantly lower than before therapy and compared with controls. Neridronate iv infusions, administered quarterly, significantly increase bone mineral density and lowered the risk of clinical fracture in adults with OI. Bisphosphonate therapy seems to provide clinical benefits, not only to children with OI, but also to adult patients.

Type V osteogenesis imperfecta: a new form of brittle bone disease

Osteogenesis imperfecta (OI) is commonly subdivided into four clinical types. Among these, OI type IV clearly represents a heterogeneous group of disorders. Here we describe 7 OI patients (3 girls), who would typically be classified as having OI type IV but who can be distinguished from other type IV patients. We propose to call this disease entity OI type V. These children had a history of moderate to severe increased fragility of long bones and vertebral bodies. Four patients had experienced at least one episode of hyperplastic callus formation. The family history was positive for OI in 3 patients, with an autosomal dominant pattern of inheritance. All type V patients had limitations in the range of pronation/supination in one or both forearms, associated with a radiologically apparent calcification of the interosseous membrane. Three patients had anterior dislocation of the radial head. A radiodense metaphyseal band immediately adjacent to the growth plate was a constant feature in growing patients. Lumbar spine bone mineral density was low and similar to age-matched patients with OI type IV. None of the type V patients presented blue sclerae or dentinogenesis imperfecta, but ligamentous laxity was similar to that in patients with OI type IV. Levels of biochemical markers of bone metabolism generally were within the reference range, but serum alkaline phosphatase and urinary collagen type I N-telopeptide excretion increased markedly during periods of active hyperplastic callus formation. Qualitative histology of iliac biopsy specimens showed that lamellae were arranged in an irregular fashion or had a meshlike appearance. Quantitative histomorphometry revealed decreased amounts of cortical and cancellous bone, like in OI type IV. However, in contrast to OI type IV, parameters that reflect remodeling activation on cancellous bone were mostly normal in OI type V, while parameters reflecting bone formation processes in individual remodeling sites were clearly decreased. Mutation screening of the coding regions and exon/intron boundaries of both collagen type I genes did not reveal any mutations affecting glycine codons or splice sites. In conclusion, OI type V is a new form of autosomal dominant OI, which does not appear to be associated with collagen type I mutations. The genetic defect underlying this disease remains to be elucidated.

Basilar invagination in osteogenesis imperfecta and related osteochondrodysplasias: medical and surgical management

Osteogenesis imperfecta (OI) is a heritable disorder of bone development caused by defective collagen synthesis. Basilar invagination is an uncommon but devastating complication of this disease. The authors present a comprehensive strategy for management of craniovertebral anomalies associated with OI and related osteochondrodysplasias. Twenty-five patients with congenital osteochondrodysplasias (18 OI, four Hajdu-Cheney syndrome, and three spondyloepiphyseal dysplasia) and basilar invagination were evaluated between 1985 and 1995. The male/female ratio in this cohort was 1:1. The mean age at presentation was 11.9 years (range 13 months-20 years). Fourteen patients (56%) presented during adolescence (11-15 years of age). Symptoms and signs included headache (76%), lower cranial nerve dysfunction (68%), hyperreflexia (56%), quadriparesis (48%), ataxia (32%), nystagmus (28%), and scoliosis (20%). Four patients (16%) were asymptomatic. Seven (28%) had undergone previous posterior fossa decompression; one had also undergone ventral decompression. Imaging findings included basilar invagination (100%), ventral brainstem compression (84%), hydrocephalus (32%), hindbrain herniation (28%), and syringomyelia/syringobulbia (16%). Patients with hydrocephalus underwent ventricular shunt placement. Reducible basilar invagination (40%) was treated with posterior fossa decompression and occipitocervical fusion. Those with irreducible ventral compression (60%) underwent transoral-transpalatopharyngeal decompression followed by occipitocervical fusion. All patients improved initially. However, basilar invagination progressed radiographically in 80% (symptomatic in 24%) despite successful fusion. Prolonged external orthotic immobilization with the modified Minerva brace afforded symptomatic improvement and arrested progression of the deformity. The mean follow-up period was 5.9 years (range 1.1-10.5 years). Ventral brainstem compression in OI should be treated with ventral decompression, followed by occipitocervical fusion with contoured loop instrumentation to prevent further squamooccipital infolding. Despite fusion, however, basilar invagination tends to progress. Prolonged immobilization (particularly during adolescence) may stabilize symptoms and halt further invagination. This study represents the largest series to date addressing craniovertebral anomalies in OI and related congenital bone softening disorders.

Reflex sympathetic dystrophy syndrome with microtrabecular fracture in a patient with osteogenesis imperfecta

A case of reflex sympathetic dystrophy syndrome (RSDS) in a patient with osteogenesis imperfecta (OI) is reported. We discuss the association of OI, manifested by microfractures of the trabecular bone due to marked bone fragility, and the appearance of RSDS. Magnetic resonance imaging (MRI) was helpful in assessing the presence and extent of the trabecular fractures.

Secondary osteoporosis

Osteoporosis with attendant increased fracture risk is a common complication of many other diseases. Indeed, almost all chronic diseases make some impact on life-style, usually by restricting physical activity and hence reducing the anabolic effect of exercise and gravitational strains on the skeleton. Restricted appetite and modified gastrointestinal tract function is another commonplace finding that has an impact on bone nutrition and synthesis, as on other systems. Sex hormone status is of particular importance for the maintenance of the normal skeleton, and the postmenopausal woman is at particular risk for most causes of secondary osteoporosis. In dealing with secondary osteoporosis in the hypo-oestrogenic woman, the question of giving hormone replacement therapy in addition to other disease-specific therapy should always be considered, as, for example, in a young amenorrhoeic woman with Crohn's disease. Similarly, in hypogonadal men the administration of testosterone is useful for bone conservation. The wider availability of bone densitometry ought to make us more aware of the presence of osteoporosis in the many disease states discussed above. This is particularly important as the life span of such patients is now increased by improved management of the underlying disease process in many instances. Even in steroid-induced osteoporosis--one of the commonest and most severe forms of osteoporosis--we now have some effective therapy in the form of the bisphosphonates and other anti-bone-resorbing drug classes. The possibility of prophylaxis against secondary osteoporosis has therefore become a possibility, although the very long-term effects of such drug regimens are still unknown. In some situations, such as thyrotoxicosis, Cushing's syndrome and immobilization, spontaneous resolution of at least part of the osteoporosis is possible after cure of the underlying problem. The shorter the existence of the basic problem, the more successful the restoration of the skeleton appears to be. A useful credo for clinicians with respect to secondary osteoporosis is: to think of it; to use specific therapy for the underlying disease; to reduce or remove completely any relevant drug or toxic material; to optimize physical activity and general nutrition; to treat hypogonadism if present and feasible; and to consider the use of specific anti-bone-resorbing or other bone active drugs.