Basilar invagination, Chiari malformation, syringomyelia: a review.

Institute and personal experience (over 25 years) of basilar invagination was reviewed. The database of the department included 3300 patients with craniovertebral junction pathology from the year 1951 till date. Patients with basilar invagination were categorized into two groups based on the presence (Group A) or absence (Group B) of clinical and radiological evidence of instability of the craniovertebral junction. Standard radiological parameters described by Chamberlain were used to assess the instability of the craniovertebral junction. The pathogenesis and clinical features in patients with Group A basilar invagination appeared to be related to mechanical instability, whereas it appeared to be secondary to embryonic dysgenesis in patients with Group B basilar invagination. Treatment by facetal distraction and direct lateral mass fixation can result in restoration of craniovertebral and cervical alignment in patients with Group A basilar invagination. Such a treatment can circumvent the need for transoral or posterior fossa decompression surgery. Foramen magnum bone decompression appears to be a rational surgical treatment for patients having Group B basilar invagination. The division of patients with basilar invagination on the basis of presence or absence of instability provides insight into the pathogenesis of the anomaly and a basis for rational surgical treatment.

Basilar invagination: craniocervical instability treated with cervical traction and occipitocervical fixation. Case report.

The upward odontoid displacement observed in basilar invagination (BI) is generally associated with a horizontal clivus and craniocervical kyphosis, conditions that exert ventral compression at the spinomedullary junction. Ventral brainstem decompression by reduction or elimination of the odontoid invagination is part of the desired treatment. The authors describe a case of BI in an adult, who was effectively treated with the easy and safe reduction of odontoid invagination via cervical traction. Normalization of kyphosis at the craniovertebral junction and the vertical position of both a previously horizontal clivus and the cerebellar tentorium demonstrated that these conditions were not part of the original malformation but instead were caused by a reducible craniovertebral instability.

Congenital anomalies of the cervical spine.

There are numerous congenital anomalies of the cervical spine. They can be simple and clinically inconsequential to complex with serious neurologic and structural implications. They can occur in isolation or as one of several maldeveloped organs in the patients. Many are discovered incidentally. The more common anomalies seen by pediatric spine surgeons include defects of the anterior or posterior arches of C1, occipital assimilation of the atlas, basilar invagination or impression, os odontoideum, and Klippel-Feil syndrome. Management begins with a detailed history, physical examination, and imaging studies. In general, those lesions that are causing or have caused neurologic injury, chronic pain, or spinal deformity or place the patient at high risk for developing these require treatment.

Progressive basilar invagination after transoral odontoidectomy: treatment by atlantoaxial facet distraction and craniovertebral realignment.

STUDY DESIGN: The issue of progression of congenital basilar invagination is evaluated on the basis of 3 clinical cases. The rationale of treatment of basilar invagination in general and, particularly, in the complex clinical situation encountered in the presented cases, by the authors' technique of atlantoaxial joint distraction, reduction of basilar invagination, and direct lateral mass plate and screw fixation is discussed. OBJECTIVE: The subject of progression of congenital basilar invagination and recurrent craniocervical cord compression after an initial transoral decompression is analyzed, and an alternative surgical treatment involving craniovertebral bone realignment is suggested. SUMMARY OF BACKGROUND DATA: This is a review of 3 cases of basilar invagination treated earlier by transoral decompression. No fixation procedure was performed. The patients presented with recurrent symptoms of high cervical cord compression. Investigations revealed a progression of basilar invagination and cord compression. The treatment of such a complex clinical situation by atlantoaxial joint distraction is discussed. METHODS: Between September 2001 and January 2004, we treated 3 patients with congenital basilar invagination who underwent transoral odontoidectomy but did not undergo any posterior atlantoaxial or occipitoaxial fixation. The patients had postoperative improvement but worsening of their neurologic condition after an average duration of 26 months after transoral surgery. Repeat investigations revealed that basilar invagination and the craniovertebral alignments worsened during the period, and there was recurrent cervicomedullary cord compression. These patients were treated by atlantoaxial facet distraction, and attempts were made toward reduction of the basilar invagination and craniovertebral junction bony realignment, and atlantoaxial fixation by the technique recently described by us. RESULTS: During the average follow-up of 25 months, all 3 patients have had a neurologic recovery. CONCLUSIONS: The probable cause of basilar invagination and its progression is a congenital malformation ofalignment of the facets of the atlantoaxial joint. Distraction of the facets and direct interarticular atlantoaxial fixation presents a unique opportunity of reduction of the basilar invagination and fixation of the region.

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.

Vertebral artery dissection related to basilar impression: case report.

A 50-year-old man with myelopathy secondary to basilar impression developed bilateral vertebral artery dissection after undergoing treatment with 8 pounds of cervical traction. The vertebral artery dissection resulted in vertebrobasilar insufficiency and posterior circulation stroke. In this report, the current management philosophies in the treatment of basilar impression are discussed, and the pertinent neurovascular anatomy is illustrated. This report suggests that vertebral artery injury may result from attempted reduction of severe basilar impression. Regardless of the cause of cranial settling, the risk of vertebral artery injury with cervical traction should be considered in patients with severe basilar impression.

Malformaciones de la union cranio-cervical / Abnormalities of the cranio-spinal junction

Las malformaciones de la union craneo-cervical, son lesiones poco frecuentes. Su importancia radica en la necesidad de distinguirlas de afecciones neurologicas actualmente clasificadas como enfermedades degenerativas. Se presentan ocho casos. Cuatro con invaginacion basilar uno de ellos con hernia cronica de las amigdalas del cerebelo y cuatro con malformacion de Arnold-Chiari los cuales se diagnosticaron y trataron quirurgicamente. El diagnostico clinico se sospecha en presencia de alteraciones motoras de las cuatro extremidades de caracter progresivo y alteraciones de la sensibilidad principalmente parestesias. En caso de invaginacion basilar, las radiografias simples muestran elevacion de la apofisis odontoides por encima de la linea palato-occipital. En la Malformacion de Arnold-Chiari la mielografia cervical generalmente evidencia la hernia de las amigdalas del cerebelo. El tratamiento en los casos sintomaticos y progresivos consiste en la decompresion quirurgica de la zona afectada.