Arnold-Chiari malformation detected by unenhanced multiplanar CT scan

Definition of the adult Chiari malformation: a brief historical overview

With the widespread use of newer neuroimaging techniques and modalities, significant tonsillar herniation is being diagnosed in more than 0.5% of patients, some of whom are asymptomatic. This puts the definition of the adult Chiari malformation to the test. The author provides a historical review of the evolution of the definition of the adult Chiari malformation in the neurosurgery, radiology, and pathology literature.

Apparent cerebellar ectopia: a reappraisal using volumetric MRI

Cerebellar ectopia, once considered rare, is apparently extremely common on magnetic resonance imaging (MRI). However, assessment of cerebellar position relative to the foramen magnum is usually made from thick sagittal sections and therefore may not be as reliable as sometimes believed. Volumetric MRI, acquired in the coronal plane with section thickness 1.5 mm, was used to assess the position of the cerebellum in 144 subjects who also had two-dimensional sagittal imaging using 5.0 mm thick sections. On these images, the frequency of cerebellar ectopia appeared to be 19% (27 cases), but volumetric coronal images indicated that the biventral lobules protruded below the foramen magnum in only 3 (2%), and the cerebellar tonsils lay well above in all cases. Hence the actual frequency of cerebellar tonsillar ectopia in this sample was zero. We concluded that cerebellar ectopia really is rare.

Spontaneous drainage of syringomyelia. Report of two cases

Two cases are reported of Arnold-Chiari type I malformation associated with syringomyelia, in which magnetic resonance (MR) imaging revealed spontaneous decompression of the syrinx. In one case axial MR imaging sections showed a communication between the syrinx and the spinal subarachnoid space, which supports the hypothesis that fissuring of the cord parenchyma is instrumental in the spontaneous resolution of syringomyelia. The MR imaging changes were not accompanied by variations in the patients' clinical course.

Craniocervical junction malformation treated by transoral approach. A survey of 25 cases with emphasis on postoperative instability and outcome

An experience with 25 consecutive cases of craniocervical junction (CCJ) malformations operated upon via the transoral route is reported. Twenty-two patients also underwent posterior occipito-cervical stabilization with alloplastic material and in only one patient was transoral odontoidectomy and fusion with bone autograph performed. Indication for the transoral route consisted of an irreducible ventral compression of the cervicobulbar junction by the abnormal bone complex. Two patients died during the early postoperative period and the remaining 23 survivors were followed for an average of 3.5 years: 17 of these showed marked improvement and 5 a stabilization of the neurological disturbances. A further patient, who refused posterior stabilization, eventually died because of progressive cranial settling. Long-term results have shown this approach to be decisive in the surgical management of well-selected CCJ anomalies.

Arnold-Chiari malformation. Review of 71 cases

The natural history of symptomatic adult Type I Arnold-Chiari malformation (ACM) is variable, and the value of surgery in the management of this disease is difficult to assess. A series of 71 patients in whom a diagnosis of Type I ACM was confirmed at operation is presented, and the progress of the patients following posterior fossa decompression is analyzed. The length of history varied greatly. Pain was the commonest symptom (69% of patients); other symptoms included weakness (56%), numbness (52%), and unsteadiness (40%). The presenting physical signs consisted of a foramen magnum compression syndrome (22%), central cord syndrome (65%), or a cerebellar syndrome (11%). Myelography was performed in 69 patients, and was the most useful investigation. Only 23% of plain radiographs were abnormal. In addition to tonsillar descent, the operative findings included arachnoid adhesions (41%) and syringomyelia (32%). All patients underwent suboccipital craniectomy and C1-3 laminectomy. Respiratory depression was the most frequent postoperative complication (14%), and one patient died from sleep apnea. Early postoperative improvement of both symptoms (82%) and signs (70%) was followed by later relapse in 21% of patients, showing an initial benefit following surgery. None of the patients with a cerebellar syndrome deteriorated, whereas 56% of patients with evidence of foramen magnum compression and 66% of those with a central cord syndrome maintained their initial improvement. The authors conclude that posterior fossa decompression appears to benefit some patients, although a significant proportion might be expected to relapse within 2 to 3 years after operation, depending upon the presenting syndrome.

Craniovertebral junction malformations. Clinicoradiological findings, long-term results, and surgical indications in 63 cases

The fate of a series of 63 patients operated on between 1953 and 1979 was studied retrospectively to assess the efficacy of neurosurgical treatment in relieving symptoms associated with craniovertebral junction (CVJ) malformations. Fifty-eight patients underwent posterior cervicomedullary decompression, and the other five underwent transoral clivus-atlanto-odontoidectomy. Long-term results with the posterior approach showed that 50% of the patients benefited from surgery, 25% remained unchanged, and 25% continued to deteriorate or died. Patients with dorsal nervous tissue and/or meningeal anomalies, such as Arnold-Chiari malformation, hydrosyringomyelia, dural fibrous ring, or obstruction of the cisterna magna, did better than patients with ventral cervicomedullary indentation caused by a clivus-atlanto-odontoid bone complex. Anterior decompression is preferable to a posterior approach only if the CVJ malformation involves a ventral deformity in the absence of dorsal compression by soft tissue.