Simultaneous cerebral and spinal fluid pressure recordings in surgical indications of the Chiari malformation without myelodysplasia.
ABSTRACT Patients with Chiari's malformation without myelodysplasia often suffer from another associated spinal cord lesion--syringomyelia. A condition entirely overriding the clinical picture, affecting adversely the results of surgery as well as the prognosis of this congenital developmental defect. Proceeding from the results of their surgical treatment of 40 patients with hindbrain malformation, the authors recommend, in accordance with the literature, a different approach to and classification of patients depending on the presence of syringomyelia (A/B classification; A: syringomyelia on MR--present, B: absent). The pathological development of the syrinx is caused by obstruction to the natural CSF circulation in the subarachnoid spaces of the craniocervical junction (Williams' dissociation theory). The authors are convinced that routine (static) imaging methods (CT, MR) cannot prove the presence or behaviour of a CSF block, and that they cannot help choose reliably the optimum type of treatment. In contrast, direct measurement (and monitoring) of CSF pressure in different compartments of the CSF pathways (intracranial/intraspinal compartment, i.e., in front of and beyond the suspected block) are a method which can help ascertain with precision the presence and behaviour of a CSF circulatory block, and which also provides dynamic information on such a block during the diurnal rhythm for a period of several days. The authors present the results of a prospective study of 25 patients with hindbrain malformation and describe a technique of parallel monitoring of the two CSF compartments using an adaptation of the Williams method, as well as two different types of dissociation tests designed to prove the presence of a CSF block. CSF flow obstruction was found in 11 patients, in 14 patients it could not be proved. In 8 out of 9 patients with a fully developed syrinx (group A) the block was found as expected. It was, however, diagnosed also in 3 patients until then without any graphic proof of a syrinx (group B). The authors also report on short-term (3-year) results of surgical treatment in patients with rhombencephalic malformation, who had 2 different modes of treatment indicated on the basis of dissociation test results. The advantages and disadvantages are discussed of direct measurement and parallel monitoring of CSF in comparison with radiological methods; emphasis is laid on inevitable radicality in the recanalization of CSF passages in patients with well established CSF blocks.
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ABSTRACT: To investigate overcrowding in the posterior cranial fossa as the pathogenesis of adult-type Chiari malformation, the authors studied the morphology of the brainstem and cerebellum within the posterior cranial fossa (neural structures consisting of the midbrain, pons, cerebellum, and medulla oblongata) as well as the base of the skull while taking into consideration their embryological development. Thirty patients with Chiari malformation and 50 normal control subjects were prospectively studied using neuroimaging. To estimate overcrowding, the authors used a "volume ratio" in which volume of the posterior fossa brain (consisting of the midbrain, pons, cerebellum, and medulla oblongata within the posterior cranial fossa) was placed in a ratio with the volume of the posterior fossa cranium encircled by bony and tentorial structures. Compared to the control group, in the Chiari group there was a significantly larger volume ratio, the two occipital enchondral parts (the exocciput and supraocciput) were significantly smaller, and the tentorium was pronouncedly steeper. There was no significant difference in the posterior fossa brain volume or in the axial lengths of the hindbrain (the brainstem and cerebellum). In six patients with basilar invagination the medulla oblongata was herniated, all three occipital enchondral parts (the basiocciput, exocciput, and supraocciput) were significantly smaller than in the control group, and the volume ratio was significantly larger than that in the Chiari group without basilar invagination. These results suggest that in adult-type Chiari malformation an underdeveloped occipital bone, possibly due to underdevelopment of the occipital somite originating from the paraxial mesoderm, induces overcrowding in the posterior cranial fossa, which contains the normally developed hindbrain. Basilar invagination is associated with a more severe downward herniation of the hindbrain due to the more severely underdeveloped occipital enchondrium, which further exacerbates overcrowding of the posterior cranial fossa.Journal of Neurosurgery 02/1997; 86(1):40-7. · 3.15 Impact Factor
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ABSTRACT: Thirty-five consecutive adults with Chiari malformation and progressive symptoms underwent surgical treatment at a single institution over a 3-year period. All patients underwent magnetic resonance imaging scan before and after surgery. Images of the craniovertebral junction confirmed tonsillar herniation in all cases and allowed the definition of two anatomically distinct categories of the Chiari malformation in this age group. Twenty of the 35 patients had concomitant syringomyelia and were classified as Type A. The remaining 15 patients had evidence of frank herniation of the brain stem below the foramen magnum without evidence of syringomyelia and were labeled Type B. Type A patients had a predominant central cord symptomatology; Type B patients exhibited signs and symptoms of brain stem or cerebellar compression. The principal surgical procedure consisted of decompression of the foramen magnum, opening of the fourth ventricular outlet, and plugging of the obex. Significant improvement in preoperative symptoms and signs was observed in 9 of the 20 patients (45%) with syringomyelia (Type A), as compared to 13 of the 15 patients (87%) without syringomyelia (Type B). Postoperative reduction in syrinx volume was observed in 11 of the 20 patients with syringomyelia, including all 9 patients with excellent results. Magnetic resonance imaging has allowed a classification of the adult Chiari malformation in adults based on objective anatomic criteria, with clinical and prognostic relevance. The presence of syringomyelia implies a less favorable response to surgical intervention.Neurosurgery 06/1991; 28(5):639-45. · 2.53 Impact Factor
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ABSTRACT: The Chiari malformation is a condition characterized by herniation of the posterior fossa contents below the level of the foramen magnum, and is categorized into three types based on the degree of herniation. The authors review their surgical experience between 1975 and 1985 with 50 patients afflicted with symptomatic Chiari malformations. Any patient with associated myelomeningocele, tethered spinal cord, lipoma, or diastematomyelia was excluded from this series. Forty-one patients had Chiari I malformations, seven were classified as having Chiari II, and two as having Chiari III. The presentation of pediatric and adult patients was identical. Treatment was directed at the posterior fossa pathology. Seven patients with accompanying ventral bone compression underwent transoral decompression of the cervicomedullary junction, 42 had posterior decompressive procedures, and six received ventriculoperitoneal shunts. The posterior decompression included opening the outlet foramina of the fourth ventricle, occluding any communication between the spinal cord central canal and the obex, shunting the fourth ventricle, and placing a dural graft. Postoperatively, 20% of the patients are asymptomatic, 66% improved, and 8% stabilized; in 6% the disease has progressed in spite of multiple procedures. Preoperative signs that are predictive of a less favorable outcome include muscle atrophy, symptoms lasting longer than 24 months, ataxia, nystagmus, trigeminal hypesthesia, and dorsal column dysfunction (p less than 0.05, chi-square test). A model based on the presence or absence of atrophy, ataxia, and scoliosis at the time of the preoperative examination has been generated that allows prediction of long-term outcome at the 95% confidence level.Journal of Neurosurgery 09/1989; 71(2):159-68. · 3.15 Impact Factor