Surgical technique for cranio-cervical decompression in syringomyelia associated with Chiari type I malformation

Summary Our purpose is to present our results with the surgical treatment of syringomyelia associated with Chiari type I malformation. Between October 1989 and October 1995, twenty-eight patients underwent a sub-occipital craniotomy and a C₁ laminectomy. After dura mater opening the cerebellar tonsils were mobilised. Neither catheter, nor plugging of the obex, nor tonsillar tissue removal was performed. The dura mater was enlarged by means of a wide graft to create a newcisterna magna of adequate size. Postoperative MRI scans showed an ascent of the cerebellum of 4.3±4.8 mm (measured by thefastigium to basal line), as well as of the brainstem (mean migration of the mesencephalon-pons junction of 4.3±3.3 mm). The tonsils emigrated cranially 6.5±4.8 mm. While preoperative mean syringo-cord ratio was 66.3%±13.3, post-operatively was 12.1%±12.7 (p<0.0001). A complete collapse of the syrinx was observed in 39% of the patients. Long-term improvements were obtained in 73% of the cases and 27% were unchanged. No patient got worse. We conclude that in the treatment of syringomyelia associated with Chiari I malformation an artificial cisterma magna of sufficient size must be created. This is achieved by means of an extensive sub-occipital craniotomy and C₁ laminectomy, followed by dural opening. Small bone removal with limited enlargement of theposterior fossa often results in failures of treatment and recurrences. Tonsillar removal is not necessary to obtain a good reconstruction of the cisterma magna.     

Outcome following hindbrain decompression of symptomatic Chiari malformations in children previously treated with myelomeningocele closure and shunts.

Between 1975 and 1989, 25 children treated with myelomeningocele closure and shunting for hydrocephalus at the Children's Hospital of Pittsburgh developed progressive lower brain-stem dysfunction from their Chiari malformation. Retrospective univariate and multivariate analyses of these cases were undertaken to assess the relationship between preoperative clinical factors and postoperative outcome. Since earlier reports have suggested that neonates with symptomatic Chiari malformations show a less favorable response than older children to craniocervical decompression, particular attention was directed at examining the effect of age on preoperative symptoms and postoperative outcome. Patients were subdivided by age into two groups, namely: 13 patients who became symptomatic before 2 months of age (neonatal group) and 12 older infants and children who developed initial symptoms between 6 months and 10 years of age. Once symptoms developed, patients in both groups deteriorated progressively until brain-stem decompression was performed. The mode of presentation and the rate and extent of neurological deterioration differed substantially in the two groups. Whereas the neonates typically showed rapid neurological deterioration and often manifested profound brain-stem dysfunction within a period of several days, the older patients experienced a more insidious symptom progression and rarely demonstrated the severe degree of impairment seen in the neonates. All patients underwent suboccipital craniectomy, cervical laminectomy, and dural decompression. A shunt from the fourth ventricle and/or syrinx to the subarachnoid space was placed in those with significant syringomyelia. Following surgery, 17 patients had complete or nearly complete resolution of all signs of brain-stem compression, three had mild to moderate residual deficits, and five showed no improvement. Outcome correlated closely with the preoperative neurological status. In particular, the presence of bilateral vocal cord paralysis was associated with a poor response to surgery (p < 0.001 on both univariate and multivariate analyses). Of the six patients (all neonates) who progressed to complete bilateral vocal cord paralysis before surgery, only one improved. In contrast, all patients with less profound but nonetheless severe deficits recovered function postoperatively. Although the neonates as a group had a poorer outcome than did the older patients (p = 0.02 on univariate analysis), this in large part reflected their more severe preoperative impairments; neonates who still had some preservation of vocal cord function before surgery subsequently did as well as the older patients. Accordingly, age did not prove to be an independent prognostic factor on multivariate analysis. Taken together, these results indicate that, in most patients with symptomatic Chiari II malformations (including neonates), neurological deficits are potentially reversible if hindbrain decompression is performed expeditiously.     

Cranio-cervical decompression for Chiari I malformation

Summary We report a series of 26 patients affected by a Chiari I malformation treated at our department between 1987 and 1993. All patients underwent pre- and postoperative evaluation by magnetic resonance imaging (MRI). Sequential perioperative motor evoked potential (MEP) recordings were performed in 8 patients. The preoperative symptoms can be divided into four subgroups: cephalgias (84.6%), cranial nerve deficits (69.2%), motor deficits (76.9%), sensory deficits (73%). Twenty-five out of 26 patients underwent craniovertebral decompression, 1 a transoral anterior decompression. One patient died 2 months after surgery because of progressive pulmonary failure. We registered following postoperative complications: transient hypoglossal palsy (1 case), vertigo (2 cases), meningitis (1 case), minor CSF leaks (3 cases). Cephalgias subsided in 17 and improved in 4 out of 22 patients. Cranial nerve deficits improved in 8 and were stabilized in 7 out of 18 patients. A limited recovery of trigeminal function was possibly due to nuclear lesions. Five patients whose vestibular disturbances were not relieved by surgery were put on a course of carbazepine. Vertigo resolved in one case and in two others improved. While hypesthesia improved after decompression, the other sensory deficits were stabilized in 5% of the patients. Spasticity improved in 12 out of 18 patients, but weakness only in 7 out of 17 patients. Motor disturbances ewre always detected by MEP-recording. MEP-characteristics were not specific, resembling those of patients with other intra-, extramedullary myelopathies. Functional recovery was not matched by an improvement of the MEP parameters. MEP may be used as a tool for survellance of patients whose clinical findings are not progressive and are not at first surgical candidates.     

脊柱侧弯并发Chiari畸形的手术治疗

[目的]探讨脊柱侧弯并发Ch iari畸形的诊断和治疗方法。[方法]本组12例脊柱侧弯并发Ch iari畸形的患者,其中有7例同时伴有脊髓空洞症,所有患者均先由神经外科行枕大孔扩大成形术或空洞分流术,二期行脊柱侧弯后路矫形术。[结果]Cobb s角术前平均71,°术后平均24°,矫正率为66%。脊柱矫形术后随访1~4 a,平均2.4 a,没有发生脱钩、断钉及假关节现象;没有出现新的神经损害表现;感觉障碍及腹壁浅反射减弱的症状没有加重。[结论]对于脊柱侧弯并发Ch iari畸形、脊髓空洞症的患者,术前应完善检查、明确诊断;先进行枕大孔扩大成形术或空洞分流术,二期行脊柱侧弯后路矫形术,可以减少脊柱侧弯矫形时引起的神经损害并发症。     

Curve progression in scoliosis associated with Chiari I malformation following suboccipital decompression

Nine children with scoliosis and Chiari I malformations were followed 1-11 years after suboccipital decompression. Eight also had syringomyelia. Despite initial curve stabilization, at final follow-up eight curves were of the magnitude to require spinal fusion. Neither bracing nor secondary neurosurgical procedures arrested progressive curves.     

Management of cerebellar ptosis following craniovertebral decompression for Chiari I malformation

OBJECT: In this report the authors review their experience in the treatment of seven patients with symptomatic cerebellar ptosis following craniovertebral decompression (CVD) for Chiari I malformation. METHODS: The mean age of the patients was 37 years and the average amount of time between the initial suboccipital craniectomy and evaluation for cerebellar ptosis was 6.8 years. Five patients presented primarily with intractable headache and the remaining two patients with neurological deficits caused by recurrent syringomyelia. Three different surgical modalities were used to treat these patients: ventriculoperitoneal shunt placement (one patient), syringoperitoneal shunt placement (two patients), and partial suboccipital cranioplasty with or without intradural exploration (four patients). The mean follow-up period was 51 months. The three patients who underwent shunt placement procedures experienced poor results, with no evidence of symptom relief and continued neurological deterioration. In contrast, all four patients who underwent cranioplasty experienced good or excellent clinical outcomes. Postoperative magnetic resonance imaging studies revealed a reduction in the size of the syrinx cavity in patients who simultaneously underwent intradural exploration. CONCLUSIONS: The emergence of symptomatic cerebellar ptosis following CVD for Chiari I malformation is primarily caused when the suboccipital craniectomy is too large for the specific patient. The cerebellar ptosis usually presents with severe headache and/or neurological deficit due to persistent or recurrent syringomyelia. Partial suboccipital cranioplasty, with or without intradural exploration, is effective in treating this condition.     

Resolution of neurogenic arterial hypertension after suboccipital decompression for Chiari malformation. Case report

A Chiari malformation Type I may remain asymptomatic until the patient has reached adulthood and acute presentation of symptoms occurs. In several clinical and experimental studies it has been shown that essential hypertension is associated with vascular compression of the brainstem, particularly of the rostral ventrolateral medulla oblongata. Nevertheless, two cases of Chiari malformation and neurogenic arterial hypertension have been reported. In this article the authors describe a patient with Chiari malformation Type I and neurogenic arterial hypertension. A simple suboccipital decompression not only provided neurological improvement, but also led to resolution of the hypertension. In cases of Chiari malformation and concomitant neurogenic arterial hypertension, careful preoperative clinical and neuroimaging assessments may reveal the cause of the arterial hypertension. Resolution of neurogenic arterial hypertension may be expected even in a case of simple suboccipital decompression.     

Extra-arachnoidal cranio-cervical decompression for syringomyelia associated with Chiari I malformation in adults: technique assessment

Summary Background. The osteo-dural decompression of the cerebellar tonsils at the cranio-cervical junction is generally considered the most effective treatment for syringomyelia-Chiari I complex. However much controversy concerning a great number of surgical adjuvants to the standard bony decompression is still present. In this work an extra-arachnoidal cranio-cervical decompression (CCD) without duroplasty is described and the surgical results are reported. Method. Between 2000 and 2005, 24 adult patients underwent surgery for symptomatic syringomyelia-Chiari I complex not associated with hydrocephalus. In all cases, the surgical procedure consisted of a limited suboccipital craniectomy and laminectomy of C1 (when necessary C2 as well) followed by dural opening leaving the arachnoid membrane intact. The dura mater is left open and stitched laterally to the muscles. Findings. With a mean clinical long term follow-up of 44 months (range, 12–78 mo), neurological disturbances improved in 21 of 24 patients (87.5%) as result of extra-arachnoidal CCD. The postoperative complications occurred when the arachnoid was accidentally violated (4 cases, 16.6%). The complications included aseptic meningitis (one patient), nucal pseudomeningocele (two patients) and postoperative hydrocephalus requiring a ventriculoperitoneal shunt (one patient). Finally, one patient received an additional C2 laminectomy in order to obtain symptoms improvement and syrinx shrinkage. Postoperative MRI studies demonstrated that the syrinx decreased in size or collapsed in 20 patients (83.3%) and stabilized in 4 (16.7%). Conclusions. The extra-arachnoidal CCD is a safe and effective treatment for syringomyelia associated with Chiari I malformation in adults without intraoperative evidence of adhesive arachnoiditis. However a larger number of patients and longer follow-up will be necessary to determine the efficacy of extra-arachnoidal CCD.     

Complete resolution of hypertension after decompression of Chiari I malformation

The Chiari I malformation has not been previously linked to sustained hypertension. Other forms of medullary compression have, however, been shown to be associated with elevated arterial pressure. This association has been demonstrated through numerous studies that have implicated compression of the rostral ventrolateral medulla, usually by vascular structures, as a factor responsible for hypertension. We present a case of a young man with a 2-year history of hypertension who was found to have a Chiari I malformation. No other cause for hypertension was found. After subsequent surgical decompression, his hypertension resolved immediately. No other therapeutic options were activated. This is the first reported case linking Chiari I malformation and sustained hypertension. This case presents further evidence linking medullary compression and elevation of hemodynamic tone.     

Anterior atlas fracture following suboccipital decompression for Chiari I malformation. Report of two cases

Chiari I malformation, a congenital disorder involving downward displacement of the cerebellar tonsils through the foramen magnum, is often treated surgically by performing suboccipital craniectomy and C-1 laminectomy. The authors report two cases in which fracture of the anterior atlantal arch occurred during the postoperative period following Chiari I decompression and C-1 laminectomy causing significant neck pain. The findings indicate that interruption of the integrity of the posterior arch of C-1, iatrogenically or otherwise, confers increased risk of anterior arch fracture. A C-1 fracture should therefore be considered in the differential diagnosis of posterior cervical pain in patients who have previously undergone decompression for Chiari I malformation.     

Effects of birth advancement in Chiari malformation in a surgical myelomeningocele model in rabbits

Background/Purpose

In myelomeningocele (MMC), Chiari II malformation progresses during gestation because of the continuous loss of cerebrospinal fluid at the site of the defect. Our purpose was to assess the impact of birth advancement (BA) and prenatal corticosteroid treatment (PCT) on Chiari malformation in a surgical MMC model in rabbits.

Methods

A surgical MMC-like defect was created in 75 fetal rabbits. Animals were distributed into 4 groups depending on the treatment received: not treated and those undergoing BA + PCT, BA, or PCT. The degree of Chiari malformation in newborn rabbits was defined as the percentage of downward protrusion of the hindbrain between the end of the occipital bone and the beginning of the first vertebral arch.

Results

The degree of hindbrain herniation was 80% (8.15) in the not treated group, 36.8% (10.57) in BA + PCT, 41.8% (8.27) in BA, and 44.4% (8.32) in PCT. The BA + PCT, BA, and PCT groups showed less severe hindbrain herniation than not treated animals (mean decrease, 39.86%; SD, 10.57; P = .000). There were no significant differences between the BA + PCT, BA, and PCT groups (P = .311).

Conclusions

Birth advancement and prenatal administration of corticosteroids decrease the severity of the hindbrain herniation component of Chiari II malformation in surgical MMC in fetal rabbits.     

Chiari malformation with syringocephaly. Case report

A 69-year-old white woman presented with a left hemiparesis which progressed to quadriparesis and encephalopathy. Computerized tomography and magnetic resonance imaging revealed a Chiari I malformation and a hydromyelic cavity extending from C-2 to T-6. Rostrally, the cavity extended through the ventral medulla, pons, and right cerebral peduncle into the right cerebral hemisphere, where the cavity enlarged and was associated with mass effect. The patient has made a dramatic neurological recovery following suboccipital craniectomy with insertion of a dural graft to decompress the Chiari malformation and upper cervical laminectomy and dorsal root entry zone myelotomy to decompress the hydromyelia.     

Negative pressure pulmonary edema following foramen magnum decompression for Chiari malformation type I

A 57-year-old obese female presented with vagal and hypoglossal nerve pareses, and magnetic resonance imaging revealed Chiari malformation type I. Standard surgical treatment for Chiari malformation type I was successfully performed. However, immediately after the patient was extubated, she developed signs of upper airway obstruction and chest radiography revealed pulmonary edema. Her ventilation was assisted by maintaining positive end-expiratory pressure at 8 cmH2O. Intravenous furosemide and hydrocortisone were administered. Her respiratory status improved 12 hours later, and she was extubated 3 days after the operation. Postextubational course was uneventful, and the patient was discharged 2 weeks after extubation. The initial neurological deficits had mostly disappeared by 10 months after the operation. This unusual case of negative pressure pulmonary edema indicates that obesity and lower cranial nerve paresis are further risk factors for pulmonary edema as a postextubational complication of surgical treatment.     

Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients

OBJECTIVE: Chiari malformations are regarded as a pathological continuum of hindbrain maldevelopments characterized by downward herniation of the cerebellar tonsils. The Chiari I malformation (CMI) is defined as tonsillar herniation of at least 3 to 5 mm below the foramen magnum. Increased detection of CMI has emphasized the need for more information regarding the clinical features of the disorder. METHODS: We examined a prospective cohort of 364 symptomatic patients. All patients underwent magnetic resonance imaging of the head and spine, and some were evaluated using CINE-magnetic resonance imaging and other neurodiagnostic tests. For 50 patients and 50 age- and gender-matched control subjects, the volume of the posterior cranial fossa was calculated by the Cavalieri method. The families of 21 patients participated in a study of familial aggregation. RESULTS: There were 275 female and 89 male patients. The age of onset was 24.9+/-15.8 years (mean +/- standard deviation), and 89 patients (24%) cited trauma as the precipitating event. Common associated problems included syringomyelia (65%), scoliosis (42%), and basilar invagination (12%). Forty-three patients (12%) reported positive family histories of CMI or syringomyelia. Pedigrees for 21 families showed patterns consistent with autosomal dominant or recessive inheritance. The clinical syndrome of CMI was found to consist of the following: 1) headaches, 2) pseudotumor-like episodes, 3) a Meniere's disease-like syndrome, 4) lower cranial nerve signs, and 5) spinal cord disturbances in the absence of syringomyelia. The most consistent magnetic resonance imaging findings were obliteration of the retrocerebellar cerebrospinal fluid spaces (364 patients), tonsillar herniation of at least 5 mm (332 patients), and varying degrees of cranial base dysplasia. Volumetric calculations for the posterior cranial fossa revealed a significant reduction of total volume (mean, 13.4 ml) and a 40% reduction of cerebrospinal fluid volume (mean, 10.8 ml), with normal brain volume. CONCLUSION: These data support accumulating evidence that CMI is a disorder of the para-axial mesoderm that is characterized by underdevelopment of the posterior cranial fossa and overcrowding of the normally developed hindbrain. Tonsillar herniation of less than 5 mm does not exclude the diagnosis. Clinical manifestations of CMI seem to be related to cerebrospinal fluid disturbances (which are responsible for headaches, pseudotumor-like episodes, endolymphatic hydrops, syringomyelia, and hydrocephalus) and direct compression of nervous tissue. The demonstration of familial aggregation suggests a genetic component of transmission.