Craniovertebral Decompression Research Articles

Endoscopic third ventriculostomy for hydrocephalus after craniovertebral decompression for Chiari malformation type I: technical nuances and surgical pitfalls.

Hydrocephalus after craniovertebral decompression (CVD) for Chiari I malformation (CM-1) is a well-recognised complication. The mainstay of management involves medical management with high-dose steroids and/or acetazolamide, repeated lumbar punctures, external ventricular drainage (EVD) or insertion of a ventriculoperitoneal shunt (VPS). Endoscopic third ventriculostomy (ETV) has only been used a handful of times to treat this type of hydrocephalus with controversial outcomes. Not much is known about this or the technical nuances of this procedure. We report our experience. All children who underwent ETV to treat hydrocephalus post CVD done for CM-1 were identified from a prospectively kept database. Three children were identified (13F, 11F, 13F). The average time to presentation of hydrocephalus was 8days after craniovertebral decompression. Two were successfully treated with ETV with brain imaging showing a reduction in the size of the ventricles post-operatively and not requiring any further cerebrospinal fluid drainage. In one patient, the procedure had to be abandoned after the peel away catheter was introduced into the right ventricle because CSF egressed under high pressure with ventricle walls collapse resulting in an obstructed view. This child ultimately required a VPS. ETV can be used to successfully treat post CVD hydrocephalus in CM-1 patients depending on the aetiology of the hydrocephalus. There are technical and anatomical commonalities between these cases which make it more challenging than an ETV performed in "typical" obstructive hydrocephalus. We describe our experience and review the cases previously reported in the literature.

A different perspective on the dilemma of durotomy or duraplasty in Chiari type 1 malformation surgery

Purpose Symptomatic Chiari type 1 malformation (CIM) patients may elect to be treated; however, choosing the optimum surgical method remains problematic: posterior fossa decompression with duraplasty (PFDD) or without duraplasty (PFD). Many studies have compared these surgical methods from several perspectives. We looked at soft tissue density (STD) at the foramen magnum to add another perspective to the comparison of PFD with PFDD. Materials and methods Eighty-six patients who underwent surgery in our clinic were included in the study. We examined preoperative and postoperative MR images taken in the 1st year. We obtained the foramen magnum area (FMA) and soft tissue at the level of the foramen magnum. The STD within the foramen magnum was calculated as the percentage ratio of soft tissue area (STA) to FMA. Anteroposterior diameters of the syrinx cavities in sagittal T2 sections were measured preoperatively and at 1-year postoperatively. Measurements were double-blind and were performed by the neurosurgeon and by the neuroradiologist. Results There was no statistically significant difference between the postoperative FMA increases, STA changes, STD changes in patients who underwent PFD and PFDD. In this study, there was no statistically significant difference between PFD and PFDD in terms of syrinx changes. Conclusions The medium-term anatomical outcome following craniovertebral decompression for CIM, is no different whether performed PFD or PFDD.

Technical Report: Durable efficacy of an endoscope-assisted syringo-panventriculoatrial shunt for concurrent hydrocephalus and syrinx

The management of syringomyelia in association with hydrocephalus can be a challenging pathology to treat with durable results. We present a durable treatment of a patient with symptomatic, idiopathic hydrocephalus, Chiari type I malformation, and syringomyelia with an endoscope-assisted placement of a single syringo-panventricular multiperforated shunt catheter via a transfrontal transaqueductal approach with simultaneous endoscopic third ventriculostomy (ETV). We discuss the technical details required for this single-shunt approach to a complex pathology, and indications for appropriate use of this novel approach in experienced hands. The patient rapidly improved radiographically and symptomatically, with a functioning shunt twelve years postoperatively. For surgeons well-versed in endoscopic techniques, this approach can be safe, durable, and obviate the need for an otherwise complex shunting system with multiple catheters, or a more traditional invasive craniovertebral decompression, in a patient with idiopathic hydrocephalus and a syrinx.

Symptom outcome after craniovertebral decompression for Chiari type 1 malformation without syringomyelia.

Specific symptom outcomes after craniovertebral decompression for patients with Chiari type 1 malformation, without accompanying syringomyelia, are not well characterised and poorly reported. We performed a retrospective review of all patients diagnosed with Chiari type 1, without syringomyelia, who underwent craniovertebral decompression in our unit. We identified 129 individuals with a minimum of 2 years' follow-up. The most common pre-operative symptoms were pressure dissociation headaches (78%), visual disturbances (33%), dizziness/balance disturbances (24%) and blackouts (17%). The symptoms most likely to respond to surgery included Valsalva-induced headache (74% response, p < 0.0001) and blackouts (86% response, p < 0.001). After successful craniovertebral decompression, most patients presenting with pressure dissociation headaches and blackouts will improve. However, the large variety of other symptoms patients often present with may not improve after surgery.

Experience with revision craniovertebral decompression in adult patients with Chiari malformation type 1, with or without syringomyelia

Background Craniovertebral decompression is performed for symptomatic Chiari malformation type 1, with or without syringomyelia. In a few patients the symptoms and/or syrinx persist or recur, in which case revision surgery may be offered. The aim of this study was to examine the cause of failure of primary surgery and to assess the outcomes for revision cranio-vertebral decompression. Methods We retrospectively reviewed all revision cranio-vertebral decompressions performed in our centre over an eighteen-year period. A total of 35 patients were identified (23 females; 12 males). Twenty patients had isolated Chiari malformation type 1 and a further fifteen had associated syringomyelia. The mean follow up period was 4-years (range:1–12 years). Results The mean time to revision was 7 years after the primary surgery. The commonest operative finding was that of dense arachnoid scar tissue, obstructing movement of CSF across the craniovertebral junction. Overall, 32 of the 35 patients reported improvement after surgery, including all 15 patients with syringomyelia. Improvement was maintained in the longer term in more than two thirds of those patients who underwent revision craniovertebral decompression. Conclusions Failure of primary craniovertebral decompression for Chiari malformation most often results from the formation dense scar tissue at the operation site, obstructing CSF movement. Revision cranio-vertebral decompression can provide early symptomatic relief in most patients and this benefit is sustained in at least two thirds of cases, in the medium term at least. Patients with concomitant syringomyelia appear to derive most benefit from revision surgery.

Surgical management of Chiari malformation type II.

Chiari malformation type II is present in almost all patients with myelomeningocele but usually remains asymptomatic. Symptoms are generally more severe in neonates, who have the worst prognosis. The association symptoms/hydrocephalus is well known, and first treatment usually consists of ensuring adequate ventricular drainage. Craniovertebral decompression may be required in patients who do not improve after drainage. However, mechanisms of symptom development are not yet completely understood, timing and techniques of surgery are not codified, long-term evolution is poorly reported, and there are few paper reporting clinical onset and treatment in older patients. We reviewed our personal series of 42 consecutive symptomatic patients that required surgical treatment. Age at surgery ranged from 1week to 44years (mean 6.6years). Surgical timing strictly depended on clinical conditions: urgent management in the more compromised patients (usually infants) and elective treatment before severe deterioration in patients with less severe conditions. All patients first underwent external ventricular drainage, which resolved the symptomatology in 17 cases (40%). Craniocervical decompression was required by 25 patients (60%) who received no benefit from the ventricular drainage. Early mortality (2 cases = 4.7%) occurred only in neonates. Clinical improvement was achieved in 37 of 40 survivors (92%). During a follow-up ranging from 2 to 20years (mean 10.3years), late mortality consisted of 4 cases (10%), mainly due to cardio-respiratory arrest. Twenty-two patients (55%) required surgery for shunt malfunction and 4 for cord detethering. Six patients (15%) required reoperation owing to symptom recurrence. Early treatment of symptomatic Chiari II malformations may warrant satisfactory results in a significant number of patients, even in neonates. Nevertheless, overall mortality remains relatively high, throughout the patient life. Formal transition programs and adult spina bifida care processes have become crucial.

Chiari 1 malformation and untreated sagittal synostosis: a new subset of complex Chiari?

Chiari 1 malformation (CM1) is a well-known association with complex craniosynostosis (CC), while it has been rarely reported in association with monosynostosis. The aim of the present study is to investigate on the association between CM1 and untreated sagittal synostosis (USS). The study included 48 cases of sagittal synostosis (SS), untreated for misdiagnosis and associated with CM1. The children were firstly diagnosed for CM1 by MRI (mean age 9) than for SS (mean age 10.5) by three-dimensional computerized tomography (3D-CT), which documented the absence of the sagittal suture, in the presence of residual indentation of all the other sutures. Syndromic cases were diagnosed by clinical evaluation and molecular studies. Of the 48 children harboring CM1 plus USS, 21 were asymptomatic for CM1 and are still on follow-up, while 27 children were operated for syringomyelia and scoliosis and/or occurrence of symptoms, three of them had an acute presentation (two papilledema and one sleep apneas) and 11 children had a documented increase of preoperative ICP. Craniovertebral decompression (CVD) was the first-line surgery in 24 children, 16 with duroplasty and five without and eighthad also cerebellar (CBL) tonsil coagulation. A cranial vault remodelling was firstly performed in three children. Fifteen percent of children submitted to CVD needed a revision for cerebrospinal fluid (CSF) collection, while two needed both the supra- and infratentorial decompressive procedure and another two needed a treatment for the associated hydrocephalus. The present study identified an USS in 27 (15.5%) of 174 CM1 children operated for a symptomatic CM1. We suggest to define this association CM1 plus USS, a new subtype of complex CM1. For the high percentage of complications and multiple procedures needed to solve the CM1, we advise to identify by 3D-CT scan these children before performing CVD. Our finding suggests also that, if left untreated, SS may lead to the delayed occurrence of a challenging subset of CM1.

The surgical procedure of syringomyelie with Chiari I in adults regarding the intrapial aspiration of cerebellar tonsils: does this procedure improve symptoms with less complication?

Introduction. Cranio-vertebral decompression remains the common denominator for the treatment of syringomyelia associated with Chiari I. On the other hand, the details of the procedure, remains controversial. The success of the surgery is to restore the circulation of cerebro-spinal fluid at the level of the foramen magnum. How is this circulation restored to the level of foramen is the question? We offer our attitude towards the treatment of syringomyelia with Chiari I.&#x0D; Material and method. Consecutive series of 32/121 patients benefiting from cranio-vertebral decompression associated with intrapial aspiration of cerebellar tonsils treated for syringomyelia with a Chiari I malformation in adults.&#x0D; Result. Motor deficits were present in 20 / 22 patients, representing 90% of the entire patient group. these motor deficits are improved in 16 out of 22 cases, and remained unchanged in 06cas. no motor aggravation occurred. in our study, bone decompression and intra pial aspiration of cerebellar tonsils (sub arachnoids manipulation) were found to be associated with favourable results on clinical signs and symptoms. However, sub arachnoids manipulation and intra pial aspiration of cerebellar tonsils showed a little more complication compared with bone decompression with dural plasty.&#x0D; Conclusion. The bone decompression with dural graft and intradural dissection of adhesions and reduction by intra pial aspiration or resection of the tonsils is indicated on the MRI aspect of cerebellar tonsils of considerable size totally obstructing the foramen Magnum, the intraoperative finding, through the arachnoid, of the absence of passage of the cerebro-spinal fluid because of the bulging of the cerebellar tonsils.

Management and birth outcomes of pregnant women with Chiari malformations: A 14 years retrospective case series

ObjectiveThe management of Chiari malformations in pregnancy is challenging due to the perceived risk of adverse maternal neurological outcomes and raising intracranial pressure during labour. Our aim was to evaluate the management and health outcomes of pregnant women cared for at a regional referral centre and highlight elements of best practice. Study DesignA retrospective case series of all pregnant women diagnosed with Chiari malformation over fourteen years (January 2004–June 2018) at the Birmingham Women’s Hospital – UK. ResultsTwenty-one women (23 pregnancies) with Chiari malformation were included, four had syringomyelia (4/21,19%) and six had previously undergone craniovertebral decompression (6/21, 29%). The median age was 34-years (range 20–41), the median gravidity was two (range 1–8), the median parity was one (range 0–6), and the median extent of tonsillar herniation was 11 mm (range 9–18). The majority of women received their preferred mode of delivery (15 normal vaginal deliveries (15/23, 65.2%) and 6 elective Caesarean sections (6/23, 26.1%)) with two pregnancies ending with an emergency caesarean section for obstetric complications (2/23, 8.7%). Five Caesarean section were performed under general anaesthetic, two under spinal (2/23, 8.7%) and one under epidural anaesthesia (1/23, 4.3%) with no neurological sequelae. There were no adverse neurological outcomes at discharge postnatally. ConclusionsOffering normal vaginal delivery with effective analgesia, for women with Chiari malformation, appears to be safe. Pregnancy care should be provided by a multi-disciplinary team with experience in managing Chiari malformation.

Fluid dynamics in syringomyelia cavities: Effects of heart rate, CSF velocity, CSF velocity waveform and craniovertebral decompression.

Purpose How fluid moves during the cardiac cycle within a syrinx may affect its development. We measured syrinx fluid velocities before and after craniovertebral decompression in a patient and simulated syrinx fluid velocities for different heart rates, syrinx sizes and cerebrospinal fluid (CSF) flow velocities in a model of syringomyelia. Materials and methods With phase-contrast magnetic resonance we measured CSF and syrinx fluid velocities in a Chiari patient before and after craniovertebral decompression. With an idealized two-dimensional model of the subarachnoid space (SAS), cord and syrinx, we simulated fluid movement in the SAS and syrinx with the Navier-Stokes equations for different heart rates, inlet velocities and syrinx diameters. Results In the patient, fluid oscillated in the syrinx at 200 to 210 cycles per minute before and after craniovertebral decompression. Velocities peaked at 3.6 and 2.0 cm per second respectively in the SAS and the syrinx before surgery and at 2.7 and 1.5 cm per second after surgery. In the model, syrinx velocity varied between 0.91 and 12.70 cm per second. Increasing CSF inlet velocities from 1.56 to 4.69 cm per second increased peak syrinx fluid velocities in the syrinx by 151% to 299% for the three cycle rates. Increasing cycle rates from 60 to 120 cpm increased peak syrinx velocities by 160% to 312% for the three inlet velocities. Peak velocities changed inconsistently with syrinx size. Conclusions CSF velocity, heart rate and syrinx diameter affect syrinx fluid velocities, but not the frequency of syrinx fluid oscillation. Craniovertebral decompression decreases both CSF and syrinx fluid velocities.

Adding Expansile Duraplasty to Posterior Fossa Decompression May Restore Cervical Range of Motion in Grade 3 Chiari Malformation Type 1 Patients

Few studies have assessed the effect of Chiari malformation type 1 (CM-1) surgical decompression on cervical lordosis and range of motion (ROM). We aimed to assess the effect of expansile duraplasty on postoperative cervical mobility and spinal stability. This was a single-center retrospective review of prospectively collected data. Patients were included if they underwent surgical treatment for symptomatic CM-1 between the years 1999 and 2009. Cervical ROM and lordosis were assessed before and after surgery in all patients. Collected data also included clinical improvement, as well as surgical complications after the procedure. Patients were divided into 2 groups. The first group underwent a posterior fossa bony decompression alone, while the second group additionally received an expansile duraplasty. Patients were further subdivided into 3 subgroups on the basis of the severity of tonsillar herniation. A total of 76 patients fit our selection criteria. Fifty-five patients belonged to the duraplasty group. Twenty-one patients underwent bony decompression alone. The 2 groups were statistically demographically and clinically similar. There was no difference in clinical outcome or in ROM and cervical lordosis between the groups except for patients with severe tonsillar herniation (CM-I grade 3). These patients had a statistically significant improvement in their postoperative cervical motility without compromising their spinal stability. Adding an expansile duraplasty to craniovertebral decompression in CM-1 patients with severe tonsillar herniation may restore cervical ROM while preserving stability and alignment. This may relieve postoperative pain and improve clinical prognosis.

Effect of craniovertebral decompression on CSF dynamics in Chiari malformation type I studied with computational fluid dynamics: Laboratory investigation.

The effect of craniovertebral decompression surgery on CSF flow dynamics in patients with Chiari malformation Type I (CM-I) has been incompletely characterized. The authors used computational fluid dynamics to calculate the effect of decompression surgery on CSF flow dynamics in the posterior fossa and upper cervical spinal canal. Oscillatory flow was simulated in idealized 3D models of the normal adult and the CM-I subarachnoid spaces (both previously described) and in 3 models of CM-I post-craniovertebral decompressions. The 3 postoperative models were created from the CM model by virtually modifying the CM model subarachnoid space to simulate surgical decompressions of different magnitudes. Velocities and pressures were computed with the Navier-Stokes equations in Star-CD for multiple cycles of CSF flow oscillating at 80 cycles/min. Pressure gradients and velocities were compared for 8 levels extending from the posterior fossa to the C3-4 level. Relative pressures and peak velocities were plotted by level from the posterior fossa to C3-4. The heterogeneity of flow velocity distribution around the spinal cord was compared between models. Peak systolic velocities were generally lower in the postoperative models than in the preoperative CM model. With the 2 larger surgical defects, peak systolic velocities were brought closer to normal model velocities (equal values at C-3 and C-4) than with the smallest surgical defect. For the smallest defect, peak velocities were decreased, but not to levels in the normal model. In the postoperative models, heterogeneity in flow velocity distribution around the spinal cord increased from normal model levels as the degree of decompression increased. Pressures in the 5 models differed in magnitude and in pattern. Pressure gradients along the spinal canal in the normal and CM models were nonlinear, with steeper gradients below C3-4 than above. The CM model had a steeper pressure gradient than the normal model above C3-4 and the same gradient below. The postoperative models had lower pressure gradients than the CM model above C2-3. The most conservative decompression had lower pressure gradients than the normal model above C2-3. The two larger decompression defects had CSF pressure gradients below those in the normal model above C2-3. These 2 models had a less steep gradient above C-3 and a steeper gradient below. In computer simulations, craniovertebral surgical defects generally diminished CSF velocities and CSF pressures.

Management of Chiari I Malformation (CM): Analysis of the Clinical Outcome after Craniovertebral Decompression with Arachnoidal Sparing Technique

Management of Chiari I Malformation (CM): Analysis of the Clinical Outcome after Craniovertebral Decompression with Arachnoidal Sparing Technique

Long-term results and complications of the syringopleural shunting for treatment of syringomyelia: a clinical study

Background. The use of drains in the treatment of syringomyelia has a simple and immediate appeal. Syringopleural shunting in syringomyelia has produced good short-term results, but limited information is available on long-term effects. We analyzed the complications and long-term outcomes after syringopleural shunting for syringomyelia. Clinical material and methods. Fourthy-four patients with large-sized syringomyelia underwent syringopleural shunting because of spinal cord compression between 1992 and 2010 in our clinic. Thirty-two patients had Chiari malformation type I (Group B), and 12 patients were associated with primary parenchymal cavitations (Group A). Their ages ranged from 14 to 71 years. Both craniovertebral decompression and syringopleural shunting were performed on 21 patients, whereas only syringopleural shunting was performed on another 21 patients. Results. The follow-up period ranged from 1 year to 17 years (mean: 9.1 years). There was no operative mortality. Early postoperative MRI revealed that syringes of 43 patients had collapsed. There were 9 (20.5%) minor complications in 9 patients, including temporary neurological deficits (6), respiratory distress (2) and headache (1). Seven (15.9%) serious complications [permanent neurological deficit (1), shunt migration (2), shunt misplacement (1), spinal instability (1), tethering (1), CSF over drainage (1)] were seen in five patients. Four of them were treated with a secondary operation. Three patients (3/9; 33.3%) who were treated by syringopleural shunt alone (Group B2) required craniovertebral decompression, although the shunt was functional. During long-term follow-up, three patients stabilized, five patients (11.3%) developed a worse neurological condition, and two of these patients died 10 and 7 years after surgery. Of all patients, 88.6% showed significant clinical improvement. Conclusions. Although there were complications and failures, syringopleural shunting produced satisfactory results at long-term follow-up.

Patient-Specific 3D Simulation of Cyclic CSF Flow at the Craniocervical Region

Flow simulations in patient-specific models of the subarachnoid space characterize CSF flow in more detail than MR flow imaging. We extended previous simulation studies by including cyclic CSF flow and patient-specific models in multiple patients with Chiari I. We compared simulation results with MR flow measurements. Volumetric high resolution image sets acquired in 7 patients with Chiari I, 3 patients who had previous craniovertebral decompression, and 3 controls were segmented and converted to mathematical models of the subarachnoid space. CSF flow velocities and pressures were calculated with high spatial and temporal resolution during simulated oscillatory flow in each model with the Navier-Stokes equations. Pressures, velocities, and bidirectional flow were compared in the groups (with Student t test). Peak velocities in the simulations were compared with peak velocities measured in vivo with PCMR. Flow visualization for patients and volunteers demonstrated nonuniform reversing patterns resembling those observed with PCMR. Velocities in the 13 subjects were greater between C2 and C5 than in the foramen magnum. Chiari patients had significantly greater peak systolic and diastolic velocities, synchronous bidirectional flow, and pressure gradients than controls. Peak velocities measured in PCMR correlated significantly (P = .003; regression analysis) despite differences between them. In simulations of CSF, patients with Chiari I had significantly greater peak systolic and diastolic velocities, synchronous bidirectional flow, and pressure gradients than controls.

A new entity: chiari zero malformation, and its surgical method

Recently, Iskandar et al described "Chiari Zero malformation" to characterize some kind of syringomyelia that exhibits classic Chiari-type symptoms with little to no herniation, but there is some dilemma about whether it is actually present. We presented a 38-year-old-man with a diagnosis of cervical syringomyelia. In his neurological examination, there was monoparesia at the left leg together with hypoesthesia below thoracal 7. He had initially been treated with syringopleural shunting successfully. Nine months after surgery, his syringomyelia had regrown and he clinically deteriorated. It was accepted as "a Chiari zero malformation". We performed craniovertebral decompression only. Although there was no tonsillar herniation, his syringomyelia was completely resolved and his neurological status was improved six months after the craniovertebral decompression, This case suggested that "Chiari zero malformation" description is remarkable and craniovertebral decompression is a suitable surgical approach for this entity.

Chiari I malformation without hydrocephalus: acute intracranial hypertension managed with endoscopic third ventriculostomy (ETV)

In a small subset of patients, a Chiari malformation can present with signs of raised intracranial pressure due to obstruction of cerebrospinal fluid flow or with the raised intracranial pressure as the primary pathological driving force resulting in tonsillar herniation. The authors report a unique case in a 14-year-old boy with a Chiari malformation type 1-syringomyelia complex with slit-like ventricles. We have successfully managed the acute presentation of raised intracranial pressure, mimicking idiopathic intracranial hypertension, utilizing a frameless stereotactic image-navigated endoscopic third ventriculostomy alone. We present the preoperative and postoperative radiological and ophthalmological findings and discuss the possible mechanisms related to the pathophysiology and treatment in this case. The patient's symptoms resolved immediately postoperatively with resolution of papilledema. At 18-month follow-up, the patient remains entirely asymptomatic and the need for craniovertebral decompression appears to have been obviated. We advocate that in the Chiari malformation type 1-syringomyelia complex with normal or small ventricles, patients presenting with isolated signs and symptoms of raised intracranial pressure alone can be safely and effectively managed with an electromagnetic-guided stereotactic endoscopic third ventriculostomy as a primary treatment option.

Surgical treatment of Arnold-Chiari malformation type I in an adult patient

Herniation of the cerebellar tonsils through the foramen magnum into the cervical spinal canal with obliteration of the cerebellomedullary cistern is the primary feature of Arnold-Chiari type I malformation (ACM I). It is considered to be congenital malformation, although there have been reported cases of an acquired form. We presented a female patient, 45-year old, with ACM I without syringomyelia as a rare and unusual clinical image, as well as the effect of decompressive surgery in the treatment of this malformation. The patient was admitted to the Department of Neurosurgery with clinical signs of truncal ataxia worsening during the last six years. Moderate quadriparesis with predominant lower extremity involvement and the signs of the cranial nerves damages occured during the last seven months before admission, with progressive clinical course up to the date of admission. Neurosurgical treatment that included suboccipital medial craniectomy with resection of posterior arch C1 vertebrae and C2 laminectomy resulted in a significant clinical improvement and a much better quality of life. Posterior craniovertebral decompression with microsurgical reduction of the cerebellar tonsils and placement of an artificial dural graft is a treatment of choice in severe forms of ACM I without syringomyelia.

Posterior fossa volume in children with Chiari malformation Type I

The authors sought to establish whether the volume of the posterior fossa in children suffering from Chiari malformation Type I (CM-I) is smaller than normal, as has been suggested previously. They also investigated the role of syringomyelia in posterior fossa development. Both posterior fossa volume (PFV) and intracranial volume (ICV) were measured using segmentation techniques on preoperative magnetic resonance images obtained in 42 children who underwent surgery for CM-I (mean age 127 months, range 36-204 months); 25 (59%) of the patients had syringomyelia. The PFV/ICV ratio was calculated to eliminate differential supratentorial growth. Patients who had deformities potentially interfering with skull growth or who had undergone a shunt insertion procedure prior to craniovertebral decompression were excluded. The results were compared with measurements of 51 healthy children using one-way analysis of variance. In patients with CM-I only, the mean PFV and PFV/ICV ratios were not statistically different than those for healthy children. In patients with both CM-I and syringomyelia (CM-S), the mean PFV and PFV/ICV ratios were statistically smaller than those for healthy children. The ICV was 1383 cm3 in the healthy group, 1459 cm3 in the CM-I only group, and 1400 cm3 in the CM-S group (p = 0.363); the PFV was 186 cm3 in the healthy group, 196 cm3 in the CM-I only group, and 171 cm3 in the CM-S group (p = 0.036); the PFV/ICV ratio was 0.135 in the healthy group, 0.134 in the CM-I only group, and 0.122 in the CM-S group (p = 0.004). These differences were more prominent in the first 10 years of life. Children with isolated CM-I do not have a PFV smaller than normal, whereas children with both CM-I and syringomyelia have a PFV significantly smaller than normal. This result indicates that the two subgroups may represent different phenotypic expression or even a different pathogenesis.

Scoliosis in children with Chiari I-related syringomyelia

To study the relationship between scoliosis and Chiari I malformation, with reference to the possible role of cranio-vertebral decompression in preventing the need for scoliosis correction. Out of a total of 36 patients with symptomatic Chiari I, who underwent primary cranio-vertebral decompression by a single paediatric neurosurgeon with an interest in Chiari malformation between 1998 and 2003, 13 had clinically detected scoliosis. Of these, ten had no other structural spine abnormality, which could influence the natural history of scoliosis and were included in this study. In all but one patient, syringomyelia improved significantly after cranio-vertebral decompression. Of the ten patients, eight had levoscoliosis (left convexity), all single curves, and two had curves to the right (both double curves). Six patients did not require corrective scoliosis surgery after cranio-vertebral decompression. The mean Cobb angle for those not requiring scoliosis correction was 29 degrees in contrast to a mean of 76 degrees for those requiring correction [p=0.001, one-way analysis of variance (ANOVA)]. The mean age of patients requiring corrective surgery was 158 months against 125 months for those not requiring correction (p=0.084, one-way ANOVA). These findings were confirmed by multivariate analysis, which also confirmed that symptom duration, syrinx length and site were not significant in predicting the need for corrective surgery following cranio-vertebral decompression. Cranio-vertebral decompression for Chiari I may prevent the need for corrective scoliosis surgery when performed before the age of ten and below a Cobb angle of 30 degrees.