Tonsillectomy without craniectomy for the management of infantile Chiari I malformation

Vocal Cord Paralysis in Pediatric Chiari Malformation: A Systematic Review and Meta-analysis

OBJECTIVE

Arnold-Chiari Malformation is one possible cause of congenital vocal cord paralysis (VCP). The natural history of VCP in children with Chiari malformation has previously been limited to small case studies. This systematic review seeks to better characterize the prognostic factors that may predict symptom severity and resolution of congenital VCP in children with Arnold-Chiari malformation. We hypothesized that the onset of stridor or VCP at a younger age would be associated with a poorer prognosis and earlier intervention with posterior fossa decompression would be associated with better outcomes.

DATA SOURCES

PubMed, Web of Science, Cochrane Library, and bibliographic review.

REVIEW METHODS

A systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Database search yielded 866 articles. Study abstracts were reviewed by 2 independent examiners. One hundred and seventy-six studies underwent full-text review. The following were extracted: age at onset of stridor or VCP, Chiari malformation type, laryngoscopy findings, type and timing of neurosurgical intervention, and tracheostomy history. Statistical analyses utilized χ2 tests.

RESULTS

Younger age at symptom onset showed statistically significant associations with decreased likelihood for symptom resolution and tracheostomy decannulation. The shorter time interval from symptom onset to neurosurgical intervention was not significantly associated with better outcomes.

CONCLUSION

This meta-analysis suggests poorer prognosis in those with earlier-onset symptoms, reinforcing prior case series findings. Additional prospective studies are needed to elucidate the natural history and utility of early intervention in children with vocal cord paralysis secondary to Chiari malformation.

Patient and operative factors associated with unanticipated intensive care admission and outcomes following posterior fossa decompressions in children: A retrospective study

INTRODUCTION

Posterior fossa decompression for Chiari I Malformation is a common pediatric neurosurgical procedure. We sought to identify the impact of anesthesia-related intraoperative complications on unanticipated admission to the intensive care unit and outcomes following posterior fossa decompression.

METHODS

Medical records of all patients <18 years who underwent surgery for Chiari I malformation between 1/1/09 and 1/31/21 at the Ann & Robert H. Lurie Children's Hospital of Chicago were included. Records were reviewed for patient characteristics, anesthesia-related intraoperative complications, postoperative complications, and surgical outcomes. The primary outcome was the incidence of unanticipated admission to the intensive care unit, and the primary variable of interest was an anesthesia-related intraoperative complication. Patient, surgical characteristics, and year of surgery were also compared between patients with and without an unanticipated admission to the intensive care unit, and a multi-variable adjusted estimate of odds of unanticipated admission to the intensive care unit admission following an anesthesia-related intraoperative complication was performed. Secondary outcomes included anesthesia factors associated with an anesthesia-related intraoperative event, and postoperative complications and surgical outcomes between patients admitted to the intensive care unit and those who were not.

RESULTS

Two hundred ninety-six patients with Chiari I Malformation were identified. Clinical characteristics associated with an unanticipated admission to the intensive care unit were younger age, American Society of Anesthesiologist (ASA) physical status >2 and an anesthesia-related intraoperative complication. 29 anesthesia-related intraoperative complications were observed in 25 patients (8.4%). Two of 25 patients (8%) with an anesthesia-related intraoperative complication compared with 3 of 271 (1%) patients without anesthesia-related intraoperative complication had an unanticipated admission to the intensive care unit, odds ratio 7.8 (95% CI 1.2-48.8, p = .010). When adjusted for age, sex, ASA physical status, presenting symptoms, concomitant syringomyelia, previous decompression surgery and year of surgery, the odds ratio for an unanticipated admission to the intensive care unit following an anesthesia-related intraoperative complication was 5.9 (95% CI 0.51-59.6, p = .149). There were no differences in surgical outcomes between patients with or without an unanticipated admission to the intensive care unit.

CONCLUSION

Our study demonstrates that although anesthesia-related intraoperative complications during posterior fossa decompression are infrequent, they are associated with an increased risk of an unanticipated admission to the intensive care unit.

Comparison of two surgical techniques in Chiari Malformation Type 1 Patients: Duraplasty alone vs duraplasty with arachnoid dissection

OBJECT

Optimal surgical technique to restore the cerebrospinal fluid flow through the foramen magnum remains to be debated in Chiari malformation type 1 (CM-1) patients.

METHOD

This study included 46 patients with CM-1 who underwent surgical treatment by one of two methods: posterior fossa bone decompression (BD) with arachnoid preserving duraplasty (Group 1) and BD with duraplasty and arachnoid dissection (Group 2). Complaints of the patient population and neurological findings were assessed with Neck Disability Index (NDI) and Europe Quality of Life 5 Dimensions (EQ-5D) in pre- and postoperative periods.

RESULTS

NDI and EQ-5D scores improved in overall patient population and in each individual surgical group. Both groups showed a significant decrease in size of syringomyelia cavity. Complications resulting in recurrent treatments and re-operations occurred in 15% of patients (n = 7); six of them were from Group 2.

CONCLUSION

CM-1 patients benefit significantly from surgical treatment. Duraplasty should be included to surgical technique. Avoiding arachnoid dissection may lead to better results regarding complication rates.

Tonsillectomy with modified reconstruction of the cisterna magna with and without craniectomy for the treatment of adult Chiari malformation type I with syringomyelia

BACKGROUND

In light of the controversies regarding the surgical treatment of adult Chiari malformation type I (CM-I) with syringomyelia, a retrospective study was conducted to evaluate the safety and efficacy of tonsillectomy followed by modified reconstruction of the cisterna magna with or without craniectomy.

METHODS

Between 2008 and 2017, 78 adult CM-I patients (36 males and 42 females, mean age 40.6 years old) with syringomyelia were treated with posterior fossa decompression (PFD) with tonsillectomy and modified reconstruction of the cisterna magna. Patients were divided into two study groups: group A (n = 40) underwent cranioplasty with replacement of the bone flap; group B (n = 38) underwent suboccipital craniectomy. Neurological outcomes were evaluated by traditional physician assessment (improved, unchanged, and worsened) and the Chicago Chiari Outcome Scale (CCOS). Syringomyelia outcomes were assessed radiologically.

RESULTS

The procedure was successfully performed in all patients, and restoration of normal cerebrospinal fluid (CSF) flow was confirmed by intraoperative ultrasonography. The median postoperative follow-up was 20.3 months (range 18-60 months). Clinical improvement was evident in 66 (84.6%) patients, with no significant differences between the two groups (85.0% vs. 84.2%, P = 0.897). According to the CCOS, 36 patients (90.0%) in group A were labeled as "good" outcome, compared with that of 34 (86.8%) in group B (P = 0.734). Improvement of syringomyelia was also comparable between the groups, which was observed in 35 (87.5%) vs. 33 (86.8%) patients (P = 0.887). The postoperative overall (7.5% vs. 23.7%, P = 0.048) and CSF-related (2.5% vs. 18.4%, P = 0.027) complication rates were significantly lower in group A than group B.

CONCLUSIONS

Tonsillectomy with modified reconstruction of the cisterna magna without craniectomy seems to be a safe and effective surgical option to treat adult CM-I patients with syringomyelia, though future well-powered prospective randomized studies are warranted to validate these findings.

Outcomes in children undergoing posterior fossa decompression and duraplasty with and without tonsillar reduction for Chiari malformation type I and syringomyelia: a pilot prospective multicenter cohort study

OBJECTIVE

Despite significant advances in diagnostic and surgical techniques, the surgical management of Chiari malformation type I (CM-I) with associated syringomyelia remains controversial, and the type of surgery performed is surgeon dependent. This study's goal was to determine the feasibility of a prospective, multicenter, cohort study for CM-I/syringomyelia patients and to provide pilot data that compare posterior fossa decompression and duraplasty (PFDD) with and without tonsillar reduction.

METHODS

Participating centers prospectively enrolled children suffering from both CM-I and syringomyelia who were scheduled to undergo surgical decompression. Clinical data were entered into a database preoperatively and at 1-2 weeks, 3-6 months, and 1 year postoperatively. MR images were evaluated by 3 independent, blinded teams of neurosurgeons and neuroradiologists. The primary endpoint was improvement or resolution of the syrinx.

RESULTS

Eight clinical sites were chosen based on the results of a published questionnaire intended to remove geographic and surgeon bias. Data from 68 patients were analyzed after exclusions, and complete clinical and imaging records were obtained for 55 and 58 individuals, respectively. There was strong agreement among the 3 radiology teams, and there was no difference in patient demographics among sites, surgeons, or surgery types. Tonsillar reduction was not associated with > 50% syrinx improvement (RR = 1.22, p = 0.39) or any syrinx improvement (RR = 1.00, p = 0.99). There were no surgical complications.

CONCLUSIONS

This study demonstrated the feasibility of a prospective, multicenter surgical trial in CM-I/syringomyelia and provides pilot data indicating no discernible difference in 1-year outcomes between PFDD with and without tonsillar reduction, with power calculations for larger future studies. In addition, the study revealed important technical factors to consider when setting up future trials. The long-term sequelae of tonsillar reduction have not been addressed and would be an important consideration in future investigations.

Telovelar surgical approach

Surgical access to lesions in the fourth ventricle may be achieved utilizing transvermian or transtelovelar trajectories. We performed a search of the PubMed database for studies describing the microsurgical details and evaluating the clinical utility of the telovelar surgical approach. The telovelar approach has proven to be a safe, effective, and versatile alternative to the transvermian approach. The operative strategy utilizes midline suboccipital craniotomy without or with C1 laminectomy, followed by cerebellar hemispheric and tonsillar retraction, and wide durotomy. Access is generously provided to the fourth ventricle from calamus scriptorius to Sylvian aqueduct and foramen Luschkae bilaterally. Anatomic dissection studies evaluating and comparing the relative benefits of the operative exposure offered by these approaches have demonstrated improved access to the lateral recess gained by the telovelar trajectory and facilitated exposure of rostral reaches of the fourth ventricle by the vermian trajectory. In general, operative exposure may be significantly improved with tonsillar retraction or resection, bilateral telovelar opening, and performing C1 laminectomy in order to improve access to the rostral fourth ventricle, which may be variably combined depending on location of pathology. Cerebellar mutism, a high incidence of which occurs with vermian approaches, is not commonly observed with use of the telovelar trajectory, though injury to the dentate nuclei may precipitate this syndrome. Deficits incurred with the vermian approach may include cerebellar mutism, dysequilibrium, truncal ataxia, posterior fossa syndrome, cranial nucleopathies and nerve palsies, and vascular injury to the posterior inferior cerebellar artery. The telovelar surgical approach has proven a safe and useful alternative to the transvermian trajectory. A significantly lower incidence of cerebellar mutism and cerebellogenic deficits represents the principal advantage of the telovelar approach. Further studies are necessary in order to prospectively evaluate and compare extents of resection, morbidity, and mortality utilizing the telovelar versus vermian approaches for microsurgically resecting fourth ventricular tumors.

Management of Chiari I malformations: a paradigm in evolution

PURPOSE

Despite decades of experience and research, the etiology and management of Chiari I malformations (CM-I) continue to raise more questions than answers. Controversy abounds in every aspect of management, including the indications, timing, and type of surgery, as well as clinical and radiographic outcomes. This review aims to outline past experiences, consolidate current evidence, and recommend directions for the future management of the Chiari I malformation.

METHODS

A review of recent literature on the management of CM-I in pediatric patients is presented, along with our experience in managing 1073 patients who were diagnosed with CM-I over the past two decades (1998-2018) at Children's National Medical Center (CNMC) in Washington DC.

RESULTS

The general trend reveals an increase in the diagnosis of CM-I at younger ages with a significant proportion of these being incidental findings (0.5-3.6%) in asymptomatic patients as well as a rise in the number of patients undergoing Chiari posterior fossa decompression surgery (PFD). The type of surgical intervention varies widely. At our institution, 104 (37%) Chiari surgeries were bone-only PFD with/without outer leaf durectomy, whereas 177 (63%) were PFD with duraplasty. We did not find a significant difference in outcomes between the PFD and PFDD groups (p = 0.59). An analysis of failures revealed a significant difference between patients who underwent tonsillar coagulation versus those whose tonsils were not manipulated (p = 0.02).

CONCLUSION

While the optimal surgical intervention continues to remain elusive, there is a shift away from intradural techniques in favor of a simple, extradural approach (including dural delamination) in pediatric patients due to high rates of clinical and radiographic success, along with a lower complication rate. The efficacy, safety, and necessity of tonsillar manipulation continue to be heavily contested, as evidence increasingly supports the efficacy and safety of less tonsillar manipulation, including our own experience.

Minimally invasive posterior fossa decompression with duraplasty in Chiari malformation type I with and without syringomyelia

Background:

Posterior fossa decompression (PFD), with and without duraplasty, represents a valid treatment in Chiari malformation Type I (CM-I) with and without syringomyelia. Despite a large amount of series reported in literature, several controversies exist regarding the optimal surgical approach yet. In this study, we report our experience in the treatment of CM-I, with and without syringomyelia, highlighting how the application of some technical refinements could lead to a good outcome and a lesser rate of complications.

Methods:

Twenty-six patients with CM-I, with and without syringomyelia, underwent PFD through a 3 cm × 3 cm craniectomy with the removal of the most median third of the posterior arch of C1 and duraplasty. Signs and symptoms included sensory deficits, motor deficits, neck pain, paresthesias, headache, dizziness, lower cranial nerve deficits, and urinary incontinence. Postoperative magnetic resonance (MR) was performed in all patients.

Results:

Signs and symptoms improved in 76.9% of cases. Postoperative MR revealed a repositioning of cerebellar tonsils and the restoration of cerebrospinal fluid circulation. In our experience, the rate of complication was 23% (fistula, worsening of symptoms, and respiratory impairment).

Conclusion:

PFD through a 3 cm × 3 cm craniectomy and the removal of the most median third of posterior arch of C1 with duraplasty represents a feasible and valid surgical alternative to treat patients with CM-I, with and without syringomyelia, achieving a good outcome and a low rate of complications.

Minimally invasive subpial tonsillectomy for Chiari I decompression

Background

A number of different surgical techniques have been used through the years to address Chiari I malformation (CMI).

Methods

This article describes how we surgically manage CMI at two high-volume centers. We call the technique the minimally invasive subpial tonsillectomy (MIST). The technique consists of a minimalistic dissection and craniectomy with a short, linear durotomy for the subpial tonsillar resection. The dura is closed without the use of a duraplasty.

Conclusions

We describe our current methods of surgery for CMI.

Electronic supplementary material

The online version of this article (doi:10.1007/s00701-016-2877-2) contains supplementary material, which is available to authorized users.

The value of multimodality intraoperative neurophysiological monitoring in treating pediatric Chiari malformation type I

INTRODUCTION

Chiari malformation type I is defined as a descent of cerebellar tonsils below the level of the foramen magnum. The traditional treatment for symptomatic patients is foramen magnum decompression (FMD) surgery. Intraoperative neurophysiological monitoring (INM) is an established surgical adjunct, which is proposed to reduce the potential risk of various surgical procedures. Though INM has been suggested as being helpful in patient positioning and in determining the optimal surgical extent of FMD (i.e., duroplasty, laminectomy, tonsillectomy), its shortcomings include prolongation of anesthesia and surgery as well as monetary costs. Multimodality INM including transcranial-electric motor evoked potential (TcMEP) is not routinely employed in most practices. This study evaluates efficacy of multimodality INM during FMD.

METHODS

This work is a retrospective analysis of prospectively collected data. Twenty-two FMD surgeries in 21 pediatric patients (aged 1-18 years) were performed at our center utilizing multimodality INM. All patients presented Chiari malformation type I, 18 of which had presented with syringomyelia, underwent posterior fossa decompression (FMD + C1 laminectomy), accompanied in some with additional cervical laminectomies, duroplasty, and partial tonsillectomies. TcMEP and somatosensory evoked potentials (SSEP) were monitored throughout the procedure including before and after positioning. INM alarms were correlated with perioperative and long-term patient outcomes.

RESULTS

INM data remained stable during 19 operations. Three cases displayed significant attenuation in the monitoring signals, all concomitant with patient positioning on the surgical table. One case showed attenuation in SSEP data only, which remained attenuated following repositioning. Another displayed altered TcMEP concomitant with positioning which partially stabilized following repositioning and resolved following bony decompression. The third case showed unilateral attenuation of both TcMEP and SSEP data, which did not rectify until closure. In each of these three cases, no new neurological deficits were observed post operatively.

CONCLUSIONS

Multimodality INM can be useful in FMD surgery, particularly during patient positioning. TcMEP attenuations may occur independent of SSEPs. The clinical implications of these monitoring alerts have yet to be defined. There is a need to establish an optimal, cost-effective monitoring protocol for FMD.

Improvement of syrinx resolution after tonsillar cautery in pediatric patients with Chiari Type I malformation

OBJECT Chiari Type I malformation involves caudal displacement of the cerebellar tonsils below the foramen magnum, which obstructs normal cerebrospinal fluid flow and increases intracranial pressure. Certain aspects of its surgical treatment remain controversial. A retrospective study was conducted to assess the efficacy of tonsillar cautery on syrinx resolution among pediatric Chiari patients undergoing cervicomedullary decompression. METHODS A retrospective cohort study was performed for patients 0-18 years of age who underwent surgical correction for Chiari Type I malformation with syrinx between 1995 and 2013. Basic demographic information was collected as well as data for preoperative symptoms, prior surgical history, perioperative characteristics, and postsurgical outcomes. Descriptive statistics were performed in addition to bivariate analyses. Candidate predictor variables were identified based on an association with tonsillar cautery with p < 0.10. Forward stepwise likelihood ratio was used to select candidate predictors in a binary logistic regression model (P_in = 0.05, P_out = 0.10) most strongly associated with the outcome. RESULTS A total of 171 patients with Chiari Type I malformation with syrinx were identified, and 43 underwent tonsillar cautery. Patients who underwent tonsillar cautery had 6.11 times greater odds of improvement in their syrinx (95% CI 2.57-14.49, p < 0.001). There was no effect of tonsillar cautery on increased perioperative complications as well as the need for repeat decompressions. CONCLUSIONS Tonsillar cautery is safe and effective in the treatment of Chiari Type I malformation with syrinx and may decrease time to syrinx resolution after cervicomedullary decompression. Tonsillar cautery does not increase postoperative complications in pediatric Chiari Type I malformation patients.

Pediatric and adult Chiari malformation Type I surgical series 1965-2013: a review of demographics, operative treatment, and outcomes

OBJECT

Chiari malformation Type I (CM-I) is a hindbrain disorder associated with elongation of the cerebellar tonsils, which descend below the foramen magnum into the spinal canal. It occurs in children and adults. Clinical symptoms mainly develop from alterations in CSF flow at the foramen magnum and the common subsequent development of syringomyelia.

METHODS

The authors reviewed English-language reports of pediatric, adult, and combined (adult and pediatric) surgical series of patients with CM-I published from 1965 through August 31, 2013, to investigate the following: 1) geographical distribution of reports; 2) demographics of patients; 3) follow-up lengths; 4) study durations; 5) spectrum and frequency of surgical techniques; 6) outcomes for neurological status, syrinx, and headache; 7) frequency and scope of complications; 8) mortality rates; and 9) differences between pediatric and adult populations. Research and inclusion criteria were defined, and all series that contained at least 4 cases and all publications with sufficient data for analysis were included.

RESULTS

The authors identified 145 operative series of patients with CM-I, primarily from the United States and Europe, and divided patient ages into 1 of 3 categories: adult (>18 years of age; 27% of the cases), pediatric (≤18 years of age; 30%), or unknown (43%). Most series (76%) were published in the previous 21 years. The median number of patients in the series was 31. The mean duration of the studies was 10 years, and the mean follow-up time was 43 months. The peak ages of presentation in the pediatric studies were 8 years, followed by 9 years, and in the adult series, 41 years, followed by 46 years. The incidence of syringomyelia was 65%. Most of the studies (99%) reported the use of posterior fossa/foramen magnum decompression. In 92%, the dura was opened, and in 65% of these cases, the arachnoid was opened and dissected; tonsillar resection was performed in 27% of these patients. Postoperatively, syringomyelia improved or resolved in 78% of the patients. Most series (80%) reported postoperative neurological outcomes as follows: 75% improved, 17% showed no change, and 9% experienced worsening. Postoperative headaches improved or resolved in 81% of the patients, with a statistical difference in favor of the pediatric series. Postoperative complications were reported for 41% of the series, most commonly with CSF leak, pseudomeningocele, aseptic meningitis, wound infection, meningitis, and neurological deficit, with a mean complication rate of 4.5%. Complications were reported for 37% of pediatric, 20% of adult, and 43% of combined series. Mortality was reported for 11% of the series. No difference in mortality rates was seen between the pediatric and adult series.

CONCLUSIONS

Before undergoing surgical treatment for CM-I, symptomatic patients and their families should be given clear information about the success of treatment and potential complications. Furthermore, surgeons may benefit from comparing published data with their own. In the future, operative CM-I reports should provide all details of each case for the purpose of comparison.

"Triple R" tonsillar technique for the management of adult Chiari I malformation: surgical note

BACKGROUND

Chiari type I malformation is a congenital disorder that is characterized by the caudal extension of the cerebellar tonsils through the foramen magnum into the cervical canal and by a reduced posterior fossa volume.

METHODS

We report our surgical technique of reposition, reduction, or resection of the cerebellar tonsils for the management of Chiari I malformation. The procedure was performed in 22 adult patients, in three different centers, with a mean age of 37 years. Clinical complaints included headaches, nuchalgia, vertigo, and upper-limb weakness or numbness. Seven patients had cervical syringomyelia. Symptoms developed within a mean time of 36 months (range, 12-70 months).

RESULTS

The cerebellar tonsils were exposed through a dura mater-arachnoid incision at the atlanto-occipital space after a 0.5-cm rimming craniectomy of the occipital bone in all patients. In seven patients the tonsils were resected, in other seven were reduced by subpial coagulation and aspiration, and in the remaining eight patients the tonsils were repositioned after coagulating their surfaces. Three patients had also a posterior fossa arachnoid cyst that was fenestrated in two of them. All patients improved postoperatively. Syringomyelia was reduced in five of seven patients. The mean length of the follow-up period was 12 months.

CONCLUSIONS

Selective reposition, reduction, or resection of herniated cerebellar tonsils may improve symptoms in adult patients with Chiari I malformation.

Suboccipital craniotomy for Chiari I results in evoked potential conduction changes

BACKGROUND

Management of Chiari I is controversial, in part because there is no widely used quantitative measurement of decompression. It has been demonstrated that brainstem auditory evoked responses (BAER) and somatosensory evoked potentials (SSEP) have decreased conduction latencies after wide craniectomy. We analyzed these parameters in a suboccipital craniectomy/craniotomy procedure.

METHODS

Thirteen consecutive patients underwent suboccipital decompression for treatment of symptomatic Chiari I. Craniectomy was restricted to the inferior aspect of the nuchal line, and in most cases the bone flap was replaced. Neuronal conduction was monitored continuously with median nerve somatosensory evoked potentials (M-SEP), posterior tibial nerve somatosensory evoked potentials (T-SEP), BAER, or a combination. The M-SEP N20, T-SEP P37, and BAER V latencies were recorded at four milestones - preoperatively, following craniotomy, following durotomy, and following closure.

RESULTS

Five males and eight females, with average age of 9 years, were studied. Clinical improvement was noted in all 13 patients. M-SEP N20 latency decreased from a mean of 18.55 at baseline to 17.75 ms after craniotomy (P = 0.01); to 17.06 ms after durotomy (P = 0.01); and to 16.68 ms after closing (P = 0.02). T-SEP P37 latency did not change significantly. BAER V latency decreased from a mean of 6.25 ms at baseline to 6.14 ms after craniotomy (P = 0.04); to 5.98 ms after durotomy (P = 0.01); and to 5.95 ms after closing (P = 0.45).

CONCLUSION

Significant improvements in conduction followed both craniectomy and durotomy. Bone replacement did not affect these results.

Posterior fossa volume increase after surgery for Chiari malformation Type I: a quantitative assessment using magnetic resonance imaging and correlations with the treatment response

OBJECT

The aim of this paper was to measure the posterior fossa (PF) volume increase resulting from a given-sized occipital craniectomy in Chiari malformation Type I surgery and to analyze its correlations with the PF size and the treatment response, with the perspective of tailoring the amount of bone removal to the patient-specific PF dimensions.

METHODS

Between January 2005 and June 2006, 11 adult patients with symptomatic Chiari malformation Type I underwent a standardized PF decompression. A prospective evaluation with clinical examination, functional grading, and MR imaging measurement protocols was performed pre- and postoperatively. A method is reported for the measurement of PF volume (PFV) after surgery. The degree of PFV increase was compared with the preoperative size of the PF and with the clinical outcome.

RESULTS

All 11 patients improved postoperatively, with complete and partial recovery in 4 and 7 patients, respectively. No postoperative complication occurred after a mean follow-up period of 45 months. The mean relative increase in PFV accounted for 10% (range 1.5%-19.7%) of the initial PFV; the increase was greater in cases in which the PF was small (r = -0.52, p = 0.09) and the basiocciput was short (r = -0.37, p = 0.2). A statistically significant positive correlation was found between the degree of PFV increase and the treatment response (p = 0.014); complete recovery was observed with a PFV increase of 15% and partial recovery with an increase of 7%.

CONCLUSIONS

The treatment response is significantly influenced by the degree of PFV increase, which is dependent on the size of the PF and the extent of the craniectomy, suggesting that the optimal patient-specific PFV increase could be predicted on the basis of preoperative MR imaging and enhancing the perspective that the craniectomy size could be tailored to the individual PFV.

Chiari type I malformation in children

The diagnosis of Chiari type I malformation (CIM) is more and more frequent in clinical practice due to the wide diffusion of magnetic resonance imaging. In many cases, such a diagnosis is made incidentally in asymptomatic patients, as including children investigated for different reasons such as mental development delay or sequelae of brain injury. The large number of affected patients, the presence of asymptomatic subjects, the uncertainties surrounding the pathogenesis of the malformation, and the different options for its surgical treatment make the management of CIM particularly controversial.This paper reports on the state of the art and the recent achievements about CIM aiming at providing further information especially on the pathogenesis, the natural history, and the management of the malformation, which are the most controversial aspects. A historial review introduces and explains the current classification. Furthermore, the main clinical, radiological, and neurophysiological findings of CIM are described to complete the picture of this heterogeneous and complex disease.

Pathophysiology of persistent syringomyelia after decompressive craniocervical surgery. Clinical article

OBJECT

Craniocervical decompression for Chiari malformation Type I (CM-I) and syringomyelia has been reported to fail in 10%-40% of patients. The present prospective clinical study was designed to test the hypothesis that in cases in which syringomyelia persists after surgery, craniocervical decompression relieves neither the physiological block at the foramen magnum nor the mechanism of syringomyelia progression.

METHODS

The authors prospectively evaluated and treated 16 patients with CM-I who had persistent syringomyelia despite previous craniocervical decompression. Testing before surgery included the following: 1) clinical examination; 2) evaluation of the anatomy using T1-weighted MR imaging; 3) assessment of the syrinx and CSF velocity and flow using cine phase-contrast MR imaging; and 4) appraisal of the lumbar and cervical subarachnoid pressures at rest, during a Valsalva maneuver, during jugular compression, and following the removal of CSF (CSF compliance measurement). During surgery, ultrasonography was performed to observe the motion of the cerebellar tonsils and syrinx walls; pressure measurements were obtained from the intracranial and lumbar intrathecal spaces. The surgical procedure involved enlarging the previous craniectomy and performing an expansile duraplasty with autologous pericranium. Three to 6 months after surgery, clinical examination, MR imaging, and CSF pressure recordings were repeated. Clinical examination and MR imaging studies were then repeated annually.

RESULTS

Before reexploration, patients had a decreased size of the CSF pathways and a partial blockage in CSF transmission at the foramen magnum. Cervical subarachnoid pressure and pulse pressure were abnormally elevated. During surgery, ultrasonographic imaging demonstrated active pulsation of the cerebellar tonsils, with the tonsils descending during cardiac systole and concomitant narrowing of the upper pole of the syrinx. Three months after reoperation, patency of the CSF pathways was restored and pressure transmission was improved. The flow of syrinx fluid and the diameter of the syrinx decreased after surgery in 15 of 16 patients.

CONCLUSIONS

Persistent blockage of the CSF pathways at the foramen magnum resulted in increased pulsation of the cerebellar tonsils, which acted on a partially enclosed cervical subarachnoid space to create elevated cervical CSF pressure waves, which in turn affected the external surface of the spinal cord to force CSF into the spinal cord through the Virchow-Robin spaces and to propel the syrinx fluid caudally, leading to syrinx progression. A surgical procedure that reestablished the CSF pathways at the foramen magnum reversed this pathophysiological mechanism and resolved syringomyelia. Elucidating the pathophysiology of persistent syringomyelia has implications for its primary and secondary treatment.

Pathogenesis of syringomyelia associated with Chiari type 1 malformation: review of evidences and proposal of a new hypothesis

The exact pathogenesis of syringomyelia associated with Chiari type 1 malformation is unknown, although a number of authors have reported their theories of syrinx formation. The purpose of this review is to understand evidences based on the known theories and to create a new hypothesis of the pathogenesis. We critically review the literatures on clinicopathological, radiological, and clinical features of this disorder. The previously proposed theories mainly focused on the driven mechanisms of the cerebrospinal fluid (CSF) into the spinal cord. They did not fully explain radiological features or effects of surgical treatment such as shunting procedures. Common findings of the syrinx in clinicopathological studies were the communication with the central canal and extracanalicular extension to the posterior gray matter. Most of the magnetic resonance imaging studies demonstrated blockade and alternated CSF dynamics at the foramen magnum, but failed to show direct communication of the syrinx with the CSF spaces. Pressure studies revealed almost identical intrasyrinx pressure to the subarachnoid space and decreased compliance of the spinal CSF space. Recent imaging studies suggest that the extracellular fluid accumulation may play an important role. The review of evidences promotes a new hypothesis of syrinx formation. Decreased absorption mechanisms of the extracellular fluid may underlie the pathogenesis of syringomyelia. Reduced compliance of the posterior spinal veins associated with the decreased compliance of the spinal subarachnoid space will result in disturbed absorption of the extracellular fluid through the intramedullary venous channels and formation of syringomyelia.

Accessing the recesses of the fourth ventricle: comparison of tonsillar retraction and resection in the telovelar approach

OBJECTIVE

To compare the effectiveness of the telovelar approach with tonsillar manipulation for approaching the recesses of the fourth ventricle.

METHODS

A telovelar approach was performed in 8 injected cadaveric heads. Areas of exposure were measured for the superolateral and lateral recesses. Horizontal angles were evaluated by targeting the cerebral aqueduct and medial margin of the lateral recess. Quantitative comparisons were made between the telovelar dissections and various tonsillar manipulations.

RESULTS

Tonsillar retraction provided a comparable exposure of the superolateral recess with tonsillar resection (26.4 +/- 17.6 vs 25.2 +/- 12.5 mm2, respectively; P = .825). Tonsillar resection significantly increased exposure of the lateral recess compared with tonsillar retraction (31.1 +/- 13.3 vs 20.2 +/- 11.5 mm2, respectively; P = .002). Compared with tonsillar retraction, the horizontal angle to the lateral recess increased after either contralateral tonsillar retraction (22.7 +/- 4.8 vs 36.7 +/- 6.5 degrees) or tonsillar resection (22.7 +/- 4.8 vs 31.5 +/- 7.6 degrees; all adjusted P < .01). The horizontal angle to the cerebral aqueduct increased significantly with tonsillar resection compared with tonsillar retraction (17.6 +/- 2.3 vs 13.2 +/- 2.8 degrees; P < .001)

CONCLUSION

Compared with tonsillar retraction, tonsillar resection provides a wider corridor to, and a larger area of exposure of, the cerebral aqueduct and lateral recess. Contralateral tonsillar retraction improves access to the lateral recess by widening the surgical view from the contralateral side.

Cerebral anomalies and Chiari type 1 malformation

OBJECTIVE

To analyze the association of diverse cerebral anomalies in a series of pediatric patients with cerebellar tonsillar ectopia.

METHODS

We reviewed the medical records of 60 children diagnosed with Chiari type 1 malformation (CM1), of these, 20 patients (11 boys and 9 girls; mean age 7.2 years, range 2-16 years) had an associated cerebral anomaly. Symptoms of tonsillar ectopia evolved over a mean of 12 months (range 3 months to 4 years). Syringomyelia was present in 5 cases. All patients underwent a posterior fossa decompression.

RESULTS

Disclosed anomalies included: congenital hydrocephalus (n = 11), cervicomedullary kinking (n = 5), focal cerebral heterotopia with epilepsy (n = 4), partial agenesis of the corpus callosum (n = 4), hypoplastic brain stem (n = 2), holoprosencephaly (n = 1), and subcortical dysplasia in the context of neurofibromatosis type 1 (n = 1). Other malformations included: subcortical hamartoma associated with neurofibromatosis type 1, craniofacial dysmorphism secondary to Noonan syndrome, congenital occipital plagiocephaly, os odontoideum, craniofacial cleft, juvenile rheumathoid arthritis with platybasia, and osteogenesis imperfecta with bathrocephaly and scoliosis.

CONCLUSION

Craniocerebral anomalies in children treated for CM1 may be found consistently. The association of hydrocephalus, which was the most common anomaly in this cohort, with cerebellar tonsillar ectopia may contribute to a poor outcome in regard to tonsillar herniation symptoms.

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

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.

Relevance of surgical strategies for the management of pediatric Chiari type I malformation

OBJECTIVE

In face of continuing controversy to the optimal treatment of Chiari type I malformation, the authors analyzed three different surgical strategies.

MATERIALS AND METHODS

Sixty patients (30 boys and 30 girls, mean age 8.2 years) presented with clinical Chiari malformation. Additional syringomyelia was present in 24 children, whereas cine flow studies showed no flow in the craniocervical junction in 48 children. All patients underwent a limited occipital craniectomy; a duraplasty was performed in 21 cases; and additional tonsillar reduction was performed in 19 cases. Clinical improvement was seen in 24 patients who underwent posterior decompression with or without duraplasty. In the tonsillar group, clinical improvement was evident in 18 patients.

CONCLUSIONS

Duraplasty and tonsillar reduction were equally effective but significantly better than bone decompression alone. Among patients with syringomyelia, tonsillar reduction was associated with a significantly better outcome. Postoperative flow studies improved in 39 patients but did not correlate to the clinical outcome.

Histological findings in cerebellar tonsils of patients with Chiari type I malformation

OBJECTIVES

Cerebellar tonsillectomy is often performed for relief of symptoms associated with Chiari type I malformation (CMI). Nonetheless, the idea of removing supposedly healthy central nervous tissue has been a source of concern for neurosurgeons. The aim of this paper is to determine the histological changes in the cerebellar tonsils of patients with a wide range of symptoms and conditions related to CMI.

MATERIALS AND METHODS

The cerebellar tonsils of 43 pediatric patients with CMI were sent to pathology for histological examination.

CONCLUSION

The cerebellar tonsils in a great majority of CMI patients can be abnormal. We suggest that the reported histological findings are secondary to injury and ischemia.

Intraoperative ultrasonography used to determine the extent of surgery necessary during posterior fossa decompression in children with Chiari malformation type I

OBJECT

In this retrospective analysis, the authors report a prospective study in which intraoperative ultrasonography was used to determine the extent of surgery necessary during posterior fossa decompression surgery for Chiari malformation Type I (CM-I) in children.

METHODS

Between 1995 and 2003, posterior fossa decompression was performed in 149 patients (mean 5.9 years of age, range 9 months-18 years of age) with CM-I. Of these, 130 underwent intraoperative ultrasonographic evaluation of the craniocervical junction (CCJ) and 15 did not. Four patients with craniosynostosis were excluded from the study. Duraplasty and tonsillar shrinkage were performed when ultrasonographic evidence showed significant decreases in cerebrospinal fluid (CSF) or abnormal tonsillar piston action. Surgical success was determined on the basis of clinical outcome and need for reoperation. One hundred and twenty-four (95.5%) of the children had successful outcomes following surgery and six (4.5%) experienced continued or worsening symptoms requiring reoperation. Forty patients did not undergo duraplasty because the ultrasonography evidence showed adequate decompression with bone removal alone. Of 90 patients with significant compression, decreased CSF dynamics, and/or abnormal tonsillar piston-like action at the CCJ, 85 underwent duraplasty and tonsillar shrinkage and five did not for various reasons. One patient in whom the dura mater was violated accidentally during bone decompression subsequently underwent duraplasty. Hospital stays lasted 6.4 +/- 3.9 days (mean +/- standard deviation) when duraplasty was performed compared with 4.3 +/- 1.1 days when it was not (p < 0.0003). After bone decompression alone, no patient experienced complications. After duraplasty, 12 patients experienced complications and had headaches, nausea, and pain more often than patients who underwent bone decompression alone. Mean tonsillar descent was 11 +/- 4 mm after bone decompression only and 13.9 +/- 4.9 mm after duraplasty, with tonsillar shrinkage (p < 0.0003) seen on magnetic resonance imaging.

CONCLUSIONS

In patients who undergo decompressive surgery for CM-I, intraoperative ultrasonography may be a useful tool to aid the surgeon in deciding whether to opt for bone removal only or bone removal plus duraplasty and tonsillar shrinkage.

Tailored Operative Technique for Chiari Type I Malformation Using Intraoperative Color Doppler Ultrasonography

OBJECTIVE

We describe an operative technique for Chiari Type I malformation that uses color Doppler ultrasonography as a guide for performing patient-specific posterior fossa decompressions. The technique has been used since 1999 in more than 300 operations.

METHODS

On the basis of real-time anatomic and physiological measurements, the following goals of surgery were monitored: 1) adequate decompression of the cervicomedullary junction; 2) creation of a retrocerebellar space of 8 to 10 cm3 volume; and 3) establishment of optimal cerebrospinal fluid flow between the cranial and spinal compartments.

RESULTS

The size of the craniectomy was tailored to conform to the area of cerebellar impaction as demarcated by compressed subarachnoid spaces. A laminectomy was not performed unless the cerebellar tonsils were herniated below C1. Before opening the dura, color Doppler ultrasonography imaging was invaluable in planning operative strategies. A simple duraplasty without additional steps was found to be appropriate treatment in occasional patients with minimal tonsillar herniation (5–8 mm). In all other cases, it was necessary to perform an internal decompression that included lysis of the arachnoid and shrinkage of the cerebellar tonsils to achieve the goals of surgery. Optimal cerebrospinal fluid flow through the foramen magnum in anesthetized, prone patients was found to have the following characteristics: a peak velocity of 3 to 5 cm/s, bidirectional movement, and a waveform exhibiting vascular and respiratory variations. The attainment of surgical goals was confirmed in most patients by postoperative neuroimaging.

CONCLUSION

Color Doppler ultrasonography imaging is an important technological advance that permits the neurosurgeon to tailor the steps of Chiari surgery according to patient-specific variables. The success of this technique depends on the mastery of a new and sophisticated monitoring modality.