Long-term outcomes of surgical management in subtypes of Chiari malformation

Chiari I malformation: management evolution and technical innovation

BACKGROUND AND DEFINITION

In recent years thanks to the growing use of radiological assessment, Chiari I malformation became one of the major diseases for a neurosurgeon to deal with. CIM can be classified according to the extent of cerebellar tonsil tip into the foramen magnum being a protrusion over five mm considered pathological. Such a disease is a heterogeneous condition with a multifactorial pathogenetic mechanism that can subdivided into a primary and secondary form. Regardless of the form, it seems that CIM is the result of an imbalance between the volume of the braincase and its content. Acquired CIMs are secondary to conditions causing intracranial hypertension or hypotension while the pathogenesis of primary forms is still controversial.

PATHOGENESIS AND TREATMENT

There are several theories in the literature but the most accepted one implies an overcrowding due to a small posterior cranial fossa. While asymptomatic CIM do not need treatment, symptomatic ones prompt for surgical management. Several techniques are proposed being the dilemma centered in the need for dural opening procedures and bony decompression ones.

CONCLUSION

Alongside the paper, the authors will address the novelty presented in the literature on management, diagnosis and pathogenesis in order to offer a better understanding of such a heterogeneous pathology.

Reoperation in Chiari-1 Malformations

(1) Background: The issue of unsuccessful surgery for Chiari-1 malformation (CM-1), as well as its potential causes and possible solutions, remains poorly documented and studied. (2) Methods: From a retrospective review of a personal series of 98 patients undergoing treatment for CM-1 during the past 10 years, we created two study groups. Group 1: 8 patients (8.1%) requiring additional surgeries owing to postoperative complications (7 cerebrospinal fluid leakage, 1 extradural hematoma); 7 patients (7.1%) undergoing reoperations for failed decompression during the follow-up. Group 2: During the same period, we also managed 19 patients who had previously been operated on elsewhere: 8 patients who required adequate CM-1 treatment following extradural section of the filum terminale; 11 patients requiring reoperations for failed decompression. Failed decompression was managed by adequate osteodural decompression, which was associated with tonsillectomy (6 cases), subarachnoid exploration (8 cases), graft substitution (6 cases), and occipito-cervical fixation/revision (1 case). (3) Results: There was no mortality or surgical morbidity in Group 1. However, one patient's condition worsened due to untreatable syrinx. In Group 2, there were two cases of mortality, and surgical morbidity was represented by functional limitation and pain in the patient who needed revision of the occipitocervical fixation. Twenty patients improved (58.8%), 6 remained unchanged (32.3%), 1 worsened (2.9%) and 2 died (5.9%). (4) Conclusions: The rate of complications remains high in CM-1 treatment. Unfortunately, a certain rate of treatment failure is unavoidable, but it appears that a significant number of re-operations could have been avoided using proper indications and careful technique.

The Small Posterior Cranial Fossa Syndrome and Chiari Malformation Type 0

Patients showing typical Chiari malformation type 1 (CM1) signs and symptoms frequently undergo cranial and cervical MRI. In some patients, MRI documents >5 mm of cerebellar tonsillar herniation (TH) and the diagnosis of CM1. Patients with 3−5 mm TH have “borderline” CM1. Patients with less than 3 mm of TH and an associated cervical syrinx are diagnosed with Chiari “zero” malformation (CM0). However, patients reporting CM1 symptoms are usually not diagnosed with CM if MRI shows less than 3−5 mm of TH and no syrinx. Recent MRI morphometric analysis of the posterior fossa and upper cervical spine detected anatomical abnormalities in and around the foramen magnum (FM) that explain these patients’ symptoms. The abnormalities include a reduced size of the posterior fossa, FM, and upper cervical spinal canal and extension of the cerebellar tonsils around the medulla rather than inferior to the foramen magnum, as in CM1. These morphometric findings lead some neurologists and neurosurgeons to diagnose CM0 in patients with typical CM1 signs and symptoms, with or without cervical syringes. This article reviews recent findings and controversies about CM0 diagnosis and updates current thinking about the clinical and radiological relationship between CM0, borderline CM1, and CM1.

Possible predictive clinical and radiological markers in decision making for surgical intervention in patients with Chiari Malformation type 1

BACKGROUND

The first aim of this study was to compare the clinical data and posterior fossa morphometry obtained during the admission to the hospital between control group individuals (who had not Chiari Malformation (CM) type 1) and CM type 1 patients treated surgically or not. The second aim was to create a valid and reliable scale that can predict the decision-making for surgical intervention simply and easily in these patients.

MATERIALS

Medical data and radiological images of 70 CM type 1 patients during their admission to the hospital were compared with the data of 69 control group individuals.

RESULTS

Conservative treatment and/or follow-up was applied to 58 (82.9%) patients, and 12 (17.1%) patients underwent surgery. ROC analysis showed that the presence of myelopathy, tonsillar herniation >8 mm, Chamberlain line >84 mm, McRae line >44.50 mm, and odontoid process-McRae line angle <10.50 degrees could be used as predictive markers in decision-making for surgical intervention (p < 0.05). Logistic Regression analysis revealed that symptoms severity, and McRae line value would be the 'best parameters' in decision-making for surgical intervention (p < 0.05). A scale named the CHIASURG scale developed using this study's parameters showed that the parameters of 'depth of tonsillar herniation', 'Chamberlain line', and 'McRae line' could predict the surgical intervention risk.

CONCLUSION

It was found that symptoms severity and McRae line value could be used as predictive markers in decision-making for surgical intervention. Additionally, it was concluded that a new scale called CHIASURG could predict surgical intervention risk validly and reliably.

Occipitocervical fusion as treatment of instability in Chiari malformation

Introduction. Occipitocervical (OC) fusion is a method for fixation of the OC junction when there is instability of that segment. Arnold Chiari malformation is a congenital disorder where cerebellar tonsils descend through the foramen magnum, which can lead to cervicomedular compression and formation of syrinx. While treating this condition, for the purpose of decompression, the foramen magnum is expanded which can potentially harm the stability of the OC junction. Case outline. We are presenting the case of a 16 year old female who was surgically treated (suboccipital craniectomy and decompression) because of Arnold Chiari malformation type I. One-year post-op multislice computed tomography verified a slight enlargement of basion-axial and basion-dens intervals, with signs of spinal cord compression. Surgery was performed - occipitocervical fusion, canal decompression on C1 and C2 levels with a plate on occipital bone and screws placed in the third, fourth, and fifth cervical vertebra. Conclusion. Occipitocervical fusion is a complex surgical procedure (vital neurovascular structures), but it is a reliable method for treatment of instability of the OC junction.