User Tools

Site Tools


Posterior fossa decompresion for Chiari type 1 deformity

The preferred treatment for Chiari type 1 deformity is foramen magnum decompression (FMD), and it is assumed to normalise ICP and craniospinal pressure dissociation.

Observations suggest that anatomical restoration of cerebrospinal fluid pathways by FMD does not lead to immediate normalisation of preoperatively altered pulsatile and static ICP in patients with CMI. This finding may explain persistent symptoms during the early period after FMD 1).

A variety of surgical techniques for CM-I have been used, and there is a controversy whether to use posterior fossa decompression with duraplasty (PFDD) or posterior fossa decompression without duraplasty (PFD) in CM-I patients.

Chen et al., compared the clinical results and effectiveness of PFDD and PFD in adult patients with CM-I. The cases of 103 adult CM-I patients who underwent posterior fossa decompression with or without duraplasty from 2008 to 2014 were reviewed retrospectively. Patients were divided into 2 groups according to the surgical techniques: PFDD group (n = 70) and PFD group (n = 33). We compared the demographics, preoperative symptoms, radiographic characteristics, postoperative complications, and clinical outcomes between the PFD and PFDD patients. No statistically significant differences were found between the PFDD and PFD groups with regard to demographics, preoperative symptoms, radiographic characteristics, and clinical outcomes(P > 0.05); however, the postoperative complication aseptic meningitis occurred more frequently in the PFDD group than in the PFD group (P = 0.027). We also performed a literature review about the PFDD and PFD and made a summary of these preview studies. Our study suggests that both PFDD and PFD could achieve similar clinical outcomes for adult CM-I patients. The choice of surgical procedure should be based on the patient's condition. PFDD may lead to a higher complication rate and autologous grafts seemed to perform better than nonautologous grafts for duraplasty 2).

The purpose of a study was to examine the utility of iMRI in determining when an adequate decompression had been performed.

Patients with symptomatic Chiari I malformations with imaging findings of obstruction of the CSF space at the foramen magnum, with or without syringomyelia, were considered candidates for surgery. All patients underwent complete T1, T2, and cine MRI studies in the supine position preoperatively as a baseline. After the patient was placed prone with the neck flexed in position for surgery, iMRI was performed. The patient then underwent a bone decompression of the foramen magnum and arch of C-1, and the MRI was repeated. If obstruction was still present, then in a stepwise fashion the patient underwent dural splitting, duraplasty, and coagulation of the tonsils, with an iMRI study performed after each step guiding the decision to proceed further.

Eighteen patients underwent PFD for Chiari I malformations between November 2011 and February 2013; 15 prone preincision iMRIs were performed. Fourteen of these patients (93%) demonstrated significant improvement of CSF flow through the foramen magnum dorsal to the tonsils with positioning only. This improvement was so notable that changes in CSF flow as a result of the bone decompression were difficult to discern.

The authors observed significant CSF flow changes when simply positioning the patient for surgery. These results put into question intraoperative flow assessments that suggest adequate decompression by PFD, whether by iMRI or intraoperative ultrasound. The use of intraoperative imaging during PFD for Chiari I malformation, whether by ultrasound or iMRI, is limited by CSF flow dynamics across the foramen magnum that change significantly when the patient is positioned for surgery 3).


Cerebrospinal fluid disturbance (CSFD) is a well-known complication after occipitocervical decompression (OCD) in patients with Chiari malformation type I (CMI). There is scarce data focusing on preoperative patients' factors predisposing to development of CSF disturbance. The aim of this study is to evaluate a prognostic value of some patients' factors in the prediction of CSFD after OCD in CMI patients.

A 10-year (2003-2013) retrospective study of all OCD in patients with CMI performed at Sahlgrenska IC, Sahlgrenska University Hospital, Sweden. A total of 52 consecutive patients were obtained from the operation database and we excluded one patient who was previously diagnosed with normal-pressure hydrocephalus. Data regarding preoperative age, body mass index, gender, degree of tonsillar herniation and syrinx were registered. Development of CSFD after OCD was noted.

Of the 51 patients reviewed, six had CSFD after OCD and were managed using a form of CSF diversion procedure. All of the patients who developed CSFD were females. They had a mean body mass index of 32.3 compared to a mean of 24.3 in patients without CSFD (p = 0.0011). There was no difference between the two groups with regard to the other examined patient factors.

CSF diversion was needed in six consecutive adult Chiari malformation type I patients who underwent occipitocervical decompression. All patients with postoperative CSFD were female and their mean BMI was significantly higher than patients without this complication 4).

Is carried out to improve passage of cerebrospinal fluid (CSF) in patients with symptomatic Chiari I malformations (CM1), but the extent and means of decompression remains controversial. Dural opening with subsequent duraplasty may contribute to clinical outcome, but may also increase complication risk.

Systematic review of observational studies reveals higher reoperation rates after bony decompression alone, but clinical improvement was not higher after primary decompression with duraplasty. There are so far no high-quality studies that offer guidance in the choice of decompressive technique in adult CM1 patients 5).

A report describes the circumstances of a patient with a cauda equina syndrome due to the development of a lumbar spinal subdural hygroma with ventral displacement of the cauda equina shortly following posterior fossa decompresion for Chiari type 1 deformity (CM-I). This unusual, but clinically significant, complication was successfully treated with percutaneous drainage of the extraarachnoid CSF collection. Although there are a few cases of intracranial subdural hygroma developing after surgery for CM-I, often attributed to a pinhole opening in the arachnoid, as far as the authors can determine, a spinal subdural hygroma associated with surgery for CM-I has not been recognized 6).

Frič R, Eide PK. Perioperative monitoring of pulsatile and static intracranial pressure in patients with Chiari malformation type 1 undergoing foramen magnum decompression. Acta Neurochir (Wien). 2016 Feb;158(2):341-7. doi: 10.1007/s00701-015-2669-0. Epub 2015 Dec 28. PubMed PMID: 26711284.
Chen J, Li Y, Wang T, Gao J, Xu J, Lai R, Tan D. Comparison of posterior fossa decompression with and without duraplasty for the surgical treatment of Chiari malformation type I in adult patients: A retrospective analysis of 103 patients. Medicine (Baltimore). 2017 Jan;96(4):e5945. doi: 10.1097/MD.0000000000005945. PubMed PMID: 28121938.
Bond AE, Jane JA Sr, Liu KC, Oldfield EH. Changes in cerebrospinal fluid flow assessed using intraoperative MRI during posterior fossa decompression for Chiari malformation. J Neurosurg. 2015 May;122(5):1068-75. doi: 10.3171/2015.1.JNS132712. Epub 2015 Feb 20. PubMed PMID: 25699415.
Almotairi FS, Tisell M. Cerebrospinal fluid disturbance in overweight women after occipitocervical decompression in Chiari malformation type I. Acta Neurochir (Wien). 2016 Mar;158(3):589-94. doi: 10.1007/s00701-015-2678-z. Epub 2016 Jan 7. PubMed PMID: 26743916.
Förander P, Sjåvik K, Solheim O, Riphagen I, Gulati S, Salvesen O, Jakola AS. The case for duraplasty in adults undergoing posterior fossa decompression for Chiari I malformation: A systematic review and meta-analysis of observational studies. Clin Neurol Neurosurg. 2014 Jul 21;125C:58-64. doi: 10.1016/j.clineuro.2014.07.019. [Epub ahead of print] Review. PubMed PMID: 25087160.
Darwish HA, Oldfield EH. Lumbar subdural cerebrospinal fluid collection with acute cauda equina syndrome after posterior fossa decompression for Chiari malformation Type I: case report. J Neurosurg Spine. 2016 Sep;25(3):328-31. doi: 10.3171/2016.2.SPINE151480. Epub 2016 Apr 15. PubMed PMID: 27081710.
posterior_fossa_decompresion_for_chiari_type_1_deformity.txt · Last modified: 2017/03/06 13:45 by administrador