Elsevier

World Neurosurgery

Volume 115, July 2018, Pages e490-e500
World Neurosurgery

Original Article
Adult Chiari I Malformations: An Analysis of Surgical Risk Factors and Complications Using an International Database

https://doi.org/10.1016/j.wneu.2018.04.077Get rights and content

Highlights

  • 30-day postoperative outcomes were analyzed for adult Chiari 1 malformations.

  • The overall cohort readmission rate was 9.3%.

  • 6.8% of patients returned to the operating room.

  • Obesity (45.7%) was predictive of both readmission and reoperation risk.

Background

Chiari I malformations are common in adults and a frequent procedure in neurosurgical practice. Despite several studies, there is no consensus about the indications or surgical technique for this common condition. Increasing emphasis on value-based care has emphasized reduction of readmissions and reoperations and is particularly relevant in Chiari, which has traditionally been associated with a high complication rate.

Objective

To provide a contemporary surgical profile of risk factors and complications for Chiari I malformations in adults.

Methods

The American College of Surgeons National Surgical Quality Improvement Program database was queried to determine 30-day outcomes after surgery for Chiari I malformations in adults between 2005 and 2016. Demographics, clinical risk factors, and postoperative events were analyzed, along with reoperation and readmission reasons.

Results

A total of 672 adult patients were identified in the cohort, with a female predominance (80%). The overall cohort readmission rate was 9.3%, and 6.8% of patients returned to the operating room. Obesity (45.7%) was predictive of both readmission and reoperation risk. Male sex and American Society of Anesthesiologists class were predictive for reoperations. The most common reason for reoperation was cerebrospinal fluid leak, which was responsible for nearly two thirds of reoperations and 4% of the cohort.

Conclusions

Surgery for Chiari in adults is common and carries a definitive risk profile, including rates of readmission and reoperation higher than other common neurosurgical procedures. This cohort provides a representative sample of contemporary neurosurgical outcomes in surgery for Chiari I malformations.

Introduction

Chiari Type I malformations are hindbrain deformities characterized by herniation of the cerebellar tonsils through the foramen magnum. First described in 1891 by Hans Chiari,1, 2, 3 Chiari I malformations are relatively common in the general population, existing in as many as 3.6% of births.4 Chiari I malformations often coexist with other structural anomalies of the skull and spine and are associated with congenitally small posterior fossa volumes.5 Although the precise mechanism is still subject to debate, caudal herniation of the cerebellar tonsils in Chiari I malformations may occlude the subarachnoid space as it passes through the foramen magnum, obstructing cerebrospinal fluid (CSF) flow. Pulsation of the cerebellar tonsils has been proposed to act as a piston, forcing CSF into the spinal cord during systole and leading to the formation of syringomyelia, present in half of patients.6, 7 Syrinx formation (Figure 1) is further associated with progressive neurologic symptoms including sensory loss and weakness seen in patients with Chiari.8

Surgical treatment for Chiari I traditionally consists of suboccipital craniectomy and C1 arch resection, with or without duraplasty.9 Although Chiari I is sometimes identified in childhood and warrants surgical treatment at a young age, often it remains asymptomatic and evades identification until later in life. Although a common neurosurgical procedure, there has been no consensus about surgical technique for Chiari I, with no large multicenter studies characterizing outcomes and complications. Existing multi-institutional studies have either focused on a pediatric population10 or covered a limited number of surgical centers.11

The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) is a large international multi-institutional quality improvement database that tracks numerous outcome variables for surgeries in a standardized database.12 Designed to provide data for patient outcome improvement, use of this database has been shown to improve outcomes at participating institutions.13 In this study, the ACS-NSQIP was used to describe surgical risk factors and postoperative complications, including 30-day readmission and reoperation rates, in patients undergoing surgical decompression for Chiari I malformations.

Section snippets

Data Acquisition and Patient Selection

A retrospective review of data collected by ACS-NSQIP was performed, querying data from 2005 to 2016. Studied cases consisted of patients with primary Current Procedural Terminology (CPT) code 61343 (craniectomy, suboccipital with cervical laminectomy for decompression of medulla and spinal cord, with or without dural graft; Arnold-Chiari malformation). Patients with additional CPT codes, such as anterior odontoid operations (22318 or 22319) or craniocervical CPTs (22590 or 22595) were excluded.

Demographics and Risk Factors

A total of 672 patients met inclusion and exclusion criteria and their data are shown in Table 1. The patient population consisted of 541 women (80.5%) and had a mean age of 37.6 years. The most common comorbidity was obesity, present in 307 patients (45.7%). Other comorbidities included smoking (n = 181, 26.9%), hypertension (n = 122, 18.1%), diabetes (n = 30, 4.5%), and chronic obstructive pulmonary disease (n = 11, 1.6%). Almost all patients (n = 652, 97.6%) had an independent functional

Discussion

Chiari type I malformations are common, with estimates suggesting that symptomatic patients with Chiari I comprise as much as 1% of all imaged patients.14 Although common on imaging, the indications for surgery for Chiari remain controversial under certain circumstances. For example, although surgery is generally recommended in patients with Chiari I with syringomyelia,15 it remains unclear whether the same is warranted in patients presenting with refractory headaches only.16 Different surgical

Conclusions

Chiari type I malformations are common in adults and a frequent procedure in neurosurgical practice. In this large international database study, 6.8% of patients with Chiari required reoperation and 9.3% readmission within 30 days of surgery, more than patients with other common neurosurgical procedures and consistent with a historically high complication rate. The most common reason for reoperation was CSF leak, which was responsible for nearly two thirds of reoperations and 4% of the cohort

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      This brought the idea that enlarging the foramen magnum through a bone decompression alone might provide satisfactory results. Proponents for bone decompression alone also suggested higher complication rates with duraplasty; however, bone decompression alone was found to be related with higher incidence of re-operations [10,17,18]. Similarly, many clinical series reported patients who were initially treated with this technique eventually needed re-operations due to persistent syringomyelia.

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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