Elsevier

World Neurosurgery

Volume 104, August 2017, Pages 213-219
World Neurosurgery

Literature Review
Chiari Malformation Type 1: A Systematic Review of Natural History and Conservative Management

https://doi.org/10.1016/j.wneu.2017.04.082Get rights and content

Background

Chiari malformation type 1 (CM-1) is a variation of hindbrain development that can sometimes occur in asymptomatic individuals. Conventional treatment is surgical decompression, but little is known about the natural history of patients who do not undergo surgical management. This information is critical to determine how these patients should be managed. We conducted a systematic literature review to determine the natural history of CM-1, particularly in patients who did not undergo surgery and in asymptomatic individuals, to help patients and physicians determine when surgery is likely to be beneficial.

Methods

The literature search was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using the electronic databases PubMed, Scopus, Cochrane Library, and Web of Science. Inclusion and exclusion criteria were predefined.

Results

In symptomatic patients who did not undergo surgery, headaches and nausea often improved, whereas ataxia and sensory disturbance tended not to improve spontaneously. Of patients, 27%–47% had an improvement in symptoms after 15 months, and 37%–40% with cough headache and 89% with nausea who were managed nonoperatively improved at follow-up. Most asymptomatic individuals with CM-1 remained asymptomatic (93.3%) even in the presence of syringomyelia.

Conclusions

The natural history of mild symptomatic and asymptomatic CM-1 in adults is relatively benign and nonprogressive; the decision to perform surgical decompression should be based on severity and duration of a patient's symptoms at presentation. It is reasonable to observe a patient with mild or asymptomatic symptoms even in the presence of significant tonsillar descent or syringomyelia.

Introduction

The Arnold-Chiari malformation type 1, which we refer to as Chiari malformation type 1 (CM-1), was originally defined by Hans Chiari as an “elongation of the tonsils and the medial parts of the inferior lobes of the cerebellum into cone-shaped projections which accompany the medulla oblongata into the spinal canal.”1 A common treatment for symptomatic CM-1 is foramen magnum decompression, and although there is debate around the technical aspects of surgery, the outcomes and risks of surgery are well documented. However, little is known about the natural history of CM-1 without surgery in symptomatic and asymptomatic individuals, and this information is necessary to decide the merits of surgical management. CM-1 is uncommon in adults, and there is little clear evidence to guide management. We present, to our knowledge, the first systematic review of the natural history and conservative management of CM-1 in adults to help surgeons and patients decide when to perform surgery for CM-1. We reviewed published studies of CM-1 to determine the following: 1) the presenting features of CM-1 in adults, 2) common indications for surgical intervention, 3) the natural history of CM-1 in adults, 4) the natural history of asymptomatic incidental CM-1, and 5) the natural history syringomyelia with CM-1.

Section snippets

Data Sources and Search Strategy

We performed a systematic literature review in the format recommended by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines.2 A literature search was performed using the electronic databases PubMed, Scopus, Cochrane Library, and Web of Science. No time limits were set during the search. Indexes were accessed between February 2, 2016, and February 22, 2016. A search strategy was created using the terms listed in Table 1. Results were reviewed to exclude duplicates,

Selected Articles

Our search strategy (Table 1) identified 344 articles, which were reduced to 198 after excluding duplicates. After title and abstract review, the number of relevant articles was reduced to 44. Following full-text review, a further 33 articles were excluded, leaving 11 articles for detailed inclusion in this systematic review.3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 Four further articles were identified from article bibliographies.14, 15, 16, 17 Therefore, 15 articles were identified for inclusion in

Discussion

There were no randomized controlled trials of surgery versus conservative management of CM-1. The best published evidence was level 2a and 2b cohort or case comparison series. Therefore, it is possible to suggest grade B recommendations for the management of symptomatic adult CM-1. Patients presenting with significant headaches, ataxia, or paresthesia are more likely to undergo surgical treatment of CM-1, although the decision to operate is a subjective one, depending on the balance of severity

Conclusions

The natural history of symptomatic and asymptomatic CM-1 in adults is relatively benign and nonprogressive, and the decision to perform a foramen magnum decompression operation should be based on the severity and duration of a patient's symptoms at the time of presentation. It is reasonable to observe a patient with mild or asymptomatic symptoms, even in the presence of significant tonsillar descent or syringomyelia. Although class 1 evidence is lacking, there is sufficient evidence to suggest

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    • Foramen Magnum Decompression for Chiari Malformation Type 1: Is There a Superior Surgical Technique?

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      Citation Excerpt :

      When symptoms do occur, clinical presentation and severity of symptoms can determine whether conservative or surgical management will be pursued. In a systematic review of the natural history and conservative management in CM1 patients, Langridge et al.2 found that 93% of asymptomatic patients remained asymptomatic, even in the presence of a syrinx, while approximately 40% of patients with cough-related headache and 89% of patients with nausea who were managed conservatively showed improvement at follow-up. At the present time, there is no consensus about surgical indications for patients with CM1; however, the presence of syringomyelia has been frequently advocated as an indicator for surgery.3,4

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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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