Health-related Quality of Life in Chiari Malformation Type 1 - A National Cross-Sectional Patient Survey

This is an observational, cross-sectional survey study investigating health-related quality of life (HRQoL) in adults with Chiari malformation type 1 (CM1).

A total of 1,004 adults with CM1 will be invited to participate, including 666 patients who have undergone surgery for CM1 and 338 patients who have not. Participants were identified through the Swedish National Board of Health and Welfare's National Patient Register, which holds data on all inpatient episodes as well as specialized outpatient visits in Sweden.

Operated patients were identified based on diagnosis of Arnold Chiari Malformation (ICD-code Q07.0) and posterior fossa decompression (procedure code ABE50) recorded in the National Patient Register between 2011 and 2024. Non-operated patients were identified based on a diagnosis of CM1 (ICD-10 code Q07.0) recorded during a visit to a neurosurgical outpatient clinic between 2021 and 2024. Patients with a diagnosis of spina bifida (ICD-10 code Q05.X) were excluded from the overall cohort. Non-operated patients with a record of duraplasty (procedure code AAK10) or another operation on the cranium or dura (procedure code AAK99) were excluded.

Participants will be contacted by mail and invited to complete an online survey administered through REDCap, hosted by Karolinska Institutet. The survey includes the Swedish version of the EQ-5D-3L, including the EQ Visual Analogue Scale (EQ-VAS), the Hospital Anxiety and Depression Scale (HADS), and a study-specific questionnaire focusing on clinical characteristics, medication use, sick leave, return to work, and attitudes toward surgical treatment.

Survey data will be linked to relevant information from the National Patient Register and the Swedish Social Insurance Agency. Register data will include information on diagnoses, surgical treatment, comorbidities, and relevant social insurance variables.

The primary outcomes are HRQoL measured using the EQ-5D-3L index score and EQ-VAS score. HRQoL will be compared with normative data collected from a general population in Stockholm, Sweden. HRQoL and associated factors will also be compared between operated and non-operated participants.

A priori power calculations indicated that, assuming a clinically relevant difference of 0.10 in EQ-5D index score, a standard deviation of 0.25, and a two-sided α of 0.05, responses from approximately 22% of the study population would be sufficient to achieve 80% power. Since the expected response rate is 30-50%, approximately 1,000 patients were chosen to ensure an adequate sample size.

Descriptive and inferential statistical methods will be used to evaluate differences between groups and identify factors associated with HRQoL. Continuous variables will generally be summarized using medians and interquartile ranges, and categorical variables using frequencies and proportions. Regression analyses will be used to identify possible predictors of better or worse HRQoL.

Participation is voluntary and requires informed consent. Personal data will be handled in accordance with applicable legislation and institutional procedures, with appropriate measures taken to protect participant confidentiality and data security.

Inclusion criteria

• diagnosis of Arnold Chiari Malformation (ICD-code Q07.0)
• for operated patients: record of posterior fossa decompression (procedure code ABE50)
• for non-operated patients: the diagnosis Q07.0 recorded during an outpatient visit to a neurosurgical unit

Exclusion criteria

• record of spina bifida diagnosis (Q05.X)
• for non-operated patients: record of the procedures duraplasty (procedure code AAK10) or another operation on the cranium or dura (procedure code AAK99)