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BACKGROUND: The symptoms of Chiari I Malformation (CIM) and fibromyalgia (FM) overlap. Some FM patients have been surgically treated for presumed CIM-type pathology.

OBJECTIVE: To determine whether CIM is more common among FM patients than pain- and fatigue-free controls.

METHODS: One hundred seventy-six participants with FM and 67 pain- and fatigue-free control subjects underwent magnetic resonance imaging of the brain and upper cervical spine. Posterior fossa cerebrospinal fluid flow was assessed with cardiac gated cine phase-contrast imaging at the craniocervical region. CIM was defined as inferior extension of cerebellar tonsils ≥ 5 mm below the basion-opisthion line of the foramen magnum or tonsillar position 3 to 5 mm below the basion-opisthion line plus abnormalities of CSF flow, posterior fossa volume, or hindbrain or cervical spinal cord movement. Visual analog scales, questionnaires, and interviews were used to collect data on sleep quality, fatigue, pain, and headache. We used regression techniques to examine the association of outcome measures with disease status and the Fisher exact test to compare the CIM prevalence in the 2 groups.

RESULTS: The FM group was older (mean age, 50 vs 40 years) and more likely to be white (89% vs 73%) and female (93% vs 54%; P < .01). Mean tonsillar position and the prevalence of CIM (2.8% vs 4.5%; P = .69) were similar in the FM and control groups. FM patients experienced more headaches, pain, fatigue, and sleep disturbances than control subjects (P < .01).

CONCLUSION: Most patients with FM do not have CIM pathology. Future studies should focus on dynamic neuroimaging of craniocervical neuroanatomy in patients with FM.

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