[Note: Chiari-1 malformation is when a bony compartment at the base of the skull is too small or malformed, causing some degree of herniation of the lower brain into the spinal canal and putting pressure on the brainstem and spinal cord. In the past it was speculated that this might cause many cases of ME/CFS and FM, for which corrective surgery could be therapeutic.]
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 if CIM is more common among FM patients than pain- and fatigue-free controls.
Methods: 176 participants with FM and 67 pain- and fatigue-free controls underwent magnetic resonance imaging of the brain and upper cervical spine. Posterior fossa CSF flow was assessed with cardiac gated cine phase-contrast imaging at the craniocervical region.
CIM was defined as:
1) Inferior extension of cerebellar tonsils 5 mm or more below the basion-opisthion line of the foramen magnum, or
2) Tonsillar position 3-5 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 Fisher's 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 Caucasian (89% vs. 73%) and female (93% vs. 54%; p-values < 0.01).
Mean tonsillar position and the prevalence of CIM (2.8% vs. 4.5%; p=0.69) was similar in the FM and control groups.
FM patients experienced more headaches, pain, fatigue, and sleep disturbances than controls (p-values < 0.01).
Conclusion: Most patients with FM do not have CIM pathology. Future studies should focus on dynamic neuroimaging of craniocervical neuroanatomy in patients with FM.
Source: Neurosurgery, Nov 30, 2010. PMID: 21135714, by Watson NF, Buchwald D, Goldberg J, Maravilla KR, Noonan C, Guan Q, Ellenbogen RG. Departments of Neurology, Medicine, and Epidemiology, Seattle VA Epidemiologic Research and Information Center; Depts of Radiology and Neurological Surgery, University of Washington, Seattle, Washington, USA.