Correlation of cerebrospinal fluid flow dynamics and headache in Chiari I malformation.

OBJECTIVE: The management of patients with a Chiari I malformation who present with headaches alone remains unclear. We studied the cerebrospinal fluid (CSF) flow dynamics of Chiari I malformation patients presenting with headaches alone so as to identify headache types that are associated with CSF flow obstruction versus those that may be unrelated to Chiari I malformations.
METHODS: Preoperative cine phase-contrast magnetic resonance imaging of the craniocervical junction was prospectively performed in 33 patients presenting with headaches alone and a Chiari I malformation (tonsillar ectopia >5 mm below the foramen magnum). Headaches were classified as frontal, occipital, or generalized. CSF flow dynamics were then prospectively compared with presenting symptomatology. A subgroup of 17 patients underwent surgical decompression of the Chiari I malformations.
RESULTS: Patients with frontal or generalized headaches were 10-fold less likely to demonstrate obstructed CSF flow (odds ratio, 0.10; 95% confidence interval, 0.02-0.52) and 8-fold less likely to have tonsillar descent greater than 7 mm (odds ratio, 0.12; 95% confidence interval, 0.03-0.62) compared with patients with occipital headaches. Adjusting for degree of tonsillar herniation in multivariate analysis, frontal and generalized headaches remained independently associated with nonobstructed CSF flow pathological findings, whereas occipital headaches remained associated with obstructed CSF flow independent of tonsil location (odds ratio, 5.84; 95% confidence interval, 1.01-34.28). In the surgical group, all patients with obstructed CSF flow did well compared with the group with normal flow, regardless of headache location.
CONCLUSION: Regardless of the degree of tonsillar ectopia, occipital headaches were strongly associated with hindbrain CSF flow abnormalities, whereas frontal and generalized headaches were not. Normal magnetic resonance imaging-cine CSF flow in the setting of a Chiari I malformation and frontal headaches alone suggests that frontal headaches are not pathologically or causatively associated with the Chiari I malformation in the vast majority of patients. Frontal headaches with obstructed flow may respond to surgery.