Posterior fossa ratio (PFR) in Chiari I malformation (CIM): Is size a predictor of improvement following decompressive surgery?

J. S. Trêves, L. G. Leibrock, D. J. Long, G. F. Moore

Research output: Contribution to journalArticlepeer-review


Accurate determination of posterior fossa ratio is possible using multiplanar MRI. PFR = (ITAS + ITAAx /STAS + STAAx) x 100. Previously, it was determined the PFR is significantly smaller in CIM compared to forme fruste CIM (FFCIM) and normal patients. Posterior fossa (PF) midsagittal area is similar in CIM and FFCIM but significantly smaller than normal. Interestingly. PF axial area is similar in normal and FFCIM patients but significantly smaller in CIM. Lack of symptomatology in FFCIM may be due to the near normal axial area of the posterior fossa. Currently, no preoperative test is predictive of improvement following decompressive surgery. A retrospective analysis was performed to determine if the PFR will be predictive in determining which clinical signs, symptoms and duration of signs and symptoms are responsive to decompression. PFR is retrospectively correlated with preoperative signs and symptomatology in 25 CIM patients who underwent decompressive surgery 1985 to present. Outcome scores and relief from signs of hindbrain compression are determined by patient questionnaire and statistically evaluated with respect to the preoperative and postoperative state. Discussion concerns usefulness of PFR as a predictive tool for preoperative selection and counseling with regard to relief of neurological deficit.

Original languageEnglish (US)
Pages (from-to)40
Number of pages1
JournalSkull Base Surgery
Issue numberSUPPL. 1
StatePublished - 1997
Externally publishedYes

ASJC Scopus subject areas

  • Clinical Neurology


Dive into the research topics of 'Posterior fossa ratio (PFR) in Chiari I malformation (CIM): Is size a predictor of improvement following decompressive surgery?'. Together they form a unique fingerprint.

Cite this