Zurich pituitary score

Last revised by Bálint Botz on 6 Dec 2021

The Zurich pituitary score (ZPS) is a quantitative classification of pituitary adenomas based on coronal T1W magnetic resonance imaging with contrast, although the score can also be obtained with computed tomography.

The ZPS is based on the ratio (R) between horizontal tumor diameter over intercarotid distance at the horizontal intracavernous C4 (Bouthillier) segment. The rationale behind this is that the further laterally to the ICA the tumor extends radiologically, the higher the risk for cavernous sinus invasion is, and the more difficult complete resection is.

R ratio: defined as the ratio of the maximum horizontal tumor diameter divided by the minimum intercarotid distance at the intracavernous horizontal C4 segment of the ICA:

  • grade I: R ≤ 0.75
  • grade II: 0.75 < R ≤ 1.25
  • grade III: 1.25 < R
  • grade IV: encasement of the intracavernous ICA

A high correlation of R Ratio and extent of resection, as well as gross total resection rate, has been observed. The ZPS is the most effective stratification of the R Ratio in this regard 4,5:

  • grade I: 92% gross total resection rate
  • grade II: 77% gross total resection rate
  • grade III: 67% gross total resection rate
  • grade IV: 15% gross total resection rate

More importantly, the ZPS correlates with the extent of resection and residual tumor volume. The score can be applied as an adjunct to predict gross total resection 3.

The ZPS has demonstrated excellent interrater reliability, which has been a problem with other classifications such as the Knosp scale 1,2.

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Cases and figures

  • Case 1: ZPS grade I
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  • Case 2: ZPS grade II
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  • Case 3: ZPS grade III
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  • Case 4: ZPS grade IV
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