The Zurich pituitary score is a quantitative classification of pituitary adenomas based on coronal T1-weighted magnetic resonance imaging with contrast, although the score can also be obtained with computed tomography.
The Zurich pituitary score is based on the ratio between the horizontal tumor diameter and the intercarotid distance at the horizontal intracavernous (C4 Bouthillier classification) 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 and the more difficult complete resection is. Therefore, it seeks to provide information similar to the Knosp scale.
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Definition
Ratio (R): is the ratio of the maximum horizontal tumor diameter divided by the minimum intercarotid distance at the intracavernous horizontal C4 segment of the ICA 4,5.
grade I: ≤ 0.75
grade II: 0.75 < ratio ≤ 1.25
grade III: 1.25 < R
grade IV: encasement of the intracavernous ICA
Clinical relevance
A high correlation of R Ratio and extent of resection, as well as gross total resection rate, has been observed. The Zurich pituitary score 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 Zurich pituitary score correlates with the extent of resection and residual tumor volume. The score can be applied as an adjunct to predict gross total resection 3.
Reliability
The Zurich pituitary score has demonstrated excellent interrater reliability, which has been a problem with other classifications such as the Knosp scale 1,2.
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