The striate sign: peritumoural perfusion pattern of infiltrative primary and recurrent gliomas

MR perfusion depicts angiogenesis as a key factor for growth and malignancy in gliomas by means of increased regional cerebral blood volume (rCBV). The rCBV increase is not limited to the tumour area, but may also produce a stripe-like pattern of peritumoural rCBV increase that we defined as the "striate sign". We evaluated if prior radiochemotherapy influences perfusion values and pattern in and adjacent to malignant gliomas comparing rCBV of treated recurrent gliomas with untreated gliomas. Ninety-three patients with primary or recurrent WHO grades II-IV glial tumours underwent T2*-weighted dynamic susceptibility-weighted contrast-enhanced (DSC)-MRI. Differences of normalised rCBV and rCBV(max) were evaluated using Kruskal-Wallis analysis with post hoc tests. The number of cases showing a hot spot of rCBV (rCBV(max)) and/or a peritumoural striate pattern of rCBV increase (striate sign) was assessed and evaluated by Fisher's exact test. Significance level was determined as p < 0.05. Normalised rCBV, rCBV(max) and number of cases with the striate sign were significantly lower in recurrent (rCBV = 3.24 +/- 1.22, rCBV(max) = 5.05 +/- 2.27 and striate sign = 10/24) compared to primary WHO grade IV tumours (rCBV = 4.44 +/- 1.39, rCBV(max) = 7.31 +/- 3.0 and striate sign = 17/21, respectively). There were fewer cases with a striate sign in treated recurrent WHO grade III tumours than in untreated malignant transformed WHO grade II tumours. The pattern and degree of rCBV increase in and around gliomas differ between untreated and previously treated tumours. These differences might be due to post-therapeutic changes of the tumour-associated microvasculature by radiochemotherapy. Spectroscopic and susceptibility-weighted MR imaging may provide further insights into the tumour biology.