Angiographic studies have demonstrated improved visibility of glial tu
mors after hyperventilation. The present study was undertaken to deter
mine whether hyperventilation would change the MR enhancement characte
ristics of various glial tumors. Eighteen patients were studied twice:
once with standard contrast-enhanced MR imaging and again with standa
rd imaging plus hyperventilation. After hyperventilation, six low-grad
e astrocytomas showed no change and three showed a small decrease in r
elative enhancement (<10%), The ependymomas showed a 10% to 13% increa
se in the degree of enhancement, but no change in the area of enhancem
ent. All the anaplastic astrocytomas showed an increase in the degree
of enhancement (mean, 38%), Three of the anaplastic astrocytomas showe
d new foci of enhancement that were not seen on the nonhyperventilatio
n study, Hyperventilation appears to be an inexpensive and safe method
for increasing the conspicuity of abnormal areas of the blood-brain b
arrier.