The effect of glucocorticoids in the normal cerebral hemisphere of brain tumour patients

Objectives - To study the potential effects of glucocorticoids (GC) in normal white matter (WM) of the contralateral cerebral hemisphere in brain tumour patients in a prospective protocol. Materials and methods - Using MR relaxation time (RT) imaging (T-1 and T-2-maps), 190 different scanning sessions were performed on 42 brain tumour patients before and after initiation of GC-treatment. RT imaging correlates closely with in vivo tissue water content (reported estimation accuracy error <4%). Repetitive studies were performed in order to study changes as a function of time. RTs were measured in the contralateral frontal and occipital white matter (WM). Results - The mean change in T-1 after initiation of GC treatment was 1.6 +/- 1.7% (P = 0.24), and 1.8 +/- 3.8% in T-2. The mean coefficient of variation for the pooled data in all patients was 1.4% for both T-1 and T-2. There were no differences in effect between different histological types of tumours or sex. Conclusion - GC treatment does not influence in vivo cerebral water content expressed as relaxation times of apparently normal WM. The neurological effects in brain tumour patients are normally evident within 24 h, but do not seem to correlate with changes in brain water content. The normal biological variation in RTs land thereby in vivo tissue water content) in normal WM of brain tumour patients is very small and approaches the expected fluctuations in the MRI measurement technique.