Magnetic resonance spectroscopy in the assessment of pilocytic astrocytomas

BackgroundPilocytic astrocytomas (PA) are common childhood brain tumours whose management and prognosis vary widely depending on location. ¹H magnetic resonance spectroscopy (MRS) measures biochemistry in vivo and shows promise for characterising brain tumours and aiding management.MethodsSingle voxel MRS (1.5 Tesla, TE 30 ms, TR 1500 ms) was performed on 27 children with PAs. Cases were designated ‘progressors’ if tumour progression led to their clinical management plan being altered.ResultsPrior to treatment, supratentorial tumours had significantly higher myo-inositol (p < 0.01, t-test) and glutamate plus glutamine (p = 0.02, t-test) than cerebellar tumours. Optic pathway or thalamic tumours that progressed had a significantly (p = 0.04, t-test) lower myo-inositol at initial MRS than those with stable disease. Myo-inositol levels decreased significantly in progressors between the initial and subsequent MRS (p = 0.03, paired t-test). Changes in myo-inositol occurred before clinical and radiological progression.ConclusionsMRS identifies differences with anatomical location in PAs and yields potential non-invasive biomarkers of prognosis.