The preoperative MRI assessment of adult intracranial diffuse gliomas

© 2018 Dr. Arian LasockiMRI (Magnetic Resonance Imaging), is an integral part of the management of intracranial diffuse gliomas, consisting of both astrocytomas and oligodendrogliomas, and ongoing improvements in MRI technology continually enhance its value. While advanced MRI techniques are adding to the functional information available, standard sequences remain the mainstay of the assessment, and are also being improved. Initially, MRI provides critical diagnostic information and aids neurosurgical planning, but its role is expanding beyond these primary functions, as outlined in this thesis. Improved identification and delineation of the tumour allows optimal management by surgical resection and adjuvant radiotherapy. MRI is also important for prognostication, by identifying features that may convey a better or worse prognosis. The addition of MRI information to clinical data and the histopathological assessment thus provides the most comprehensive assessment of the individual patient. The recent 2016 update to the WHO classification of central nervous system tumours has led to significant changes in the histological characterisation of gliomas, now providing an integrated genotypic and phenotypic classification1. The two steps in the genotypic classification of gliomas is testing for an isocitrate dehydrogenase (IDH) mutation, and if present, determination of 1p/19q status1. There are logistic and cost issues, however, and MRI can aid decision-making. The value of MRI in this context is greatest when access to definitive testing methods is limited, and the focus on the molecular phenotype in the new WHO classification increases the potential for a combined histologic-MRI assessment method at such centres. Due to its ability to assess the entire tumour and provide non-invasive characterisation over time, MRI also has the potential to overcome some of the limitations of both the phenotypic and genotypic assessment, including sampling error, intra-tumoural heterogeneity and monoallelic gene expression. Information obtained by MRI is also increasing our understanding of the disease, well demonstrated by the growing interest in the non-enhancing component of tumour. Gliomas are essentially incurable, with recurrence almost inevitable despite optimal therapy. There is thus growing interest in advanced surgical techniques aimed at more aggressive management, and accurate delineation of the tumour by MRI provides a critical guide to the surgeon