The typical case of low-grade glioma is of a young adult who has had an epileptic fit, who has no neurological deficit, and in whom a brain scan has shown an intrinsic cerebral tumor without any contrast enhancement. The tumor may be remarkably large or relatively small. It may appear to be relatively well circumscribed, or it may be diffusely infiltrating. It may be very close to eloquent brain, or it may be located in the tip of one of the frontal, temporal or occipital lobes, or deep within the basal ganglia. It can be appreciated at once that there can be no single treatment policy for a tumor type that can be so variable. This variety of forms also explains why the neurosurgical literature is so unsatisfactory on the subject of low-grade gliomas, since few, if any, of the published papers stratify their results in accordance with the varied macroscopic anatomy.
The question that arises with this "typical" patient is whether any treatment should be offered at all, given the lack of evidence that treatment makes any significant difference to overall survival or median time to progression if patients with low-grade gliomas are taken as a whole. The central problem in the management of low-grade gliomas is whether radical or debulking surgery in patients without raised intracranial pressure makes any difference to long term prognosis. In other words, it is simply not known whether the extent of surgical resection has any impact on prognosis or not in these patients. A further problem is that there is no easy way of defining the extent of surgical resection; surgeons talk about "radical" or "subtotal" removal, or "debulking" of these tumors, but have no way of quantifying this. Post-operative MRI scanning clearly helps to some extent, but for the reasons mentioned earlier, these scans can be hard to interpret. Nevertheless, despite this central uncertainty, the neurosurgeon must make a decision on whether to operate or not, and if so, what form the operation should take.
For practical purposes, the management of low-grade gliomas can be divided into five groups. For the purposes of this discussion, "complete" resection is taken to mean "curative" resection, as shown by subsequent, long-term follow-up scanning, whereas "radical" resection only means that initial follow-up scanning shows no residual tumor. The groups are:
Large tumors in eloquent areas that, on the basis of the pre-operative scan, are too large for extensive resection to be possible without an unacceptably high risk of producing a major post-operative neurological deficit
Small tumors where, on the basis of the pre-operative scan, complete or radical resection is anticipated with little risk of neurological damage
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