Neurosurgery Notes

Neurosurgical Treatment of Low Grade Glioma

An interview with Lee Kesterson, M.D.
Center for Neurological Disorders, Fort Worth

Some physicians separate gliomas into "benign" or "malignant", and some classify them by grade. Low grade tumors, grade 1 and 2, often grow over a period of years. High grade gliomas, usually called anaplastic astrocytomas (grade 3) and glioblastoma multiforme (grade 4) grow much more rapidly, often causing death within months of diagnosis. However, low grade tumors can still cause death and for this reason they are not truly benign.

How do you evaluate a patient suspected of having a low grade glioma?
Sometimes the symptoms of the patient are so insidious that they will continue for years before the patient seeks medical attention. Occasionally such a patient even had a previous CT scan that was normal. An MRI scan is more sensitive than a CT scan and should be ordered if there is a strong suspicion of a tumor based on the patient's symptoms. Based on the appearance of an MRI scan, a neurosurgeon may suspect the diagnosis even before a biopsy, but other tumors may have a similar appearance. Therefore, treatment of a low grade glioma is not undertaken without confirmation by surgery.

Occasionally a patient will present with a seizure and an area on MRI scan will appear to be a low grade glioma. Some of these patients can be followed for months or years without the need for biopsy because the seizures respond to medical therapy and the tumor is unresectable and not otherwise symptomatic.

How do you decide whether a patient should have a surgical removal of the tumor or just a biopsy?
Many low grade gliomas are infiltrating tumors that can be only be partially removed. Removing some of the tumor mass, particularly if it has created pressure on the normal brain, may bring about an improvement in the patient's symptoms.

A "sampling" of the tumor, or biopsy, may be performed safely in most patients, but a biopsy would not be expected to relieve symptoms. A biopsy may be done with three-dimensional calculation of its location (a stereotactic procedure) or with a limited removal of the tumor under direct vision (an open procedure).

Complete surgical removal or resection of a low grade glioma may be considered by the neurosurgeon if he or she determines that it is safe to do so. The size and location of the tumor, as well as the general health of the patient, are important considerations in planning extensive surgery.

Does surgical removal alone ever cure low grade glioma?
The difficulty of completely removing most low grade gliomas is a barrier to surgical "cure." These tumors grow slowly, and a tumor may reappear many years later. Furthermore, low grade tumors can recur after surgery, radiation therapy, and chemotherapy.

If the tumor returns, is another surgery recommended?
Re-resection of a low glioma may be indicated in certain patients. Sometimes the patient has had radiation therapy and cannot have more radiation to this area, but nevertheless has tumor regrowth. If the patient is symptomatic, removal of the tumor a second time or even a third time can be considered.

Some low grade tumors return at the original site and, under the microscope, are identical to the first tumor. However, a large number of low grade tumors (up to fifty percent in some studies) take on more aggressive characteristics over time. The low grade tumors can evolve into anaplastic astrocytoma or glioblastoma multiforme, which are malignant gliomas.

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