Astrocytes are intimately related to the neurons of the brain. They
act as a scaffold upon which the neurons and their processes are arranged.
They are involved in guiding the growth of neurons during development.
They may also be involved the regulation of ionic fluxes in the microscopic
environs immediately surrounding the neurons. Neurons of course, are the
basic cellular elements of the brain. Their concerted actions control the
Two types of astrocytes have been identified: protoplasmic and fibrous.
The concentrations of either differ with respect to the geographic location
within the brain. Protoplasmic being found in grey matter( the location
of neuron cell bodies), and fibrous types more common in white matter(made
up of the processes of neurons).
Basically there are two types of these tumours: benign and malignant.
The most common type to occur in adults are the aggressively-growing or
malignant type: glioblastoma multiforme and anaplastic astrocytoma. Adolescents
and younger children are more likely to have low grade astrocytomas.
Benign or low grade astrocytomas are typically slow growing. Infiltration
of adjacent normal brain is very common. Typical locations in children
and adolescents include the cerebellum, visual pathways, and other central
locations. Sometimes the tumour presents as a discrete nodule in the wall
of a fluid-filled cyst. The pressure exerted on the brain by this enlarging
sac, which is actually fluid secreted by the tumour, causes an increase
in the pressure within the head. This may manifest as headaches or nausea
and vomiting. Centrally located tumour may also announce themselves in
this way. Tumours located in the visual pathways may cause a change in
vision or possibly bulging of one eye more than the other.
Surgery has been proven to be curative if the resection is complete.
Sometimes the effects of the surgical procedure are enough to cause a halt
in the growth of the tumour. If there are significant amounts of residual
tumour left after an operation, supplemental radiation may be necessary.
Remnants of tumour may be left behind in some instances because a complete
removal of the tumour would entail an unacceptable side effect such as
blindness or paralysis. Determination of the growth characteristics of
the tumour specimen can be performed to assess for the need for radiation
after surgery. If the growth potential of the tumour is low, a wait and
see attitude may be adopted. This is undertaken especially in younger children
so that the ill effects of the radiation treatments may be delayed until
the brain has reached its full potential. If the tumour shows more aggressive
characteristics, then radiation therapy is the standard fare after surgery.
Conventional radiation delivery techniques are usually employed. Radiosurgical
uses in this field are still under investigation. Long-term survival for
these patients depends on the completeness of surgery. The prognosis for
the faster growing types of low grade astrocytomas is unfavorable but certainly
longer than their malignant brethren.
The most common brain tumour in adults arising from within the brain
itself is the glioblastoma multiforme. A very aggressively growing and
relatively radiation-resistant tumour, infiltration of surrounding brain
tissue is the rule. The best chances for survival lie in the patients'
age and functional status prior to surgery. An age greater than 65 years
and the inability to function independently portend a swift demise. The
best treatment consists of surgery combined with radiation. No surgery
has been proven to be curative. The estimated survival for patients with
anaplastic astrocytomas is maybe two years. Patients with glioblastomas
survive from upwards of 6-9 months. Promising results with regard to extending
survival have been reported with delivery of a boost of radiation to the
operative bed. This involves the use of brachytherapy or radiosurgery.
Brachytherapy involves the temporary implantation of radioactive seeds
in the brain adjacent to the previously located tumour(brachy means short).
Radiosurgery delivers an additional boost of radiation through the use
of x-rays or gamma rays, obviating the need for another open surgery. Reoperation
for removal of dead, irradiated brain tissue may be necessary at a later
date because of local swelling effects. Only a select group of patients
may benefit from this additional therapy.
May 8, 1996
Astrocytoma Links Page
Disclaimer:These links are provided for information purposes only. The
author of this page claims no responsibility for any of the content provided
by these sites. The worldwide web can sometimes contain false or misleading
information. Use this information at your own risk and discretion.
Back to Jim Kenzig's Home