Neurosurgical Consultants: Nervous System Tumors - Malignant: Cerebellar Astrocytomas

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BRAINSTEM GLIOMA

Brain Stem Gliomas tend to occur during childhood and adolescence although adult varieties are well known and sufficiently frequent in our Neurosurgical Practice to warrant special mention.

SYMPTOMS

The most common initial presenting complaints are:

gait (walking) disturbance
headache
nausea/vomiting
double vision
facial weakness
trouble swallowing
hoarse voice
motor weakness

hydrocephalus

DIAGNOSIS

These tumors are primarily diagnosed by MRI scans.

TREATMENT

Surgery

Although treatment is usually non-surgical, there are some significant exceptions, such as in cases where there is an exophytic (extending outside the Brain Stem) component, a large cystic component within the Brain Stem or a small, discrete lesion that is close to a surface of the Brain Stem.

The direct surgical management of Brain Stem tumors is generally regarded as "controversial" by a majority of Neurological Surgeons with few having any real interest in attempting these operations. Any direct Neurosurgical Operation on these lesions requires considerable experience, judgment and meticulous Microsurgical Technique.

Figure 2: MRI Scan (Transaxial View Same patient as Figure 1)
This is an extensive Brain Stem tumor in a 38 year old female indicated by the Curved Arrow.
The tumor was surgically accessible through a Posterior Fossa Craniotomy in a plane along the Right lateral aspect of the 4^th Ventricle (Arrow) without producing any additional neurological deficits. The tumor proved to be a highly malignant.
The 4th Ventricle (Horizontal Arrow) is only minimally displaced by the Tumor.
Radiation therapy and chemotherapy were effective in controlling the tumor for 5 years. Ultimately the patient succumbed to this dreadful lesion.

Figure 3: MRI Scan (Sagittal View - Gadolinium enhanced). Cystic Brainstem "Mixed Glioma" in a 41 year old lady with Neurofibromatosis. The Cystic (Curved Arrow) Brainstem lesion progressively enlarged resulting in severe Brainstem compression and neurological compromise.
Gadolinium "enhancing" infiltrating "Mixed Glioma" of the Brainstem and upper portion of the Cervical Spinal Cord (Horizontal Arrow.)

Figure 4: MRI Scan (Transaxial View) Cystic Brainstem "Mixed Glioma" (Same Patient as Figure 3).
Note the thin remnant of the severely compressed Brainstem (represented by the dark "crescent-shaped" structure) that remains Anteriorly and Laterally as if it was draped around the Cyst (Horizontal Arrow).

Figure 5: MRI Scan (Sagittal View) Post-operative study after excision of the posterior wall of the Cyst (Curved Arrow.)
COMPARE this to the pre-operative MRI in Figure 3.
Focused Beam Radiosurgery and Chemotherapy followed the surgical treatment.
OPERATIVE VIDEOS OF THIS OPERATION ARE AVAILABLE ON THIS WEBSITE

Radiation therapy

Radiation therapy is generally regarded as the primary treatment method for the majority of Brain Stem Tumors, particularly when incorporating Radiosurgery (Focused Beam Radiation) as the "delivery" system.

Chemotherapy

Modern Chemotherapy is the third arm of a comprehensive effort to prolong and maintain a high quality of life for these patients. While some traditional and common chemotherapeutic regimens remain in use, we favor the newer medications such as Temodar (temozolamide), Avastin (bevacizumab, an anti-angiogenesis agent) and CPT-11, either alone (or more commonly) in combination or with other drugs. These new regimens have been utilized to produce encouraging results by one of our Neuro-oncologists Additional information regarding these treatments is available at the "Virtual Trials" website.

CEREBELLAR ASTROCYTOMAS

Cerebellar Astrocytomas are one of the more common pediatric Brain tumors (10%), comprising 27% of pediatric Posterior Cranial Fossa tumors. They are much less common in adults. The post-operative survival is longer than other types of Astrocytomas.

SYMPTOMS

The most frequent and almost universal symptom is Headache with or without Nausea and Vomiting (these latter symptoms usually occur later in the course of the disease when the intracranial pressure is abnormally increased.) In additional to all of the symptoms present in patients with increased intracranial pressure, tumors in the Posterior Cranial Fossa can cause Gait Disturbance, increased Clumsiness as well as Double Vision (Diplopia.)

DIAGNOSIS

MRI Scan is the most reliable and accurate neuroimaging procedure.

TREATMENT

Surgery

Surgical excision of the maximal amount of the tumor that can be removed, without producing neurological deficits, is the appropriate treatment. In tumors composed of a nodule and a cyst, excision of the nodule is usually definitive therapy. These patients generally have a high rate of long term (5 to 10 or more year) survival.

Figure 4: Operative Photo (Same Patient)
Opening of the Left Cerebellar Hemisphere to reveal the "Mural Nodule" (Curved Arrow)
Part of the Cyst wall can be seen just below the "Nodule" (Horizontal Arrow.)

Figure 5: Operative Photo same patient)
There is a large residual "Cystic Cavity" (Arrows) AFTER the "Mural Nodule" has been widely excised.
The Cyst "Wall" is made of "compressed normal" tissue.
There is no reason to remove any further tissue.
See Follow-up MRI Scans below.

Radiation Therapy

Radiation therapy is not recommended in these cases, since the complication rates of Radiation Therapy in patients whose expected survival for 5 or more years, is quite high.

Follow-up Required

Careful attention to follow up is required using repeat MRI scans. Repeat operation is appropriate, if there is a recurrence of the tumor.

Figure 8: MRI Scan (Sagittal View-Post-Gadolinium)
Compare this to the Pre-operative MRI in Figure 3.
The patient made a rapid post-operative recovery and remains without symptoms.
Note the tiny remnant of "scarred" Cyst wall (Arrow). THIS MUST BE FOLLOWED with MRI Scans.

Chemotherapy

Chemotherapy is not appropriate for these tumors since the lesions are not aggressive and are usually definitively managed by direct surgical resection.

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This page last edited on 5/9