Brain surgery shows
success in removing blood vessel tangles
BY KRISTA CONGER
A large-scale study by
Stanford physicians has shown for the first time that
innovative surgical techniques and lots of experience can
aid surgeons in safely removing malformed blood vessels
lurking deep within the brains of affected people. Until
now, discovery of such a renegade vessel nestled within a
forest of critical brain structures forced a nightmarish
choice on patients and their doctors.
Without medical
intervention, the abnormally thin walls of the
cauliflower-shaped masses can spontaneously rupture.
Blood from the resulting hemorrhage can compresses
adjacent tissue and cause a devastating stroke with
serious neurological consequences or even death. But
surgeons are often reluctant to attempt removal of this
type of deep lesion for fear of damaging the surrounding
regions, which control such basic functions as
respiration, circulation, movement and consciousness.
"It's extremely
difficult to get there without injuring other important
brain structures or cranial nerves," said Gary
Steinberg, MD, PhD, professor and chairman of the
department of neurosurgery.
Steinberg, lead author on
a paper appearing in this month's issue of the journal
Neurosurgery, operated on 56 patients with deep vascular
malformations from 1990 to 1998. By mapping an individual
brain's geography during surgery and altering the
surgical entry site based on the location of the lesion,
he and his team were able to completely remove the
lesions more than 90 percent of the time.
Although some of the
patients experienced a temporary worsening of their
symptoms of partial paralysis, muscle weakness and
numbness, the majority of patients experienced an overall
improvement after about six months of healing.
Neurological symptoms improved over the long term in 52
percent of patients, and in 43 percent their extended
outlook remained unchanged. Only five percent of the
patients saw their long-term conditions worsen after
surgery.
Even if a patient's
symptoms remain unchanged after surgery, a complete
removal of the faulty vessels eliminates any risk of
another bleeding episode. Estimates of the risk of
hemorrhage from the lesions vary, but it may be as high
as 29 percent each year for some malformations in certain
patients, said Steinberg.
To make matters worse, the
same faulty vessels can rupture multiple times, and each
bleeding episode carries with it the threat of permanent
neurological damage or death.
Known as angiographically
occult vascular malformations, or AOVMs, the
tongue-twisting name of the distorted vessels comes from
their ability to hide from an angiogram, the traditional
screening method used to pinpoint strange vascular
formations or abnormal blood flow throughout the body.
The flow of blood through AOVMs is simply too slow for an
angiogram to visualize
Most AOVMs are thought to
be congenital, and they "blossom" periodically
as they leak, accumulating blood within and surrounding
the AOVM. Surgeons use magnetic resonance imaging (MRI)
to diagnose most AOVMs, because these scans can detect
the blood that gathers from repetitive leakage of the
thin-walled vessels.
Steinberg estimates that
up to one in 300 people may be harboring the dangerous
malformations, although not all are situated in deep
locations or need medical treatment. Not all AOVMs need
to be treated because some are less prone to bleeding and
causing clinical problems, and some are located in less
critical areas where a small leak would not cause serious
symptoms, Steinberg said.
Although physicians
sometimes stumble upon an undiagnosed AOVM during testing
for other conditions, most AOVMs are discovered after a
bleeding episode has caused noticeable problems. Patients
usually experience stroke-like symptoms such as partial
paralysis, numbness or double vision. Sometimes the only
clue is a severe headache.
"Once it has bled
clinically, we become more concerned," said
Steinberg. And that's when the new surgical techniques
come into their own. Steinberg uses an MRI scan to
precisely pinpoint the three-dimensional location of the
troublesome vascular malformation before surgery. A laser
pointer calibrated to a computer-generated image in three
planes helps guide his scalpel as he looks through the
microscope during surgery.
As he begins the
operation, sophisticated equipment monitors the
electrical potential of the surrounding brain regions,
measuring sensory signals from the arms and legs, as well
as from the patient's facial muscles. The interactive
feedback allows Steinberg to determine when he is getting
dangerously close to critical brain structures.
Finally, tailoring the
surgical entry point to the location of the AOVM can also
increase the chances of a successful removal. Steinberg
has found that entering the brain from the base of the
skull affords him a less-hazardous path to the brainstem,
thalamus and basal ganglion, where the lesions are often
found.
Steinberg's experience and
success rate with the complex surgery have helped make
Stanford the place to send patients with deep AOVMs. He
estimates that he performs the complex surgery about once
a month.
Co-authors on the study
were Steven Chang, MD, current cerebrovascular surgery
fellow; Robert Gewirtz, MD, previous cardiovascular
surgery fellow; and Jaime Lopez, MD, assistant professor
of neurology. The study was supported by funding from
Bernard and Ronni Lacroute, by the William Randolph
Hearst Foundation, and by John and Dodie Rosekrans. SR
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