By Victoria White
GAINESVILLE, Fla.---An increasingly popular surgical technique to alleviate
symptoms of Parkinson's disease also improves memory--a finding that surprised
researchers, a new University of Florida study shows.
Pallidotomy surgery, which involves precision burning of a small spot in the
brain, provides relief for many patients from some of the tremors and muscle
rigidity associated with the central nervous system disorder.
Parkinson's patients also frequently have problems with memory, but
researchers did not expect the procedure to help.
"The surgery is done in an area of the brain that is not thought to affect
cognition--the process by which we learn about the world around us," said Dawn
Bowers, a neuropsychologist at UF's College of Medicine. She presented her
findings (4/16/97) at a recent meeting of the American Academy of Neurology in
Parkinson's is an incurable chronic movement disorder affecting 500,000 to
1.5 million Americans. Sufferers produce too little dopamine, a chemical that
helps transmit messages between regions in the brain that facilitate muscle
movement. This leads to increased activity in an area of the brain known as
the globus pallidus and contributes to Parkinson's tremors and rigidity.
In pallidotomy, a neurosurgeon probes through a small hole in the skull,
guided to the pallidus by the body-scanning technique known as magnetic
resonance imaging. The neurosurgeon stimulates the area, testing to see which
sites affect disease symptoms. Those spots are then heated to interrupt the
overactive brain circuitry. At UF, the surgery is performed by Dr. William
Friedman, of UF's Brain Institute and College of Medicine.
The procedure is not a cure, and patients continue to need medication. But it
does improve the quality of life for many who typically have had trouble with
routine tasks because of their tremors, stiffness and difficulties with
walking and balance. Pallidotomy generally is considered appropriate only when
medication loses effectiveness or its side effects become too disabling.
"Often what we see in patients with Parkinson's disease is that they have
become much slower at all tasks, including the retrieval of memory. It's not
to the same degree as with Alzheimer's disease, but they do show mild to
moderate problems with memory and slowness in their thinking," Bowers said.
In the research presented in Boston, 21 patients were included in the
analysis. The improved-memory trends continued with 25 patients not included
in the original group, she said.
Three months after undergoing the procedure at Shands Neurological Center at
UF, patients generally scored better than before the operation on a word
memorization test. Specifically, they improved on a section in which they were
"Their cued recall improved, but their free recall did not," said Bowers, an
associate professor of neurology and clinical psychology.
Across the board, individuals tended to remember, with assistance, two or
three more items out of a list of 16 common words than they had before the
surgery. "For example, we would ask, `Which of the words were vegetables?'
That sort of clue was more helpful after pallidotomy," Bowers said. Different
lists were used before and after surgery.
"A final part of the test assessed something called recognition memory. There
we would ask a yes -or-no question about individual words. `Was pencil on the
list?' They also improved in that area," Bowers said.
Many patients had not noticed any improvements in their memory. "For others,
it was strong enough that they noted it and were pleased, but usually they're
happier about the improvements in their motor symptoms. That is much more
important to them," Bowers said.
A study published last year in the Annals of Neurology provides one possible
explanation for the unexpected improvements, Bowers said.
"The study showed increased activity in the front part of the brain after
pallidotomy. One area that was more active was the dorsolateral frontal lobe.
That may be significant because it plays a role in the retrieval of memory."
Bowers plans follow-up assessments of the patients in the coming years to
determine if the memory improvements are fleeting or long-lasting.
The research is supported in part by grants from the National Parkinson
Foundation, which has established a Center of Excellence at UF.
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