Below is the abstract of another study on neuropsychological effects of
DBS, that found opposite results from the Un. of Toronto study. This one
found no adverse effects in a study of about 60 patients,  12 months
after surgery.
BUT a critical sentence about the subjects which was not included in this
abstract, but was found in the full article is: "No other neurologic
impairment was found and brain MRI was normal.Patients were relatively
young and had no significant cognitive or mood impairment before surgery.
"
Again, let me know if you wish to read the full article (about 14pages).
Also below is a report on DBS from "Highlights From the Sixth
International Congress of Parkinson's Disease and Movement Disorders"
(the full reports is available on Medscape (www.medscape.com) -- requires
free registration) As you'll read there is some difference of opinion
among the experts on many of the questions about dbs and other surgery.
However the benefits and risks of surgery over the long term are being
studied, and it seems the research is starting to give some clues about
which people might be at a higher risk for negative results.
Any comments, opinions? How can people considering surgery best make an
informed decision?
Linda

ABSTRACT:
     National Library of Medicine: IGM Full Record Screen
TITLE:  Neuropsychological changes between "off" and "on"
            STN or GPi stimulation in Parkinson's disease.
 AUTHORS: Pillon B; Ardouin C; Damier P; Krack P; Houeto JL;
                   Klinger H; Bonnet AM; Pollak P; Benabid AL; Agid Y
 AUTHOR    INSERM EPI 007 and U 289, Federation de Neurologie
 AFFILIATION:  and Centre d'Investigation Clinique, Hopital de la
                    Salpetriere, Paris, France.
                    [log in to unmask]
 SOURCE:    Neurology 2000 Aug 8;55(3):411-8
 CITATION IDS: PMID: 10932277 UI: 20392490
 ABSTRACT:

 BACKGROUND: In a previous study on a consecutive series of 62 patients
with PD, the authors showed that bilateral subthalamic or pallidal
continuous
high-frequency deep brain stimulation (DBS) affects neither memory nor
executive functions 3 to 6 months after surgery.

OBJECTIVE: To investigate the specific effects of DBS by comparing the
performance  of patients with the stimulator turned "on" and off."

METHODS: The performance of 56 patients on clinical tests of executive
function was compared after 3 and 12 months of DBS of the subthalamic
nucleus (STN; n = 48) or the internal globus pallidus (GPi; n = 8) with
the stimulator "on" or offf." Global intellectual efficiency, verbal
learning, and mood were also evaluated with the  stimulator "on." The
performance of another group of  20 patients was compared after 6 months
of DBS of  the STN (n = 15) or the GPi (n = 5) with the stimulator "on"
or "off" on more experimental tests recently shown to be more sensitive
to l-dopa  therapy.

RESULTS: When the stimulator was "on," STN  patients showed a mild but
significant improvement in psychomotor speed and working memory. In
comparison with the presurgical state, STN patients had no cognitive
deficit at 12 months, except for  lexical fluency. There was no
differential effect of STN or GPi stimulation.

CONCLUSIONS:
1) The specific effect of DBS seems to mimic the action of l-dopa
treatment in the cognitive as in the motor domain;
 2) the surgery associated with DBS does not appear to affect the
cognitive performance of patients with PD 12 months later, except for a
mild deficit in
lexical fluency.

 MAIN MESH          Cognition/*physiology
 HEADINGS:          *Electric Stimulation Therapy
                    Parkinson Disease/*drug therapy
                    Parkinson Disease/*physiopathology
PUBLICATION TYPES: CLINICAL TRIAL
                    JOURNAL ARTICLE

------------------------------------------------------------------------

Conference Highlights From the Sixth International Congress of
Parkinson's Disease and Movement Disorders
www.medscape.com/

Deep Brain Stimulation

Dr. Pierre Pollak of the University of Grenoble, France reviewed the
merits
and disadvantages of placing deep brain stimulators in the globus
pallidum
pars interna (GPi) vs the subthalamic nucleus (STN).[20] DBS has several
advantages over permanent lesions in the treatment of PD. GPi was the
site
of choice until recently, when studies suggested that placement of the
stimulators in the STN is followed by improvement in a greater variety of
symptoms than with GPi placement. Dr. Pollak's main point was that
because
there have not yet been any studies directly comparing the 2 procedures
in
a prospective fashion, no firm general conclusion can be reached.
However, based on the experience so far reported, the following is likely
true:
1.      STN placement allows greater reduction in the dose of levodopa still
required after surgery;
2.      Dyskinesias are relieved by the 2 procedures to a similar degree, but
require less energy consumption for the STN;
3.      the risk of neurologic sequelae seems similar when each procedure is
performed unilaterally, whereas it may be lower for the STN when a
bilateral procedure is required.
The second advantage may seem trivial, but it may imply a significant
difference in how often the subcutaneous battery powering the stimulator
needs to be replaced. Thus, STN may indeed turn out to be the site of
choice for DBS placement in PD treatment. However, new applications of
GPi
DBS placement are also currently being evaluated, and in some cases are
very promising (as for generalized dystonia). Thus, GPi may turn out to
be
the site of choice for DBS in the treatment of other movement disorders.

Panel Discussion: Surgery for PD
At the end of the session on surgical treatments, a panel of speakers
addressed several questions in a forum format. The panel was chaired by
Dr.Andres Lozano of the Toronto Western Hospital, (Toronto, Canada) and
included Dr. Fahn, Dr. Pollak, Dr. José Obeso (Clinica Universitaria,
Pamplona, Spain, and Dr. Mahlon Delong (Emory University, Atlanta,
Georgia). The following questions were addressed:

How many patients with PD should undergo surgical treatment?
The range of responses was 10% to 30%. Dr. Delong added that he expects
this number to grow with continued progress in the surgical approach. Dr.
Fahn commented that surgery should be saved for later stages of the
disease, given its
risk of irreversible complications. Dr. Pollak, on the other hand, added
that a younger age is the critical factor for a good outcome, adding
difficulty to the choice of the ideal stage at which to consider surgery.
At what point in the illness should surgery be offered?
Dr. DeLong
suggested not waiting too long. Even early in the course of PD, patients
may lose employability, confidence, and social contacts, which may never
be
regained. Thus, surgery should be offered before irreversible changes in
quality of life. Dr. Obeso felt it is too early to decide; now is the
time
to focus on obtaining more data to answer this question adequately. Dr.
Pollak recommended not too early but not too late: 6 to 7 years after the
diagnosis is made seems like a good compromise between the ever-present
risk of surgical complications and the time when PD-related complications
become serious. Dr. Fahn recommended maximizing medical treatment before
considering surgery but also avoiding waiting for too advanced an age
because of the higher risk of surgical complications at later ages.

How do you select a target for the surgical procedure?
Dr. Obeso acknowledged a bias in favor of the STN but also pointed out
that comparative studies are needed before we really know the answer. Dr.
Pollak, on the other hand, questioned the worth of a large-scale
randomized  study for this question. He argued that we already know from
smaller studies that STN placement of DBS allows a greater reduction of
levodopa. A randomized study may require more than 200 patients to detect
this advantage, and he expressed doubt that such a study would be
worthwhile.

Which is preferable, surgical lesion or DBS?
Dr. Fahn acknowledged that stimulators are very expensive, both in
equipment cost and amount of time required for adjustment of parameters
after the procedure. However, he said he has so far found the improvement
more impressive with DBS than with  lesions and that the possibility of
removal of the current or even the hardware is very attractive in case of
adverse effects. Thus, he favored DBS.
Dr. Obeso pointed out that lesions may need to remain part of our
armamentarium simply because many centers may never be able to develop
the
resources needed to follow a large number of patients with stimulators.
Along the same lines, Dr. Delong mentioned that lesions may be the only
option for many years in poor countries. Finally, Dr. Pollak suggested an
option for the future, which might resolve the differences between the
techniques: progressive formation of lesions through increased
stimulation
via a DBS electrode.

How concerned should patients be about the neurocognitive adverse effects
of surgery, such as visual hallucinations, cognitive deficits, and
depression?
Dr. Pollak said these are relatively rare, except for apathy. The latter
seems to occur in about one fourth of patients and often improves by
resuming treatment with dopamine agonists. Hypomania is rare, usually
occurring transiently just after surgery and responding to short-term
treatment with clozapine.
END