Gary Crowe,
The answer to your question as to why it takes 9 hours plus to do a
Pallidotomy here in the U.S. and only an hour in Sweden lies in different
perspectives on locating the ideal target for the placement of the lesion.
Medical centers such as Emory and John Hopkins believe the target is best found
by doing endless micro-electrode recordings to help establish their
neuroanatomical location and to determine which areas in the globus pallidus are
the most active. Hence the lengthy procedure of 9 plus hours to do one side.
Whereas in Sweden Dr. Lauri V. Laitinen performs stimulation trials at
various frequencies which help him find the target.
However, not all medical centers in the U.S. are bound by the
micro-electrode recording method. Speaking about the center with which I am
most familiar, Loma Linda University Medical Center, an MRI is used to perform
initial target acquisition. Knowing that the PVP target lies within the globus
pallidus interna and subjacent ansa lenticulularis, 2-3 mm anterior to the
midpoint of the anterior commissure to posterior commisssure (AC-PC) line, 3-6
mm below the AC-PC line, and 18-23 mm lateral to the midpoint of the third
ventricle final target acquisition is found using a combination of
ventriculographs, standard brain maps, and stimulation trials performed at
various frequencies with impedance recorded and changes in tremor, rigidity,
dyskinesia, and akinesia being duly noted.
Synchronous motor induction at 2 Hz , especially of the face or tongue,
implies IC proximity, while induction of flashing lights at 2 Hz or colors in
the pericentral visual fields at higher frequencies and voltages implies optic
tract proximity.
If evaluation reveals no visual changes, lesions are performed at 75
degrees C for 60 seconds. The probe is inserted 2 mm further, or until it
reaches the depth parallel to the level of the floor of the third ventricle;
wherein the stimulation, evaluation, and lesion sequence is repeated.
I know that such a procedure is being used at Stanford, in Little Rock,
St. Louis, Rochester, and other centers whose neurosurgeons have trained under
Dr. Iacono.
This past Friday I sat in on a bilateral Pallidotomy performed by Dr.
Iacono in 3 hours.
Gary, I hope this adequately answers your question.
Regards,
Don
Dr. Don Berns
4943 Del Monte Rd.
La Canada, CA 91011
818-790-8812
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