DEEP
BRAIN STIMULATION
Philip A. Hanna, MD
Parkinson's Disease and Movement Disorders Center
New Jersey Neuroscience Institute
Edison, New Jersey
Essential tremor (ET) and Parkinson's disease (PD) are the two most
common disorders with severe tremor. Despite optimal medical therapy,
a number of patients continue to have disabling tremor, and these
patients may be candidates for surgical intervention. Until recently,
thalamotomy was the neurosurgical treatment of choice in such cases.
In this procedure, after making an incision in the scalp and an
opening in the skull on the side opposite of the most tremulous limb(s),
the surgeon advances an electrode into the thalamus, which contains
"pacemakers", or group of nerve cells involved in generating
tremor. The surgeon then passes a current through the tip of the
electrode thus creating a lesion and stopping the tremor on the
opposite side of the body. Although effective, tremor recurs in about
20% of patients, and there is a risk of weakness, numbness, and
incoordination on the other side of the body, and changes in speech.
In the late 1980's Prof. A. Benabid and colleagues in France
discovered that tremor can also be relieved by high frequency
stimulation of the thalamus and other areas of the brain. This
technique, called deep brain stimulation (DBS), involves 1.) a DBSTM
lead with four electrodes that are surgically inserted and fixed at
the skull, 2.) a wire passing from the scalp area under the skin to
3.) an implantable pulse generator (IPG), a pacemaker-like device,
which has adjustable parameters, and which is placed just under the
skin in the upper chest area. The patient can turn the DBS system
"on" or "off" by placing a magnet over the IPG.
In a recent publication (Ondo et al) patients with ET and PD
demonstrated an 83% and 82% reduction, respectively, in contralateral
arm tremor. In the ET patients, functional testing and disability
scores significantly improved. While similar improvement was seen in
tremor in the patients with PD, functional aspects of the disease were
not notably improved, likely because thalamic DBS helps tremor but
other features of PD such as rigidity, slowness of movement, and gait
difficulty. DBS into the subthalamic nucleus and globus pallidus has
shown beneficial results not only with regards to these other
parkinsonian features, but also in reducing levodopa-related
complications such as dyskinesias and fluctuations.
The major advantage of DBS over lesioning procedures, such as
thalamotomy, is that the electrode parameters are adjustable, and thus
can be customized to the needs of the individual patient.
Additionally, side effects, if they occur, are usually reversible and
bilateral stimulation is possible with much reduced risk of speech or
swallowing difficulties, compared with bilateral thalamotomy.
Ondo W, Jankovic J, Schwartz K, Almaguer M, Simpson RK. Unilateral
thalamic deep brain stimulation for refractory essential tremor and
Parkinson's disease tremor. Neurology 1998;51:1063-1068.
Pollak P, Benabid AL, Krack P, Limousin P, Benazzouz A. Deep brain
stimulation. In: Jankovic J, Tolosa E, eds. Parkinson's Disease and
Movement Disorders, 3rd edition, Williams and Wilkins, Baltimore,
Maryland, 1998:1085-1102.
Hanna PA, Jankovic J. Comparison of mouse bioassay and
immunoprecipitation assay for botulinum toxin antibodies. J Neurol
Neurosurg Psychiatry 1999;66:612-616.
Hanna PA, Kwak CH, Jankovic J. Botulinum toxin in the treatment of
tics. 3rd International Scientific Symposium on Tourette Syndrome. New
York, NY, June 4-6, 1999.
Hanna PA, Jankovic J. Mouse bioassay versus western blot assay for
botulinum toxin antibodies: correlation with clinical response.
Neurology 1998;50:1624-1629.
Jankovic J. Use of botulinum toxin in neurology. In: Kennard C, ed.
Recent Advances in Clinical Neurology. Vol. 8, Churchill Livingstone,
London, 1995:89-110.
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