Parkinson's Disease:
Thalamotomy, Pallidotomy and Deep Brain Stimulation

Introduction

    Recent developments in imaging and computer technology have resulted in dramatically new and effective surgical treatment for the Parkinson's disease (PD) and other movement disorders. PD is a progressive brain disorder characterized by tremor, rigidity and slowness of movement (bradykinesia). Effective surgical treatment evolved in the 1940's and 1950's to provide relief from these devastating symptoms. Using stereotactic guidance technology, surgeons defined portions of the deep brain, the basal ganglia in which destructive lesions effectively lessened tremor and rigidity.

    The introduction of L-dopa in the late 1950's brought a temporary end to stereotactic surgery for PD. L-dopa alleviates bradykinesia, rigidity and tremor, allowing patients to improve in activities of daily living.  Unfortunately, after many years use, higher doses of L-dopa are required.   Many patients develop jerking and writhing movements (dyskinesias) and rapid fluctuations in symptoms (on-off phenomenon) as well as other side effects. The short amount of time L-dopa lasts after oral dosage, and interference with its absorption from the stomach by food protein further complicated its use.

    As these pitfalls in the medical management of PD were becoming recognized, important advances in stereotactic surgery were occurring. The invention of CT and MR brain imaging allowed direct visualization of the basal ganglia. Powerful and inexpensive computers improved stereotactic technique. Finally there has been a rediscovery of the ventrolateral globus pallidus as very effective target to relieve rigidity, bradykinesia, tremor and the dyskinesias of L-dopa use. An exciting alternative is the use of deep brain stimulation for the control of PD tremor and essential (familial) tremor.

Pallidotomy for Parkinson's Disease

    Discrete destructive lesions in the ventromedial portion of the globus pallidus  bring effective control of most of the signs of PD. The results of targeting in the thalamus differ from those of pallidotomy:

    The  indications for surgery are the following:

• ideopathic Parkinson's disease with at least two cardinal signs:
      tremor; rigidity; bradykinesia/akinesia; postural instability

• good response to L-dopa

• mild to moderate disease (or worse) on both sides

• intractable and disabling motor fluctuations:
      dyskinesias; severe "off" periods; freezing spells

• unsatisfactory response to optimal medical management

  The technique of pallidotomy involves the placement of a stereotactic head frame on the morning of surgery, using sedation and local anesthesia. The head is imaged by MR or CT scan. Sophisticated computer graphics software is used to establish the exact position of the target (the globus pallidus interna) in relationship to the frame. Next, a small perforation is made in the skull, again using local anesthesia, and a stereotactic guidance system is affixed to the head frame. Once the system is adjusted to the coordinates of the target, the surgeon can safely and accurately advance the electrode to the target. Stimulation at various levels helps to determine the effectiveness of the radiofrequency lesion. The patient is awake during this process. One or two lesions are made with a radiofrequency current which heats the electrode tip. The electrode is removed and the small skin incision closed.

    The results reported by Dr. Lauri V. Laitinen and others in 1992 has been supported by other more recently published results [2]. Pallidotomy effectively abolishes the signs of PD in most patients:

• tremor - excellent or good and long lasting effect in 81%

• rigidity - excellent or good relief in 92%

• bradykinesia - very effective relief in 92%

• gait improvement similar to the results of bradykinesia

• dystonia disappeared in 92%

• speech volume and articulation improved 

• significant improvement in physical and social functioning                                                   

  Complications include hemorrhage leading to permanent weakness in 1-2%, infection in less than 1%, transient weakness in the leg or arm in a few percent, visual loss on the affected side only on a few percent.                                                         

Deep Brain Stimulation for PD and Essential Tremor

    Years ago surgeons noted that high frequency stimulation within the thalamic target for tremor control (nucleus ventralis intermedius or Vim) temporarily stopped tremor. Neurosurgeons use this technique to determine the position of the Vim nucleus prior to making a permanent, radiofrequency lesion. Recently, Benebid and others have developed the tactic of implanting a small stimulator (Medtronic ITREL® II) beneath the skin of the upper chest wall which is attached  to a thalamic electrode (Medtronic® DBS)[1]. Use of the stimulator controls the tremor without the need for a permanent, destructive lesion within the brain. An extensive, international trial of deep brain stimulation has shown the value of DBS for the treatment of PD and essential or familial tremor [4]:

    The surgical technique is similar to radiofrequency pallidotomy. The surgeon places a stereotactic head frame with local anesthesia. The head is imaged and the thalamic target coordinates computed. After the stereotactic guidance system is adjusted to the target coordinates and fixed to the head frame, the DBS electrode is advanced to the target and connected to the Medtronic ITREL® II stimulator, which is implanted beneath the skin below the collarbone. The stimulator may be turned on or off by passing a special magnet over the unit. After several years the battery may be changed. The procedure is intended for individuals with tremor of the upper extremity which is unresponsive to medical management.

    Side effects included transient tingling in the face or extremities in 78% of patients when the stimulator is first turned on, disequilibrium 5%, weakness 5%, slurred speech 9%, dystonia 3%, gait disorder 3%. Complications included intracranial hemorrhage 4%, stimulation not effective 4%, post op pain 3%, lead dislodgment 2%, tingling 1%, weakness 1%. In the 13 patients who suffered an intracranial hemorrhage, the effects resolved spontaneously in 11  [4].

    Visit the Metronics web site for more information, including movie clips of patients.  

Gamma Knife Radiosurgery

   Professor Lars Leksell developed  Gamma Knife radiosurgery 40 years ago to treat functional brain diseases, such a pain conditions and movement disorders. Just as modern imaging techniques have revolutionized stereotactic surgery, they have also led to the increasing use of radiosurgery in the treatment of brain tumors and vascular malformations of the brain. There is increasing evidence that Gamma Knife lesions in the globus pallidus or the thalamus may produce results similar to radiofrequency lesions. This option has the advantage of avoiding the rare complications of brain hemorrhage or infection. On the other hand, it takes weeks or months for the radiosurgery to produce a result, and the technique does not have the potential advantage of intraoperative physiological testing (deep brain stimulation and recording prior to radiofrequency lesion production) to improve the effectiveness of the radiofrequency lesion.
    Two recent reports outline the effectiveness and safety of GK radiosurgical treatment of PD. Dr. Christopher Duma and associates from the Good Samaritan Hospital in Los Angeles treated 38 thalami in 34 patients for tremor. In 24% there was complete relief of tremor, and in 26% there was excellent relief. Ten percent failed. There were no complications reported. These results were confirmed and extended by Dr. Ronald Young and his associates from the Northwest Hospital Gamma Knife Center in Seattle, Washington.  In this series 88% of 27 patients undergoing thalamotomy were tremor free, or nearly tremor free. GK radiosurgical treatments were also made in the globus pallidus in an additional 27 patients with dyskinesia, bradykinesia, rigidity... the usual indications for radiofrequency pallidotomy. His results were comparable to stereotactic, radiofrequency pallidotomy: 86% of individuals with DOPA induced dyskinesias were totally or near-totally relieved of symptoms and 64% were improved from their bradykinesia and rigidity. These interesting results will be confirmed as more patients undergo non-invasive and safe radiosurgery for their Parkinson's disease.
       

references:

   1.  Benebid AL, Pollak P, et al. Chronic electrical stimulation of the ventralis intermedius nucleus of the thalamus as a treatment of movement disorders. J Neurosurg 1996; 84:203-214.
   2.  Laitinen, LV et al. Leksell's posteroventral pallidotomy in the treatment of Parkinson's disease. J Neurosurg 1992; 76:53-61
   3.  Iocono PR, et al. Stereotactic pallidotomy results for Parkinson's disease exceed those of fetal graft. Amer Surg 1994; 60:777-782.
   4.  Medtronic North American and European Safety and Efficacy Study
   5.  Duma CM, Jacques DM, Kopyov, OV, Mark RJ, Copcutt B, Farokhi HK. Gamma Knife radiosurgery for thalamotomy in parkinsonian tremor: a five year experience. J Neurosurg 1998; 88:1044-1049.
   6.  Young RF, Shumway-Cook A, Vermuelen SS, Grimm P, Blasko J, Posewitz A, Burkhart WA, Goiney RC. Gamma knife radiosurgery as a lesioning technique in movement disorder surgery. J Neurosurg 1998; 89:183-193.