Role of cryosurgery and MRI for Parkinson's disease

Three basic principles underlie the techniques of stereotactic cryosurgery for Parkinson's disease: (1) high-resolution MRI of the surgical target using thin sequential coronal, axial and sagittal views; (2) clinical-physiological verification of localization of the surgical target by a reversible inhibition test, and (3) production of the cryosurgical freezing lesion in a conscious, cooperative patient. The cryosurgical lesion is created in the ventrolateral nucleus of the thalamus for control of tremor and rigidity or in the posterior ventral area of the pallidum for control of rigidity and bradykinesia. An initially reversible inhibition is produced by cooling the probe tip to -10 degrees C. This cools the brain tissue within 3 mm of the probe to 2-15 degrees C. If parkinsonian symptoms are suppressed, the cryoprobe tip temperature is then lowered incrementally, resulting in a gradually enlarging lesion surrounded by a reversible buffer zone. The final temperature is that in which parkinsonian symptoms are abolished and/or side effects appear. After performing and evaluating over 1,000 cryothalamotomies and cryopallidotomies on patients for whom medical treatments had failed, the author concludes that cryosurgical techniques are safer and produce lesions that are better controlled for size and location than other techniques, resulting in lasting, successful therapeutic results.