Intracranial cryosurgery in a canine model: a pilot study.

Although virtually abandoned decades ago following the introduction of levodopa for the treatment of movement disorders, intracranial cryosurgery potentially offers a simple and accurate means of destroying deep-seated lesions when coupled with computed tomographic-stereotaxic placement techniques. We performed a pilot investigation of the size and histology of brain cryolesions in six dogs, using a 3-mm probe maintained at -160 degrees C for 6 minutes while simiultaneously monitoring the process by real-time ultrasound. Lesion diameter was 1.4 +/- 0.1 cm at less than or equal to 2 days but enlarged to 2.25 +/- 0.21 cm at 1 week, primarily at the expense of white matter. Ultrasound appearance of the lesion was characterized by a hyperechoic ice ball, the size of which consistently underestimated true size (determined by histology). By microscopy, the lesion was a hemorrhagic infarction that incited little surrounding edema and exhibited a sharp transitional zone. These data indicate that the cryosurgical probe can lesion significant volumes of brain in a reproducible and discrete fashion with minimal reaction to the surrounding tissue. Further work is required to clarify the observed "growth" of lesion size between days 2 and 7.