Parkinson's surgery. Coloured computed tomography (CT) scan of a sagittal (side) section of a head, showing the path of a surgical probe used to treat Parkinson's disease. For neurosurgeons to target the correct area, detailed anatomic maps of the brain must be created. The path the probe will take during the operation is in yellow. Once in position the probe's tip creates a lesion in the basal ganglia (nerve cell clusters) of the central brain, greatly reducing unwanted tremors and rigidity. This procedure is known as pallidotomy. In Parkinson's, the basal ganglia, that help to control muscle movement, deteriorate. The disease progresses to severe weakness and incapacity.