5.3.2\ Pallidotomy

5.3.2.1\ Discussion

Pallidotomy is a procedure that can be performed in Parkinson’s disease patients who do not experience adequate symptom relief from medical therapy. The surgery consists of introducing probes via frontal burr holes for ablation of the posteroventral portion of the globus pallidus interna (Fig. 5.32). The goal of the procedure is to interrupt excessive inhibitory output from the basal ganglia. On CT, the pallidotomy lesions appear as hypoattenuating foci of encephalomalacia that become more pronounced over time. On MRI, acute pallidotomy lesions are usually hyperintense centrally on T1 and hypointense centrally on T2 due to hemorrhage surrounded by a rim of T2 hyperintensity and hypointensity on T1 and GRE, which represents edema. Restricted diffusion due to focal cytotoxic edema can also be encountered. Eventually, the lesion-edema complex evolves into a smaller focus of low T1 signal and high T2 signal. Lesion sizes can be variable depending upon technique implemented.

Fig. 5.32  Pallidotomy. The patient has a history of Parkinson’s disease and underwent pallidotomy approximately 1 year prior to imaging on the left side and several days earlier on the right side. Axial CT image (a) shows hypoattenuating foci in the bilateral globus pallidi. The lesion on the right is more recent and slightly less hypoattenuating than the lesion on the left. Axial T2-weighted (b) and axial T1-weighted (c) images show subacute blood products within the right pallidotomy lesion surrounded by edema and fluid within the chronic left pallidotomy lesion

a

b

c