Objective: To describe an infrequent and late complication of STN-DBS in a patient with PD.

Background: DBS is a safe procedure for patients with PD. It has a very low rate of complications if performed in a specially qualified center. Immediate complications related to the implantation system include edema, hemorrhage, infections or convulsions. The most common late complication is infection, related to the pulse generator or the implantation system. Complications related to the electrode like breakage, migration or disconnection are less common. Cysts and edema around the electrode have been reported in occasions.

Methods: A 41 year old woman with PD starting at age 22 had STN-DBS implant in 2008 at age 31 with excellent clinical outcome. Her pre-operative off-medication UPDRS III was exceptionally high (86), spending 4 hours/day in severe off motor state, with a Schwab and England score (S&E) of 30%. Post-DBS, her UPDRS-III on-stimulation/off-medication score was 15 (83% improvement) and S&E was 90% all day long.

Results: In 2015 she had a quick onset right III cranial nerve paresia and mild motor deterioration of her left hemibody, scoring 28 in UPDRS-III. The DBS system proved to work adequately, with no changes in impedance or other parameters. The brain MRI showed a white matter edema around the right electrode with mesencephalic involvement. Treatment was started with 12mg/day of dexamethasone and tapered through 2 weeks. The patient had a progressive improvement of her symptoms until complete resolution. The control MRI 3 months later showed complete disappearance of the edema.

Conclusions: Edema development around the electrode after a few years of DBS, in our case 7 years, is an exceptional finding, with only a few cases found in literature. Its outcome was excellent with a conservative treatment. In our case, we do not know the cause of the edema. The patient had no traumatism, cephalic dystonia or Twiddler syndrome. Reconstruction of electrode location showed no migration of the electrode. New hypothesis should be considered, to explain edema as the development of new erratic communication between subthalamus and other nuclei, autoimmune inflammatory processes or wearing of the electrodes in some patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/spontaneous-peri-electrode-edema-7-years-after-subthalamic-nucleus-deep-brain-stimulation-stn-dbs-in-a-patient-with-parkinsons-disease-pd-a-case-report/