NEW ORLEANS—Deep brain stimulation (DBS) has been shown to be effective in controlling the tremors of some patients with Parkinson’s disease, essential tremor, and medically refractory dystonia. But there can be troubling complications with DBS as well. Three examples of these—including complications caused by an apparent allergy to the electrode, severe rebound tremor when an electrode was incorrectly placed, and dislodging of an electrode that caused a recurrence of levodopa-induced dyskinesias—were presented at the Ninth International Congress of Parkinson’s Disease and Movement Disorders.

HARD WEAR

Jeff A. Kraakevik, MD, and Matthew A. Brodsky, MD, reported that hardware problems associated with deep brain stimulation occur in 2% to 13% of patients; these include fractures or migration of the leads, infection, erosion, intracranial hemorrhage, and foreign body reaction.

Dr. Kraakevik, a fellow at the Parkinson Center of Oregon in Portland, and Dr. Brodsky, Assistant Professor of Neurology at the Oregon Health and Science University, also in Portland, described a 73-year-old patient with advanced Parkinson’s disease involving severe motor fluctuations, and disabling peak-dose dyskinesias, as well as painful “off” dystonias. The patient had an uneventful DBS electrode implantation, with one pass for placement on the right side and four passes required on the left side.

On postoperative day 3, however, he developed a slowly progressive confusion, as well as dysarthria and right-sided hemiparesis involving the arm and the leg. A head CT was negative for acute bleeding, although MRI revealed edema along the paths of the electrodes on FLAIR and T2 imaging.

The patient’s white blood cell count ranged from 7.2 to 11.3, and his eosinophils were moderately elevated, at 6.9. He remained afebrile, but his mental status continued to deteriorate, and by postoperative day 11, he was difficult to arouse, the researchers noted. Therefore, the electrodes were removed and the patient was placed on broad-spectrum antibiotics, though cultures from the electrodes proved to be negative. As he became more alert, however, he evidenced an expressive aphasia.

On day 29, the patient was discharged on the initial drug regimen. Over the next several months, his right hemiparesis improved, although mild word-finding problems were in evidence at a six-month follow-up, and the patient continues to have disabling dyskinesias, the researchers indicated.

“This case demonstrates the possibility of an allergic reaction to DBS electrodes,” Drs. Kraakevik and Brodsky said. “This is supported by imaging that shows edema in the absence of ischemia or hemorrhage, and negative cultures of the DBS leads.” They also pointed out that other cases have been reported of possible allergic reactions to spinal cord stimulation.

Although the researchers said that there have been no previous reports of specific allergies related to DBS, the company that manufactures the device “does supply a skin test kit upon request to test for allergic reactions to components of the electrode,” they noted.

The investigators stressed that “allergic reactions to deep brain stimulation leads are possible and should be included in the differential of postoperative neurologic decline.” They added, “Treatment for an allergic reaction is removal of the electrode.”

ON THE REBOUND

In another report of DBS complications, Diana Apetauerova, MD, of the Department of Neurology at the Lahey Clinic in Burlington, Massachusetts, and colleagues described a severe rebound tremor occurring after DBS in a 77-year-old patient with tremor-predominant Parkinson’s disease. The patient initially had a complete response to DBS but then deteriorated. Stimulator voltage was therefore increased to 10 volts. Repeated attempts to discontinue DBS resulted in increasingly severe rebound tremor, and over the next two weeks the patient became increasingly unresponsive with the DBS on.

Four months later, the electrode was explanted and then reimplanted, which led to complete tremor control until the patient’s death from cancer two years later.

The researchers concluded that incorrect electrode placement produced temporary tremor control only, requiring increasing stimulation. But the use of such high currents then resulted in a huge rebound tremor.

ON THE MOVE

A third case of DBS-associated problems involved a patient with advanced Parkinson’s disease who had undergone successful bilateral DBS. Several months later, a right ventral lead moved roughly 6 mm; the movement probably occurred during skin erosion repair, postulated Jay L. Shils, PhD, of Beth Israel Medical Center in New York City. This movement prompted a recurrence of severe dyskinesias, as well as double vision. Revision of the lead’s position, however, performed under local anesthesia and fluoroscopy control, produced immediate correction of the dyskinesias and diplopia.

Dr. Shils and colleagues noted that “this is the second known case of a dorsal revision in DBS placement solving untreatable dyskinesias.” They recommended that such revision be done only under fluoroscopy control, to ensure that there is no movement in the lead above the burr hole cap, and added that “the commonly held belief that medication reduction is the only method for controlling levodopa-induced dyskinesias needs to be rethought.”

NR

—Jean McCann

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