MIAMI BEACH — Operator errors are responsible for more than half of the failures of deep brain stimulation to lessen essential tremor or Parkinson's symptoms, according to the findings of one study presented at the American Academy of Neurology annual meeting.
Many of these patients benefit when deep brain stimulation (DBS) is repeated at movement disorder centers by more experienced physicians.
The Food and Drug Administration approved a DBS system (Activa, manufactured by Medtronic Inc.) to treat patients with essential tremor or Parkinson's disease in August 1997. The agency expanded the system's indication to include patients with dystonia in April 2003.
DBS improves quality of life for many patients, but others do not respond. Incorrect diagnosis, surgical lead misplacement, and device-related errors are among the preventable problems identified by Michael S. Okun, M.D., and his associates.
“There has been a surge in centers providing DBS after its FDA approval and an increasing number of patients presenting to experienced DBS centers with complaints,” said Dr. Okun, co-director of the Movement Disorders Center at the University of Florida in Gainesville. “About 12 patients per year are seen by centers of excellence for these referred problems.”
A lack of consensus on patient screening, provider training, and the best multidisciplinary approach contribute to the failure rate, Dr. Okun said. In addition, there is no consensus on management of complications, some of which spur referral of the patient to an experienced DBS center for management.
Records of 41 consecutive patients treated at the University of Florida movement disorders center or the movement disorders center at the Beth Israel Medical Center in New York City were reviewed. The average age was 63 years. Thirty patients (73%) saw a movement disorders specialist prior to DBS implantation. Five patients (12%) had significant cognitive dysfunction before implantation. The patients underwent the following types of DBS implantation: 21, bilateral subthalamic nucleus; 8, unilateral subthalamic nucleus; 8, unilateral ventral intermediate nucleus; 1, unilateral globus pallidus interna; 1, bilateral ventral intermediate nucleus; and 1, bilateral globus pallidus interna.
All participants saw a movement disorders neurologist upon referral.
More than one-third, 36%, of patients had no improvement, and 15% had minimal improvement. However, “51% had significant improvement or were rescued with good outcomes,” Dr. Okun said.
“The reasons for DBS failures were not only surgical,” Dr. Okun said.
The researchers identified a timeline of preventable problems associated with DBS surgery. “It is quite interesting because many things were quite correctable,” Dr. Okun said. “There is an expertise factor we can improve on.”
Preventable problems included:
▸ Incorrect diagnosis (10 instances).
▸ Inadequate medication trial/dementia (10).
▸ Misplaced leads (19).
▸ Inadequate device programming (15).
▸ Medication adjustments (30).
Preoperative diagnoses included 31 with Parkinson's disease, 9 with essential tremor, and 1 patient with dystonia. The actual diagnoses were 26 with Parkinson's disease, 5 with essential tremor, 1 with dystonia, 3 with Parkinson's disease with dementia, 2 with multiple system atrophy, 1 with Parkinson's disease/essential tremor, 1 with corticobasal ganglionic degeneration, 1 with progressive nuclear palsy, and 1 with myoclonus.
Patients improved after 7 of the 19 misplaced leads were replaced, and partially improved after 3 others were replaced.
Programming problems included inadequate programming (15 patients), no or poor access to programming (7 patients), and difficult access to follow-up because of relocation (2 patients, 2 physicians). Reprogramming was successful for 15 patients and partially successful for 6.
A majority, 73%, of participants required medication changes. Dr. Okun said, “This brings home the point that even after surgery patients often need medication adjustments.”
Selection bias was a possible shortcoming of the study.
He said there are many improvements that can be made to prevent DBS failures and to improve outcomes.
Dr. Okun teaches programming the Activa DBS system for Medtronic.
Operator errors caused more than half of all cases of deep brain stimulation failure. Shown are examples of DBS lead misplacement: in the ventricle (left), atop the thalamus (right). Photos courtesy Dr. Michael S. Okun