Newly developed back pain after subthalamic nucleus stimulation in Parkinson’s disease

Abstract

Dear editor, Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been widely performed for medically refractory Parkinson’s disease (PD). We have encountered patients with newly developed back pain after successful STNDBS surgery. In this report, we review these cases and discuss the pathogenesis of newly developed back pain after STN-DBS. Between November 2003 and December 2008, 148 patients with medically refractory PD underwent implantation of bilateral STN-DBS electrodes in Nagoya City University Hospital, Nagoya, Japan. STN-DBS was indicated in most patients for significant motor complications from levodopa such as fluctuation and dyskinesia. Among these patients, seven complained of newly developed back pain in the early period after STN-DBS despite having had no experience of back pain before STN-DBS. None of the patients showed camptocormia. The demographic details for all patients are shown in Table 1. STN-DBS yielded marked improvement in the UPDRS III motor score and UPDRS IV dyskinesia/fluctuation score, and reduced the need for dopaminergic medication in all patients. The time until they complained of back pain varied from 2 weeks to 5 months after surgery. Imaging study of lumbar X-ray, CT or MRI revealed various lumbar spine pathologies such as lumbar disc herniation, lumbar spinal stenosis, scoliosis, spondylolisthesis, and old compression fracture. Two patients subsequently underwent lumbar surgery for their lumbar pathology. We performed lumbar laminectomy and discectomy for disc herniation, and laminectomy and pedicle screw-rod fixation for spondylolisthesis. One patient was treated with epidural injections, and the other four patients were treated conservatively with analgesic medication. Consequently, the back pain was controlled well in all of the patients. Several types of pain occur frequently in PD. Ford classified pain in PD into several categories: musculoskeletal pain, radicular or neuropathic pain, dystonia-related pain, central or primary pain, and akathitic discomfort [2]. The most prevalent painful sensations in PD seem to be musculoskeletal pain and dystonia-related pain. Depression in PD may also confound and aggravate pain. Back problems in particular seem to be common in PD. Broetz et al. reported that the prevalence of back pain in PD (74%) was significantly higher than in control patients (27%) [1]. Postural abnormalities or truncal dystonia in PD seem to put stress on the lumbar disc structures and cause lumbar disc herniation. Increased muscle tone and reduced flexibility of the spine may also cause nonradicular back pain originating from the muscle, soft tissues, and skeletal structures. Some previous studies demonstrated that STN-DBS improved fluctuating pain, namely, pain in the "off" period [3, 6]. STN-DBS also improves painful "off" period dystonia [4]. Nevertheless, we showed that a significant incidence (approximately 5%) of newly developed back pain occurs after STN-DBS in spite of the marked improvement of cardinal PD symptoms. Kim et al. also reported that new pain developed in some patients A. Umemura (*) :Y. Oka :A. Okura :K. Yamada Department of Neurosurgery, Nagoya City University Graduate School of Medicine, 1 Kawasumi, Mizuho-ku, Nagoya 467-8601, Japan e-mail: aume@med.nagoya-cu.ac.jp