Amantadine improves gait in PD patients with STN stimulation.
Parkinsonism & Related Disorders
Chan H-F, Kukkle PL, Merello M, Lim SY, Poon YY, Moro E. Amantadine improves gait in PD patients with STN stimulation. Parkinsonism & Related Disorders, Parkinsonism and Related Disorders. 2012 Dec 6. pii: S1353-8020(12)00438-5. doi: 10.1016/j.parkreldis.2012.11.005.
Intro: Although DBS STN has been shown to be efficacious to improve classic motor symptoms of Parkinson’s disease (PD) such as tremor, rigidity, and slowed movement it has not shown comparable results in regards to “axial symptoms” such as speech, balance, and walking difficulties which have been found to worsen as the disease progresses. Studies have also found that speech difficulties can worsen, specifically after DBS STN. Clinicians and researchers alike continue to search for treatments for classic motor as well axial symptoms. Amantadine is such a drug treatment. It is an antiviral drug that has multiple uses including for the flu (influenza A)1, reducing fatigue in autoimmune disorders2, as well as it works on multiple neurotransmitters (dopamine and acetylcholine) related to movement disorders. Treatment with amantadine for PD has been around for some time (1960’s) and has been shown to reduce dyskinesias but has mixed findings on gait. According to this article, there were no published studies looking at the use of amantadine to improve speech in people with Parkinson’s disease (PWP). However, they used clinical experience from a patient who showed improvement in the aforementioned axial symptoms when taking this drug so the authors wanted to evaluate formally such possibilities in a multicenter study.
Methods: Forty-six PWP (M=36, F=10; Mean age at surgery: 57 years; duration of PD: 13 years) were evaluated across three international surgical sites. Each PWP had DBS STN (all but one bilateral) and remained on levodopa as well as had maximal stimulator settings during the study. The amantadine was introduction slowly and increased over a few weeks. The authors used a portion of a motor rating scale (UPDRS III) as well as asked for subjective ratings by the PWP regarding their speech, gait, and balance before and after the amantadine.
Findings: The amantadine was started at various times after surgery (3-120 months) specifically for difficulties with the axial symptoms. It was notable that 72% of the PWP had tried amantadine prior to DBS with no improvements in the axial symptoms. After DBS STN, the study showed that around 30% of the PWP taking amantadine had improvements in walking, but there was not improvement in balance. Speech symptoms showed a trend of improvement but not at the level of statistical significance. When looking at the subjective ratings of the PWP, approximately half reported improved speech, two-thirds improved gait and balance, and one third improved in all three areas. As with any drug, there can be side effects that are not tolerable to some who take it. In this study, 11% of the participants had adverse effects from the amantadine including hallucinations, confusion, or edema. An additional 4% did not find the medicine to be helpful.
Conclusion: There are many challenges in having PD and the classic motor symptoms have received a great deal of attention in the research arena. However, it is important to continue to evaluate treatments for the PWP related to difficulties that can cause decreased quality of life due to significant disability such as the axial symptoms of speech, balance, and gait. This study’s results are promising in that PWP experienced measurable improvement in gait as well as felt as though they had improvement in all three axial areas. It was noted that many of the patients experienced an improvement after stimulation with the amantadine compared to no improvement prior to DBS from the amantadine with minimal adverse effects, suggesting there could be an interaction with the stimulator and the medication, which should be further explored.