The later stages of Parkinson's disease (PD) are characterized by altered gait patterns. Although decreased arm swing during gait is the most frequently reported motor dysfunction in individuals with PD, quantitative descriptions of gait in early PD have largely ignored upper extremity movements. This study was designed to perform a quantitative analysis of arm swing magnitude and asymmetry that might be useful in the assessment of early PD. Twelve individuals with early PD (in "off" state) and eight controls underwent gait analysis using an optically-based motion capture system. Participants were instructed to walk at normal and fast velocities, and then on heels (to minimize push-off). Arm swing was measured as the excursion of the wrist with respect to the pelvis. Arm swing magnitude for each arm, and inter-arm asymmetry, were compared between groups. Both groups had comparable gait velocities (p=0.61), and there was no significant difference between the groups in the magnitude of arm swing in all walking conditions for the arm that swung more (p=0.907) or less (p=0.080). Strikingly, the PD group showed significantly greater arm swing asymmetry (asymmetry angle: 13.9±7.9%) compared to the control group (asymmetry angle: 5.1±4.0%; p=0.003). Unlike arm swing magnitude, arm swing asymmetry unequivocally differs between people with early PD and controls. Such quantitative evaluation of arm swing, especially its asymmetry, may have utility for early and differential diagnosis, and for tracking disease progression in patients with later PD. KeywordsParkinson's Disease; gait; biomechanics; arm swing; arm swing asymmetry © 2009 Elsevier B.V. All rights reserved.Corresponding Author: Xuemei Huang MD, PhD Penn State University-Milton S. Hershey Medical Center, H037 Department of Neurology, 500 University Drive Hershey, PA 17033-0850 Phone: 717-531-1803 Fax: 717-531-0465 xuemei@psu.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Conflict of interest statement:The authors have nothing to disclose related to any financial and personal relationships with other people or organizations that could inappropriately influence (bias) our work. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptParkinson's disease (PD) is the second most common age-related, neurodegenerative disorder. Tremor, rigidity, bradykinesia, and postural instability are hallmarks for the diagnosis of PD. 1 Abnormal gait (i.e., small "shuffling" steps) is common in the later stages of PD, and can be characterized by reduced walking velocity, stride length, swing/s...

Patients with functional pain disorders often complain of generalized sensory hypersensitivity, finding sounds, smells, or even everyday light aversive. The neural basis for this aversion is unknown, but cannot be attributed to a general increase in cortical sensory processing. Here we quantified the threshold for aversion to light in patients with fibromyalgia, a pain disorder thought to reflect dysregulation of brain pain-modulating systems. These individuals expressed discomfort at light levels substantially lower than healthy controls. Complementary studies in lightly anesthetized rat demonstrated that a subset of identified pain-modulating neurons in the rostral ventromedial medulla unexpectedly responds to light. Approximately half of the pain-facilitating “ON-cells” and pain-inhibiting “OFF-cells” sampled exhibited a change in firing with light exposure, shifting the system to a pro-nociceptive state with activation of ON-cells and suppression of OFF-cell firing. The change in neuronal firing did not require a trigeminal or posterior thalamic relay, but was blocked by inactivation of the olivary pretectal nucleus. Light exposure also resulted in a measurable but modest decrease in the threshold for heat-evoked paw withdrawal, as would be expected with engagement of this pain-modulating circuitry. These data demonstrate integration of information about light intensity with somatic input at the level of single pain-modulating neurons in the brainstem of the rat under basal conditions. Taken together, our findings in rodents and humans provide a novel mechanism for abnormal photosensitivity, and suggest that light has the potential to engage pain-modulating systems such that normally innocuous inputs are perceived as aversive or even painful.

Background Results of previous studies suggest that β-adrenoreceptor activation may augment pain, and that β-adrenoreceptor antagonists may be effective in reducing pain, particularly in individuals not homozygous for the catechol-O-methyltransferase (COMT) high activity haplotype. Methods Consenting patients admitted for thermal burn injury at participating burn centers were genotyped; those who were not high activity COMT homozygotes were randomized to propranolol 240mg/day or placebo. Primary outcomes were study feasibility (consent rate, protocol completion rate) and pain scores on study days 5-19. Secondary outcomes assessed pain and posttraumatic stress disorder (PTSD) symptoms 6 weeks post-injury. Results Seventy-seven (61/79) percent of eligible patients were consented and genotyped, and 77% (47/61) were genotype-eligible and randomized. Ninety-one percent (43/47) tolerated study drug and completed primary outcome assessments. In intention to treat and per protocol analyses, patients randomized to propranolol had worse pain scores on study days 5-19. Conclusions Genotype-specific pain medication interventions are feasible in hospitalized burn patients. Propranolol is unlikely to be a useful analgesic during the first few weeks after burn injury.