Richard P. Di Fabio’s research while affiliated with University of Wisconsin–La Crosse and other places

The use of transcranial magnetic stimulation (TMS) to assess changes in cortical excitability is a tool used with increased prevalence in healthy and impaired populations. One factor of concern with this technique is how to achieve adequate statistical power given constraints of a small number of subjects and variability in responses. This paper compares a single pulse excitability measure using traditional group-level statistics vs single subject analyses in a patient population of subjects with focal hand dystonia, pre and post repetitive TMS (rTMS). Results show significant differences in cortical excitability for 4/5 subjects using a split middle line analysis on plots of individual subject data. Group level statistics (ANOVA), however, did not detect any significant findings. The consideration of single subject statistics for TMS excitability measures may assist researchers in describing the variably of rTMS outcome measures.

ABSTRACT The objective of this study was to compare fall-risk models for the prediction of 1-year fall history in community-dwelling elderly persons. The study design was a descriptive analysis of factors associated with retrospective fall history for individuals living in community-based independent living facilities. Thirty-three older adults (10 men and 23 women, mean age ± standard deviation, 82.6 ± 5.5 years) volunteered to participate. The main outcome measure was multivariate logistic regression models using a minimal set of predictor variables for predicting 1-year fall history and fall-risk status. The results showed that a fall history prediction model using age, gait velocity, and time to complete Trails Making Test Part B yielded 76% of overall predictive accuracy (75% sensitivity, 76% specificity). A second logistic regression with gait speed eliminated was used to identify fall-risk status (fall history plus a positive score on the Timed Up and Go test) with similar results. These findings suggest that these variables are critical for identifying elderly fallers and those at risk for falls.

One of the main oculomotor findings in progressive supranuclear palsy (PSP) is the inability to saccade downward. In addition, people with PSP have difficulty suppressing fixation, which may contribute to vertical gaze palsy. The objective was to investigate the effectiveness of a rehabilitation intervention tailored to enhance suppression of fixation and gaze shift in participants with PSP. Controlled trial with a quasi-randomized design. Measures occurred at week 1 and 5. Researchers assessing participants were blind to the group assignments. Movement disorders assessment laboratory. Nineteen adults with possible or probable PSP who were ambulatory for short distances and had far visual acuity of 20/80 and a Folstein Mini-Mental State score of more than 23. Balance training complemented with eye movement and visual awareness exercises was compared with balance training alone. Gaze control was assessed using a vertical Gaze Fixation Score and a Gaze Error Index. Gaze control after the balance plus eye exercise significantly improved, whereas no significant improvement was observed for the group that received balance training alone. These preliminary findings support the use of balance and eye movement exercises to improve gaze control in PSP.

Visually guided stepping is an essential function in many normal activities of daily living requiring the coordination of eye movements with precise foot placement. The objective of this investigation was to compare the saccade-footlift latency in community dwelling elderly identified as high-risk for falling with elderly who are at a low-risk of falling during a walking task that requires precise foot placement. A non-randomized between-group repeated measures design was employed using independently living elderly volunteers from the Minneapolis, MN community. Thirty older adults volunteered to participate in the study; fifteen who had a history of a fall in the previous 12 months or a prolonged score on a fall risk screening instrument (Timed Up and Go test), and fifteen elders who had not fallen and had a negative score on the screening instrument. Subjects were required to walk along a pathway of 4 irregularly spaced stepping targets. The time between horizontal saccadic eye movement to the initiation of footlift (saccade-footlift latency) was the primary dependent measure. The mean saccade- footlift latency between high-risk (H-R) elderly and low-risk (L-R) elderly was statistically different (mean H-R 940 ms, L-R 825 ms; F1,3=7.45, p=0.006). The H-R elderly also performed more slowly on the cognitive test - Trail Making Test Part B (mean H-R 195 s, L-R 129 s; F1,2=7.21, p=0.01). The results suggest that there is an association between horizontal saccades, stepping and cognition for elderly at risk for falling. The timing of saccades and precise foot placement in older persons living in the community are associated with fall risk status and cognitive status. The prolonged time for saccade-footlift in H-R elderly may be attributed to greater central nervous system processing time necessary to plan precise foot placements or volitional processing delays in postural control due to fall risk status. In addition, age related changes in cognitive functions appear to be associated with saccade stepping interaction when performing a visually guided stepping pattern and may influence the ability to coordinate precise lower extremity movements.

Although vertical gaze palsy and gait instability are cardinal features of progressive supranuclear palsy (PSP), little research has been done to address oculomotor and gait rehabilitation for PSP. The purpose of this study was to compare the benefits of a program of balance training complemented with eye movement and visual awareness training versus balance training alone to rehabilitate gait in people with PSP. Nineteen people moderately affected by the disease were assigned to either a treatment group (balance plus eye movement exercises, n=10) or a comparison group (balance exercises only, n=9) in a quasi-random fashion. The baseline characteristics assessed were diagnosis (possible versus probable), sex, age, time of symptom onset, dementia, and severity of symptoms. Within-group, between-group, and effect size analyses were performed on kinematic gait parameters (stance time, swing time, and step length) and clinical tests (8-ft [2.4-m] walk test and Timed "Up & Go" Test). The within-group analysis revealed significant improvements in stance time and walking speed for the treatment group, whereas the comparison group showed improvements in step length only. Moderate to large effects of the intervention were observed for the treatment group, and small effects were observed for the comparison group. The between-group analysis did not reveal significant changes for either group. These preliminary findings support the use of eye movement exercises as a complementary therapy for balance training in the rehabilitation of gait in people with PSP and moderate impairments. Additional studies powered at a higher level are needed to confirm these results.

Does gaze control influence lower-extremity motor coordination in people with neurological deficits? The purpose of this study was to determine whether foot kinematics during stair climbing are influenced by gaze shifts prior to stair step initiation. Twelve subjects with gaze palsy (mild versus severe) secondary to progressive supranuclear palsy were evaluated during a stair-climbing task in a cross-sectional study of mechanisms influencing eye-foot coordination. Infrared oculography and electromagnetic tracking sensors measured eye and foot kinematics, respectively. The primary outcome measures were vertical gaze fixation scores, foot lift asymmetries, and sagittal-plane foot trajectories. The subjects with severe gaze palsy had significantly lower lag foot lift relative to lead foot lift than those with a mild form of gaze palsy. The lag foot trajectory for the subjects with severe gaze palsy tended to be low, with a heading toward contact with the edge of the stair. with severe gaze palsy were 28 times more likely to experience "fixation intrusion" (high vertical gaze fixation score) during an attempted shift of gaze downward than those with mild ocular motor deficits (odds ratio [OR]=28.3, 95% confidence interval [CI]=6.4-124.8). Subjects with severe gaze shift deficits also were 4 times more likely to have lower lag foot lift with respect to lead foot lift than those with mild ocular motor dysfunction (OR=4.0, 95% CI=1.7-9.7). The small number of subjects and the variation in symptom profiles make the generalization of findings preliminary. Deficits in gaze control may influence stepping behaviors and increase the risk of trips or falls during stair climbing. Neural and kinematic hypotheses are discussed as possible contributing mechanisms.

The relative sparing of visual fixation in parallel with disruption of saccade function in progressive supranuclear palsy (PSP) creates a unique human model for the study of gaze-shift strategies which are adopted when vertical gaze palsy impairs primarily the eye-movement component of gaze control. It was hypothesized that people with PSP would rely on head pitch as a primary component of gaze shift during a platform stepping task and that there would be a predominance of fixation behavior (counter rotation of the eyes during head pitch) while attempting a down-gaze shift. Fourteen subjects with probable and 5 subjects with possible PSP participated in two experiments to measure visual fixation and gaze shift on the same continuum (using a derived vertical gaze fixation score, vGFS). Experiment #1 required gaze fixation during passive head pitch at 0.1-0.2 Hz, whereas experiment #2 required gaze shifts during a continuous platform step on, over, and off task. The primary gaze-shift strategy involved pitching the head downward to compensate for a loss in vertical saccade function. This strategy produced head pitch velocity that leads vertical eye velocity on the order of 200-500 ms. Gaze shifts during platform stepping showed greater fixation suppression (e.g., lower vGFS) in both groups of PSP compared to the visual stabilization task, but some subjects showed "fixation intrusion" during attempted gaze shift. The amount of eye movement was relatively constant when corrected for orbit height, whereas the extent of head pitch varied in proportion to the task demands. The mechanism controlling gaze in PSP, therefore appears to modulate head pitch independently of eye movement, but the gaze strategy seems dependent upon the extent of gaze dysfunction. These findings support the view that the desired gaze signal is parsed into separate eye and head pathways upstream from the burst neurons.

Progressive supranuclear palsy is a parkinsonian syndrome commonly misdiagnosed as PD. The progression of the disease is much faster, and the impairment of gait and balance is more dramatic, than in PD. We believe that the demand for rehabilitation in this population will increase; however, there is no evidence in the literature to guide clinical practice. More research is necessary to answer basic questions regarding the effectiveness of rehabilitation for patients with PSP.

With head movement, suppression of vestibular inputs during visual exploration is necessary not only for reorienting gaze, but also to direct attention to new visual targets. People with progressive supranuclear palsy (PSP) have difficulty suppressing the vestibuloocular reflex (VOR) and it was hypothesized that the magnitude of VOR suppression deficit correlates with the degree of degradation of attention and visuospatial performance. We evaluated cognitive and visuomotor function in 8 subjects with PSP (4 men and 4 women; ages 59-83 years). Gaze control was studied by measuring the accuracy of eye-head coordination during passive vertical and horizontal head-on-trunk movements. Fixation was assessed when subjects viewed either an earth-fixed or head-fixed target. A gaze fixation score (GFS) was calculated to represent the amount of error between eye and head movement in each plane (eye-head root mean square error normalized to the range of head rotation). The vertical but not horizontal GFS during attempted suppression of the VOR was significantly related to attention (r = -0.70; P = 0.05) and visuospatial ability (r = -0.76; P = 0.03). These findings suggest that the ability to suppress the VOR during vertical smooth movements of the head is associated with the magnitude of cognitive deficit in PSP.

To assess the validity of retrospective versus prospective criterions of change. Single cohort pretest-posttest design. Physical or occupational therapy outpatient clinics. Volunteer sample of 211 patients with upper-extremity musculoskeletal problems. Not applicable. Disabilities of the Arm, Shoulder, and Hand questionnaire, the Shoulder Pain and Disability Index, the Patient-Rated Wrist Evaluation, the Medical Outcomes Study 12-Item Short-Form Health Survey; global disability rating (GDR), retrospective global rating of change (GRC), and patient satisfaction. Correlations were calculated among the baseline, 3-month follow-up, and change scores for each outcome measure with the change criterion instruments. Retrospective GRC and patient satisfaction ratings showed moderate correlations with the 3-month follow-up scores, but nonsignificant correlations with baseline scores. By contrast, the prospective GDR criterion showed significant correlations with both baseline and 3-month follow-up scores ranging between 0.3 and 0.4 (absolute value). Retrospective self-report measures of change do not accurately reflect true change over time. The retrospective GRC and patient satisfaction were heavily influenced by current (posttreatment) status whereas the prospective global change measure reflected both baseline and posttreatment status equally and thus appeared to be a more valid measure of change over time. This study demonstrates the need for an alternative criterion for establishing true individual change.