Posturography and locomotor tests of dynamic balance after long-duration spaceflight.

The currently approved objective clinical measure of standing balance in astronauts after space flight is the Sensory Organization Test battery of computerized dynamic posturography. No tests of walking balance are currently approved for standard clinical testing of astronauts. This study determined the sensitivity and specificity of standing and walking balance tests for astronauts before and after long-duration space flight. Astronauts were tested on an obstacle avoidance test known as the Functional Mobility Test (FMT) and on the Sensory Organization Test using sway-referenced support surface motion with eyes closed (SOT 5) before and six months after (n=15) space flight on the International Space Station. They were tested two to seven days after landing. Scores on SOT tests decreased and scores on FMT increased significantly from pre- to post-flight. In other words, post-flight scores were worse than pre-flight scores. SOT and FMT scores were not significantly related. ROC analyses indicated supra-clinical cut-points for SOT 5 and for FMT. The standard clinical cut-point for SOT 5 had low sensitivity to post-flight astronauts. Higher cut-points increased sensitivity to post-flight astronauts but decreased specificity to pre-flight astronauts. Using an FMT cut-point that was moderately highly sensitive and highly specific plus SOT 5 at the standard clinical cut-point was no more sensitive than SOT 5, alone. FMT plus SOT 5 at higher cut-points was more specific and more sensitive. The total correctly classified was highest for FMT, alone, and for FMT plus SOT 5 at the highest cut-point. These findings indicate that standard clinical comparisons are not useful for identifying problems. Testing both standing and walking balance will be more likely to identify balance deficits.

Variability and persistence of aspirin response in lower extremity peripheral arterial disease patients.

OBJECTIVE: To determine the prevalence of poor response to aspirin (ASA) therapy over 12-month follow-up in patients with lower extremity peripheral arterial disease (PAD), and to compare the classification agreement among different ASA response assays. METHODS: Patients with PAD on ASA therapy at baseline were included from the ongoing Effect of Lipid Modification on Peripheral Arterial Disease after Endovascular Intervention Trial (ELIMIT), which is a randomized trial testing whether combination treatment with ezetimibe, niacin, and a statin will halt/regress atherosclerosis compared with statin monotherapy. Patients who had baseline platelet testing and repeat testing at 6-month or 12-month follow-up were included. ASA responsiveness was tested using three different assays: Optical aggregation with 0.5 mg/mL of arachidonic acid (AA), optical aggregation with 10 µM of adenosine diphosphate (ADP), and platelet function analyzer-100 (PFA-100) testing with collagen/epinephrine (Epi) loaded cartridges. ASA response was defined as AA aggregation <30%, ADP aggregation <70%, or PFA-100 Epi >164 seconds. Patients who showed response to ASA at baseline were classified as Responders. Poor response to ASA was defined as AA aggregation ≥ 30%, ADP aggregation ≥ 70%, or PFA-100 Epi ≤ 164 seconds. Patients who showed poor response (PR) to an assay at baseline, but then were responsive at follow-up visits were classified as Initial PRs. Patients who showed poor response at baseline and all follow-up visits were classified as Persistent PRs. The classification agreement between assays was tested using the kappa statistic. RESULTS: Of 102 patients randomized in ELIMIT, 80 patients satisfied inclusion criteria. There were no significant baseline demographic differences between Responders, Initial PRs, and Persistent PRs. The prevalence of persistent poor response varied by the assay used; 5% of subjects (4/80) were Persistent PRs by AA aggregation, compared with 27.5% (22/80) of subjects by ADP aggregation and 9.9% (7/71) of patients by PFA-100 Epi. Regarding the agreement of the assays, only AA aggregation and PFA-100 Epi agreed significantly (K = 0.3223; 95% confidence interval [CI] 0.15-0.493; P = .0001), and though statistically significant, the magnitude of this agreement is small. AA aggregation and ADP aggregation did not agree (K = 0.1161; 95% CI -0.004-0.236; P = .029), nor did ADP aggregation and PFA-100 Epi (K = 0.0044; 95% CI -0.151-0.160; P = .48). CONCLUSIONS: Between 5% and 27.5% of PAD patients were Persistent PRs to ASA over 6- to 12-month follow-up using different platelet assays. Further, these commonly used platelet assays show weak agreement in determining poor response to aspirin.

Differences in responses of platelets to fluid shear stress in patients with peripheral artery disease (PAD) and coronary artery disease (CAD).

Information on differences in platelet function between patients with peripheral arterial disease (PAD) and patients with coronary artery disease (CAD) is limited. We sought to examine the differences in the platelets response to shear stress in patients with PAD compared to those with CAD. Men with symptomatic PAD (ankle brachial index [ABI] < 0.9; n = 29) were compared with similarly aged men with CAD (post coronary artery bypass grafting; n = 40) but without PAD. All participants were on aspirin, and none were on clopidogrel. We measured changes in shear-induced platelet aggregation (SIPA) and shear-induced P-selectin expression (SIPE) under fluid shear rates of 5000 and 10,000 s(-1)which are typically found in arterioles and stenosed arteries, respectively. Aggregation was also induced by a combined stimulation of collagen, fluid shear stress, and adenosine diphosphate (ADP) or epinephrine using a platelet function analyzer (PFA-100) as well as optical aggregometry (arachidonic acid, collagen and epinephrine). Analyses of covariance adjusted for age, aspirin dose, and statin use were used to estimate differences between the groups. Values of SIPA at fluid shear rates of 5000 and 10,000 s(-1) were significantly higher in the PAD group, while there were no differences between the PAD and CAD groups in SIPE at both fluid shear rates. However, baseline shear-induced P-selectin expression was higher in patients with PAD than CAD (mean fluorescence intensity [MFI] = 2.93 +/- 1.37 vs.1.94 +/- 0.67; p = 0.01), while the percentage increases in SIPA and SIPE at fluid shear rates of 5000 and 10,000 s(-1) were significantly higher in patients with CAD when compared to PAD (p < 0.001 for all comparisons). Although there were several similarities in platelet function between men with PAD and men with CAD, significant differences in platelet responses to shear stress were observed in men with PAD when compared to those with CAD. Although the mechanism for these observed differences are not clear, we hypothesize that in vivo platelet activation in PAD patients may contribute to the differences and will need to be further investigated.

Usefulness of some current balance tests for identifying individuals with disequilibrium due to vestibular impairments.

The goal of this study was to determine which of several clinical balance tests best identifies patients with vestibular disorders. We compared the scores of normals and patients on the Berg Balance Scale (Berg), Dynamic Gait Index (DGI), Timed Up and Go (TUG), Computerized Dynamic Posturography Sensory Organization Test (SOT), and a new obstacle avoidance test: the Functional Mobility Test (FMT). The study was performed in an out-patient balance laboratory at a tertiary care center. Subjects were 40 normal adults, and 40 adults with vestibular impairments. The main outcome measures were the sensitivity of tests to patients and specificity to normals. When adjusted for age the Berg, TUG, DGI and FMT had moderate sensitivity and specificity. SOT had moderately high sensitivity and specificity. SOT and FMT, combined, had high sensitivity and moderate specificity. Therefore, the kinds of tests of standing and walking balance that clinicians may use to screen patients for falling are not as good for screening for vestibular disorders as SOT. SOT combined with FMT is better. When screening patients for vestibular disorders, when objective diagnostic tests of the vestibular system, itself, are unavailable, tests of both standing and walking balance, together, give the most information about community-dwelling patients. These tests may also indicate the presence of sub-clinical balance problems in community-dwelling, asymptomatic adults.

Effectiveness of treatments for benign paroxysmal positional vertigo of the posterior canal.

OBJECTIVE: To determine which common, nonpharmacological, nonsurgical treatments are most effective for treatment of benign paroxysmal positional vertigo (BPPV). STUDY DESIGN: Prospective, randomized, sham-controlled. PATIENTS: Patients (n = 124) with BPPV of the posterior semicircular canal. SETTING: Tertiary care center. INTERVENTIONS: Random assignment to one of five groups: modified canalith repositioning maneuver (CRP), modified liberatory maneuver (LM), sham maneuver, Brandt and Daroff's exercise, and vertigo habituation exercises. Subjects received a standard educational lecture about BPPV and the purpose of the intervention. No vestibular-suppressant medication or special instructions for head positioning were used. Post-tests were given at 1 week after treatment and at approximately 3 months and 6 months later. MAIN OUTCOME MEASURES: Vertigo intensity and frequency. RESULTS: Multilevel analyses showed that vertigo decreased significantly after LM, CRP, and Brandt-Daroff exercise; those three groups did not differ significantly. The habituation group did not differ from sham, Brandt-Daroff, LM, or CRP groups. Changes in scores were maintained throughout the 6-month follow-up period. CONCLUSION: LM, CRP, and exercises are all effective interventions; patient education plus the sham maneuver, however, had some beneficial effect. These results support two possible mechanisms of BPPV: displaced otoconia and a neural mechanism affecting interpretation of semicircular canal signals.

Tracking regression and progression of atherosclerosis in human carotid arteries using high-resolution magnetic resonance imaging.

BACKGROUND AND PURPOSE: Magnetic resonance imaging (MRI) can accurately and reproducibly measure the volume of atherosclerotic plaque in human carotid arteries. Atherosclerotic plaques may either progress or regress over time, depending on individual risk factors and treatment regimens. This study was designed to determine if regression or progression of human carotid atherosclerosis in patients receiving statin therapy over 24 months can be detected by high-resolution MRI. METHODS: In 11 subjects who had undergone unilateral carotid endarterectomy and were on statin therapy, volumes for total carotid artery, concentric wall (normal wall), eccentric wall (plaque), and lumen were quantified at 0, 16 and 24 months using a 1.5-T human imager equipped with 6-cm phased array coils. RESULTS: The interobserver mean coefficient of variation (CV) was lowest for the lumen volume (3.1%) and highest for the plaque volume (9.8%). The interscan mean CV was lowest for the total artery volume (3.2%) and highest for the plaque volume (9.9%). As much as 26% regression and 35% progression were observed in individual subject's carotid artery eccentric wall (plaque) volumes over time. Mean eccentric wall volume increased 5% by 16 months and 8% by 24 months. Mean total wall volume increased slightly at both 16 and 24 months (+1.2% and +1.8%). CONCLUSIONS: High-resolution MRI provides a noninvasive reproducible method of tracking changes in carotid atherosclerosis. This pilot study detected changes in individual subjects at both 16 and 24 months. MRI tracking of changes in atherosclerotic plaques should prove useful in assessing vascular disease risk and monitoring the efficacy of interventions designed to induce regression or retard progression.

Changes in a repetitive head movement task after vestibular rehabilitation.

OBJECTIVE: Many papers describe vestibular rehabilitation programmes to reduce vertigo and disequilibrium caused by peripheral vestibular disorders, but few studies have assessed performance on purposeful activities. This study determined if performance on a purposeful activity improves after vestibular rehabilitation exercises, and if the speed of treatment exercises influences performance. SETTING: Medical school practice; tertiary care facility. SUBJECTS: Fifty-three patients with chronic vertigo caused by peripheral vestibular weakness. INTERVENTIONS: Subjects performed vestibular rehabilitation head movement exercises to habituate vertigo, in either slow or rapid movement groups. MAIN MEASURES: Time to perform a repetitive head movement task and intensity of vertigo elicited by that task, questionnaires about independence in activities of daily living and reported usual intensity of vertigo. RESULTS: Both groups significantly decreased the time to perform the task and the intensity of elicited vertigo. Results were related to improved independence in activities of daily living and to decreased vertigo. CONCLUSION: Vertigo decreases and speed of head movement improved after a programme of vestibular rehabilitation, regardless of speed of treatment exercises. A simple purposeful activity can be useful to evaluate improvements after vestibular rehabilitation.

Benign paroxysmal positional vertigo and comorbid conditions.

PURPOSE: To determine the prevalence of comorbid disease in patients with benign paroxysmal positional vertigo (BPPV) and the relationship of comorbid disease to symptoms of vertigo, disequilibrium, and anxiety. PROCEDURES: Patients who had posterior semicircular canal BPPV and who had been referred for vestibular rehabilitation at a tertiary care center completed a health status questionnaire and the Vertigo Symptom Scale, answered questions about level of vertigo, and were tested on computerized dynamic posturography. RESULTS: Subjects had high rates of diabetes, mild head trauma, and probable sinus disease. Balance was generally impaired, worse in diabetics and subjects with significant vestibular weakness. Subjects who smoked or had had mild head trauma had higher levels of anxiety. CONCLUSIONS: Comorbid conditions, particularly diabetes, mild head trauma, and sinus disease, are unusually prevalent in BPPV patients. Message: Patients with comorbid disease are at risk for having increased vertigo, anxiety, and disequilibrium compared to other patients.

Decreased ataxia and improved balance after vestibular rehabilitation.

OBJECTIVES: To determine the effects of vestibular rehabilitation on gait ataxia and balance. SETTING: Tertiary care center. Study design Subjects were patients with chronic vertigo due to peripheral vestibular impairments, referred for vestibular rehabilitation. They were assessed on the Timed Up and Go test, ataxia during a path integration test, computerized dynamic posturography, level of vertigo, independence in activities of daily living, and psychological locus of control. They were randomly assigned to three home program treatment groups. RESULTS: Ataxia decreased significantly, and posturography scores and time to perform Timed Up and Go improved significantly, for all subjects. Improvements were significantly related to scores on the ambulation subtest of the Vestibular Disorders Activities of Daily Living Scale, decreases in vertigo, and increases in locus of control. CONCLUSIONS: For many patients, a simple home program of vestibular habituation head movement exercises is related to reduced symptoms of imbalance during stance and gait.

Treatment variations on the Epley maneuver for benign paroxysmal positional vertigo.

PURPOSE: To determine if using more head rotation during the Epley maneuver or specific posttreatment instructions for sleeping position would affect treatment effectiveness, compared with the usual maneuver without extra instructions. MATERIALS AND METHODS: Patients with unilateral benign paroxysmal positional vertigo of the posterior semicircular canal were randomized to a standard Epley maneuver group, a group that received an additional 45 degrees head rotation during the maneuver (Augmented Epley), and a group that received instructions about sleeping position after treatment. RESULTS: Posttests from 1 week to 6 months showed no differences in vertigo intensity or frequency or responses to the Dix-Hallpike maneuver. All groups showed significant decreases in vertigo and Dix-Hallpike responses. Some subjects in each group had abnormal pretreatment scores on computerized dynamic posturography. Those subjects in the Augmented Epley group who had abnormal pretreatment posturography scores had significantly better posttreatment scores than those subjects in the Home Instruction group who had abnormal pretreatment scores. All subjects with abnormal responses, however, showed improvement. CONCLUSIONS: Although clinicians continue to give patients home instructions and to use additional head rotation during the maneuver, these variations are not essential for achieving improvement in symptoms.

Driving disability and dizziness.

PROBLEM: People with dizziness caused by vestibular (i.e., inner ear) disorders complain of difficulty driving. Physicians occasionally warn their patients with vestibular disorders not to drive. Few studies have asked patients about their driving performance, so little data are available. METHOD: Using the Driving Habits Questionnaire, the authors did structured interviews with people with several different vestibular disorders and with normal subjects. The self-reported crash rate and rate of citations for moving violations did not differ between the subject groups. RESULTS: Patients report reduced driving skills, particularly in situations when visual information is reduced, rapid head movements are used, and specific path integration or spatial navigation skills are needed.

Increased independence and decreased vertigo after vestibular rehabilitation.

OBJECTIVE: We sought to determine the effectiveness in decreasing some symptoms, such as vertigo, and increasing performance of daily life skills after vestibular rehabilitation. STUDY DESIGN AND SETTING: Patients who had chronic vertigo due to peripheral vestibular impairments were seen at a tertiary care center. They were referred for vestibular rehabilitation and were assessed on vertigo intensity and frequency with the use of the Vertigo Symptom Scale, the Vertigo Handicap Questionnaire, the Vestibular Disorders Activities of Daily Living Scale, and the Dizziness Handicap Inventory. They were then randomly assigned to 1 of 3 home program treatment groups. RESULTS: Vertigo decreased and independence in activities of daily living improved significantly. Improvement was not affected by age, gender, or history of vertigo. CONCLUSION: For many patients a simple home program of vestibular habituation head movement exercises is related to reduction in symptoms and increasing independence in activities of daily living.

Bilateral symmetry of human carotid artery atherosclerosis.

BACKGROUND AND PURPOSE: Atherosclerosis is a principal cause of stroke and myocardial infarction. The carotid arteries provide a site at which progression of atherosclerosis can be monitored reproducibly and noninvasively. This study was conducted to determine the similarity of atherosclerotic plaques in the left and right carotid arteries. This question was explored with the use of perfusion-fixed cadaveric carotid arteries and 2 noninvasive clinical imaging techniques, MRI and electron-beam CT. METHODS: Fifty pairs of carotid arteries from cadaveric donors (aged 48 to 98 years) were imaged with MRI and electron-beam CT. Thirty-eight of the pairs met the criteria for rigorous analysis. Carotid artery wall volumes were measured from the MRI images, and calcification scores were computed from the electron-beam CT images. RESULTS: Total wall volumes of the left (972.5+/-241.6 mm3) and right (1016.3+/-275.0 mm3) carotid arteries were moderately correlated (concordance correlation coefficient [r(c)]=0.71). Calcification scores were highly correlated, with r(c)=0.95 for the Agatston scores and r(c)=0.94 for the calcium volume scores. CONCLUSIONS: Total wall volume and plaque calcification in the left and right human carotid arteries are substantially similar. These results suggest that atherosclerosis of the human carotid arteries is generally a bilaterally symmetrical disease. This evidence of symmetry suggests that diagnostic information about atherosclerotic plaque in one carotid artery can be used to infer information about the composition and volume of atherosclerotic plaque in the contralateral artery.

Effects of normal aging on visuo-motor plasticity.

Normal aging is associated with declines in neurologic function. Uncompensated visual and vestibular problems may have dire consequences including dangerous falls. Visuo-motor plasticity is a form of behavioral neural plasticity, which is important in the process of adapting to visual or vestibular alteration, including those changes due to pathology, pharmacotherapy, surgery or even entry into microgravity or an underwater environment. To determine the effects of aging on visuo-motor plasticity, we chose the simple and easily measured paradigm of visual-motor rearrangement created by using visual displacement prisms while throwing small balls at a target. Subjects threw balls before, during and after wearing a set of prisms which displace the visual scene by twenty degrees to the right. Data obtained during adaptation were modeled using multilevel modeling techniques for 73 subjects, aged 20 to 80 years. We found no statistically significant difference in measures of visuo-motor plasticity with advancing age. Further studies are underway examining variable practice training as a potential mechanism for enhancing this form of behavioral neural plasticity.

Improvements in path integration after vestibular rehabilitation.

Fifty-three subjects with peripheral, chronic vestibulopathies, who were referred for vestibular rehabilitation, were tested on a path integration task before and after doing four weeks of five times daily habituation exercises for vertigo reduction. The task involved walking over a 7.62 m path with eyes closed. Dependent measures were velocity and angle of veering from the straight ahead. At the post-test and at succeeding follow-up tests for up to six months, subjects had significant increases in velocity and significant declines in angle of veering. Length of time subjects had vertigo prior to starting rehabilitation, and speed of head movement exercises were not associated with improvements. These data support the previous finding that patients with vestibular impairments have decreased performance on this task. The data also suggest that vestibular rehabilitation, given as a simple home program, is associated with improvements in this skill.

Factors affecting recovery after acoustic neuroma resection.

In order to determine which variables influence recovery from acoustic neuroma resection, acutely postoperative patients were divided into two groups and treated twice daily at bedside as inpatients at a tertiary care center. Treatment times were increased gradually from 5 to 30 min. Exercise subjects underwent passive and active head movements and walking with augmented head movements. Control subjects received attention without exercise. Pre- and post-tests included vertigo intensity and frequency, low-frequency vestibulo-ocular reflex (VOR), posturography and path integration. Post-tests were given at discharge and at approximately 4-week intervals for 3 months. Multilevel statistical analyses showed that neither group assignment nor age affected the outcome. All measures were abnormal at discharge but improved towards normal within 3 weeks. VOR on the unoperated side returned to normal values but on the lesioned side did not. Therefore, compensation is influenced by tumor size but not by age or early postoperative vestibular rehabilitation. Most compensation occurs within 3 weeks, probably due to central mechanisms, although some measures may not recover completely.