Calibrating balance perturbation using electrical stimulation of the vestibular system.

BACKGROUND: Supra-threshold galvanic vestibular stimulation (GVS) can be used to challenge the balance control system by disrupting vestibular inputs. The goal of this study was to propose an objective method to assess variability across subjects in the minimum safe GVS level that causes maximum balance degradation. New method: Thirteen healthy young subjects stood on a compliant foam surface with their eyes closed and tried to maintain a stable upright stance. Variables related to the stability of the trunk and whole body were quantified to characterize the relationship between postural responses and GVS at amplitudes from 0 to 4.5 mA in 0.5 mA increments. The relationship between decrements in postural responses and GVS was linear up to a minimum GVS level (called KNEE). An increase in the stimulation level above that did not lead to any further degradation of balance performance. The KNEE was determined by iteratively performing linear fits to the performance measure at different stimulation levels. RESULTS: There were individual differences in KNEE; it was in the range of 1-2.5 mA across subjects. GVS caused an average performance decrement of 27-99% across six variables at the KNEE level compared to a no-stimulus condition. Comparison to existing methods: We propose a method to consistently attain the maximum level of impairment across subjects using the minimum current intensity, to minimize all types of adverse effects usually observed at high intensities. CONCLUSIONS: Individual differences in the disruption of posture control in response to GVS have important implications for testing and training paradigms.

Prototype tests of vertical and torsional alignment nulling for screening vestibular function.

BACKGROUND: We have developed a non-invasive, behavioral measure of ocular alignment using a computer tablet, colored lenses, and touch screen software. OBJECTIVE: The goal of this study was to determine if these tests differentiate healthy controls from patients with vestibular disorders. METHODS: In the vertical alignment nulling test (VAN), subjects were asked to adjust a horizontal line that was offset vertically from a fixed horizontal line. In the torsional alignment nulling test (TAN) subjects were asked to adjust a line that was rotationally offset (i.e. clockwise) from a fixed horizontal line. We measured VAN and TAN in 14 healthy controls and 8 patients with known vestibular disorders. RESULTS: Patients had significantly worse scores than controls on TAN, (mean 2.2 vs 0.75, p = 0.01), and no differences for scores compared to controls on VAN, (mean 0.4 vs 0.8, p = 0.07). CONCLUSIONS: These results suggest that TAN, and possibly VAN, have potential for identifying misalignments in ocular position. After further technical development these tests might be useful in the future for screening patients in facilities that are not equipped to perform cervical and ocular vestibular evoked myogenic potentials.

Calcium chloride in neonatal parenteral nutrition: A 15 year experience.

OBJECTIVE: The objective of this study was to determine if outcomes at our neonatal intensive care units (NICUs) since we began using calcium chloride (CaCl2) as our preferred calcium additive in order to reduce aluminum (Al) exposure are within expected outcome ranges for NICUs in the U.S. where calcium gluconate in glass vials (CaGlu-Gl) has been the preferred additive. STUDY DESIGN: A retrospective study of very low birth weight infants born between January 1, 2000 and December 31, 2014. Outcomes in two intensive care units (NICUs) using CaCl2 were compared to all U.S. NICUs in the Vermont Oxford Network. Primary outcomes were chronic lung disease (CLD), percent requiring supplemental oxygen at 28 days, and mortality excluding early deaths (MEED). The incidence of IV infiltrates of all admissions to the study NICUs in 2013-2014 was compared to the literature. RESULTS: The incidence of CLD and those requiring oxygen at 28 days were 24.0% vs 28.6% and 46.2% vs 51.8% for the study NICUs compared to all U.S. NICUs, respectively (both p < 0.0001). The MEED was 8.7% vs 10.3% (p < 0.002). All major morbidities were lower at the study NICUs. The incidence of infiltrates was lower than that in the literature. CONCLUSION: The use of CaCl2 was not associated with any detectable adverse effects. Calcium chloride appears to be a safe alternative to the use of CaGlu-Gl based upon studies of clinical outcomes.

Fall frequency and associated factors among men and women with or at risk for HIV infection.

OBJECTIVES: Falls and fall-related injuries are a major public health concern. HIV-infected adults have been shown to have a high incidence of falls. Identification of major risk factors for falls that are unique to HIV infection or similar to those in the general population will inform development of future interventions for fall prevention. METHODS: HIV-infected and uninfected men and women participating in the Hearing and Balance Substudy of the Multicenter AIDS Cohort Study and Women's Interagency HIV Study were asked about balance symptoms and falls during the prior 12 months. Falls were categorized as 0, 1, or ≥ 2; proportional odds logistic regression models were used to investigate relationships between falls and demographic and clinical variables and multivariable models were created. RESULTS: Twenty-four per cent of 303 HIV-infected participants reported at least one fall compared with 18% of 233 HIV-uninfected participants (P = 0.27). HIV-infected participants were demographically different from HIV-uninfected participants, and were more likely to report clinical imbalance symptoms (P ≤ 0.035). In univariate analyses, more falls were associated with hepatitis C, female sex, obesity, smoking, and clinical imbalance symptoms, but not age, HIV serostatus or other comorbidities. In multivariable analyses, female sex and imbalance symptoms were independently associated with more falls. Among HIV-infected participants, smoking, a higher number of medications, and imbalance symptoms remained independent fall predictors, while current protease inhibitor use was protective. CONCLUSIONS: Similar rates of falls among HIV-infected and uninfected participants were largely explained by a high prevalence of imbalance symptoms. Routine assessment of falls and dizziness/imbalance symptoms should be considered, with interventions targeted at reducing symptomatology.

Vestibular-somatosensory convergence in head movement control during locomotion after long-duration space flight.

Space flight causes astronauts to be exposed to adaptation in both the vestibular and body load-sensing somatosensory systems. The goal of these studies was to examine the contributions of vestibular and body load-sensing somatosensory influences on vestibular mediated head movement control during locomotion after long-duration space flight. Subjects walked on a motor driven treadmill while performing a gaze stabilization task. Data were collected from three independent subject groups that included bilateral labyrinthine deficient (LD) patients, normal subjects before and after 30 minutes of 40% bodyweight unloaded treadmill walking, and astronauts before and after long-duration space flight. Motion data from the head and trunk segments were used to calculate the amplitude of angular head pitch and trunk vertical translation movement while subjects performed a gaze stabilization task, to estimate the contributions of vestibular reflexive mechanisms in head pitch movements. Exposure to unloaded locomotion caused a significant increase in head pitch movements in normal subjects, whereas the head pitch movements of LD patients were significantly decreased. This is the first evidence of adaptation of vestibular mediated head movement responses to unloaded treadmill walking. Astronaut subjects showed a heterogeneous response of both increases and decreases in the amplitude of head pitch movement. We infer that body load-sensing somatosensory input centrally modulates vestibular input and can adaptively modify vestibularly mediated head-movement control during locomotion. Thus, space flight may cause central adaptation of the converging vestibular and body load-sensing somatosensory systems leading to alterations in head movement control.

Frequency of sinus disease in normal subjects and patients with benign paroxysmal positional vertigo.

BACKGROUND/AIMS: To determine if patients with benign paroxysmal positional vertigo (BPPV) have a higher frequency of rhinosinusitis than people with normal vestibular function. METHODS: The subjects were 52 patients with BPPV and 46 normal people. Every subject had a sinus CT scan, a blood draw for IgE and a rhinologic examination by an otolaryngologist. RESULTS: The frequency of rhinosinusitis based on physician diagnosis was 49% and based on CT scan findings 59%. This difference approached significance (p = 0.08). The observed frequency of rhinosinusitis was higher than predicted by survey data about the southern US region. The data trended toward higher prevalence of rhinosinusitis (by physician diagnosis) in the BPPV patients versus controls (58 vs. 39%, p = 0.06). CONCLUSION: BPPV patients have a higher frequency of sinus disease compared to people with normal vestibular systems, perhaps due to age differences, but physiologic factors may also be involved. The higher frequency of rhinosinusitis in this geographical area than reported rates based on survey data raises concerns about the usefulness of questionnaire data for estimating population prevalence.

Variable practice with lenses improves visuo-motor plasticity.

Novel sensorimotor situations present a unique challenge to an individual's adaptive ability. Using the simple and easily measured paradigm of visual-motor rearrangement created by the use of visual displacement lenses, we sought to determine whether an individual's ability to adapt to visuo-motor discordance could be improved through training. Subjects threw small balls at a stationary target during a 3-week practice regimen involving repeated exposure to one set of lenses in block practice (x 2.0 magnifying lenses), multiple sets of lenses in variable practice (x 2.0 magnifying, x 0.5 minifying and up-down reversing lenses) or sham lenses. At the end of training, adaptation to a novel visuo-motor situation (20-degree right shift lenses) was tested. We found that (1) training with variable practice can increase adaptability to a novel visuo-motor situation, (2) increased adaptability is retained for at least 1 month and is transferable to further novel visuo-motor permutations and (3) variable practice improves performance of a simple motor task even in the undisturbed state. These results have implications for the design of clinical rehabilitation programs and countermeasures to enhance astronaut adaptability, facilitating adaptive transitions between gravitational environments.

Effects of adaptation of vestibulo-ocular reflex function on manual target localization.

The goal of the present study was to determine if adaptive modulation of vestibulo-ocular reflex (VOR) function is associated with commensurate alterations in manual target localization. To measure the effects of adapted VOR on manual responses we developed the Vestibular-Contingent Pointing Test (VCP). In the VCP test, subjects pointed to a remembered target following passive whole body rotation in the dark. In the first experiment, subjects performed VCP before and after wearing 0.5X minifying lenses that adaptively attenuate horizontal VOR gain. Results showed that adaptive reduction in horizontal VOR gain was accompanied by a commensurate change in VCP performance. In the second experiment, bilaterally labyrinthine deficient (LD) subjects were tested to confirm that vestibular cues were central to the spatial coding of both eye and hand movements during VCP. LD subjects performed significantly worse than normal subjects. These results demonstrate that adaptive change in VOR can lead to alterations in manual target localization.

Application of the vestibular disorders activities of daily living scale.

OBJECTIVE: Existing scales of functional performance are either insufficiently sensitive or omit some important daily life tasks. This paper demonstrates that a new scale of self-perceived disablement in the vestibularly impaired population-the Vestibular Disorders Activities of Daily Living Scale (VADL)-differentiates between disabled and healthy persons and evaluates the associations of this assessment with other measures of vestibular disorders. STUDY DESIGN: Prospective. METHODS: Subjects were 1) asymptomatic, healthy adults, 2) patients with benign paroxysmal positional vertigo, 3) patients with chronic vestibulopathy excluding Meniere's disease, postsurgical vertigo, and postconcussion vertigo, and 4) family members. Patient were assessed on the VADL, the Dizziness Handicap Inventory, level of vertigo, and computerized dynamic posturography. Healthy subjects and family members completed the VADL. RESULTS: The VADL differentiates healthy persons from patients but does not differentiate between patient groups. Patients perceived themselves as more independent than their spouses perceived them to be. Scores are weakly correlated with vertigo frequency and posturography scores for conditions with unreliable kinesthesia and absent or unreliable vision. The VADL is more responsive to higher levels of impairment than the Dizziness Handicap Inventory. CONCLUSIONS: This well-normed, self-administered scale of self-perceived disablement is useful for evaluating the functional status of patients with peripheral vestibular disorders. Perceptions of patients and significant others vary, but scores are moderately correlated with some standard measures of vestibular function. As it assesses a different domain of function than do standard diagnostic tests, the VADL will augment these tests during initial evaluation and may be useful for assessing posttreatment change.

Development of the vestibular disorders activities of daily living scale.

BACKGROUND: Existing scales of self-perceived disablement in patients with vestibular impairment either are too broad to detect the subtle deficits in this population or omit some important daily life tasks. OBJECTIVES: To develop a scale to assess self-perceived disablement in patients with vestibular impairment and to describe the development and initial testing of this new assessment tool. DESIGN: A list of items was developed, sent to a panel of expert therapists for review, and then revised to yield the preliminary 31-item, 10-point scale that was administered to subjects. The scale was revised again, yielding the final 28-item scale, which was administered to a new group of subjects. SETTING: Data were collected from patients in an outpatient clinic of a tertiary care center. PARTICIPANTS: Patients diagnosed as having benign paroxysmal positional vertigo and patients diagnosed as having chronic vestibulopathy, excluding Ménière disease, postsurgical vertigo, and postconcussion vertigo. RESULTS: The final scale has 3 subscales: functional, ambulation, and instrumental. It has good face validity, high internal consistency (alpha> or =.90), and high test-retest reliability (r(c)> or =0.87). Scale ratings ranged from 1 (independent) to 10 (ceasing to participate in the activity), but median scores for most subjects were 4 or less. From 41% (39/94) to 44% (41/94) of subjects considered themselves to be independent on those tasks. CONCLUSIONS: This scale has good face validity, high internal consistency, and high test-retest reliability. It may be useful for evaluating functional limitation and perceived handicap or disability before and after intervention and for helping patients become more realistic in understanding their own capabilities.

Vestibular disorders and impaired path integration along a linear trajectory.

The goal of this study was to determine if people use vestibular information to keep track of their positions while walking through a simple course. Subjects were normals and patients with chronic peripheral vestibulopathies-- each of whom were tested once--and patients with acoustic neuromas tested pre-operatively and one and three weeks post-operatively. Subjects walked over a straight course, 7.62 m, with their eyes open and then with their eyes closed. The time needed for task performance, the forward distance subjects walked before veering, and the lateral distance subjects veered from the straight ahead were recorded. The angle of veering was then calculated. Normals were able to perform this task easily with eyes open or closed. With eyes closed pre-operative acoustic neuroma subjects walked significantly shorter distances before veering than normals but did not veer significantly more than normals or take longer than normals to perform the task. Chronic vestibulopathy subjects, by contrast, were significantly impaired compared to normals on all measures. With eyes open within a week after acoustic neuroma resection subjects could perform the task as well as normals. With eyes closed, however, post-operative subjects were impaired compared to their own pre- operative levels, but they had returned to their pre-operative levels at the second post-operative test. Ataxia was only weakly correlated to any measures and tumor size was not related to performance. These findings support the hypothesis that vestibular input is used for spatial orientation during active motion.

Long-term vestibulo-ocular reflex changes in patients with vestibular ablation.

Long-term changes in the parameters of the vestibulo-ocular reflex (VOR) were evaluated using recently developed multilevel statistical modelling techniques in a group of patients who had undergone ablative inner ear procedures. Data from 84 patients were available for study. The most dramatic recovery in the VOR occurred during the first 60 postoperative days, however, slow changes continued, levelling off at about 120 days. While frequency was a highly significant predictor of outcomes in all parameters, age showed significant predictive value only to phase measures (p = 0.006) and gender had no effect. Sum gain at the lowest frequency tested remained below the 5th percentile and at the higher frequencies remained below the 50th percentile for normal subjects. Phase decreased exponentially, but remained above the 95th percentile for normal subjects, except at the highest frequency where it remained above the 50th percentile. DC bias decreased exponentially, dropping to the 50th percentile by day 146. Asymmetry stayed between the 50th and 95th percentile, except at the highest frequency, where it was at the 50th percentile by day 125.

Dynamic visual acuity while walking in normals and labyrinthine-deficient patients.

We describe a new, objective, easily administered test of dynamic visual acuity (DVA) while walking. Ten normal subjects and five patients with histories of severe bilateral vestibular dysfunction participated in this study. Subjects viewed a visual display of numerals of different font sizes presented on a laptop computer while they stood still and while they walked on a motorized treadmill. Treadmill speed was adapted for 4 of 5 patients. Subjects were asked to identify the numerals as they appeared on the computer screen. Test results were reasonably repeatable in normals. The percent correct responses at each font size dropped slightly while walking in normals and dropped significantly more in patients. Patients performed significantly worse than normals while standing still and while walking. This task may be useful for evaluating post-flight astronauts and vestibularly impaired patients.

Efficacy of treatments for posterior canal benign paroxysmal positional vertigo.

OBJECTIVE: This study was performed to determine the relative effectiveness of several passive head maneuvers for treating benign paroxysmal positional vertigo. STUDY DESIGN: This prospective study used 87 subjects diagnosed by their physicians with unilateral benign paroxysmal positional vertigo of the posterior semicircular canal. METHODS: Subjects were randomly assigned to three treatment groups: modified Epley maneuver, modified Epley maneuver with augmented head rotations, and modified Semont maneuver. They were interviewed 1 week after receiving one maneuver. If subjects desired further treatment, they were treated again with the same maneuver, a methodology repeated until subjects desired no further treatment; they were telephoned 3 and 6 months after the last treatment. RESULTS: The groups did not differ significantly, but subjects decreased significantly on vertigo intensity and frequency and improved significantly on independence in activities of daily living. Before treatment, tasks requiring pitch rotations of the head induced vertigo; common comorbid conditions were osteoporosis, cervical spine problems, and head trauma. CONCLUSIONS: These data suggest that augmented head rotations are unnecessary and that the modified Epley and Semont maneuvers are equally effective in the remediation of vertigo in this population.

Breast cancer histology in Caucasians, African Americans, Hispanics, Asians, and Pacific Islanders.

STUDY OBJECTIVES: To investigate the association between race/ethnicity and histologic types of breast cancer. DESIGN: Cross-sectional study. SETTING: Population-based data from the Northern California Tumor Registry, which is part of the National Cancer Institute's Surveillance, Epidemiology and End Results Program. PARTICIPANTS: A total of 2759 breast cancer cases diagnosed in 1988. MAIN RESULTS: Tumors were classified as ductal, lobular, and mixed/unspecified carcinoma. Ductal carcinoma was the most common (83.6%) and lobular carcinoma was the rarest. Most cases were diagnosed in the localized stage (56.3%). Caucasian women had the highest rates of total breast cancer (240.9/100,000), ductal and lobular. In African-American women, the odds of ductal carcinoma were twice that of lobular carcinoma, compared with Caucasian women (odds ratio [OR] = 2.0, 95% confidence interval [CI] 1.0-3.9) after adjusting for age, site, and stage at diagnosis. Similarly, Asian and Hispanic women also had higher, non-statistically significant odds of ductal versus lobular carcinoma compared with Caucasians (OR = 1.8 [95% CI 0.9-3.7] and 1.6 [95% CI 0.8-3.4], respectively). CONCLUSIONS: Future studies should investigate how racial/ethnic differences in histology among breast cancer patients will influence life expectancy, against a backdrop of health care access, sociocultural issues, lifestyle habits, reproductive history, family history, and tumor characteristics.

A task for assessing vertigo elicited by repetitive head movements.

OBJECTIVE: We developed a simple, inexpensive test for assessing vertigo in persons with peripheral vestibular disorders. METHOD: The test was administered to 16 asymptomatic adults and 16 patients with chronic vertigo caused by peripheral vestibular disorders. Participants sat in a chair and as rapidly as possible transferred 25 beanbags one at a time from a basket placed on the floor to a basket held .91 m up in the air. The task was timed, and the participants rated the level of vertigo elicited on a 10-point scale. RESULTS: Patients took significantly more time to perform the task and reported significantly greater levels of vertigo than did the asymptomatic adults. Test scores did not differ significantly across test sessions or raters. CONCLUSION: Performance on this task reliably differentiated patients with vestibular disorders from asymptomatic adults. The test is inexpensive, takes less than 1 min to perform, and has minimal technical requirements, making it suitable for a variety of facilities and levels of staff expertise.

Job stress and preeclampsia.

We conducted a case-control study to determine whether job strain (or stress) during pregnancy resulted in an increased risk of preeclampsia. We compared 110 nulliparous Caucasian and African-American women who had preeclampsia with 115 healthy nulliparous controls. All subjects gave birth between 1984 and 1987 in Chapel Hill, NC. Occupation was ascertained during a telephone interview. We assigned each job title a strain (or stress) score in accordance with the occupational database developed by Karasek. Overall, 54 (49%) of the control women worked during pregnancy, 14 in high-stress jobs. Logistic regression analysis indicated a 3.1-fold [95% confidence interval (CI) = 1.2-7.8] increased risk of preeclampsia for women employed in high-stress jobs (high psychological demand, low decision latitude) and an odds ratio of 2.0 (95% CI = 1.0-4.3) for low-stress jobs compared with nonworking women, while simultaneously adjusting for age, race, family history of preeclampsia, history of hypertension in the subject's mother, gravidity, smoking during pregnancy, timing of the first prenatal visit, and type of birth control used by the couple before the pregnancy. Furthermore, working women had 2.3 times the risk of developing preeclampsia (95% CI = 1.2-4.6) compared with nonworking women. Work-related psychosocial strain increased the risk of preeclampsia in our study.

A case-control study of routine and death scene sleep position and sudden infant death syndrome in Southern California.

OBJECTIVE: To investigate whether infants who died of sudden infant death syndrome (SIDS) were routinely placed in different sleep positions compared with healthy infants in a multiethnic diverse population in the United States. DESIGN: A population-based case-control study. SETTING: Five counties in Southern California including Los Angeles, Orange, San Bernardino, Riverside, and San Diego. PARTICIPANTS: Parents of 200 white, African-American, Hispanic, and Asian infants who died of SIDS between January 1989 and December 1992 and parents of 200 healthy, living infants matched on the basis of birth hospital, birth date, race, and gender. Information was obtained from detailed telephone interviews with the parents and validated with obstetric and pediatric records. MAIN OUTCOME MEASURES: Routine sleep position, type of bedding, and objects in bed were determined for both case and control infants, while the last-placed and found sleep and face positions at death were reported for SIDS infants. RESULTS: Approximately 66% of SIDS infants and 64% of comparison infants routinely slept on their abdomens (P = .91). At the time of death, 80% of cases were found sleeping on their abdomens. There was no difference in routine sleep position for SIDS infants and comparison infants (odds ratio = 0.76; 95% confidence interval, 0.42 to 1.38), while simultaneously adjusting for birth weight (in grams), medical conditions at birth, breast-feeding, passive smoking, maternal recreational drug use, prenatal care, and infant vomiting. Hispanic parents routinely placed their infants on their abdomens less frequently than white parents (P < .01). However, the prone sleep position (face down) was the most commonly found sleep position at death in both Hispanic and non-Hispanic infants. CONCLUSIONS: Routine prone sleep position was not associated with an increased risk of SIDS in this study population. The results need to be confirmed with other parents of SIDS infants interviewed before the height of publicity regarding prone sleep position in the United States.