Gerard Boyle

Correlation of accelerometry with clinical balance tests in older fallers and non-fallers

BACKGROUND falls are a common cause of injury and decreased functional independence in the older adult. Diagnosis and treatment of fallers require tools that accurately assess physiological parameters associated with balance. Validated clinical tools include the Berg Balance Scale (BBS) and the Timed Up and Go test (TUG); however, the BBS tends to be subjective in nature, while the TUG quantifies an individuals functional impairment but requires further subjective evaluation for balance assessment. Other quantitative alternatives to date require expensive, sophisticated equipment. Measurement of the acceleration of centre of mass, with relatively inexpensive, lightweight, body-mounted accelerometers is a potential solution to this problem. OBJECTIVES to determine (i) if accelerometry correlates with standard clinical tests (BBS and TUG), (ii) to characterise accelerometer responses to increasingly difficult challenges to balance and (iii) to characterise acceleration patterns between fallers and non-fallers. STUDY DESIGN AND SETTING torso accelerations were measured at the level of L3 using a tri-axial accelerometer under four conditions; standing unsupported with eyes open (EO), eyes closed (EC) and on a mat with eyes open (MAT EO) and closed (MAT EC). Older patients (n = 21, 8 males, 13 females) with a mean age of 78 (SD +/- 7.6) years who attended a day hospital were recruited for this study. Patients were identified as fallers or non-fallers based on a comprehensive falls history. MEASUREMENTS Spearmans rank correlation analysis examined the relationship between acceleration root mean square (RMS) data and the BBS while Pearsons correlation was used with TUG scores. Differences in accelerometer RMS between fallers and non-fallers and between test conditions were examined using t-test and non-parametric alternatives where appropriate. RESULTS there was a stepwise increase in accelerometer RMS with increasing task complexity, and the accelerometer was able to distinguish significantly between sway responses to all test conditions except between EO and EC (P < 0.05). Acceleration data for MAT EO were significantly and inversely correlated with BBS scores (P = -0.829, P < 0.001) and positively correlated with TUG values (r = 0.621, P < 0.01). There was a significant difference in acceleration RMS for MAT EO between fallers and non-fallers (P < 0.011). CONCLUSIONS this is the first study of its kind to show a high correlation between accelerometry, the BBS and TUG. Accelerometry could also distinguish between sway responses to differing balancing conditions and between fallers and non-fallers. Accelerometry was shown to be an efficient, quantitative alternative in the measurement of balance in older people.

The validity of Rehabilitative Ultrasound Imaging for measurement of trapezius muscle thickness

The purpose of the study was to establish the validity of Rehabilitative Ultrasound Imaging (RUSI) against Magnetic Resonance Imaging (MRI) for measuring trapezius muscle thickness. Participants were asymptomatic subjects recruited from Trinity College Dublin and associated teaching hospitals. Four MRI axial slices were made through each of the C6, T1, T5 and T8 spinous processes, with the subject supine. RUSI was performed immediately after MRI at the same vertebral levels, with the subject prone. Linear measurements of trapezius muscle thickness were made off-line on both the MRI and Ultrasound scans, in three regions: lower, middle and upper trapezius. Bland and Altman limits of agreement and Pearsons correlation coefficient were used to analyse the relationship between thickness measures taken from MRI and RUSI. Eighteen subjects (9 women) participated, (age-range 21-42 years). Results demonstrated good agreement between MRI and RUSI measurements of the lower trapezius muscle at T8 (r=0.77) and moderate agreement at T5, (r=0.62). Results were poor for the middle (T1) and upper (C6) trapezius muscles, (r=-0.22 to 0.52) but may be explained by differences in both positioning and imaging planes between the 2 modalities. It was concluded that RUSI is a valid method of measuring lower trapezius muscle thickness.

Orthostatic Hypotension Is Associated With Lower Cognitive Performance in Adults Aged 50 Plus With Supine Hypertension

OBJECTIVES This study investigated the association between orthostatic hypotension (OH), supine hypertension (SH), and cognitive performance. METHODS Four thousand six hundred and ninety participants of The Irish Longitudinal Study on Ageing (TILDA) were studied. SH was defined as systolic blood pressure (SBP) greater than or equal to 140 mmHg and/or diastolic blood pressure (DBP) greater than or equal to 90 mmHg, measured following supine rest (10 minutes). OH was defined as a sustained drop of greater than or equal to 20 mmHg SBP or greater than or equal to 10 mmHg DBP at 20, 30, 60, and 90 seconds following orthostasis. Cognitive performance tests assessed global function, executive function, processing speed, memory, and attention from which z-scores were computed. Multivariate adjusted analysis was performed comparing cognitive scores by OH status overall and in SH and non-SH groups separately. RESULTS Thirty-nine percent had baseline SH (n = 1,868) and demonstrated a greater orthostatic fall in SBP (p < .0001) and DBP (p < .0001). This group had a higher prevalence of OH at all time-points, and scored lower in tests across all cognitive domains. No overall association between OH and cognitive performance was seen. However, SH subjects with OH scored significantly worse (adjusted) than SH subjects without OH, in domains of global cognition (30 seconds poststand β = -0.15; 99% confidence interval -0.29, -0.14; p = .004) and executive function (20 seconds poststand; β = -0.11; 99% confidence interval -0.22, -0.01; p = .006). There was also an indication toward lower cognition in all nonsignificant analyses. OH was not associated with cognitive performance in non-SH subjects. CONCLUSION In conclusion, individuals with SH (defined as BP > 140/90 mmHg) coupled with OH measured using phasic BP had lower global and executive cognitive performance than those with SH but without OH.

Cognitive performance in orthostatic hypotension: findings from a nationally representative sample.

To compare the cognitive profile of a population representative sample with orthostatic hypotension (OH) with the profile of a sample without.

Simultaneous recordings of ocular microtremor and microsaccades with a piezoelectric sensor and a video-oculography system

Our eyes are in continuous motion. Even when we attempt to fix our gaze, we produce so called “fixational eye movements”, which include microsaccades, drift, and ocular microtremor (OMT). Microsaccades, the largest and fastest type of fixational eye movement, shift the retinal image from several dozen to several hundred photoreceptors and have equivalent physical characteristics to saccades, only on a smaller scale (Martinez-Conde, Otero-Millan & Macknik, 2013). OMT occurs simultaneously with drift and is the smallest of the fixational eye movements (∼1 photoreceptor width, >0.5 arcmin), with dominant frequencies ranging from 70 Hz to 103 Hz (Martinez-Conde, Macknik & Hubel, 2004). Due to OMT’s small amplitude and high frequency, the most accurate and stringent way to record it is the piezoelectric transduction method. Thus, OMT studies are far rarer than those focusing on microsaccades or drift. Here we conducted simultaneous recordings of OMT and microsaccades with a piezoelectric device and a commercial infrared video tracking system. We set out to determine whether OMT could help to restore perceptually faded targets during attempted fixation, and we also wondered whether the piezoelectric sensor could affect the characteristics of microsaccades. Our results showed that microsaccades, but not OMT, counteracted perceptual fading. We moreover found that the piezoelectric sensor affected microsaccades in a complex way, and that the oculomotor system adjusted to the stress brought on by the sensor by adjusting the magnitudes of microsaccades.

Impact of family history and depression on amygdala volume

Family history of depression significantly impacts life-long depression risk. Family history could impact the stress and emotion regulation system that involves the amygdala. This studys purpose was to investigate family historys effect on amygdala volumes, and differences in first degree relatives with and without major depressive disorder (MDD). Participants, aged 18-65, were healthy volunteers (N=52) with (n=26) and without (n=26) first degree family history, and patients with MDD (N=48) with (n=27) and without (n=21)first-degree family history recruited for structural magnetic resonance imaging (MRI). Participants underwent clinical assessment followed by manual amygdala tracing. Patients with MDD without family history showed significantly larger right amygdala compared to patients with a MDD family history.MDD without family history also had larger right amygdala than healthy controls without MDD family history.These effects were pronounced in females. Family history and gender impacted amygdala volumes in all participants providing rationale for the inconsistent results in MDD amygdala studies [corrected]. Higher familial risk in depression seems to be associated with smaller amygdala volumes, whereas depression alone is associated with larger amygdala volumes. Ultimately, these findings highlight consideration of family history and gender in research and treatment strategies.

Functional anomalies in healthy individuals with a first degree family history of major depressive disorder

BackgroundIndividuals with major depressive disorder (MDD) process information with a bias towards negative stimuli. However, little is known on the link between vulnerability to MDD and brain functional anomalies associated with stimulus bias.MethodsA cohort of 38 subjects, of which 14 were patients with acute MDD and 24 were healthy controls (HC), were recruited and compared. The HC group included 10 healthy participants with a first degree family history of depression (FHP) and 14 volunteers with no family history of any psychiatric disease (FHN). Blood oxygen level dependence signals were acquired from functional magnetic resonance imaging (fMRI) during performance in a dot-probe task using fearful and neutral stimuli. Reaction times and the number of errors were also obtained.ResultsAlthough MDD patients and HC showed no behavioral difference, the MDD group exhibited smaller activation in the left middle cingulum. The MDD group also showed smaller activation in the left insula when compared to the HC group or the FHN group. Finally, FHP participants exhibited higher activation in the right Heschls gyrus compared to FHN participants.ConclusionsThe present study shows that family risk for MDD is associated with increased activation in the Heschls gyrus. Our results also suggest that acute MDD is linked to reduced activation in the insula and anterior cingulate cortex during processing of subliminal, not recognizable, masked fearful stimuli. Further research should confirm these results in a larger cohort of participants.

White matter alterations in patients with MRI-negative temporal lobe epilepsy and their asymptomatic siblings

The identification of “endophenotypes”—measurable variations along the pathways between genes and distal disease state—may help deconstruct focal epilepsies into more sensitive phenomena and improve future efforts to map the genetic underpinnings of the disorder. In this study, we set out to determine if diffusion tensor imaging (DTI)–inferred white matter (WM) alterations represent a suitable structural endophenotype for focal epilepsy.

Mayer wave activity in vasodepressor carotid sinus hypersensitivity

AIMS Mayer waves are low frequency blood pressure waves, whose modulation involves central/peripheral baroreflex pathways. Although vasodepressor carotid sinus hypersensitivity (VDCSH) is a common hypotensive disorder in ageing, the mechanism of VDCSH is unknown. We hypothesize that VDCSH is due to impaired baroreflex function and that Mayer wave amplitude and oscillation frequency are therefore altered. METHODS AND RESULTS Ten minutes ECG and continuous beat-to-beat blood pressure (TNO Finapres(c)) recordings were taken in supine position. Blood pressure variance, spectral power (0.04-0.15 Hz) and centre of frequency was examined across a number of frequency bands. Vasodepressor carotid sinus hypersensitivity was defined as 50 mmHg drop in systolic blood pressure (SBP) during carotid sinus massage. Syncope facility was used in this study. Twelve patients with VDCSH median age 72 range (50-92) were compared with 36 case-controls median age 78 range (48-88). Diastolic blood pressure variability (median SD) was significantly higher in the VDCSH 6.6 (1.9-12.9) mmHg compared with controls 4.0 (1.7-9.5) mmHg; P < 0.05. Mean arterial blood pressure (MAP) variability (median SD) was significantly higher in the VDCSH 6.6 (2.9-10.1) mmHg compared with controls 4.6 (2.5-9.1) mmHg; P < 0.05. Low frequency Mayer wave activity in MAP in VDCSH compared with controls was increased at 0.06 Hz [controls -21.7 mmHg(2)/Hz (IQR: 30.8); VDCSH -31.5 mmHg(2)/Hz (IQR: 72.0) P < 0.05] and at 0.1 Hz [controls -4.9 mmHg(2)/Hz (IQR: 9.4); VDCSH -11.5 mmHg(2)/Hz (IQR: 12.9) P < 0.1]. High frequency blood pressure fluctuations were significantly increased at 0.3 Hz in VDCSH group in SBP [controls -4.1 mmHg(2)/Hz (IQR: 10.4); VDCSH -17.4 mmHg(2)/Hz (IQR: 47.9) P < 0.05] and MAP records [controls -32.5 mmHg(2)/Hz (IQR: 76.9); VDCSH -64.6 mmHg(2)/Hz (IQR: 59.8) P < 0.01]. CONCLUSION Blood pressure variability in particular activity at Mayer wave frequencies was higher in VDCSH. Future work will investigate this approach as a basis for diagnosis of VDCSH, with implications for syncope and falls management.

Compact portable ocular microtremor sensor: design, development and calibration

Ocular microtremor (OMT) is a physiological high-frequency (up to 150 Hz) low-amplitude (25-2500 nm peak-to-peak) involuntary motion of the human eye. Recent studies suggest a number of clinical applications for OMT that include monitoring the depth of anesthesia of a patient in surgery, prediction of outcome in coma, and diagnosis of brain stem death. Clinical OMT investigations to date have used mechanical piezoelectric probes or piezoelectric strain gauges that have many drawbacks which arise from the fact that the probe is in contact with the eye. We describe the design of a compact noncontact sensing device to measure OMT that addresses some of the above drawbacks. We evaluate the system performance using a calibrated piezoelectric vibrator that simulates OMT signals under conditions that can occur in practice, i.e., wet eye conditions. We also test the device at low light levels well within the eye safety range.