Eliminating rote postoperative radiographs for surgically managed pediatric supracondylar humerus fractures.

BACKGROUND: Use of postoperative radiographs after surgical management of supracondylar humerus (SCH) fractures is often based on rote practice rather than evidence. The purpose of this study was to determine the frequency with which 3-week postoperative radiographs at the time of pin removal altered management plans in pediatric SCH fractures that were intraoperatively stable after closed reduction and percutaneous pinning (CRPP). METHODS: We prospectively recruited pediatric patients with SCH fractures managed by CRPP at our institution from June 2020 until June 2022, and reviewed retrospective data on pediatric SCH fractures managed surgically at our institution between April 2008 and March 2015. Patients were assessed for post-CRPP fracture alignment and stability. For prospective patients, we asked clinicians to document their management decision at the 3-week follow-up visit before evaluating the postoperative radiographs. Our primary outcome was change in management because of radiographic findings. RESULTS: Overall, 1066 patients in the retrospective data and 446 prospectively recruited patients met the inclusion criteria. In the prospective group, radiographic findings altered management for 2 patients (0.4%). One patient had slow callus formation and 1 patient was identified as having cubitus varus. Altered management included prolonged immobilization or additional radiographic follow-up. Radiographic findings altered management in 0 (0%) of 175 type II fractures, in 2 (0.9%) of 221 type III fractures, and in 0 (0%) of 44 type IV fractures. We obtained similar findings from retrospective data. CONCLUSION: Rote use of 3-week postoperative radiographs after surgical management of SCH fractures that are intraoperatively stable has minimal utility. Eliminating rote postoperative radiographs for SCH fractures can decrease the time and financial burdens on families and health care systems without affecting patient outcomes.

The association of moderate-to-vigorous and light-intensity physical activity on static balance in middle-aged and older-aged adults.

BACKGROUND: Falls are the leading cause of injury among adults ≥ 65 years of age. Participation in physical activity (PA) is associated with improved balance, though it is impact in the middle-age population is not well understood. AIM: The purpose of the current study was to examine the influence of PA intensity on static balance in middle-aged and older aged individuals. METHODS: Included were middle-aged adults (40-64 years) and older adults (≥ 65 years) from the 2003-2004 years of the National Health and Nutrition Evaluation Survey. Light physical activity (LPA) and moderate-vigorous physical activity (MVPA) were collected via accelerometer and static balance via the Romberg Test of Standing Balance. RESULTS: No significant odds ratio relationship was found between MVPA or LPA and having good static balance in the middle-aged population; 1.04 (95% CI 0.95, 1.13) p = 0.427 and 1.05 (95% CI 0.97, 1.14) p = 0.182, respectively. Whereas, in older adults, every 60-min increase in LPA was significantly associated with 28% higher odds of good balance (95% CI 1.15, 1.41; p < 0.001), and every 10-min increase in MVPA with 25% higher odds of good balance (95% CI 1.08, 1.45; p = 0.006). DISCUSSION: LPA and MVPA were not associated with good static balance in middle-aged adults, but in older adults LPA was significantly associated with good static balance. CONCLUSION: A significant relationship is found between age and fall risk, which is a major concern in the aging population.

Strength training as a dynamical model of motor learning.

This paper outlines a framework for strength training as a dynamical model of perceptual-motor learning. We show, with emphasis on fixed-point attractor dynamics, that strength training can be mapped to the general dynamical principles of motor learning that arise from the constraints on action, including the distribution of practice/training. The time scales of the respective dynamics of performance change (increment and decrement) in discrete strength training and motor learning tasks reveal superposition of exponential functions in fixed-point dynamics, but distinctive attractor and parameter dynamics in oscillatory limit cycle and more continuous tasks, together with unique timescales to process influences (including practice, learning, strength, fitness, fatigue, warm-up decrement). Increments and decrements of strength can be viewed within a dynamical model of change in motor performance that reflects the integration of practice and training processes at multiple levels of learning and skill development.

Is the presence of tumor-infiltrating lymphocytes predictive of outcomes in patients with melanoma?

BACKGROUND: The significance of tumor-infiltrating lymphocytes (TILs) in melanoma is debated. This article presents a multicenter, retrospective study assessing the predictive and prognostic value of TILs. METHODS: The Sentinel Lymph Node Working Group database was queried from 1993 to 2018 for cases with known TIL data. TILs were categorized as absent or present, which included nonbrisk (NB), brisk (B), and present but unspecified TIL levels. Clinicopathologic factors were correlated with TILs, sentinel lymph node (SLN) status, and melanoma-specific survival (MSS). RESULTS: Overall, 3203 patients were included. The median thickness was 1.5 mm, and 469 cases had SLN metastases. TILs were present in 2458 cases (76.7%), with NB, B, and unspecified TILs seen in 1691 (68.8%), 691 (28.1%), and 76 (3.1%), respectively. Multivariable analysis showed that the presence of TILs significantly predicted a negative SLN biopsy (P < .05). The median follow-up was 25.2 months. MSS was significantly better for cases with TILs than cases without TILs (P < .001). According to multivariable analysis, age, gender, thickness, mitotic rate, ulceration, lymphovascular invasion, and SLN status were significantly prognostic of MSS (all P values < .05). Although TILs were not prognostic of MSS, when multiple imputation was used and the SLN status was excluded, the presence of TILs was significantly prognostic of improved MSS (hazard ratio, 0.78; 95% confidence interval, 0.64-0.95; P = .0154). CONCLUSIONS: TILs are a favorable marker because their presence significantly predicts a negative SLN, and the absence of TILs may be a prognostic marker of worse survival in patients with a positive SLN but not a negative SLN. TILs may also serve as a prognostic marker of survival when the SLN status is not considered.

Is There a Relationship Between TILs and Regression in Melanoma?

BACKGROUND: The relationship between tumor-infiltrating lymphocytes (TILs) and regression in melanoma is unknown. This report describes a large multicenter study assessing the association between TILs and regression. METHODS: The Sentinel Lymph Node Working Group database was queried from 1993 to 2018 for cases with TILs and regression data. Clinicopathologic factors were correlated with regression and TIL status, sentinel lymph node (SLN) status, and overall survival (OS). RESULTS: The study enrolled 2450 patients. In 1811 cases, TILs (73.9%) were present, with regression present in 328 of these 1811 (18.1%) cases and in 49 (7.7%) of 639 cases without TILs. The presence of TILs was significantly associated with regression (p < 0.0001) as well as a negative SLN (p < 0.05). However, when TILs were stratified by regression status, only absence or presence of both TILs and regression were significantly associated with SLN metastases (p = 0.038). Although the presence of TILs was associated with OS (p < 0.05), regression status by itself was not (p = 0.2058 and 0.252, respectively). Furthermore, when TILs were stratified by regression status, only the presence of TILs with or without regression was significantly associated with improved OS (p = 0.0081 and 0.0137, respectively) versus the absence of both TILs and regression, with regression status not significantly affecting OS for patients with or without TILs (p = 0.2314 and 0.65, respectively). CONCLUSIONS: Regression is highly correlated with TILs, but only TILs are significantly associated with SLN metastasis and OS in melanoma patients, whereas regression is not. The impact of regression on outcomes ultimately appears dependent upon the absence or presence of TILs.

Changes in trunk and head acceleration during the 6-minute walk test and its relation to falls risk for adults with multiple sclerosis.

For persons with multiple sclerosis (MS), the general decline in neuromuscular function underlies diminished balance, impaired gait and consequently, increased risk of falling. During gait, optimal control of head motion is an important feature which is achieved partly through control of the trunk-neck region to dampen gait-related oscillations. The primary aim of this study was to examine the effect performing a 6-minute walk test (6MWT) has on head, neck and trunk accelerations in individuals with MS. This was addressed using a repeated measures generalized linear model. We were also interested in assessing whether the 6MWT has an impact on a person's falls risk and specific physiological measures related to falls. Finally the relation between the amplitude (i.e., mean RMS) of head and trunk accelerations and falls risk was examined using linear regression. The main results were that over the course of the 6MWT, individuals progressively slowed down coupled with a concurrent increase in gait-related upper body accelerations (p's > 0.05). Despite the increased acceleration, no significant changes in attenuation from the trunk to the head were observed, indicating that persons were able to maintain an optimal level of control over these oscillations. Performing the 6MWT also had a negative impact on posture, with falls risk significantly increasing following this test (p > 0.05). Interestingly, the overall falls risk values were strongly linked with vertical accelerations about the trunk and head, but not average walking speed during the 6MWT. Overall, performing the 6MWT leads to changes in walking speed, upper body acceleration patterns and increases in overall falls risk.

Sentinel Lymph Node Biopsy Is Prognostic in Thickest Melanoma Cases and Should Be Performed for Thick Melanomas.

BACKGROUND: Sentinel lymph node biopsy (SLNB) is recommended for intermediate thickness melanoma, but for thick melanoma, guidelines are less definitive about the use of SLNB in this population. We present a study on thick melanoma evaluating for prognostic factors. PATIENTS AND METHODS: The Sentinel Lymph Node Working Group database was queried for thick (> 4 mm) melanoma cases that had a SLNB from 1993 to 2018. Clinicopathologic characteristics were correlated with SLN status and melanoma-specific survival (MSS). RESULTS: There were 1235 patients. Median follow-up was 28 months. Median thickness was 5.9 mm, with 956, 175, and 104 cases presenting thickness > 4-8, > 8-12, and > 12 mm, respectively. SLN metastases were seen in 439 of 1235 (35.5%) cases and in 33.9%, 40.6%, and 42.3% of melanomas > 4-8, > 8-12, and > 12 mm, respectively. In each thickness group, MSS was significantly worse for SLN-positive compared with SLN-negative cases (all P < 0.005). Multivariable analysis showed that SLN metastasis, male gender, increasing thickness, lymphovascular invasion, and microsatellitosis significantly predicted worse MSS for melanomas > 4-8 mm, with SLN metastasis showing the greatest risk (HR 2.17, 95% CI 1.64-2.87, P < 0.0001). For melanomas > 8 mm, only SLN metastasis significantly predicted MSS (> 8-12 mm: HR 3.93, 95% CI 2.00-7.73, P < 0.0001; > 12 mm: HR 3.58, 95% CI 1.56-8.22, p < 0.0027). CONCLUSIONS: Thick melanoma patients with SLN metastasis have significantly worse MSS compared with SLN-negative patients, even in the thickest cases, and SLN status is the most powerful and/or only predictor of MSS. Given these results, SLNB shows important prognostic value in this population and is indicated for clinically localized thick melanoma.

The relation between falls risk and movement variability in Parkinson's disease.

Falls are a major health concern for older adults with Parkinson's disease (PD). This study was designed to examine differences in falls risk and its relation to changes in the average and variability (i.e. intra-individual variability) of reaction time (RT), finger tapping, standing balance and walking between healthy older adults and persons with PD. Thirty-nine adults with PD (70.0 ± 8.1 years) and 29 healthy older adults (66.8 ± 10.4 years) participated in this study. Falls risk (using the physiological profile assessment), gait, RT, balance and tapping responses were assessed for all persons. Results demonstrated that individuals with PD exhibited a greater risk of falling coupled with a general slowing of motor function covering declines in walking, RT and finger tapping. In addition, the movement responses of the PD group were more variable than the healthy older adults. Correlation results revealed group differences with regards to the neuromotor measures which were significantly correlated with falls risk. For the PD group, gait measures were highly correlated with their falls risk while, for the healthy older adults, falls risk was linked to balance measures even though PD persons had increased sway. Overall, persons with PD were at greater falls risk, moved slower and with increased variability compared to the healthy older adults. Further, while there are some similarities between the two groups in terms of those measures related to falls risk, there were also several differences which highlight that persons with PD can have different risk factors for falling compared to healthy adults of similar age.

Re-evaluation of Sentinel Lymph Node Biopsy for Melanoma.

OPINION STATEMENT: The vast majority of patients newly diagnosed with melanoma present with clinically localized disease, and sentinel lymph node biopsy (SLNB) is a standard of care in the management of these patients, particularly in intermediate thickness cases, in order to provide important prognostic data. However, SLNB also has an important role in the management of patients with other subtypes of melanoma such as thick melanomas, certain thin melanomas, and specific histologic variants of melanoma such as desmoplastic melanoma. Furthermore, there have been technical advances in the SLNB technique, such as the development of newer radiotracers and use of SPECT/CT, and there is some data to suggest performing a SLNB may be therapeutic. Finally, the management of patients with a positive sentinel lymph node (SLN) has undergone dramatic changes over the past several years based on the results of recent important clinical trials. Treatment options for patients with SLN metastases now include surveillance, completion lymph node dissection, and adjuvant therapy with checkpoint inhibitors and targeted therapy. SLNB continues to play a crucial role in the management of patients with melanoma, allowing for risk stratification, potential regional disease control, and further treatment options for patients with a positive SLN.

Bonds and signals underlie the music learning experience.

The music learning environment is a context in which fundamental forces and values underlying human musicality may be evident. Social bonding within music-making groups is characterized by a high degree of complexity whereas issues of clarity, accuracy, and coordination remain the focus of learning. Physical and cognitive impairments that compromise music learning opportunities offer a critical test of music's link to social bonding.

Effect of immunized egg proteins on the performance and neonatal diarrhoea incidence in newborn calves.

The aim of this study was to assess the effects of feeding immunized egg proteins (IEP) on the health and performance of newborn dairy calves. Sixty-four Holstein calves, both male and female, were divided over two treatments. Calves either received IEP or a placebo (PCB) in their colostrum and calf milk replacer (CMR) for the first 14 days of their life. Until day 49, CMR was offered at 15% of birth weight (BW), at 10% on days 49-57 and at 5% on days 57-63. In addition, calves received starter concentrate, chopped straw and water from 3 days old until 70 days old at the end of study. Individual CMR and concentrate intake were measured daily whilst BW was recorded weekly. Visual faecal scoring and health observations were conducted daily. Faecal samples were collected weekly up to 4 weeks and during the first 4 days of scouring to screen for presence of Cryptosporidium parvum, rotavirus, coronavirus, E. coli and Salmonella. Results indicated that feeding IEP increased BW (p < .05) at 42 and 56 days old, and BW also tended (p = .06) to be higher after weaning at 63-70 days old compared to the PCB group. When analysed using a repeated measures model, compared to feeding PCB, feeding IEP increased total concentrate consumption (p = .001) by 3.6kg/calf. Over the entire study, daily water intake was higher (p = .002) for the IEP group when compared with the PCB group. In the IEP group, 12 calves were scored as scouring whereas there were 14 calves in the PCB group. There were no significant differences between treatments in faecal pathogen load of neither healthy nor scouring calves. In conclusion, supplementing IEP during the first 14 days of calf life improved the performance of newborn calves. Further work is warranted to understand the mode of action of IEP in calves.

Age-related changes in neuromotor function when performing a concurrent motor task.

Aging is associated with physiological changes which can manifest as age-related slowing of voluntary movements. Dual-task conditions can magnify this slowing process in older adults. The current study describes healthy adult chewing patterns and examined effects of concurrent chewing on performance of simple reaction time (RT), finger tapping, and gait. Chewing rates were measured from electromyographic (EMG) activity from the masseter muscle. Stepping rates were calculated using accelerometers mounted on the lower trunk and leg. Tapping rates were collected using accelerometers secured to a fixed surface. Simple RT was attained from a purposely designed switch. Results demonstrated that older adults walked slower, tapped slower, and had slower reaction times compared to young individuals, however chew rates were similar. This dichotomy became more pronounced when motor tasks were performed at faster speeds, with the exception being chewing. Additionally, chewing altered performance of secondary motor tasks for all individuals. Strong coupling emerged between cyclical actions (i.e., chewing-gait and chewing-tapping), reflecting entrainment between the respective neural oscillators driving the actions. In contrast, RT responses slowed appreciably when chewing was performed concurrently, indicating an interference effect. Taken together, these results illustrate the contrasting effects of chewing on a secondary motor task and highlights bidirectional effects of dual tasking on performance.

Anterior cruciate ligament reconstructed individuals demonstrate slower reactions during a dynamic postural task.

INTRODUCTION: To determine whether individuals with a history of anterior cruciate ligament reconstruction (ACLR) exhibit altered neuromotor function compared to healthy controls. It was hypothesized that the ACLR group would have slower postural responses compared to healthy individuals of similar age. MATERIALS AND METHODS: Sixteen adults with a unilateral ACLR and 16 matched healthy controls participated. General assessments of neuromotor function were gathered and included measures of reaction time (both seated and postural conditions), walking ability, balance, ankle ROM, proprioception, knee joint laxity, patellar tendon reflex latency, and quadriceps strength. Data were analyzed using mixed generalized linear models with between-subject (ie, controls, ACLR) and within-subject factors (ie, affected, unaffected limb). RESULTS: Individuals with an ACLR exhibited a significant slowing of their postural reaction times compared to the control individuals. The ACLR group was slower under both the simple (ACLR: 484 ± 6.17 ms, control: 399 ± 1.95 ms) and choice reaction time conditions (ACLR: 550 ± 43 ms, control: 445 ± 43 ms). No other group differences were found in any of the other measures. CONCLUSION: Overall, ACLR individuals had a reduced ability to respond quickly under more challenging postural conditions (ie, stepping response). This finding would indicate that the impact of an ACLR is not purely mechanical and restricted to the joint. Rather, injury and reconstruction of the ACL impact neural mechanisms, altering individuals' ability to respond under challenging balance tasks.

Complications of type II supracondylar humerus fractures treated at a specialized paediatric centre.

BACKGROUND: Supracondylar humerus (SCH) fractures are the most common operatively treated paediatric fracture in Canada. Previous literature describing the low-energy (Gartland type II) subtype reports varying complication rates from a variety of practice settings. We sought to examine complications of type II SCH fractures treated at a Canadian specialized paediatric centre. METHODS: We conducted a retrospective cohort study of patients aged 0 to 14 admitted to SickKids, Toronto, Ontario for surgical treatment of a type II SCH fracture from 2008 to 2015. The primary outcome of this study was relevant perioperative complications including: open fracture, compartment syndrome, pre- and postoperative vascular compromise, pre- and postoperative neurological compromise, failure to obtain a closed reduction (i.e., open reduction), postoperative infection, and reoperation within 3 months. RESULTS: There were 370 patients included in the study with mean (standard deviation) age 5.14 years (±2.51). The overall rate of relevant complications in the study cohort was 3.6% (13/358, 12 missing), with 12 cases of nerve palsy (3.3%; 2 iatrogenic [0.6%]) that resolved by final follow-up and one case of preoperative nerve palsy (0.3%) that did not. Importantly, there were no cases of vascular compromise, open fracture, compartment syndrome, or infection. DISCUSSION AND CONCLUSION: Complications associated with type II SCH fractures managed at a specialized paediatric centre that result in long-term morbidity are extremely rare (0.3%). Perioperative inpatient monitoring for patients with these fractures may not be justified based on these data. Prospective studies are required to confirm safety, evaluate patient perspectives, and demonstrate cost savings of outpatient surgical management.

Cross-limb dynamics of postural tremor due to limb loading to fatigue: neural overflow but not coupling.

Many experiments have shown independence of the index finger dynamics under bilateral postural tremor protocols. Here we investigated in young adults the dynamics of bilateral multidirectional postural tremor and forearm muscle activity under the progressively fatiguing conditions supporting an external weight to the point of induced postural failure. When no loads were applied, tremor in the vertical (VT) and mediolateral (ML) directions was similar with prominent peaks within 2- to 4-Hz and 8- to 12-Hz bandwidths. Contrastingly tremor in the anterior-posterior (AP) direction was characterized by a single peak between 0 and 2 Hz. Although no tremor coupling occurred cross limbs, strong within-limb coupling was found between ML and VT directions when no loads were applied (coherence range: 0.77-0.85), implying that these oscillations are related and likely derived from mechanical sources. Applying an external load to the index finger(s) led to significant increases in the amplitude of VT tremor and EMG activity within that limb but also caused increases in tremor directions not aligned with the gravitational vector (AP and ML). Significant increases in VT and ML tremor and EMG activity in the contralateral (unloaded) limb were also found when a single index finger was loaded; however, this bilateral increase did not align with increases in interlimb coupling (coherence <0.21). The effects of fatigue caused by prolonged loading were widespread, affecting tremor and muscle activity in both limbs through a combination of neural and mechanical mechanisms. The single- and dual-limb loading to fatigue increased neural overflow but not tremor coupling between the index fingers.NEW & NOTEWORTHY This study investigated bilateral multidirectional tremor under unloaded and loaded conditions. We found that tremor in the mediolateral and vertical directions within a limb were strongly coupled, a result not reported previously. Furthermore, when holding a weight to failure, tremor in all directions increased. Tremor also increased in the contralateral (unloaded) limb despite no interlimb coupling. This contralateral increase in tremor following loading a limb until fatigue is hypothesized to stem from motor-overflow effects.

Neuromotor and cognitive responses of adults with autism spectrum disorder compared to neurotypical adults.

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder, whose core symptom domains include impaired social communication and narrowed interests and/or repetitive behaviors; in addition, deficits of general cognition, neuromotor function, and movement ability can be observed. This study was designed to examine differences in neuromotor and cognitive functions for a group of young adults with ASD and age-matched controls. It was also of interest to assess whether changes in the intra-individual variability (IIV) of these selected neuromotor and cognitive tasks also occurred. Increased IIV in persons with ASD may reveal important organizational features of their neuromotor system that differ from neurotypical controls. Twenty neurotypical adult individuals (24.3 ± 2.8 years) and twenty adults with a clinician-assigned diagnosis of ASD (21.2 ± 4.4 years) participated in this study. Specific cognitive and motor assessments included Trails Making Tests A&B, Symbol Digit Modalities Test, Purdue Pegboard Test, simple reaction time, finger tapping, hand grip strength, balance, and gait. Results revealed that the ASD adults exhibited decreased upper limb strength and slower responses for finger tapping, hand dexterity, reaction times, and gait compared to the non-ASD controls. The general slowing of motor responses for the persons with ASD was also associated with increased within-subject variability during the reaction time, finger tapping, hand grip, and gait assessments compared to neurotypical adults, illustrating that IIV measures may be a useful marker of widespread neuromotor dysfunction for adults with ASD. Overall, these findings are consistent with clinical observations that abnormalities of movement performance and cognitive performance are an associated feature of ASD in young adults.

Does maternal HSV-2 coinfection increase mother-to-child transmission of HIV? A systematic review.

BACKGROUND: Reducing HIV mother-to-child transmission (MTCT) is critical to ending the HIV pandemic. Reports suggest that herpes simplex virus-2 (HSV-2), a common coinfection in HIV-infected individuals, is associated with increased MTCT, but results have been conflicting. We conducted a systematic review of observational studies to quantify the magnitude of this relationship (PROSPERO no. CRD42016043315). METHODS: We searched Medline (1981 to June week 3, 2016), EMBASE (1981 to week 26, 2016), relevant conferences (2013-2016) and bibliographies of identified studies for cohort and case-control studies enrolling HIV-positive women during pregnancy or peripartum that quantified the effect of HSV-2 infection on MTCT. The primary outcome was the risk of perinatal HIV transmission associated with maternal HSV-2 status. Risk of bias was evaluated using a standardised tool, and results were meta-analysed where appropriate using a random-effects model, with studies weighted using the inverse variance method. RESULTS: From 2103 hits, 112 studies were considered for inclusion, and 10 were ultimately included. Of the included studies, three used a case-control design, three were retrospective cohorts and four were prospective cohorts. Risk of bias was low in three studies, moderate in six and high in one. The median sample size was 278.5 mother-infant pairs (range: 48-1513). The most common strategy for classifying maternal HSV-2 status was type-specific serology (n=6), followed by genital shedding (n=3) or genital culture (n=3), clinical diagnosis of herpes (n=2) or genital ulcer disease (n=1). Results from five studies that provided quantitative estimates of the association between HSV-2 seropositivity and MTCT were meta-analysed, yielding a pooled unadjusted OR=1.17 (95% CI=0.69 to 1.96, I2=58%). Three of these studies further considered key confounding variables, specifically antiretroviral use and/or viral load (n=3), and mode of delivery (n=2), yielding a pooled adjusted OR=1.57 (95% CI=1.17 to 2.11, I2=0). CONCLUSIONS: Maternal HSV-2 coinfection appears to be associated with increased perinatal HIV transmission. Further study of the effect of HSV-2 treatment on MTCT is warranted.

Differences in postural tremor dynamics with age and neurological disease.

The overlap of dominant tremor frequencies and similarly amplified tremor observed for Parkinson's disease (PD) and essential tremor (ET) means differentiating between these pathologies is often difficult. As tremor exhibits non-linear properties, employing both linear and non-linear analyses may help distinguish between the tremor dynamics of aging, PD and ET. This study was designed to examine postural tremor in healthy older adults, PD and ET using standard linear and non-linear metrics. Hand and finger postural tremor was recorded in 15 healthy older adults (64 ± 6 years), 15 older individuals with PD (63 ± 6 years), and 10 persons with ET (68 ± 7 years). Linear measures of amplitude, frequency, and between-limb coupling (coherence) were performed. Non-linear measures of regularity (ApEn) and coupling (Cross-ApEn) were also used. Additionally, receiver operating characteristic analyses were performed for those measures that were significantly different between all groups. The results revealed that the linear measures only showed significant differences between the healthy adults and ET/PD persons, but no differences between the two neurological groups. Coherence showed higher bilateral coupling for ET but no differences in inter-limb coupling between PD and healthy subjects. However, ApEn values for finger tremor revealed significant differences between all groups, with tremor for ET persons being more regular (lower ApEn) overall. Similarly, Cross-ApEn results also showed differences between all groups, with ET persons showing strongest inter-limb coupling followed by PD and elderly. Overall, our findings point to the diagnostic potential for non-linear measures of coupling and tremor structure as biomarkers for discriminating between ET, PD and healthy persons.