The Orthostatic Discriminant and Severity Scale (ODSS): an assessment of orthostatic intolerance.

PURPOSE: To assess the ability of the Orthostatic Discriminant and Severity Scale (ODSS) to distinguish symptoms of orthostatic intolerance from non-orthostatic symptoms. METHODS: Clinical evaluations and questionnaire responses were collected in 73 healthy controls and 132 patients referred to the Autonomic Disorders Clinic from September 1, 2016, through April 30, 2018, for queries regarding autonomic dysfunction. A receiver operating characteristic (ROC) curve analysis was used to interpret sensitivity and specificity and to determine cutoff scores for symptom assessment. Inter-item reliability was assessed using Cronbach's alpha. To calculate positive and negative predictive powers, patient data were collected in a single-blinded fashion where the researcher collecting questionnaire data was blinded to the clinical evaluation and diagnosis. Predictive powers were calculated using a chi-squared cross-tabulation. RESULTS: The orthostatic and non-orthostatic symptoms scores produced ROC curves with an area under the curve of 0.89 and 0.79, respectively. The orthostatic scores yielded a positive and negative predictive power value of 73% and 81%, respectively. Combined, the ODSS identified patients with and without orthostatic symptoms with an overall accuracy of 76%. The reliability of the ODSS was significant, with a Cronbach's alpha of 0.88, and all dichotomous items were deemed worthy of retention following an inter-item reliability assessment. CONCLUSIONS: The ODSS demonstrated a strong ability to distinguish patients with and without orthostatic intolerance and demonstrated sensitivity and specificity equivalent to that of other standardized measures. Overall, the ODSS produces symptom scores that are both reliable and useful for both research and clinical practice.

Initial validation of symptom scores derived from the orthostatic discriminant and severity scale.

OBJECTIVE: To develop a scale to quantify and discriminate orthostatic from non-orthostatic symptoms. In the current study, we present validation and reliability of orthostatic and non-orthostatic symptom scores taken from the orthostatic discriminate and severity scale (ODSS). METHODS: Validity and reliability were assessed in participants with and without orthostatic intolerance. Convergent validity was assessed by correlating symptoms scores with previously validated tools [autonomic symptom profile (ASP) and the orthostatic hypotension questionnaire (OHQ)]. Clinical validity was assessed by correlating scores against standardized autonomic testing. Test-retest reliability was calculated using an intra-class correlation coefficient. RESULTS: Convergent validity: orthostatic (OS) and non-orthostatic (NS) symptom scores from 77 controls and 67 patients with orthostatic intolerance were highly correlated with both the orthostatic intolerance index of the ASP (OS: r = 0.903; NS: r = 0.651; p < 0.001) and the composite score of the OHQ: (OS: r = 0.800; NS: r = 0.574; p < 0.001). Clinical validity: symptom scores were significantly correlated with the total composite autonomic severity score (OS: r = 0.458; NS: r = 0.315; p < 0.001), and the systolic blood pressure change during head-up tilt (OS: r = - 0.445; NS: r = - 0.354; p < 0.001). In addition, patients with orthostatic intolerance had significantly higher symptom scores compared to controls (OS: 66.5 ± 18.1 vs. 17.4 ± 12.9; NS: 19.9 ± 11.3 vs. 10.2 ± 6.8; p < 0.001, respectively). Test-retest reliability: Both orthostatic and non-orthostatic symptom scores were highly reliable (OS: r = 0.956 and NS: r = 0.574, respectively; p < 0.001) with an internal consistency of 0.978 and 0.729, respectively. INTERPRETATION: Our initial results demonstrate that the ODSS is capable of producing valid and reliable orthostatic and non-orthostatic symptom scores. Further studies are ongoing to test sensitivity, specificity and symptom severity.

Cerebellar impairment during an orthostatic challenge in patients with neurogenic orthostatic hypotension.

OBJECTIVE: Compare activation patterns within the cortical autonomic network in patients with neurogenic orthostatic hypotension (NOH) versus healthy age-matched controls during an orthostatic challenge. METHODS: Fifteen health controls and 15 NOH patients performed 3 Valsalva maneuvers, and 5-min of lower-body negative pressure (LBNP) during a functional brain MRI. RESULTS: Compared to controls, NOH patients had significantly less activation within the cerebellum during both LBNP and VM. Both groups had significant activation of the bilateral insula and left thalamus during LBNP. No significant differences were found during the recovery phase of LBNP. CONCLUSIONS: The cerebellum, which plays an important role in vestibulo-sympathetic reflexes, important for blood pressure adjustments during postural changes, appear to be affected in patients with NOH. The cerebellum also appears to be affected during other baroreflex mediated stressors such as the VM. SIGNIFICANCE: Orthostatic reflexes mediated by the cerebellum may be impaired in patients with NOH. The results suggest an additional pathological pathway in patients with autonomic failure.

Impaired cortical autonomic responses during sympathetic activation in neurogenic orthostatic hypotension characterized by postganglionic autonomic dysfunction.

Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic dysfunction. The cortical autonomic network (CAN) is a network of brain regions associated with autonomic function. Therefore, our objective was to investigate whether impairment of CAN structures is involved in the pathophysiology of NOH. Fifteen controls (63 ± 13 yr) and 15 NOH patients (67 ± 6 yr; P = 0.2) with peripheral autonomic dysfunction completed standard tests of parasympathetic [deep breathing (DB)] and sympathetic [Valsalva maneuver (VM)] activation during a functional MRI. Blood-oxygen-level dependent (BOLD) contrasts were obtained and contrasted. Compared with controls, patients had significantly smaller heart rate responses to DB (control: 15.23 ± 9.6 vs. NOH: 5.7 ± 2.1) and Valsalva ratios (control: 2.1 ± 0.47 vs. NOH: 1.2 ± 0.1; P < 0.001). NOH patients had absent adrenergic phases (late phase II and phase IV) during VM as per a qualitative analysis. During VM, controls had greater activation in the right hippocampus (T-value: 8.03), left posterior cingulate (TL: 7.6), and bilateral thalamus (TR: 7.41, TL: 8.45; P < 0.05). During phase IV, controls had greater activation in the right hippocampus (TR: 5.78l P < 0.05). Following subtraction analysis, no significant differences were evident during DB. In conclusion, NOH patients have significantly less CAN activation during sympathetic, but not parasympathetic, activation. Impaired CANs associated with sympathetic activation may be involved in the pathophysiology of NOH. NEW & NOTEWORTHY Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic dysfunction characterized by failure of reflexive sympathetic activation. Our result reveal that patients with autonomic dysfunction caused by postganglionic sympathetic impairment also have impaired activation of structures within the cortical autonomic network. Impaired activation is evident during a test of sympathetic, but not parasympathetic, activation. Impaired cortical autonomic networks associated with sympathetic activation may be involved in the pathophysiology of NOH.

Older men are more fatigable than young when matched for maximal power and knee extension angular velocity is unconstrained.

The underlying factors related to the divergent findings of age-related fatigue for dynamic tasks are not well understood. The purpose here was to investigate age-related fatigability and recovery between a repeated constrained (isokinetic) and an unconstrained velocity (isotonic) task, in which participants performed fatiguing contractions at the velocity (isokinetic) or resistance (isotonic) corresponding with maximal power. To compare between tasks, isotonic torque-power relationships were constructed prior to and following both fatiguing tasks and during short-term recovery. Contractile properties were recorded from 9 old (~75 years) and 11 young (~25 years) men during three testing sessions. In the first session, maximal power was assessed, and sessions 2 and 3 involved an isokinetic or an isotonic concentric fatigue task performed until maximal power was reduced by 40 %. Compared with young, the older men performed the same number of contractions to task failure for the isokinetic task (~45 contractions), but 20 % fewer for the isotonic task (p < 0.05). Regardless of age and task, maximal voluntary isometric contraction strength, angular velocity, and power were reduced by ~30, ~13, and ~25 %, respectively, immediately following task failure, and only isometric torque was not recovered fully by 10 min. In conclusion, older men are more fatigable than the young when performing a repetitive maximal dynamic task at a relative resistance (isotonic) but not an absolute velocity (isokinetic), corresponding to maximal power.