Cerebral blood flow during HUTT in young patients with orthostatic intolerance

Novel brain SPECT imaging unravels abnormal cerebral perfusion in patients with postural orthostatic tachycardia syndrome and cognitive dysfunction

Cognitive dysfunction is frequently reported in individuals with postural orthostatic tachycardia syndrome (POTS), possibly resulting from reduced cerebral blood flow (CBF). We used brain SPECT, an accessible imaging modality that has not been systematically evaluated in this patient group. Retrospective review of participants from our registry was undertaken to identify those who had a brain SPECT performed for investigation of cognitive dysfunction. Abnormal CBF was taken as z-score > 2 standard deviations of healthy control reference values. Patient reported outcome measures (PROMs) such as autonomic, gastric and quality of life symptom scores were analyzed. From a total of 56 participants (mean 34.8 ± 10.7 years, 88% females), PROMs indicate: moderate to severe autonomic dysfunction in 75%; at least mild to moderate gastroparesis in 23%; low global health rating and utility scores. Abnormal CBF was seen in 61% but did not differ by POTS triggers. The regions with the lowest mean z-scores were the lateral prefrontal and sensorimotor cortices. Hierarchal regression analyses found number of brain regions with abnormal CBF, autonomic and gastric symptoms to account for 51% of variances in health utility. Cerebral hypoperfusion is prevalent in those with POTS and cognitive dysfunction even whilst supine, contributing to reduced quality of life.

Arterial Baroreceptor Physiology: Differences Between Normal Subjects and Pediatric Patients with Postural Tachycardia and Neurocardiogenic Syncope

The arterial baroreceptor reflex in children and adolescents has not been well studied in the current literature with a lack of agreed upon normal values, particularly in postural orthostatic tachycardia syndrome (POTS) or neurocardiogenic syncope (NCS). We used the sequence method and head-up tilt test (HUTT) to evaluate baroreceptor function in 3 phases: baseline supine position for 10 min, head-up position at 70° for 30 min or until syncope, and post-tilt supine reposition for 10 min. We measured the number of baroreceptor events, baroreceptor effectiveness index (BEI), and the magnitude of sensitivity of the events at each phase of HUTT. We studied 198 individuals (49 normal subjects, 67 POTS, 82 NCS) with age ranges from 8 to 21 years. The data show a statistically significant decrease in slope and BEI in patients with POTS and NCS during the head-up phase, with an increase in activity in the lag 1 and 2 portions of all phases in patients with POTS. This study provides terminology to describe baroreceptor function and identifies the slope and BEI portions of the baroreceptor reflex as the most useful objective measures to differentiate pediatric patients with POTS and NCS from normal subjects.

Orthostatic Headaches Associated With Spontaneous Intracranial Hypotension and Autonomic Dysfunction-A Case Series in Young Patients

Background: Orthostatic headaches can be noted in spontaneous intracranial hypotension and orthostatic intolerance. We present a case series of young patients diagnosed with spontaneous intracranial hypotension and were treated for the same but subsequently developed orthostatic intolerance. Methods: We retrospectively reviewed charts for seven young patients with orthostatic headaches related to spontaneous intracranial hypotension and orthostatic intolerance. Results: Patients were diagnosed with spontaneous intracranial hypotension. Diagnosis was confirmed by identifying epidural contrast leakage and three of seven patients were noted to have early renal contrast excretion on computerized tomography myelography. Patients were treated with epidural blood patches. All patients showed persistent symptoms of autonomic dysfunction after treatment of spontaneous intracranial hypotension and orthostatic intolerance was confirmed with head-up tilt table test. Conclusions: Patients with spontaneous intracranial hypotension failing to improve following epidural blood patching should be evaluated for orthostatic intolerance.

Cutaneous manifestations of orthostatic intolerance syndromes

Dysautonomia refers to a group of autonomic nervous system disorders that affect nearly 70 million people worldwide. One subset of dysautonomia includes syndromes of orthostatic intolerance (OI), which primarily affect adolescents and women of childbearing age. Due to the variability in disease presentation, the average time from symptom onset to diagnosis of dysautonomia is 6 years. In general, there is a paucity of dermatological research articles describing patients with dysautonomia. The objective of this review is to summarize the existing literature on cutaneous manifestations in dysautonomia, with an emphasis on syndromes of OI. A PubMed database of the English-language literature (1970–2020) was searched using the terms “dysautonomia”, “orthostatic intolerance”, “cutaneous”, “skin”, “hyperhidrosis”, “hypohidrosis”, “sweat”, and other synonyms. Results showed that cutaneous manifestations of orthostatic intolerance are common and varied, with one paper citing up to 85% of patients with OI having at least one cutaneous symptom. Recognition of dermatological complaints may lead to an earlier diagnosis of orthostatic intolerance, as well as other comorbid conditions.

Functional Near-Infrared Spectroscopy and Its Clinical Application in the Field of Neuroscience: Advances and Future Directions

Similar to functional magnetic resonance imaging (fMRI), functional near-infrared spectroscopy (fNIRS) detects the changes of hemoglobin species inside the brain, but via differences in optical absorption. Within the near-infrared spectrum, light can penetrate biological tissues and be absorbed by chromophores, such as oxyhemoglobin and deoxyhemoglobin. What makes fNIRS more advantageous is its portability and potential for long-term monitoring. This paper reviews the basic mechanisms of fNIRS and its current clinical applications, the limitations toward more widespread clinical usage of fNIRS, and current efforts to improve the temporal and spatial resolution of fNIRS toward robust clinical usage within subjects. Oligochannel fNIRS is adequate for estimating global cerebral function and it has become an important tool in the critical care setting for evaluating cerebral oxygenation and autoregulation in patients with stroke and traumatic brain injury. When it comes to a more sophisticated utilization, spatial and temporal resolution becomes critical. Multichannel NIRS has improved the spatial resolution of fNIRS for brain mapping in certain task modalities, such as language mapping. However, averaging and group analysis are currently required, limiting its clinical use for monitoring and real-time event detection in individual subjects. Advances in signal processing have moved fNIRS toward individual clinical use for detecting certain types of seizures, assessing autonomic function and cortical spreading depression. However, its lack of accuracy and precision has been the major obstacle toward more sophisticated clinical use of fNIRS. The use of high-density whole head optode arrays, precise sensor locations relative to the head, anatomical co-registration, short-distance channels, and multi-dimensional signal processing can be combined to improve the sensitivity of fNIRS and increase its use as a wide-spread clinical tool for the robust assessment of brain function.

Blood Pressure Drop Rate After Standing Up Is Associated With Frailty and Number of Falls in Geriatric Outpatients

Background

The relationship between orthostatic hypotension and clinical outcome in older adults is poorly understood. Blood pressure drop rate (ie, speed of blood pressure drop) may particularly reflect the imposed challenge to the baroreflex and the associated clinical outcome (ie, frailty and number of falls). This study aimed to compare orthostatic blood pressure drop rate and drop magnitude with regard to their association with frailty and number of falls.

Methods and Results

Blood pressure was measured continuously during a standardized active stand task in 168 patients (mean age 81.4±7.0; 55.4% female) who visited a geriatric outpatient clinic for cognitive or mobility problems. The association of orthostatic blood pressure drop rate, blood pressure drop magnitude, and baroreflex sensitivity (ie, increase in heart rate divided by systolic blood pressure drop magnitude) with frailty (Fried criteria and 4 frailty markers) and self‐reported number of falls was assessed using linear regression models, adjusting for age and sex. Systolic blood pressure drop rate had the strongest association with frailty according to the 4 frailty markers (β 0.30; 95% CI, 0.11–0.49; P=0.003) and number of falls (β 1.09; 95% CI, 0.19–1.20; P=0.018); diastolic blood pressure drop magnitude was most strongly associated with frailty according to the Fried criteria (β 0.37; 95% CI, 0.15–0.60; P<0.001). Baroreflex sensitivity was associated with neither frailty nor number of falls.

Conclusions

Orthostatic blood pressure drop rate was associated with frailty and falls and may reflect the challenge to the baroreflex rather than drop magnitude.

Demographic and clinical features of pediatric patients with orthostatic intolerance and an abnormal head-up tilt table test; A retrospective descriptive study

BACKGROUND

Clinical presentation varies in children with Orthostatic Intolerance. This study aimed to evaluate the epidemiological and clinical characteristics of pediatric patients with orthostatic intolerance (OI) and positive head-up tilt test (HUTT).

METHODS

This study was a retrospective review of clinical data from outpatients over 18 months period.

RESULTS

We included 112 patients with abnormal HUTT results. Females were 78 (70%). Mean age of presentation was 15.6 years (sd: 3.3). Fifteen percent were overweight, and 14% were obese. A headache and syncope were the most frequent presenting symptoms (46% and 29% respectively). Review of systems identified more patients with headaches (84%), Syncope (61%), presyncope (87%) and abdominal pain (29%). Except for fatigue being more prevalent during a review of systems among patients with severe OI (69%) compared to those with moderate OI (46%, p = 0.02), there was no statistically significant difference in the clinical presentation between investigator-defined moderate and severe OI. Comorbidities identified in this cohort were Chiari malformations (9%), idiopathic intracranial hypertension (9%), electroencephalographic abnormalities (8%) and patent foramen ovale (43%).

CONCLUSIONS

Adolescents, mainly females had OI. Patients with OI and abnormal HUTT predominantly had a headache, syncope, and presyncope during the presentation. Eliciting review of systems and using tools such as clinical questionnaire identifies significant clinical presenting features and comorbidities.

Prefrontal hemodynamic changes measured using near-infrared spectroscopy during the Valsalva maneuver in patients with orthostatic intolerance

The Valsalva maneuver (VM) with beat-to-beat blood pressure and heart rate monitoring are used to evaluate orthostatic intolerance (OI). However, they lack the ability to detect cerebral hemodynamic changes, which may be a cause of OI symptoms. Therefore, we utilized near-infrared spectroscopy during VM. Patients with OI symptoms and normal healthy subjects were recruited. Patients were subgrouped according to VM results: patients with normal VM (NVM) and abnormal VM (AbVM). Oxyhemoglobin (HbO), deoxyhemoglobin, and total hemoglobin changes were measured at four different source-detector distances (SD) (15, 30, 36, and 45 mm), and latency, amplitude, duration, and integrated total signal were calculated. Those parameters were compared between a normal healthy control (HC) group and the two OI patient subgroups. We found that HbO increment latency at 30-mm SD in the HC, NVM, and AbVM groups was as follows: [Formula: see text], [Formula: see text], and [Formula: see text], respectively ([Formula: see text]). Among the four parameters we evaluated, latency of HbO increment was the best marker for differentiating OI.

Transcranial Doppler in autonomic testing: standards and clinical applications

When cerebral blood flow falls below a critical limit, syncope occurs and, if prolonged, ischemia leads to neuronal death. The cerebral circulation has its own complex finely tuned autoregulatory mechanisms to ensure blood supply to the brain can meet the high metabolic demands of the underlying neuronal tissue. This involves the interplay between myogenic and metabolic mechanisms, input from noradrenergic and cholinergic neurons, and the release of vasoactive substrates, including adenosine from astrocytes and nitric oxide from the endothelium. Transcranial Doppler (TCD) is a non-invasive technique that provides real-time measurements of cerebral blood flow velocity. TCD can be very useful in the work-up of a patient with recurrent syncope. Cerebral autoregulatory mechanisms help defend the brain against hypoperfusion when perfusion pressure falls on standing. Syncope occurs when hypotension is severe, and susceptibility increases with hyperventilation, hypocapnia, and cerebral vasoconstriction. Here we review clinical standards for the acquisition and analysis of TCD signals in the autonomic laboratory and the multiple methods available to assess cerebral autoregulation. We also describe the control of cerebral blood flow in autonomic disorders and functional syndromes.

Tilt table testing to diagnose pseudosyncope in the pediatric population

OBJECTIVE

Pseudosyncope can be difficult to distinguish from true syncope. Often, pediatric patients with pseudosyncope undergo multiple tests and referrals before the appropriate diagnosis is reached. The purpose is to describe the utility of the head-up tilt table test to elicit the diagnosis of pseudosyncope in the pediatric population.

DESIGN

Retrospective chart review from November 2012 to December 2015 of patients age ≤23 years referred for 30-minute, 80-degree tilt table test. Pretest probability for pseudosyncope was high if there was no response to traditional management, atypical episodes, occurrence during undesirable exercise, or prolonged episode duration. Inductive techniques were utilized to persuade patients of the likelihood of experiencing an episode during the procedure. Pseudosyncope was confirmed when a patient had normal vital signs during their event and had reflex responses to disruptive maneuvers.

RESULTS

Tilt table testing was performed on 89 patients [median age 16 years (5-23); 26% male] with the majority (60%) being negative for pseudosyncope, including 51 true negatives and 2 false-negatives. Of the 36 patients with syncope during tilt table testing, 28 were diagnosed with vasovagal syncope and 8 with pseudosyncope [median age 16 years (15-21); 38% male]. Pseudosyncope episodes were observed immediately in 2 patients. All patients with late-onset pseudosyncope required inductive techniques prior to the recorded episode.

CONCLUSIONS

Pseudosyncope can be identified during tilt table testing if inductive techniques are utilized in patients with a high index of suspicion. Disruptive maneuvers are excellent adjunctive methods to confirm the diagnosis. Tilt table testing is an effective means to identify pseudosyncope and allow appropriate diagnosis and treatment.

Dominant Transmission Observed in Adolescents and Families With Orthostatic Intolerance

BACKGROUND

Orthostatic intolerance is typically thought to be sporadic and attributed to cerebral autonomic dysfunction. We sought to identify families with inherited autonomic dysfunction manifest as symptomatic orthostatic intolerance to characterize mode of inheritance and clinical features.

METHODS

Sixteen families with two or more first- or second-degree relatives with autonomic dysfunction and orthostatic intolerance were enrolled. A clinical diagnosis of autonomic dysfunction defined by symptomatic orthostatic intolerance diagnosed by head-up tilt table testing was confirmed for each proband. Clinical features and evaluation were obtained from each proband using a standardized intake questionnaire, and family history information was obtained from probands and available relatives.

RESULTS

Comprehensive pedigree analysis of 16 families (39 individuals with orthostatic intolerance and 40 individuals suspected of having orthostatic intolerance) demonstrated dominant transmission of autonomic dysfunction with incomplete penetrance. Affected individuals were predominantly female (71.8%, 28/39; F:M, 2.5:1). Male-to-male transmission, although less common, was observed and demonstrated to transmit through unaffected males with an affected parent. Similar to sporadic orthostatic intolerance, probands report a range of symptoms across multiple organ systems, with headaches and neuromuscular features being most common.

CONCLUSIONS

Familial occurrence and vertical transmission of autonomic dysfunction in 16 families suggest a novel genetic syndrome with dominant transmission, incomplete penetrance, and skewing of the sex ratio. Elucidation of potential genetic contributions to orthostatic intolerance may inform therapeutic management and identification of individuals at risk. Adolescent evaluation should include identification and treatment of potential at-risk relatives.

Syncope: Case Studies

Syncope, or the sudden loss of consciousness, is a common presenting symptom for evaluation by neurologists. It is not a unique diagnosis but rather a common manifestation of disorders with diverse mechanisms. Loss of consciousness is typically preceded by a prodrome of symptoms and sometimes there is a clear trigger. This article discusses several cases that illustrate the various causes of syncope. Reflex syncope is the most common type and includes neurally mediated, vasovagal, situational, carotid sinus hypersensitivity, and atypical forms. Acute and chronic autonomic neuropathies and neurodegenerative disorders can also present with syncope.