Cerebral syncope in children

Common syndromes of orthostatic intolerance

The autonomic nervous system, adequate blood volume, and intact skeletal and respiratory muscle pumps are essential components for rapid cardiovascular adjustments to upright posture (orthostasis). Patients lacking sufficient blood volume or having defective sympathetic adrenergic vasoconstriction develop orthostatic hypotension (OH), prohibiting effective upright activities. OH is one form of orthostatic intolerance (OI) defined by signs, such as hypotension, and symptoms, such as lightheadedness, that occur when upright and are relieved by recumbence. Mild OI is commonly experienced during intercurrent illnesses and when standing up rapidly. The latter is denoted "initial OH" and represents a normal cardiovascular adjustment to the blood volume shifts during standing. Some people experience episodic acute OI, such as postural vasovagal syncope (fainting), or chronic OI, such as postural tachycardia syndrome, which can significantly reduce quality of life. The lifetime incidence of ≥1 fainting episodes is ∼40%. For the most part, these episodes are benign and self-limited, although frequent syncope episodes can be debilitating, and injury may occur from sudden falls. In this article, mechanisms for OI having components of adrenergic hypofunction, adrenergic hyperfunction, hyperpnea, and regional blood volume redistribution are discussed. Therapeutic strategies to cope with OI are proposed.

Cerebral Syncope: Insights from Valsalva Maneuver

BACKGROUND AND PURPOSE

Cerebral syncope refers to a loss of consciousness associated with cerebral vasoconstriction in the absence of systemic hypotension. The diagnosis of cerebral syncope could be established by the head-up tilt test (HUT) and transcranial Doppler ultrasonography. Valsalva maneuver (VM) permitted assessment of cerebral autoregulatory function by provoking blood pressure (BP) changes. To develop a path-physiological approach for vasomotor reactivity of cerebral syncope, the authors combined these maneuvers (HUT/transcranial Doppler/VM).

METHODS

Using transcranial Doppler ultrasonography, we simultaneously recorded systemic arterial BP in the radial artery and flow velocities in both middle cerebral arteries (MCAFV) in 10 cerebral syncope patients (4 males and 6 females, 35.24 +/- 4.5 years old) during the Valsalva maneuver.

RESULTS

The characteristic changes in BP (phases I-IV) were seen in all subjects, accompanying distinct changes in cerebral blood flow velocity. The BP/heart rate responding to VM was within normal limit in all subjects. There was no orthostatic hypotension. Instead, BP increased during the tilting test in 2 subjects (20.00%). The MCAFV dropped 25.4 +/- 2.3% from baseline. Abnormal flattening of MCAFV during late phase II (IIb), the paradoxical drop of flow velocity despite restoration of BP, was noted in 9 subjects (90.00%).

CONCLUSION

During VM there are complex changes in relevant cardiovascular and cerebrovascular variables within a short time span. The paradoxical drop of MCAFV during phase IIb was the result of complex parameters. Among them, a failure in cerebrovascular resistance reduction and even paradoxical vasoconstriction might further compromise cerebral perfusion pressure and lead to syncope.

Síncope en el adolescente. Orientación diagnóstica y terapéutica

Syncopal episodes are frequent in adolescence. Syncope is usually a benign, self-limiting condition but it may be a warning sign of serious disease that must be diagnosed and appropriately treated. The present article provides a review of the basic principles of the differential diagnosis of syncope in the adolescent patient and treatment recommendations.

Near-infrared spectroscopy in evaluation of cerebral oxygenation during vasovagal syncope

Near-infrared spectroscopy (NIRS) offers a non-invasive, real-time monitoring of cerebral oxygenation. This method is based on the oxygenation and the light wavelength dependent absorption of near-infrared light by tissue chromophores, e.g. oxyhaemoglobin and deoxyhaemoglobin. The objective of the present study was the application of NIRS for evaluation of the brain function during vasovagal syncope (VVS). The VVS is a clinical syndrome affecting ca 3.5% of the population and for which the widely used diagnostic examination in this disease entity is the head-up tilt table test (HUT). In this study 69 patients with a history of VVS were examined using HUT. In 42 patients VVS was provoked. Results of the examination have shown that the changes in cerebral oxygenation measured by the NIRS technique are distinctly visible before the syncope. A gradual decrease of oxyhaemoglobin followed by its sudden drop was observed in all the VVS patients. Changes in the oxyhaemoglobin concentration measured by NIRS were observed on average 3.3 min before the syncope. They preceded the presyncope symptoms about 1.3 min (p < 0.005), the blood pressure and heart rate drop 2.2 min (p < 0.0001) and the arterial blood saturation 2.6 min (p < 0.00001).

Autonomic syncope in pediatrics: a practice-oriented approach to classification, pathophysiology, diagnosis, and management

This paper presents a practice-oriented approach to the problem of syncope in pediatrics. Autonomic syncope is the major etiologic category in pediatrics and consists of 2 types: reflex and dysautonomic. The latter type is rare in pediatrics. Reflex syncope has 4 subtypes: neurocardiogenic, central, situational, and cerebral. Neurocardiogenic syncope, the most common subtype, is easily diagnosed by taking a careful, detailed history; identifying diagnostic red flags; performing a complete physical examination; and ordering a minimum of laboratory tests. Patient and parent education is essential, and usually, without medication, outcomes are good.

Dysautonomia and neurocardiogenic syncope

Syncope in childhood is a common problem. In most children, syncope is benign, secondary to a disturbance in autonomic control of heart rate and blood pressure. It is increasingly evident that neurally mediated syncope is a heterogeneous group of conditions, necessitating a reclassification of autonomic disorders. New entities, such as postural orthostatic tachycardia and cerebral vasoconstrictive syncope, are recognized. The key to the diagnosis of syncope is a careful history. Tilt testing can be useful when the history is unclear. Unfortunately tilt test protocols vary, affecting specificity and sensitivity. The mainstay of therapy is reassurance. If symptoms are troublesome, Fludrocortisone and B-blockers remain the favored drugs. The efficacy of Midodrine and Serotonin Uptake Inhibitors is currently under review. Cardiac pacing is effective for those patients with severe episodes and demonstrated asystole. It is not known whether pacing would be effective for the majority who have neurally mediated syncope without significant bradycardia.