Reflex asystolic syncope

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Reflex asystolic syncope
Other namesReflex anoxic seizure

Reflex asystolic syncope (RAS) is a form of syncope encountered mainly, but not exclusively, in young children. Reflex anoxic seizures are not epileptic seizures or epilepsy. [1] This is usually a consequence of a reduction in cerebral perfusion by oxygenated blood. It can be a result of either a sudden reduction in the blood flow to the brain, a drop in the oxygen content of the blood supplying the brain, or a combination of the two. Syncope can have different meanings ranging from transient loss of consciousness, usually accompanied by a decrease or loss in postural tone (the principal manifestations of "simple faints"), to tonic and myoclonic events and nonepileptic spasms.

Contents

Signs and symptoms

A minor bump to the head is the most commonly reported precipitant. Usually the toddler trips and falls; the child's caregiver may hear the bump. Most commonly, the child does not cry, although some parents give descriptions of the child “trying to cry” (Stephenson 1978), or there may be a gasp or a sob. Syncope rapidly ensues. Indeed the short latency between the stimulus and the attack has been emphasized as an important distinction from the more familiar (at least in older children and adults) vasovagal syncope. The child loses awareness and postural tone, falling to the ground. There may be down-beat nystagmus. The child is likely to be pale, sometimes described as “deathly white,” which is entirely appropriate given that they are likely to be asystolic; however, it is important to note that not all children go pale (or at least are perceived as going pale by their caregivers). Doctors have recorded descriptions from parents of “blue or purple lips,” “yellow patches through the blue,” and of no noticeable color change. In some attacks, the child rapidly returns to normal following the limp or pallid phase. However, more usually there is a convulsive phase. This is usually manifested with tonic stiffening, often amounting to opisthotonus, and often includes clenching of the jaw and hands. Video recordings of other forms of anoxic seizures (vasovagal syncopes) suggest that there may be marked asymmetry. Parents may report the eyes to have rolled or to be “popping out of the head.” A few clonic jerks of the limbs or spasms are often noted. Urinary incontinence is not uncommon. Any initial limpness may be so short that the whole attack is dominated by the convulsive components.

Recovery

Recovery is often rapid, but usually the child is sleepy after the attack, and there may be persisting pallor. Doctors reported that the length of the postictal stupor reflected the duration of the asystole up to a maximum of 3 minutes of stupor. Some cases recorded took longer to recover.

Cause

Reflex anoxic seizures are a particular type of anoxic seizure, most commonly seen in young children in whom an anoxic seizure or syncope is provoked or precipitated by a noxious stimulus (hence “reflex”). Various precipitants have been identified, but the most common is an unexpected bump to the head. Breath-holding attacks have been recognized for centuries. However, it is only relatively recently that their pathophysiology has begun to be understood, and in consequence, their separation from reflex anoxic seizures has been recognized. Indeed, the distinction between the two may not be complete.

Although minor bumps to the head are reported as the most common precipitants to reflex anoxic seizures, many other stimuli may also be involved. Doctors emphasized the importance of minor injuries and sudden fright. They noted that occipital blows to the head appeared to be particularly provocative. Pain, especially from emotion (surprise, fear, annoyance, frustration, and excitement), crying, and fever were provocative factors. Fever was reported as a provocative factor in 14% of cases. Some cases of fever-induced reflex anoxic seizures are likely to be misdiagnosed as febrile (epileptic) seizures, as has been emphasized by a number of authors. Many, if not most, cases of venipuncture fits are reflex anoxic seizures. When one considers the vast range of situations in which a child (or adult) can be surprised, frightened, upset, or merely excited, it is easy to understand how reflex anoxic seizures can occur in special settings, such as bathing and water immersion; in the anesthetic room; when witnessing “blood and gore”; at the dentist office, school, place of worship, or the hairdresser's; and whilst watching television.

The precipitants and the manifestations of reflex anoxic seizures may change with age. Hence, in unsteady toddlers, minor bumps to the head are likely to predominate, whilst in the older child, adolescent and adult factors such as the sight of blood or venipuncture are likely to be more relevant. The adult physician is likely to classify such events as vasovagal syncopes rather than as reflex anoxic seizures and indeed progression through reflex anoxic seizures to vasovagal syncope is recognized. In this regard, note that beyond the toddler stage, children with reflex anoxic seizures may report out-of-body experiences with a dream-like quality. [2]

Types

Numerous types have been described. The best known, if not necessarily the best understood, is the “simple faint” or vasovagal syncope. At least in infants and children, breath-holding attacks are also widely recognized as reflex anoxic seizures. Other types include cardiac syncope (including long QT disorders, other cardiac arrhythmias, and structural cardiac disease), syncope due to standing (see orthostatic hypotension), hyperventilation, compulsive Valsalva maneuvers, gastroesophageal reflux disease, and imposed upper airway obstruction(suffocation). In addition, anoxic seizures are a feature of both hyperekplexia and familial rectal pain syndrome. Finally, there are likely to be other types of anoxic seizure or syncope not yet characterized.

Epidemiology

There is considerable variation in the frequency of reflex anoxic seizures. Some subjects undoubtedly only ever have a single attack whilst other well-documented cases have multiple daily attacks. The attacks have been reported to generally reach a peak in frequency towards the end of the first or beginning of the second year of life.

Reflex anoxic seizures occur in otherwise normal children, although there is no reason to suppose that children with disorders such as cerebral palsy and mental retardation are protected from them. They usually start in infancy or early childhood. Presumably because the precipitants to the attacks generally require a degree of mobility, descriptions of reflex anoxic seizures before the age of 6 months are rare. Also, there are many descriptions of attacks starting in later childhood and in adult life, although in such cases, the precipitants tend to be different, for example, involving bloodletting (Roddy et al. 1983) or dental extractions.

Related Research Articles

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An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with loss of consciousness, to shaking movements involving only part of the body with variable levels of consciousness, to a subtle momentary loss of awareness. Most of the time these episodes last less than two minutes and it takes some time to return to normal. Loss of bladder control may occur.

Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when standing up or sitting down. Primary orthostatic hypertension is also often referred to as neurogenic orthostatic hypotension. The drop in blood pressure may be sudden, within 3 minutes or gradual. It is defined as a fall in systolic blood pressure of at least 20 mmHg or diastolic blood pressure of at least 10 mmHg when a person assumes a standing position. It occurs predominantly by delayed constriction of the lower body blood vessels, which is normally required to maintain adequate blood pressure when changing the position to standing. As a result, blood pools in the blood vessels of the legs for a longer period, and less is returned to the heart, thereby leading to a reduced cardiac output and inadequate blood flow to the brain.

Hypotension Abnormally low blood pressure

Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure and the diastolic blood pressure, which are the maximum and minimum blood pressures, respectively. A systolic blood pressure of less than 90 millimeters of mercury or diastolic of less than 60 mm Hg is generally considered to be hypotension. Different numbers apply to children. However, in practice, blood pressure is considered too low only if noticeable symptoms are present.

Reflex syncope Brief loss of consciousness due to a neurologically induced drop in blood pressure.

Reflex syncope is a brief loss of consciousness due to a neurologically induced drop in blood pressure and/or a decrease in heart rate. Before an affected person passes out, there may be sweating, a decreased ability to see, or ringing in the ears. Occasionally, the person may twitch while unconscious. Complications of reflex syncope include injury due to a fall.

Carotid sinus

In human anatomy, the carotid sinus is a dilated area at the base of the internal carotid artery just superior to the bifurcation of the internal carotid and external carotid at the level of the superior border of thyroid cartilage. The carotid sinus extends from the bifurcation to the "true" internal carotid artery. The carotid sinus is sensitive to pressure changes in the arterial blood at this level. It is the major baroreception site in humans and most mammals.

Status epilepticus Medical condition

Status epilepticus (SE) is a single seizure lasting more than 5 minutes or 2 or more seizures within a 5-minute period without the person returning to normal between them. Previous definitions used a 30-minute time limit. The seizures can be of the tonic–clonic type, with a regular pattern of contraction and extension of the arms and legs, or of types that do not involve contractions, such as absence seizures or complex partial seizures. Status epilepticus is a life-threatening medical emergency, particularly if treatment is delayed.

Fear of needles, known in medical literature as needle phobia, is the extreme fear of medical procedures involving injections or hypodermic needles. This can lead to avoidance of medical care, including vaccine hesitancy.

Light dizziness is a common and typically unpleasant sensation of dizziness or a feeling that one may faint. The sensation of lightheadedness can be short-lived, prolonged, or, rarely, recurring. In addition to dizziness, the individual may feel as though their head is weightless. The individual may also feel as though the room is "spinning" or moving (vertigo). Most causes of lightheadedness are not serious and either cure themselves quickly, or are easily treated.

Non-epileptic seizures (NES), also known as non-epileptic events, are paroxysmal events that appear similar to an epileptic seizure but do not involve abnormal, rhythmic discharges of neurons in the brain. Symptoms may include shaking, loss of consciousness, and loss of bladder control.

Breath-holding spells (BHS) are the occurrence of episodic apnea in children, possibly associated with loss of consciousness, and changes in postural tone.

Tilt table test Medical procedure often used to diagnose dysautonomia or syncope

A tilt table test (TTT), occasionally called upright tilt testing (UTT), is a medical procedure often used to diagnose dysautonomia or syncope. Patients with symptoms of dizziness or lightheadedness, with or without a loss of consciousness (fainting), suspected to be associated with a drop in blood pressure or positional tachycardia are good candidates for this test.

Reflex seizures are epileptic seizures that are consistently induced by a specific stimulus or trigger making them distinct from other epileptic seizures, which are usually unprovoked. Reflex seizures are otherwise similar to unprovoked seizures and may be focal, generalized, myoclonic, or absence seizures. Epilepsy syndromes characterized by repeated reflex seizures are known as reflex epilepsies. Photosensitive seizures are often myoclonic, absence, or focal seizures in the occipital lobe, while musicogenic seizures are associated with focal seizures in the temporal lobe.

Stokes–Adams syndrome or Adams–Stokes syndrome is a periodic fainting spell in which there is intermittent complete heart block or other high-grade arrhythmia that results in loss of spontaneous circulation and inadequate blood flow to the brain. Subsequently named after two Irish physicians, Robert Adams (1791–1875) and William Stokes (1804–1877), the first description of the syndrome is believed to have been published in 1717 by the Carniolan physician of Slovene descent Marko Gerbec. It is characterized by an abrupt decrease in cardiac output and loss of consciousness due to a transient arrhythmia; for example, bradycardia due to complete heart block.

Paroxysmal extreme pain disorder originally named familial rectal pain syndrome, is a rare disorder whose most notable features are pain in the mandibular, ocular and rectal areas as well as flushing. PEPD often first manifests at the beginning of life, perhaps even in utero, with symptoms persisting throughout life. PEPD symptoms are reminiscent of primary erythromelalgia, as both result in flushing and episodic pain, though pain is typically present in the extremities for primary erythromelalgia. Both of these disorders have recently been shown to be allelic, both caused by mutations in the voltage-gated sodium channel NaV1.7 encoded by the gene SCN9A. A different mutation in "SCN9A" causes congenital insensitivity to pain.

The Bezold–Jarisch reflex involves a variety of cardiovascular and neurological processes which cause hypopnea, hypotension and bradycardia in response to noxious stimuli detected in the cardiac ventricles. The reflex is named after Albert von Bezold and Adolf Jarisch Junior. The significance of the discovery is that it was the first recognition of a chemical (non-mechanical) reflex.

Panayiotopoulos syndrome is a common idiopathic childhood-related seizure disorder that occurs exclusively in otherwise normal children and manifests mainly with autonomic epileptic seizures and autonomic status epilepticus. An expert consensus has defined Panayiotopoulos syndrome as "a benign age-related focal seizure disorder occurring in early and mid-childhood. It is characterized by seizures, often prolonged, with predominantly autonomic symptoms, and by an EEG [electroencephalogram] that shows shifting and/or multiple foci, often with occipital predominance."

Syncope (medicine) Transient loss of consciousness and postural tone

Syncope, commonly known as fainting, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from low blood pressure. There are sometimes symptoms before the loss of consciousness such as lightheadedness, sweating, pale skin, blurred vision, nausea, vomiting, or feeling warm. Syncope may also be associated with a short episode of muscle twitching. Psychiatric causes can also be determined when a patient experiences fear, anxiety, or panic; particularly before a stressful event usually medical in nature. When consciousness and muscle strength are not completely lost, it is called presyncope. It is recommended that presyncope be treated the same as syncope.

Blood-injection-injury (BII) type phobia is a type of specific phobia characterized by the display of excessive, irrational fear in response to the sight of blood, injury, or injection, or in anticipation of an injection, injury, or exposure to blood. Blood-like stimuli may also cause a reaction. This is a common phobia with an estimated 3-4% prevalence in the general population, though it has been found to occur more often in younger and less educated groups. Prevalence of fear of needles which does not meet the BII phobia criteria is higher. A proper name for BII has yet to be created.

People with epilepsy may be classified into different syndromes based on specific clinical features. These features include the age at which seizures begin, the seizure types, and EEG findings, among others. Identifying an epilepsy syndrome is useful as it helps determine the underlying causes as well as deciding what anti-seizure medication should be tried. Epilepsy syndromes are more commonly diagnosed in infants and children. Some examples of epilepsy syndromes include benign rolandic epilepsy, childhood absence epilepsy and juvenile myoclonic epilepsy. Severe syndromes with diffuse brain dysfunction caused, at least partly, by some aspect of epilepsy, are also referred to as epileptic encephalopathies. These are associated with frequent seizures that are resistant to treatment and severe cognitive dysfunction, for instance Lennox-Gastaut syndrome and West syndrome.

A frequent type of syncope, termed vasovagal syncope is originated by intense cardioinhibition, mediated by a sudden vagal reflex, that causes transitory cardiac arrest by asystole and/or transient total atrioventricular block. It is known as “Vaso-vagal Syncope”, “Neurocardiogenic Syncope” or “Neurally-mediated Reflex Syncope”. Although many different therapies have been tried in this condition, severe and refractory cases have been treated with pacemaker implantation despite great controversies about its benefit.

References

  1. ↑ Prasher, Vee P.; Kerr, Mike P., eds. (2008). Epilepsy and intellectual disabilities. New York: Springer. p. 63. ISBN   9781848002593.
  2. ↑ "Authoritative Neurology Information".
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