Vasovagal syncope is the most familiar and predominant form of neurally mediated syncope. If classical reflex anoxic seizures (with reflex asystolic syncope) represent a fairly pure vagal attack, vasovagal syncope involves a vasodepressor component with variable vagal accompaniment. Episodes may begin in infancy, sometimes with reflex anoxic seizures, and thereafter are seen at all ages, becoming most dramatic perhaps in old age (21).
Tables in medical textbooks or works of epileptol-ogy tend to perpetuate gross errors with respect to the distinction between vasovagal syncope and epileptic seizures with comparable signs. This may be in part because many authors equate syncope with some sort of limp, pallid swooning in the Victorian manner. Here, for example, are the features previously said to distinguish between syncope and seizures:
• Posture: upright
• Pallor and sweating: invariable
• Convulsive jerks: rare
• Incontinence: rare
• Unconsciousness: seconds
• Postictal confusion: rare
• Frequency: infrequent
• Precipitating factors: crowded places, lack of food, and unpleasant circumstances.
In reality the situation is different. Vasovagal syncope may occur supine, particularly in the case of venepunc-ture fits; though some (13) would call these reflex anoxic seizures insofar as the mechanism is strongly car-dioinhibitory. Pallor and sweating are certainly not invariable, nor need onset be gradual. There is no difference between the liability to injury in convulsive syncope as opposed to a comparable convulsive epileptic seizure. Convulsive jerks are certainly not rare but occur in perhaps 50% of vasovagal syncopes (22) and more often in experimental syncope (23). Urinary incontinence is common (24), occurring in 10% of cases in one experimental study (1). Unconsciousness may be much more than seconds and recovery, although it may be rapid in mild syncope, is not necessarily complete early on (3). It is true that postictal confusion proper is rare, but it can occur (3). The frequency of vasovagal syncope may be very great, up to more than once a day. Stimuli may be very subtle, but it is true that some sort of stimulus should be detected for at least some attacks in any individual.
The setting and stimulus are indeed the most important factors in allowing the presumptive diagnosis of vasovagal syncope, together with elicitation of the warning symptoms or aura, which are commonly present. A seizure that occurs after a bath while the child is having her hair blow-dried, or brushed, is— without need for further investigation—a vasovagal nonepileptic convulsive syncope. Premonitory symptoms are usually present in older children, even if the duration is only a second or two, but sometimes these are forgotten and only recalled when syncope is reproduced, as in the head-up tilt test. All physicians are aware of the usual symptoms of cerebral ischemia, such as dizziness and greying out of vision and tinnitus, but an important additional symptom is abdominal pain. It may be difficult to tell whether abdominal pain is a symptom or trigger of a vasovagal syncope or an intestinal symptom of a strong vagal discharge. The latter is quite common (1), and sometimes leads to confusion with the so-called epigastic aura, which may precede the complex partial component of the temporal lobe epileptic seizure. Almost all children with vasovagal syncope have a first-degree relative, commonly a parent, affected (25). It is unfortunately common [histories are included in (1)] to find that the parent who now seems convincingly to have vasovagal convulsive syncope has become irredeemably "epileptic" and too habituated (or too frightened of losing a precious driving license) to discontinue years of useless (and perhaps embryopathic) antiepileptic medication.
Such considerations have led to the use of head-up tilt testing, not only as a diagnostic aid but as a diagnostic reinforcer. If, for example, a child patient, a family doctor, and a pediatrician have all been convinced that the child has had "grand mal epilepsy" since the age of 3, then some dramatic theater may be necessary at the age of 12 to 14 years to make the switch from epilepsy to the correct diagnosis of vasovagal syncope. There are no good data on this point, but there is an impression that if the diagnosis is not properly instilled by this age, it may be too late to prevent a life of being "epileptic".
A case history illustrates the transition from reflex anoxic seizures in infancy through short latency pain-induced vasovagal syncope to blood-injury phobia (26,27) in adolescence: the history was given by the mother when her affected daughter was aged 13 years. The previous diagnoses had included epilepsy, hypo-glycemia, and hysterical behavior.
Case study #2. The first episode occurred at the age of 10 months, after a very slight bump to the infant's head. The appearance of the attacks has been similar from then to now, except that severity has varied and tended to increase with the passage of time. Typically there is a latency of 10 to 20 seconds during which she may say "oh mum I've hurt myself." By this time the blood has drained from her face, she goes limp, and falls as if dead, then goes totally rigid, making a noise like a cackle or gurgle, with her hands and feet turned in and her back sometimes forming the shape of an arc. Sometimes her arms and legs jerk, but not violently, as though pedaling her bicycle, but on occasion thrashing wildly like a full seizure (as her mother describes it). Again, she looks like death and then wakes up as if coming out of a very deep sleep. She is then very disorientated, does not know what has happened or where she is, but within a couple of minutes she has come to herself and may then want to lie down again and have a proper sleep. Since about the age of 7 or 8 years she has described an aura. She hears a noise like a high-pitched screaming and sometimes hears a voice but cannot describe the voice precisely. Sometimes she sees red, a color she does not like. More recently she has had strange hallucinations during the warning period, such as seeing a train rushing towards her. The stimuli have modified over the years after the first head bump. All episodes in earlier years followed small pains like her finger being bent back. Then she developed the same reaction to seeing a minor injury such as a scab that had come off a wound, and then inevitable syncope at the sight of blood. Most recently merely the thought of self-injury was sufficient.
On the evening before the intended consultation she was told (wrongly) that her eyeballs would be pressed down (ocular compression) and within 2 minutes she was stiff and snorting. Although the mother's sister had had some type of genuine epilepsy, a family history of syncope of any kind was denied. Actually, the mother later admitted to several faints during adolescence and pregnancy, but did not mention them because she did not have a "fit." The results of a recent study suggest that adults with blood or injury phobia have a "constitutional autonomic dysregulation" predisposing them to neurally mediated syncope even in the absence of any blood or injury stimulus, and that repeated syncopes resulting from such stimuli secondarily lead to the blood or injury phobia (28).
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