Determining the cause of transient loss of consciousness

October 8, 2020

A study examines whether examining presymptoms can help clinicians find the cause of transient loss of consciousness.

To find out the cause of a transient loss of consciousness (TLOC), your best bet may be to evaluate the youngster’s presymptoms and then administer appropriate tests, according to a retrospective study conducted in Korea. In this study of 160 children and adolescents, TLOC most often resulted from vasovagal syncope and epileptic seizures.

Investigators analyzed the medical records of participants who visited the hospital for “syncope and collapse,” noting age, sex, pre-symptoms (such as dizziness, headache, nausea, and blurred vision), accompanying signs (such as the presence of an aura, eye deviation, convulsions, or cyanosis), and trigger factors (such as standing up, exercise, emotional stress, urination, and defecation). They also took note of cardiographic and neurologic evaluations that were performed, including electrocardiograms, computed tomography scanning, magnetic resonance imaging, electroencephalograms, echocardiograms, and head-up tilt tests (HUTTs). Participants then were divided into 3 groups according to their final diagnoses: vasovagal syncope (63.8% of participants), epileptic seizures (10.6%), and “others” (25.6%). Mean age of onset did not differ significantly among the vasovagal syncope, epileptic seizure, or others groups: 14, 12.7, and 13.5 years, respectively.

A comparative analysis showed that presymptoms and accompanying signs often pointed the way to a diagnosis. Specifically, patients with a final diagnosis of vasovagal syncope were more likely than others to have pre-symptoms of dizziness or light-headedness and blurred vision, whereas patients diagnosed with epileptic seizures were more likely to have convulsions as an accompanying sign. Additionally, standing up was the most significant trigger factor for TLOC among those diagnosed with vasovagal syncope.

As for testing, the vasovagal syncope group had the greatest proportion of positive HUTT results, with 95% of patients with positive results diagnosed with vasovagal syncope. Head-up tilt tests showed high sensitivity (95.1%), positive predictive value (95.1%), and accuracy (91.8%), far better results than other group tests performed. Electroencephalograms, on the other hand, proved to be the test of choice for patients with epileptic seizures; they demonstrated a sensitivity, specificity, and accuracy of 80.0%, 70.6%, and 80.0%, respectively (Choi YJ, et al. Pediatrics & Neonatology. 2020; Epub ahead of print.).

Thoughts from Dr. Farber

It is not clear that investigators in this study ever followed my preferred approach, which is to do no testing if the history suggests vasovagal syncope, especially for a first faint. The teenager who faints on a hot day (not during exercise or the like) and has prodromal symptoms does not require a work-up to my mind.

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