Study: Combined EEG & Tilt-Table Testing Weeds Out Psychogenic Loss of Consciousness

People faint or experience syncope for all kinds of reasons, from the mundane — like standing too long in a stuffy room — to the much more serious, like heart disease or epilepsy.
Sometimes even non-physical (psychogenic) stressors can cause this kind of temporary loss of consciousness. Unfortunately, it’s not easy to tell the difference by observation alone.
For this reason, clinicians use objective measures such as EEG studies, blood pressure, pulse, and tilt-table testing to help make a differential diagnosis. According to a new protocol published in the Neurodiagnostic Journal, combining these usually independent tests may offer the best chance at quickly determining why a patient keeps fainting, especially when providers suspect it’s psychogenic.

More Common Than People Think?

Psychogenic pseudosyncope (PPS) is the appearance of a short-term loss of consciousness and motor functions (syncope) that is not an actual or true loss of consciousness. Internal stressors manifesting physically – something physicians call a conversion disorder – are believed to be the cause.
The authors of the Neurodiagnostic Journal article say that PPS “can be misdiagnosed as syncope or epileptic seizures, potentially leading to incorrect treatment and allowing episodes to continue.” They also hypothesize that PPS is more common than people think.
PPS is under-diagnosed because there is no objective measure to rule it in, plus it can so closely resemble other causes of syncope. It is usually a matter of ruling out other conditions such as epilepsy and vasovagal syncope, the most common cause of this kind of unresponsiveness.
PPS can share many of the same symptoms as vasovagal, including pre-syncopal changes in vision, shivering, sweating, shortness of breath, and falling over. A PPS diagnosis has long relied on careful history taking and mental health assessments. More recently, it also includes tilt-table and EEG testing to rule out other causes.

Making a Diagnosis

A tilt-table test is used to see if slow heart rate, low blood pressure, or ECG changes are causing fainting/syncope. It is most often done in a non-invasive cardiac monitoring environment equipped with this kind of a mechanized table.
The patient lies strapped to a tilt table, which is then raised from supine to near upright. A positive test is indicative of problems such as low blood sugar, prolonged bed rest, medication side effects, dehydration, or abnormal heart rhythms.
This test is negative when there is no reproduction of symptoms or changes in vital signs. It cannot rule out seizures or psychogenic pseudosyncope.
An EEG test, typically performed in an epilepsy center, is needed to confirm seizures as the cause of unresponsiveness. EEG tests do pick up signs of voltage attenuation that are typical of syncope, like the appearance of delta waves and changes in wave amplitude. However, these alone are not enough to definitively diagnose true syncope.

Tackling Deceptive Problems

Both EEG and tilt-table testing are traditionally done in separate locations, with separate technologists and physician specialists. The authors of the study at Albany Medical Center in Albany, New York, created a protocol that involved combining these tests as a collaboration between their cardiac and epilepsy centers. They performed this combined monitoring 50 times over the course of six years.
Patients with EEG leads were positioned supine on a tilt table and connected to blood pressure, pulse, and ECG monitors. The tilt table was angled to between 60 and 70 degrees and the patient was monitored for 20 minutes. If nothing happened, the test was repeated with a vasoactive drug.
More than 60 percent of tests were negative; there was no reproduction of symptoms and both ECG and EEG tests came back normal. This was not unexpected – most tilt-table tests are normal. Just 8 percent of tests were positive for EEG changes indicative of focal seizures, and 12 percent were positive for true syncope (confirmed by ECG and EEG changes).
The surprising result was that a full 14 percent of patients became unresponsive but had normal ECG and EEG readings. This indicated psychogenic pseudosyncope, they concluded.
In total, 26 percent of the studies led to a “diagnosis of syncope with EEG verification or helped to distinguish true syncope from psychogenic pseudosyncope,” the authors wrote.
Though this study was small, it is a good reminder of the value of combining existing tests in new ways when dealing with illusive conditions. Perhaps more importantly, it also shows us the power of inter-departmental cooperation in tackling these kinds of deceptive problems.
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