Head up tilt testing has a place in distinguishing certain conditions from epilepsyBMJ 1997; 314 doi: https://doi.org/10.1136/bmj.314.7086.1048 (Published 05 April 1997) Cite this as: BMJ 1997;314:1048
- Amir Zaidi, Research fellowa,
- Lawrence Cotter, Consultant cardiologista,
- Adam Fitzpatrick, Consultant cardiologista
Editor—In their editorial J W A S Sander and M F O'Donoghue place great reliance on clinical characteristics to differentiate between epilepsy, convulsive syncope, and non-epileptic attacks.1 This seems unwise because the diagnostic success rate even of specialists may be as low as 50% on the basis of history and examination alone.2 Furthermore, direct observation of seizures by trained staff in a specialised inpatient unit resulted in only 80% diagnostic accuracy.2
One important omission in the editorial was the failure to mention head up tilt testing, which has assumed an important role in diagnosing syncope in recent years.3 Even when used in reported cases of epilepsy head up tilt testing has been shown to be valuable in detecting convulsive syncope and seizures of psychogenic origin.3 We recently reported four cases of primary cardiovascular disease misdiagnosed as epilepsy.4 One of these patients was a middle aged woman with classic tonic-clonic seizures who had 38 seconds of asystole on head up tilt testing, followed by a short lived generalised seizure. Her seizures resolved with permanent pacing. We subsequently identified two additional patients with suspected epilepsy who had profound vasodepressor reactions to head up tilt testing associated with reported seizures. Another patient with so called intractable epilepsy developed violent, semipurposeful shaking of the limbs within two minutes of head up tilt testing but without associated haemodynamic or electroencephalographic changes and was concluded to have non-epileptic attack disorder.
In the first three patients the seizure activity was clearly genuine, but the cause was mistaken. The cause was global cerebral hypoxia, which in turn was the result of global cerebral hypoperfusion due to sudden profound hypotension. What must be recognised is that cerebral hypoperfusion may cause what look like epileptiform movements. To both lay and skilled observers this phenomenon may be indistinguishable from epilepsy caused by a generalised discharge of cerebral neurones while cerebral perfusion is preserved. If seizure activity due to hypotension is mistaken for epilepsy many young patients who are prone to reflex syncope may be labelled epileptic. This has profound effects on prospects for life, work, marriage, childbearing, and driving. Indeed, data on patients with a first seizure show that most do not have epilepsy confirmed by electroencephalographic abnormalities.5 Many of these patients might have reflex syncope with seizure activity that is misinterpreted as a primary cerebral disturbance. Although reflex syncope is not always benign, its diagnosis has far less severe connotations than a diagnosis of epilepsy.
It is important that reflex syncope is considered in patients presenting with seizure activity. Although far from perfect in sensitivity and specificity, head up tilt testing provides a tool for objective assessment of such patients and avoids relying solely on the well documented limitations of a clinical evaluation.