Psychogenic non-epileptic seizures (PNES) are defined as
paroxysmal episodes which clinically resemble epileptic seizures but, unlike
the latter, do not show an epileptiform discharge on ictal vEEG
electrodes. An estimated 15% to 30% of
patients referred to epilepsy-monitoring units for drug-resistant epilepsy walk
away with a diagnosis of PNES. Seizures that do not produce an epileptiform
discharge on the ictal video electroencephalogram (vEEG) will likely garner the
‘rule in’ diagnosis of PNES, or Conversion Disorder in modern nomenclature. The
absence of an epileptiform discharge is considered proof that the seizure is
not epileptic and thus, it presumably has a psychological origin. For decades,
the scalp EEG has been hailed as the ‘gold standard’ for distinguishing PNES
from epilepsy and a great deal of empirical data has been amassed on the PNES
patient population. Though the PNES diagnostic entity is treated as a proven
fact, in truth, it rests on but one hypothesis that might explain a negative
scalp EEG. The purpose of this paper is to review the literature and assess
whether the hypothesis that underlies the PNES diagnosis is supported or
refuted by the empirical data. Since not all epileptic seizures produce a scalp
EEG correlate, an epileptic seizure is a recognised competing hypothesis for a
negative scalp finding. Studies that gather data from both scalp and
intracranial EEG recordings show that scalp-negative epileptic seizures are not
uncommon, but in modern epilepsy-monitoring units, they are at high risk of
being mislabeled PNES. Both epilepsy and PNES patient populations show
pervasive brain disease, including structural alterations and both are
considered network disorders. Both seizure types have remitted or failed to
remit on AEDs, and both conditions demonstrate instances of prolonged seizure
activity, designated status epilepticus and pseudo-status epilepticus in
patients with epilepsy and PNES, respectively. To assess for such diagnostic
error, it must turn to the empirical evidence, which shows that the clinical
profiles of PNES and epilepsy patient populations are identical. The
similarities are striking, and the only data the PNES hypothesis can explain is
a negative scalp EEG. Conversely, the competing epileptic hypothesis seamlessly
accounts for the bulk of the findings on patients with seizures labelled PNES.
The diagnostic terrain is further muddied by the ongoing conflation of
conscious feigning with conversion disorder, which represents a long-standing
conceptual error. The data establishes that the PNES patient population
consists primarily of patients with epilepsy, along with a smattering of
factitious and likely psychotic disorders, thereby exposing the PNES diagnostic
entity as a hypothetical construct that does not exist. Diagnostic theory and
practice in epilepsy-monitoring units must be revisited. Intracranial monitoring, seizure-alert
trained dogs, high-density scalp EEG, scalp-negative seizure detectors, and
scalp EEG zero-crossing patterns could all provide further proof that the PNES
population consists primarily of patients with epilepsy.
Author (s) Details
Catherine A Carlson
Psychological Services Division, Minnesota Judicial Branch, USA.
Please see the book here:- https://doi.org/10.9734/bpi/msraa/v5/5144
