Approach Considerations
Laboratory studies are useful only in excluding metabolic or toxic causes of seizures (e.g., hyponatremia, hypoglycemia, drugs).
Prolactin and creatine kinase (CK) levels rise after generalized tonic-clonic seizures and not after other types of episodes. However, sensitivity is too low to be of any practical value (i.e., lack of elevation does not exclude epileptic seizures).
Although imaging findings are normal in psychogenic nonepileptic seizures (PNES), images should be obtained to exclude organic pathology.
Incidental abnormalities are occasionally seen on imaging. However, they should not confound the diagnosis if results of EEG video monitoring firmly establish PNES.
EEG and Ambulatory EEG
Because of its low sensitivity, routine EEG is not helpful in confirming a diagnosis of PNES. However, repeatedly normal EEG findings, especially in light of frequent attacks and resistance to medications, can be viewed as a red flag.
Ambulatory EEG is increasingly used, it is cost effective, and it can contribute to the diagnosis by recording the habitual episode and documenting the absence of EEG changes.
However, because of the difficulties in conveying the diagnosis (see Treatment), PNES should always be confirmed with EEG video monitoring.
EEG Video Monitoring
EEG video monitoring is the criterion standard for diagnosis and indicated in all patients who have frequent seizures despite taking medications. With an experienced epileptologist, combined electroclinical analysis of both the clinical semiology of the ictus and the ictal EEG findings allows for a definitive diagnosis in nearly all cases. If an episode is recorded, the diagnosis is usually easy, and PNES can usually be differentiated from epilepsy. The principle is to record an episode and demonstrate that no change in the EEG occurs during the clinical event and that the clinical episode is not consistent with seizures unaccompanied by EEG changes. Ictal EEG has limitations because of occasional false-negative results or uninterpretable results if movements generate excessive artifact.
Analysis of the ictal semiology (i.e., video) is at least as important as ictal EEG because it often shows behaviors that are obviously and unquestionably nonorganic and incompatible with epileptic seizures. Certain characteristics of the motor phenomena are strongly associated with PNES: gradual onset or termination; pseudosleep; and discontinuous (stop-and-go), irregular, or asynchronous (out-of-phase) activity (e.g., side-to-side head movement), pelvic thrusting, opisthotonic posturing, stuttering, and weeping. A useful sign is preserved awareness during bilateral motor activity; this is relatively specific for PNES because unresponsiveness is almost always present during bilateral motor activity.
In experienced hands, EEG video monitoring is a highly reliable tool, and in the vast majority of cases, the diagnosis of PNES is not difficult. A small percentage of difficult cases account for the less-than-perfect interrater reliability. [9]
Using video EEG of patients, Hubsch et al. conducted multiple correspondence analysis and hierarchical cluster analysis to construct a practical and useful semiologic classification of PNES, which identified 5 clusters of signs: dystonic attack with primitive gestural activity, pauci-kinetic attack with preserved responsiveness, pseudosyncope, hyperkinetic prolonged attack with hyperventilation and auras, and axial dystonic prolonged attack. [10]
For more information, see the Medscape Reference article EEG Video Monitoring.
Short-term Outpatient EEG Video Monitoring with Activation
When the clinical findings strongly suggest PNES, patients can undergo short-term outpatient EEG video monitoring with activation. This study can be cost-effective while retaining the same specificity as other tests and reasonably high sensitivity.
In one series, 10 of 15 patients had their habitual nonepileptic seizures with hyperventilation plus photic stimulation plus suggestion.
At the author's center, this test is routinely used, and the typical episode is observed in 70-80% of patients, obviating long-term EEG video monitoring. [11]
Inductions
Provocative techniques, activation procedures, or inductions, can be extremely useful for the diagnosis of PNES, particularly when the diagnosis is uncertain and no spontaneous episodes occur during monitoring.
Many epilepsy centers use a provocative technique to aid in the diagnosis of PNES. An intravenous injection of saline is traditionally and most commonly used, but other techniques may be preferable.
The principle behind provocative techniques is suggestibility, which is a feature of somatoform disorders in general. For example, in psychogenic movement disorders, for which the diagnosis rests solely on phenomenology (sometimes aided by EMG), the response to placebo or suggestion is considered a diagnostic criterion for a definite psychogenic mechanism.
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Psychogenic nonepileptic attacks. The event is provoked by an induction (or provocative) technique. Note the typical irregular nonclonic nontonic and asynchronous movements (including bicycling) with stop-and-go phenomenon.
