Prolactin and Diagnosis of Pseudoseizures

Gregory L. Krauss, MD

Disclosures

December 31, 2002

Question

If there is an elevation (twice the baseline) of prolactin following a "seizure," and if close monitoring with Holter/video, etc. has convinced the neurologists that it is not a true seizure, but the patient continues to experience convulsions, should you treat for a period with anticonvulsants to see if you can end the "seizures"?

Response from Gregory L. Krauss, MD

The diagnosis of pseudoseizures is based on a combination of clinical factors, not all of which need to be present in individual patients.[1,2,3] These typically include: a pattern of atypical clinical events, eg, stress-induced shaking with retained awareness; psychiatric comorbidity, particularly somatization or dissociative disorders; the absence of interictal spiking and ictal activity on electroencephalogram (EEG); and a failure to respond to antiepileptic drugs (AEDs). The most reliable test for identifying seizures and pseudoseizures is evaluation of actual clinical events with video-EEG monitoring. However, up to 30% of patients with pseudoseizures may also have epilepsy; thus, occasionally patients are accurately diagnosed with pseudoseizures by video-EEG monitoring and then experience seizures when their AEDs are discontinued.

An elevated prolactin level (usually 2 times baseline or 3 standard deviations above normal) is fairly predictive of a seizure or other major neurologic events, such as syncope.[4,5] Some patients with pseudoseizures may have modest elevations in prolactin levels.[6] A normal prolactin is less predictive of pseudoseizures, since it is frequently normal in partial seizures and may be mistimed following convulsions.

For a patient with markedly elevated prolactin following seizure-like events, it would be important to exclude syncope, to evaluate the quality of the video-EEG monitoring, and to exclude a mixed seizure/pseudoseizure disorder. Common diagnostic pitfalls are that some clinical events produce muscle artifact that interferes with the EEG recording of ictal activity. Some seizures, particularly those originating in the superior frontal lobe, may be associated with major motor activity and no ictal changes on scalp EEG. A normal interictal EEG does not exclude epilepsy. A normal EEG with a waking background during a period of unresponsiveness, however, is fairly convincing evidence that the patient is having a psychogenic event and requires treatment for an emotional disorder. If the prolactin level were significantly elevated following a seizure and you suspect that the patient's episodes may be seizures (eg, they are stereotyped brief events), you may wish to repeat the video-EEG monitoring.

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