Serum prolactin concentrations are elevated after syncope

Abstract

S ince the initial paper by Trimble in 1978 1 highlighting postictal levels of serum prolactin as a way to separate epileptic from nonepileptic seizures, PubMed has logged approximately 300 articles retrievable by the search terms "epilepsy" and "prolactin." Despite this considerable body of work, the role of serum prolactin in diagnosis of seizures remains uncertain. In this issue of Neurology ® Clinical Practice, Abubakr and Wambacq 2 evaluated serum prolactin levels 20 minutes after a behavioral seizure-like event in 200 patients undergoing video-EEG recordings in an epilepsy monitoring unit. Using the video-EEG as the "gold standard," they found prolactin to be elevated in all 22 patients with tonic-clonic seizures, 27 of 32 patients with complex partial seizures, and 42 of 146 patients with psychogenic seizures. For tonic-clonic seizures sensitivity was 100% and for complex partial seizures sensitivity was 84.4%. Overall, elevated prolactin occurred in 84.4% of patients with epileptic events and 28.8% of patients with nonepileptic events. Sensitivity and specificity in this study were comparable to the pooled sensitivity (52.6%) and specificity (92.8%) for all epileptic seizures in a previously published American Academy of Neurology Therapeutics and Technology Assessment Subcommittee review of 10 studies. 3 Because the present study includes a large number of patients evaluated at a single center, it provides useful new information on the utility of serum prolactin as a marker for seizures. Certain study limitations need to be considered. As the authors indicate, the study was retrospective and was performed in a selected population of patients referred to an epilepsy monitoring unit. Obtaining prolactin assay 20 minutes after a seizure in the outpatient setting is difficult, although possible by a finger-stick method. 4 Some conditions that can elevate serum prolactin, such as syncope, 5 are not well represented in video-EEG monitoring populations. The criterion used in this study for identifying elevated serum prolactin is debatable, because different studies 3 require either a doubling over baseline or elevation above some absolute value ranging from 16.5 to 45 ng/mL. The absolute value matters; for example, a doubling of serum prolactin from 1 to 2 ng/mL would not represent an impressive increase. My own view is that prolactin should at least double and achieve a minimum value of 15 ng/mL in order to meet criteria for marking an epileptic seizure. Conditions that affect baseline serum prolactin, such as dopaminergic or neuroleptic medications, pregnancy, or pituitary abnormalities, should be excluded. The main debatable issue with the findings of this study is the conclusion that "serum prolactin levels do not provide any additional support for distinguishing psychogenic non-epileptic seizures from epileptic seizures." This is an interpretive matter of glass half-full or half-empty. This gloomy interpretation is not supported by the sensitivity and specificity reported in the study. In an epilepsy moni...

Use of serum prolactin in diagnosing epileptic seizures

“…Psychogenic or physiologic nonepileptic events also can influence serum PRL level. Several studies [7][8][9][10] have suggested that serum PRL can increase after syncope, a common imitator of epilepsy.Recent interest in the use of PRL has diminished …”

“…(table 4). In one study of subjects with a mean age of 70 years, 7 11 syncopal subjects showed an elevated mean PRL level of 44 ng/mL (95% CI 27 to 61) when tested within 5 minutes of syncope, compared with a mean baseline PRL level of 10 ng/mL (95% CI 7 to 14). Ten nonsyncopal subjects showed no significant PRL change following head-up tilt.…”

Serum prolactin levels in diff erential diagnosis of pediatric epileptic and nonepileptic (pseudo-SEIZURES) seizures

“…Again consistent with other studies, our results showed that serum PRL levels did not help diff erentiate epilepsies and syncopes. In these studies, Oribe et al (16) showed that serum PRL levels were as high as those seen in epilepsies in 21 patients in whom they induced syncopes with tilt test. Leuf (15) showed that PRL was not helpful in diff erentiation of epileptic seizure and syncope; and fi nally Chen et al (14) showed that serum PRL levels were not helpful in diff erentiating epileptic seizure and syncope.…”

Does serum prolactin indicate the presence of seizure in the emergency department patient?

“…However, as a distinguishing feature hyperprolactinemia can be seen in either seizure or syncope. Oribe performed a tilt table analysis with 11 of 21 patients demonstrating a four fold rise in PRL (9-52 ng/ml), while it remained unchanged in those without tilt induced syncope [8].…”