Can Prolactin Levels Help to Determine the Nature of a "Spell?"

Gregory L. Krauss, MD


November 07, 2000


Is the measurement of prolactin helpful in determining the nature of a spell? Is it elevated in nonconvulsive seizures? Is it elevated in dissociative states?

Walter Panis, MD

Response from Gregory L. Krauss, MD

The answer is, "sometimes." A very high serum prolactin level after a convulsion is evidence that the episode was a seizure and not a pseudoseizure. Serum prolactin is unlikely to be elevated in dissociative states, unless caused by other causes, such as medications or pregnancy. However, low prolactin levels do not discriminate between complex partial and simple partial seizures and nonepileptic events.[1,2]

Postictal hyperprolactinemia is present in approximately two thirds of patients with complex partial seizures and in a few patients with simple partial seizures. Some patients with pseudoseizures have moderate elevations in prolactin, although levels are usually lower than those associated with major convulsions.[3] Prolactin levels may be markedly increased during vasodepressor syncope, limiting the use of prolactin levels to distinguish seizures and syncope.[4] Prolactin levels are usually normal after myoclonic and absence seizures and also in patients with unexpected death in epilepsy (SUDEP).[5]

Prolactin blood levels should be drawn 10-40 minutes after the clinical episode (optimally 10-20 minutes) and should be compared with a baseline, drawn before or several hours after the clinical episode (the same time the next day is OK). Hyperprolactinemia is usually defined as a high level, which is more than twice the baseline level.

The type of episode (convulsive vs nonconvulsive), the EEG, and clinical factors (use of dopamine agonists, presence of sleep, age) should be considered in evaluating prolactin elevations. Repetitive seizures may blunt postictal prolactin elevations. Children have postictal hyperprolactinemia, which can distinguish convulsions and nonepileptic events.[6] However, cerebrospinal fluid prolactin is normal, and neurologic injuries rather than seizures may increase serum prolactin levels in infants.