Giant PRLomas cause neurologic complications due to their massive extension into the surrounding structures. The aim of the treatment of giant PRLomas is rapid improvement of neurologic symptoms, such as visual disorders, increased intracranial pressure, and palsies of the cranial nerves. The treatment is required to reduce the size of the tumor remarkably. There are several therapeutic approaches, including DA therapy, surgery, radiotherapy, and combinations of these therapies. We chose DA therapy alone in our patient’s case for two reasons: (1) According to previous reports, DA is the first-line medical treatment even for giant PRLomas, and (2) surgical resection may cause severe complications in important surrounding structures [
4,
5]. CAB has emerged as a drug for DA therapy owing to its excellent efficacy and safety. Headache, nausea and vomiting, orthostatic hypotension, depression, and cerebrospinal fluid rhinorrhea are known as common side effects of DA therapy [
6,
7]. However, a small proportion of patients have rare complications, including herniation of the optic chiasm, each cerebral lobe, and the brainstem [
8‐
10]. Moles Herbera
et al. reported a giant PRLoma showing pons herniation into the skull base caused by tumor shrinkage after DA therapy [
11]. In addition, some authors reported cases of frontal lobe herniation as a rare complication of DA therapy (Table
2) [
8‐
10,
12].
Table 2
Reported cases of complication of dopamine agonist therapy for prolactinoma
Papanastasiou et al. (2014) [ 8] | 42/M | 2000 | 1.5 | Optic chiasma | Visual field loss |
Dhanwal et al. (2011) [ 9] | 36/M | 183 | 1.0 | Frontal lobe and optic chiasma | Visual field loss, seizure |
Raverot et al. (2009) [ 10] | 64 /M | 1785 | 1.0 | Optic chiasma | Visual field loss |
30 /M | 660 | 3.0 |
57 /M | 482 | 3.0 |
Herbera et al. (2015) [ 11] | 59 /M | 1108 | 1.0 | Pons | Dysarthria, a left hemiplegia |
According to the package insert of CAB, neurologic and psychiatric side effects were somnolence, aggression, and psychotic behavior. An increase in the risk of epilepsy has not been known as a side effect of CAB. Most previous reports of PRLoma described epileptic seizures as initial symptoms before treatment. Deepak
et al. reported that epilepsy often occurred in patients with invasive macro-PRLomas and that DA therapy could reduce the frequency of seizures and the doses of antiepileptic drugs [
12].
In our patient, however, epileptic seizures occurred immediately after DA therapy for giant PRLoma without a previous history of seizures. The mechanism of the epileptic seizure in our patient is speculative and might be multifocal. On the basis of his clinical course, we concluded that the rapid reduction of the tumor by DA therapy, resulting in retraction of brain matter, especially the temporal lobe around the tumor, could have been the mechanism of the epileptic seizures. This mechanism is a known cause of brain herniation with DA therapy for giant PRLomas [
8,
9,
11]. The appearance of a hyperintense area in left frontal lobe on T2-weighted images may support our hypothesis of the pathogenic mechanisms of the epileptic seizure in our patient. Clinicians should be aware that DA therapy for PRLoma which is effective therapy, can induce epileptic seizures. Furthermore, medical therapies and chemotherapies with excellent efficacy for brain tumors, such as germinomas, may be a risk factor for epileptic seizure as a side effect following rapid reduction of the tumor, similarly to DA therapy for PRLoma.