Regional cerebral blood flow in a patient with restless legs syndrome exhibiting pramipexole-induced hypersexuality

Abstract

Background: Impulse control disorders (ICDs), including hypersexuality, are associated with adverse effects of dopamine agonists, such as pramipexole, particularly in the treatment of Parkinson's disease and restless legs syndrome (RLS). The underlying mechanisms remain unclear in ICDs in patients with RLS, and no neuroimaging studies have investigated regional cerebral blood flow (rCBF) changes in RLS patients with ICDs.

Case presentation: A 60-year-old man with RLS developed hypersexuality after initiating pramipexole at 0.5 mg/day. He exhibited inappropriate sexual behaviors toward hospital staff. Single-photon emission computed tomography revealed increased rCBF in the bilateral orbitofrontal cortex and medial frontal cortex, as well as in the left striatum and thalamus. The hypersexuality gradually resolved following pramipexole discontinuation.

Conclusion: This case suggests that pramipexole-induced hypersexuality in RLS may be linked to increased rCBF within the mesocorticolimbic network, including orbitofrontal cortex, medial frontal cortex, and striatum, thereby impairing impulse control. Despite the relatively low dose of pramipexole (0.5 mg/day), individual susceptibility factors, such as depressive symptoms and intellectual disability, may have contributed to ICD onset. Given the lack of prior studies examining rCBF in RLS patients with ICDs, further research is needed to elucidate the pathophysiological mechanisms and risk factors associated with pramipexole-induced ICDs in RLS.

Keywords: hypersexuality; pramipexole; regional cerebral blood flow; restless legs syndrome; single‐photon emission computed tomography (SPECT).

Figure 1

Neuroradiological findings. (a) Transverse fluid‐attenuated inversion recovery magnetic resonance imaging findings were unremarkable except for the presence of a cavum Vergae, which is considered to have no pathological significance. (b) ^99mTc‐ethyl cysteinate dimer brain perfusion single‐photon emission computed tomography (SPECT) easy Z‐score Imaging System analysis (PDRadiopharma Inc, Tokyo, Japan) shows relative hyperperfusion in the bilateral orbitofrontal cortex and the left thalamus. The color scale for the Z‐score is shown in the right part of the figure. Colored areas indicate a Z‐score >2. (c) ¹²³I‐N‐omega‐fluoropropyl‐2‐beta‐carbomethoxy‐3‐beta‐(4‐iodophenyl) nortropane SPECT shows normal findings in dopamine transporter availability in the bilateral whole striatum based on a visual assessment and quantitative analysis. The average SBR for the whole striatum, calculated using the DaTView software (Nihon Medi‐Physics, Tokyo, Japan), was 5.72 (right striatal SBR = 5.80, left striatal SBR = 5.64). (d) ¹²³I‐metaiodobenzylguanidine cardiac scintigraphy showing normal findings in the heart‐to‐mediastinum ratio in both the early and delayed phase (early phase= 3.33, delayed phase = 3.29).