Agrypnia Excitata: a microneurographic study of muscle sympathetic nerve activity.

OBJECTIVE: Agrypnia Excitata (AE) is characterized by autonomic over-activity and cardiovascular fluctuations but direct evidence of sympathoexcitation is lacking. AE is a common feature of acquired (i.e. Morvan's syndrome--MS) and genetic (i.e. fatal familial insomnia--FFI) conditions where a dysfunction of the thalamo-limbic system has been suggested. The aim of this study is to report the first microneurographic recordings of sympathetic activity in acquired and genetic AE to investigate the pattern of sympathetic activation.

METHODS: We describe two patients presenting acquired AE (MS) as demonstrated by elevated serum antibody levels to voltage-gated potassium channels and one patient with genetically confirmed FFI. Patients and fifteen sex and age-matched healthy controls underwent microneurography from peroneal nerve to assess muscle sympathetic nerve activity (MSNA) and heart rate (HR).

RESULTS: Mean level of resting awake MSNA and HR was significantly increased in patients compared to controls. Patients presented a similar pattern of MSNA with a normal cardiac rhythmicity and a very high burst incidence expressed in approximately each cardiac beat.

CONCLUSIONS: Acquired and genetic AE presented a resting awake sympathetic over-activity.

SIGNIFICANCE: AE patients may develop high blood pressure and/or cardiovascular instability potentially increasing the morbidity/mortality of the underlying disorders.