Lower wake resting sympathetic and cardiovascular activities in narcolepsy with cataplexy

Conflicting data have been reported on resting autonomic tone in narcolepsy with cataplexy (NC), including reduced or increased sympathetic activity; to settle this important point, we aimed to measure the resting sympathetic and cardiovascular activities in patients with NC by direct microneurographic monitoring of muscle sympathetic nerve activity (MSNA) during wakefulness.

We studied 19 untreated patients with established criteria for NC and hypocretin deficiency and 19 sex- and age-matched healthy subjects. Subjects underwent resting microneurographic recording of MSNA from peroneal nerve and heart rate (HR), whereas blood pressure (BP) was measured with a sphygmomanometer after the end of microneurographic recording. The awake state was continuously monitored by an ambulatory polygraphic recorder.

Patients with NC displayed lower resting MSNA, HR, and BP values than controls. Pearson regression analysis showed a correlation between CSF hypocretin-1 level and MSNA or HR, whereas no correlation was found with BP; however, patients with virtually absent hypocretin-1 displayed lower BP than patients with the highest hypocretin-1 value.

(1) Patients with NC displayed decreased resting MSNA, HR, and BP during wakefulness, lowering their cardiovascular risk profile; (2) CSF hypocretin-1 deficiency was correlated with MSNA or HR, supporting a direct effect of hypocretin on autonomic regulation; (3) although hypocretin-1 was not correlated with BP, patients with absent hypocretin-1 had lower BP.