Increased sympathetic nerve activity correlates with neurovascular compression at the rostral ventrolateral medulla.
We used microneurography to measure muscle sympathetic nerve activity (MSNA) in 25 hypertensive subjects and correlated these results with the presence or absence of signs of neurovascular compression (NVC) at the rostral ventrolateral (RVL) medulla on MRI. Subjects were divided into 3 groups based on MRI findings: NVC-, no MRI evidence of NVC (N=9); NVC+contact, image showing artery in contact but not compressing the RVL medulla (N=8); and NVC+compression, image showing arterial compression of the RVL medulla (N=8). The MSNA measurements were performed at rest, after a hypothermic stimulus, and during isometric exercise. The MSNA during rest in the NVC+compression group was significantly higher than that in the NVC+contact and NVC- groups (30.4+/-3.4 versus 17.5+/-1.1 and 21.4+/-3.2 spikes per minute, respectively). However, the blood pressure in the NVC+compression group was slightly but not significantly higher than that in the other 2 groups (183+/-7/115+/-8, 174+/-6/108+/-7, and 171+/-5/110+/-5 mm Hg, respectively). The increases in MSNA, blood pressure, and heart rate during the cold pressor and isometric exercise tests were similar. Our results show that, although resting MSNA is elevated in patients with true NVC of the RVL medulla, patients without NVC or with arterial contact but not overt compression of the RVL medulla have similar MSNA. These findings are important for identifying, among hypertensive patients with NVC, individuals who may have associated physiological repercussions, such as increased sympathetic activity.
Heart Institute-InCor, São Paulo, Brazil.
Mauricio M
MM
Sendeski
Fernanda Marciano
FM
Consolim-Colombo
Claudia Costa
CC
Leite
Marcelo Custódio
MC
Rubira
Patricia
P
Lessa
Eduardo Moacyr
EM
Krieger
D000328:Adult; D001794:Blood Pressure; D001808:Blood Vessels / Q000503:physiopathology; D003080:Cold Temperature; D005260:Female; D006439:Hemodynamics; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000503:physiopathology*; D007537:Isometric Contraction; D008279:Magnetic Resonance Imaging; D008297:Male; D008526:Medulla Oblongata / Q000098:blood supply* / Q000503:physiopathology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation*; D009408:Nerve Compression Syndromes / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*