Baroreflex-sympathoneural without baroreflex-cardiovagal failure in neurogenic orthostatic hypotension.

We describe a patient with neurogenic orthostatic hypotension (nOH) after brainstem neurosurgery in whom baroreflex-cardiovagal function was normal despite baroreflex-sympathoneural failure. We also cite other conditions entailing differential alterations in the two efferent limbs of the baroreflex. Any condition involving nOH from selective loss of sympathetic noradrenergic innervation, interference with sympathetic pre-ganglionic transmission in the thoracolumbar spinal cord, sympathectomies, or attenuated intra-neuronal synthesis, storage, or release of norepinephrine would be expected to manifest with selective baroreflex-sympathoneural dysfunction. We advise caution in relying on indices of baroreflex-cardiovagal function for diagnosing nOH, since normal values for these indices do not exclude nOH.