Microneurographic evidence of excessive sympathetic outflow in the Guillain-Barré syndrome.

We investigated 3 patients with moderate to severe Guillain-Barré syndrome (GBS) who had transient hypertension and tachycardia during the illness. Microelectrode recordings of muscle nerve sympathetic activity were made in the peroneal nerve once during the acute phase when hypertension and tachycardia were present and twice after recovery from these symptoms. During the acute recording the level of sympathetic activity was considerably higher than after recovery, when the two recordings showed reproducible levels. The normal cardiac rhythmicity was preserved except during brief periods in one patient. Control recordings were made during the acute phase and after recovery in 4 GBS patients without clinical signs of autonomic involvement and twice in 15 healthy subjects. In each control subject the level of sympathetic activity was reproducible, although recordings were made with intervals of two days to four years. The findings show that in the GBS with transient elevations of blood pressure and heart rate there is sympathetic hyperactivity. It is suggested that the increased activity is due to reduced inhibition of the vasomotor centres caused by lesions of the afferent limbs of arterial and perhaps mainly intrathoracic baroreflexes.