Posterior fossa neurovascular anomalies in essential hypertension.

Intraoperative observations, necropsy, and angiographic studies support the presumption that neurovascular compression of the left ventrolateral medulla may cause neurogenic hypertension. Pulsatile irritation of the ventrolateral medulla at the root-entry zone of cranial nerves IX and X increases blood pressure in animals. To identify and assess the distribution of neurovascular compression at the ventrolateral medulla in human beings, we did a prospective single-blind study in 24 patients with essential hypertension, in 14 patients with renal hypertension, and in 14 normal subjects. To detect neurovascular compression, we used axial and coronal double-echo and magnetic-resonance angiography sequences. Blood pressure control and duration of hypertension were not different in the two groups of patients. 20 patients with essential hypertension had magnetic tomographic evidence of left-sided neurovascular compression at the ventrolateral medulla; 2 patients with renal hypertension and 1 of the normal subjects had a positive finding on the left. On the right side, we found signs of neurovascular compression in 4 patients with essential hypertension, in 4 with renal hypertension, and in 2 of the normal subjects. With magnetic resonance tomography, it is possible to evaluate the neurovascular relations in the posterior fossa and detect neurovascular compression at the ventrolateral medulla. These data in living subjects give further evidence of an association between neurovascular compression at the left ventrolateral medulla and essential hypertension.