MR screening for brain stem compression in hypertension

To determine the clinical usefulness of MR imaging to screen for vascular compression of the lateral medulla, considered by some to be responsible for neurogenic hypertension.

MR images and clinical records of 120 adults who had received brain MR imaging for any reason were divided into two groups: group 1 (n = 60) consisted of patients with essential hypertension and group 2 (n = 60) included patients who lacked a diagnosis of hypertension. No patient manifested symptomatic cranial neuralgias. The root entry zone of cranial nerves IX and X into the left lateral medulla was examined by MR imaging for proximity to the ipsilateral vertebral artery or its branches. Images lacking any contact between visible vascular structures and the root entry zone were recorded as normal. Vascular compression was graded according to the degree of proximity to the root entry zone. Lateral medullary contact only (grade I), contact and depression (grade II), or lower brain stem displacement or rotation (grade III) of the root entry zone were recorded in both hypertensive and normotensive patients. Among hypertensive patients, additional data were gathered from electrocardiographic, echocardiographic, and urinary protein reports.

We found compression in 34 (57%) of the patients from group 1 and in 33 (55%) of the patients from group 2. Compressions in group 1 were grade I in 22 (37%) of the patients, grade II in 8 (45%), grade II in 4 (7%), and grade III in 2 (3%). There were no statistically significant differences in MR findings between the two groups. Among group 1 patients, MR grading did not predict end-organ changes in the heart (left axis deviation and left ventricular hypertrophy) or kidneys (proteinuria).

Vascular compression of the root entry zone of cranial nerves IX and X into the left lateral medulla is not an adequate lesion to produce systemic hypertension. This finding is as common among normotensive patients as among hypertensive populations. Neither the presence nor the severity of changes in the root entry zone on MR images increases the occurrence of common end-organ responses in the heart or kidneys among hypertensive patients. MR screening is not warranted among hypertensive patients lacking symptomatic cranial neuralgias.