Atlas and blood pressure

Anatomical abnormalities of the cervical spine at the level of the Atlas vertebra are associated with relative ischaemia of the brainstem circulation and increased blood pressure (BP). Manual correction of this mal-alignment has been associated with reduced arterial pressure. This pilot study tests the hypothesis that correcting mal-alignment of the Atlas vertebra reduces and maintains a lower BP. Using a double blind, placebo-controlled design at a single center, 50 drug naive (n=26) or washed out (n=24) patients with Stage 1 hypertension were randomized to receive a National Upper Cervical Chiropractic (NUCCA) procedure or a sham procedure. Patients received no antihypertensive meds during the 8-week study duration. The primary end point was changed in systolic and diastolic BP comparing baseline and week 8, with a 90% power to detect an 8/5 mm Hg difference at week 8 over the placebo group. The study cohort had a mean age 52.7+/-9.6 years, consisted of 70% males. At week 8, there were differences in systolic BP (-17+/-9 mm Hg, NUCCA versus -3+/-11 mm Hg, placebo; P<0.0001) and diastolic BP (-10+/-11 mm Hg, NUCCA versus -2+/-7 mm Hg; P=0.002). Lateral displacement of Atlas vertebra (1.0, baseline versus 0.04 degrees week 8, NUCCA versus 0.6, baseline versus 0.5 degrees , placebo; P=0.002). Heart rate was not reduced in the NUCCA group (-0.3 beats per minute, NUCCA, versus 0.5 beats per minute, placebo). No adverse effects were recorded. We conclude that restoration of Atlas alignment is associated with marked and sustained reductions in BP similar to the use of two-drug combination therapy.


From the Full-Text Article:

Introduction

It is well known that achievement of blood pressure (BP) goals in more than 70% of hypertensive individuals requires two or more antihypertensive agents. [1] Based on the most recent NHANES 1999–2000 data, BP control in the US has not improved significantly. [2] Moreover, many people have searched for alternative methods for lowering arterial pressure.

Since the early 1940s, a small cadre of chiropractic specialists have foregone typical ‘full-spine manipulations’, limiting their practice to precise, delicate manual alignment of a single vertebra, C-1 or Atlas; these practitioners make up the National Upper-Cervical Chiropractic Association (NUCCA). Unlike other vertebrae, which interlock one to the next, the Atlas relies solely upon soft tissue (muscles and ligaments) to maintain alignment; therefore, the Atlas is uniquely vulnerable to displacement. Displacement of C-1 is pain free and thus, remains undiagnosed and untreated, whereas health-related consequences are attributed to other aetiologies.

Minor misalignment of the Atlas vertebra can potentially injure, impair, compress and/or compromise brainstem neural pathways. The relationship between hypertension and presence of circulatory abnormalities in the area around the Atlas vertebra and posterior fossa of the brain has been known for more than 40 years. [3-5] Studies by Jannetta et al. [6] note arterial compression of the left lateral medulla oblongata by looping arteries of the base of the brain in 51 of 53 hypertensive patients who underwent left retromastoid craniectomy and microvascular decompression for unrelated cranial nerve dysfunctions. Such compression was not present in normotensive patients. Treatment by vascular decompression of the medulla was performed in 42 of the 53 patients and amelioration of hypertension was noted in 76%. [6] Moreover, studies to clarify the mechanism by which decompression of the left rostral ventrolateral medulla relieves neurogenic hypertension are summarized in a review. [7] It is clear from these studies that a sub-population of hypertensive patients improved their BP after microvascular decompression.

Changes in the anatomical position of the Atlas vertebra and resultant changes in the circulation of the vertebral artery lend itself to worsening of hypertension. Recent studies by Akimura et al. [8] using magnetic resonance (MR) imaging examined hypertensive patients and compared them to controls, evaluating the relationships between the upper ventrolateral medulla and vertebral arteries and branches. They noted compression in 90.6% of 32 hypertensive cases, this was in contrast to controls and those with secondary hypertension who failed to demonstrate a significant incidence of compression. Furthermore, two other studies using MR imaging techniques also demonstrated a significant association between compression of the vertebral artery and changes in the posterior fossa of hypertensive but not normotensive individuals. [9, 10] Thus, alterations in Atlas anatomy can generate changes in the vertebral circulation that may be associated with elevated levels of BP.

This pilot study examines the relationship between nonsurgical interventions to align the Atlas vertebra and long-term changes in BP and heart rate. The criteria used in this study to establish efficacy of an antihypertensive effect are those defined by the Food and Drug Administration for approval of a new antihypertensive drug. Specifically, it would require a blinded design with a placebo-subtracted reduction in diastolic BP of 5mm Hg or more and be free of serious side effects to be approvable.


Discussion

The findings of this pilot study represent the first demonstration of a sustained BP lowering effect associated with a procedure to correct the alignment of the Atlas vertebra. The improvement in BP following the correction of Atlas misalignment is similar to that seen by giving two different antihypertensive agents simultaneously. [11, 12] Moreover, this reduction in BP persisted at 8 weeks and was not associated with pain or pain relief or any other symptom that could be associated with a rise in BP.

Other studies support the notion that changes in the cerebral circulation that is related to the position of the Atlas vertebra can affect BP. Coffee et al. [9] reviewed MR images and demonstrated a significant association between pulsatile arterial compression of the ventrolateral medulla and presence of hypertension. They concluded that subjects with hypertension should have an evaluation of their posterior fossa for evidence of anatomic abnormalities. [9 ] In fact, data linking changes in Atlas anatomy and posterior fossa circulatory changes associated with hypertension date back more than 40 years and are reviewed by Reis. [4]

The mechanism as to why this improvement in BP occurs is unknown and cannot be determined by this study. What is clear is that a significant change in sympathetic tone is probably not a major contributing mechanism as heart rate was not significantly changed. The data presented, however, raises a number of important questions including: (a) how does misalignment of C1 affect hypertension? (b) If there is a cause and effect relationship between C1 misalignment and hypertension is malposition of C1 an additional risk factor for the development of hypertension?

What is clear is that misalignment of the Atlas vertebra can be determined by assessment of the alignment of the pelvic crests. This should be considered in those who have a history of hypertension and require multiple medications for treatment. Additionally, it should be considered in those with refractory hypertension and a history of neck injuries, independent of the presence of pain. Note that pain was not present in any of the patients randomized in this study.

As discussed in the Methods section of this paper, techniques are now available to screen for atlas misalignment. This type of screening should be the responsibility of the primary care physician and should be performed on patients who have a history of head and neck trauma even if it is deemed insignificant. Those patients who present with pain related to head and neck trauma should not be screened. At a time when the prevalence of hypertension is increasing and its control more difficult due to a variety of factors, linking the correction of C1 misalignment to the subsequent lowering of BP may represent an important advancement in the screening of such patients.

This pilot study has limitations including the fact that it was dependent on the skill of one practitioner to do the manipulation. It was designed, however, to test the concept that nonsurgical manipulation can alleviate elevations in BP, thus it cannot be generalized until confirmed in a larger trial, which is being planned.