Neck adjustments reduces hypertension
Atlas vertebra realignment and achievement of arterial pressure goal in hypertensive patients
From: Journal of Human Hypertension (2007), 1–6
It is well known that achievement of blood pressure goals in more than 70% of hypertensive individuals requires two or more antihypertensive agents. Based on the most recent NHANES 1999– 2000 data, blood pressure control in the US has not improved significantly. 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. Studies by Jannetta et al. 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. It is clear from these studies that a sub-population of hypertensive patients improved their blood pressure 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. 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. Thus, alterations in Atlas anatomy can generate changes in the vertebral circulation that may be associated with elevated levels of blood pressure.
This pilot study examines the relationship between nonsurgical interventions to align the Atlas vertebra and long-term changes in blood pressure 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 blood pressure of 5mm Hg or more and be free of serious side effects to be approvable.
The findings of this pilot study represent the first demonstration of a sustained blood pressure lowering effect associated with a procedure to correct the alignment of the Atlas vertebra. The improvement in blood pressure following the correction of Atlas misalignment is similar to that seen by giving two different antihypertensive agents simultaneously. Moreover, this reduction in blood pressure 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 blood pressure.
Other studies support the notion that changes in the cerebral circulation that is related to the position of the Atlas vertebra can affect blood pressure. Coffee et al. 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. 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.
The mechanism as to why this improvement in blood pressure 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.
