The authors of this study claim that, in the aging brain, reduction in the pulsation of cerebral vasculature and fluid circulation causes impairment in the fluid exchange between different compartments and lays a foundation for the neuroinflammation that results in Alzheimer disease (AD). The knowledge that lymphatic vessels in the central nervous system play a role in the clearance of brain-derived metabolic waste products opens an unprecedented capability to increase the clearance of macromolecules such as amyloid β proteins. However, currently, there is no pharmacologic mechanism available to increase fluid circulation in the aging brain.
Based on these considerations, the authors conducted a study to demonstrate the influence of an osteopathic cranial manipulative medicine (OCMM) technique, specifically, compression of the fourth ventricle, on spatial memory and changes in substrates associated with mechanisms of metabolic waste clearance in the central nervous system using the naturally aged rat model of AD.
The rats in the OCMM group received the CV4 technique every day for 7 days for 4 to 7 minutes at each session. Rats were anesthetized with 1.5% to 3% isoflurane throughout the procedure. Rats in the UT group were also anesthetized to nullify any influence of isoflurane in spatial learning. During the CV4 procedure, the operator applied mechanical pressure over the rat’s occiput, medial to the junction of the occiput and temporal bone and inferior to the lambdoid suture to place tension on the dural membrane around the fourth ventricle. This gentle pressure was applied to resist cranial flexion with the aim of improving symmetry in the cranial rhythmic impulse (CRI), initiating a rhythmic fluctuation of the CSF, and improving mobility of the cranial bones and dural membranes. This rhythmic fluctuation is thought to be primarily due to flexion and extension that takes place at the synchondrosis between the sphenoid and basiocciput. The treatment end point was achieved when the operator identified that the tissues relaxed, a still point was reached, and improved symmetry or fullness of the CRI was felt. Currently, there is no quantitative measure for the pressure used in this treatment.
The results showed a significant improvement in spatial memory in 6 rats after 7 days of OCMM sessions. Live animal positron emission tomographic imaging and immunoassays revealed that OCMM reduced amyloid β levels, activated astrocytes, and improved neurotransmission in the aged rat brains.
The authors concluded that these findings demonstrate the molecular mechanism of OCMM in aged rats. This study and further investigations will help physicians promote OCMM as an evidence-based adjunctive treatment for patients with AD.
If there ever was an adventurous, over-optimistic extrapolation, this must be it!
Even assuming that all of the findings can be confirmed and replicated, they would be a very far shot from rendering OCMM an evidence-based treatment for AD:
- Rats are not humans.
- Aged rats do not have AD.
- OCMM is not a plausible treatment.
- An animal study is not a clinical trial.
I am at a complete loss to see how the findings of this bizarre animal experiment might help physicians promote OCMM as an evidence-based adjunctive treatment for patients with AD.