Here are more studies:
Cranial Bone and Sutural Mobility Studies
Cranial sutures play a critical role in calvarial morphogenesis. Opperman et. al., (1993,1995), demonstrated that the traditional model of cranial suture morphogenesis invoking biomechanical tensional forces (not unlike the analogy of "tectonic plates" abutting against one another) arising in the cranial base is an incomplete explanation. It was established that when calvarial rudiments encompassing the coronal sutures of neonatal rats were transplanted into adult hosts, the sutures developed normally, and if the donor dura mater was included, the sutures remained patent. In the absence of dura mater, sutural obliteration eventually ensued. It was felt that growth factors in the dura mater (e.g.TGF-b) participated in a regulatory cascade (e.g. cell signal) that permitted the calvarial sutures to be major bone growth centers during the expansion of the neonatal skull.
Oudhof (1982) demonstrated that as the skull develops, the tissue of the coronal and sagittal sutures assume a specific structure which is nearly identical to a gomphosis classification of a joint. These sutures then may be regarded as a type of "multi-gomphosis". This arrangement permits the suture to resist mechanical forces exerted against it. The differentiation of connective tissue fibers and its resemblance to a gomphosis, suggests that the suture can resist forces in directions that widen and those that narrow the suture.
Wagemans, et. al. (1988) citing the work of Bjork has demonstrated that sutural growth normally ceases at age 17 years in males. However, if growth ceases, the suture does not necessarily close immediately. Citing Chopra and Kokich, Wagemans notes that the frontozygomatic and zygomaticomaxillary sutures of pigtail macaque monkeys remain patent until at least 20 years of age. In humans this observation is consistent that the analogous sutures do not fuse until the seventh decade.
Pritchard, et.al. (1956), in a classic study on suture development used fetal animal or newborn human subjects. Their proposal that viable sutures may permit slight movement is limited to this population of subjects. Interestingly, Pritchard is noted to have remarked: "obliteration of sutures and synostoses of the adjoining bones, if it happens at all, occurs usually after all growth has ceased, but in man and most laboratory animals sutures may never completely close".
Retzlaff, et. al., (1979), performed gross and microscopic analysis of sagittal and parietotemporal sutures in 17 cadavers ranging in age from 7 to 78 years. The authors reported no evidence of sutural obliteration by ossification in any of the samples they studied.
Verhulst et. al., (1997), citing the classic studies of Todd and Lyon of the 1920's, noted that suture closure exhibits a definite periodicity, the most extreme activity occurs between twenty-six and thirty years. Additional periods of activity occur in the fifties and the late seventies. Todd and Lyon, found that the degree of closure of some of the cranial sutures demonstrated fluctuations during the fourth, fifth and sixth decades. The squamous suture is the latest suture to close with ossification starting around the age of 63 years, and a second pulse at the age of 78years.
A study by Michael and Retzlaff (1975) while at Michigan State University, utilizing a pressure transducer surgically affixed to the parietal bones of squirrel monkeys (Saimiri sciureus), demonstrated parietal bone displacement with some of the displacement patterns corresponding to respiratory frequency and another pattern of 5-7 cycles per minute that corresponded to neither heart rate nor changes in central venous pressure.
In the classic study on living human subjects performed by Frymann (1971), wherein she developed a non-invasive apparatus for mechanically measuring the changes in cranial diameter. The apparatus consisted of a "U" shaped frame with a differential transformer placed laterally on each side of the subject's skull. Cranial motion was recorded simultaneously with thoracic respiration. On the basis of extensive recordings, Frymann was able to conclude that a rhythmic pattern to cranial mobility exists that is different than that of thoracic respiration.
Retzlaff, et. al., (1982), demonstrated the presence of nerve and vascular tissue imbedded within cranial sutures. They also were able to trace nerve endings from the sagittal sinus through the falx cerebri and third ventricle to the superior cervical ganglion in primates and mammals. The argument could be made, that what purpose would nature design a cranial suture with a neurovascular bundle imbedded within it, if not to provide some type of vascular nutrient supply and sensory capability to the suture.
Cohen (1993), in his work discussing the correlates of craniosynostosis, clearly believed that all cranial sutures eventually fuse, and his work was directed to explore the reasons why some sutures prematurely close in conditions such as craniosynostosis. He concludes that sutural initiation may take place by overlapping of sutures, in which case results in a beveled suture. Or it may occur by end to end approximation, which creates a non-beveled, end-to end type of suture. All end-to-end types of sutures reside in the midline (e.g. metopic and sagittal). It is felt that biomechanical forces on either side of the developing suture tend to be equal in magnitude. This point of view does not take into account the work of Opperman (1993, 1995), that as alluded to above, also indicates that local dural tissue growth factors (e.g. TGF-b) play an etiological role in cranial sutural morphogenesis, as well as biomechanical tensional forces as the calvarial plates abut up against one another.
Moskolenko (1980, 1996,1998), utilizing a variety of technologies (e.g. reoencephalography, reoplethysmography, and electroplethysmography) combined with a computer analysis, was able to demonstrate cranial bone motion ("fluctuations") at a frequency of 6-14 cycles per minute.
I found that here...
http://www.osteodoc.com/research.html
I don't think theese people are making it up, there are likely more studies that agree with them.
The bones don't move much, but it doesn't take much movement to affect the volume of the cranial vault.
Next time you yawn you might hear a "crack" type sound, it doesn't happen every time you yawn, but once in a while you will hear that cracking sound, it almost sounds like its between the ears at the top of the back of the neck. This cracking sound could be the movement of your temporal bone(s). You can live in denial or hear it for yourself by simply paying attention when you yawn.
Yes, I am aware of that. It's called suboccipital craniectomy. Many symptomatic people need a shunt anyway, regardless of the surgery.
