Surgical Radiologlc Anatomy
Surg Radiol Anat (1991) 13 : 165-170
Journal of Clinical Anatomy
© Springer-Verlag 1991
The osteopathic cranial concept: fact or fiction ? JC Ferr6 and JY Barbin CNERB, 15, rue Charles Monselet, F-44000 Nantes, France
The osteopathic cranial concept, though long-known, seems to be currently attracting fresh attention and has been discussed or mentioned in numerous recent articles or books. It therefore seems useful to specify in this article the viewpoints of engineers, physicians, surgeons, anatomists, those concerned with biomechanics and others engaged in problems of functional morphology, whether of the skull or the axial and appendicular skeleton.
Offprint requests : JC Ferr6
The osteopathic cranial concept
Cranial rhythm This concept was first described by Sutherland in 1939 and has been revived by Karni and Upledger in 1979 as well as in m o r e r e c e n t works by cranial osteopaths such as Clauzade and Daraillans (1989). The consensus is that the brain is a biphasic fluid system enclosed by dural membranes. It has a double origin, with the cerebrospinal fluid in the subarachnoid space and interstitial fluid in the subpial space. These are subject to the pulsatile
movements of the arterial, nervous and p u l m o n a r y s y s t e m s , which transmit their stresses to the dura mater via vertebral connections over the cervical segments of the vertebral column. Although the pulsatile movements of the arterial system do seem to correspond to reality, and while neurosurgeons consider that there certainly exist modifications of intracranial pressure and hence of cerebral volume in relation to respiration (this arising from the repercussions of pressure changes during emptying of the jugular veins into the right side of the heart), it is also the case that the cerebrospinal and interstitial fluids, like all fluids, are incompressible while the calvarium and base of the skull, totally synostosed in adult life, constitute a closed system resistant to deformation. This incompressibility of fluids is a basic physical law admitting of no exceptions save in the field of very high pressures. H o w e v e r , the o s t e o p a t h s do regard them as compressible and have measured a "modular mass" which they define as the amount of increase in pressure due to their change in volume. The values indicate that these variations in the volume of the fluids cannot be totally compensated by their compressibility. Thus, part of the increase in volume of the cerebrospinal and
166
JC Ferr6 and JY Barbin : The osteopathic cranial concept: fact or fiction?
interstitial fluids would take place at the expense of displacement of the b o n e s c o n s t i t u t i n g the c a l v a r i u m a n d the b a s e o f the s k u l l s i n c e , a c c o r d i n g to Sutherland, the nonsynostosed calvarial and basicranial sutures, which are j o i n e d by "soft sutural tissues" remain mobile t h r o u g h o u t life. T h e s e d i s p l a c e m e n t s are not n e g l i g i b l e , and are given as 10 to 25 ].t in the mediolateral direction at the parietal bone by Karni and as 1 m m by Sutherland. They are perceptible to palpation, even in the adult. In short, changes in the internal pressure of the fluid system are supposed to produce shifts of each bony component, the sum of these leading to a r h y t h m i c d i s p l a c e m e n t of the whole of the calvarium. This "cranial rhythm", which is the essence o f c r a n i a l o s t e o p a t h y , o c c u r s in c o n j u n c t i o n w i t h the b r a i n , v e n tricles and intracranial membranes. Sutherland ascribes to it a frequency of 6 to 12 cycles per minute, a primarily "respiratory" rhythm which is palpable at the ends of the limbs, particularly in the thumbs. A n y cause capable of restricting this physiologic mobility constitutes the origin of a symptomatology hitherto consid e r e d as i d i o p a t h i c ; h e n c e the importance of cranial manipulations i n t e n d e d to free the bones of the skull and so to reestablish the primary respiratory rhythm.
1
The craniofacial skeleton, membranes of reciprocal constraint, craniosacral unity According to Delaire, Deshaye and Clauzade and Darraillans, the cran i o f a c i a l s k e l e t o n is in p e r p e t u a l dynamic evolution, due particularly to the m e m b r a n o u s s y s t e m of the dura mater (Fig. 1). This comprises a median sagittal system, consisting of the falx cerebri and falx cerebelli, and a horizontal system: the tentor i u m c e r e b e l l i , the w a l l s o f the cavernous sinus and the dura mater adherent to the anterior cranial fossa. These authors consider this dural system as responsible for the linearity of the anterior cranial fossa, the position and orientation of the foramen magnum, the positioning of the external and internal occipital protuberances, the orientation of the crista galli and hence of the perpendicul a r l a m i n a o f the e t h m o i d b o n e . Through its mediation, and that of the galea aponeurotica, the calvarium and the skull base are influenced by the constraints developed by the nuchal muscles and by the muscles attached on and around the mastoid processes (Fig. 1). Deshaye spells out the ideas of Delaire by indicating that the modifications of the neural tube precociously subject the primitive mesodermal sheet to constraints leading to a virtual endocranial bracing of
the calvarium. These constraints, in the midst of the membranous vault, demarcate the bony territories according to a system of plate tectonics by delineating lines of junction between the two mesodermal sheets which cover the neural vesicles. In these j u n c t i o n a l zones there intersect fibrous bundles which are later colonised by b o n y spicules. Thus, the orientation of the bony trabeculae is d e t e r m i n e d by the m e m b r a nous constraints. As a result of the f o r e g o i n g , the o s s i f i c a t i o n o f the b o n y v e r g e s r e s u l t s in b e v e l l e d e d g e s , first e n d o c r a n i a l and then e x o c r a n i a l , the b o n y e v i d e n c e o f t h e s e r e c i p r o c a l c o n s t r a i n t s , and each skeletal component, guided by its dural envelopes and attachments, possesses a functional capacity for a d a p t a t i o n to the p h e n o m e n o n o f flexion of the skull base. Craniofacial harmony, or c o n c o r d a n c e , w o u l d t h u s b e an equilibrium between this phenomenon of evolutional accommodation of the constituent elements of the calvarium and the increasing flexion o f the skull base, l i n k e d with the pull o f the s p h e n o - o c c i p i t a l sync h o n d r o s i s . T h e r e is a c l a s s i c a l explanation of the very real bevelring which is effected, sometimes at the e x p e n s e o f the o u t e r t a b l e , sometimes at that of the inner table. During delivery there develops an often very m a r k e d o v e r l a p p i n g of
Fig. 1
Action of the posterior and lateral cervical muscles on the occipital squama, petrous bones, skull vault (via the epicranial aponeurosis and the falxes of the cerebrum and cerebellum) and the base of the skull (via the tentorium cerebelli). The sternomaxillarystrip which connects the sternocleidomastoid to the angle of the mandible contributes to the morphogenesis of this bone (From: Functional, surgical and orthopedic rehabilitation of congenital labio-maxillo-palatine clefts, Delaire 1989, Vol. II, p 141) 1 Epicranial aponeurosis and scalp 2 falx cerebri 3 tentorium cerebelli 4 falx cerebelli 5 cervical muscles Action des muscles cervicaux postrrieurs et latrraux sur l'rcaille de l'occipital, les rochers, la vofite du cr~ne (par l'aponrvrose 6picr~nienne et les faux du cerveau et du cervelet) et base du crgme(par la tente du cervelet). La bandelette stemo-maxillaire qui unit le stemo-clrYdo-mastridien ~t l'angle de la mandibule contribue ~t la morphogrnrse de cet os (In J. Delaire 1989 La rrhabilitation fonctionnelle, chirurgicale et orhoprdique des fentes labio-maxillo-palatinescongrnitales, Tome IIP. 141) ALPS) 1 Apondvrose 6picranienne et cuir chevelu 2 faux du cerveau 3 tonte du cervelet 4 faux du cervelet 5 mm. cervicaux postrrieurs et latrraux
5
JC Ferr6 and JY Barbin : The osteopathic cranial concept: factor fiction?
167
Fig. 2 Microradiograph of a metopic suture: note the total synostosis of the suture (A Dhem, Department of Human Anatomy, UCL Louvain en Woluve, Belgium) Microradiographie d'une suture m&opique. Noter la totale synostose de la suture (A Dhem, Unit6 d'AnatomieHumaine UCL Louvain en Woluve - Belgique)
Fig. 3 Superior view of adult cranium: note total synostosis of sutures (A Dhem) Vue sup6rieure d'un cr~ne adulte. Noter ia totale synostose des sutures (A Dhem)
Figs. 4, 5 Thick frontal sections at level of coronal suture: note that these sutures, though completely synostosed, are still represented at the inner table in the form of low serrations. The inverted Y seen on the lower photograph represents the extremity of the coronal and lambdoid sutures Coupes frontales 6paisses au niveau de la suture coronale. Noter sur ces deux photographies que ces sutures, totalement synostos6es, subsistent au niveau de la lame interne sous forme de dentelures de faible profondeur. L'Y invers6 visible sur la photographie du bas repr6sente l'extr6mit6 de la suture coronale et la suture lambdofde
Discussion
The sutural system of the cranial container the bony components of the calvarium. This cranial adjustment during passage through the inferior part of the birth canal is evidently enhanced by t h i s a n a t o m i c a r r a n g e m e n t . C e r t a i n o s t e o p a t h s , s u c h as C l a u z a d e and D a r a i l l a n s f u r t h e r suggest that during each contraction of the neuroglia the neuraxis undergoes a m o v e m e n t of ascent towards the c r a n i u m , w h i l e the s a c r u m , a f f e c t e d by the s a m e m o v e m e n t , simultaneously becomes more verti-
cal. T h e y explain this by the fact that the i n t r a s p i n a l m e m b r a n e is attached cranially around the perimeter o f the foramen m a g n u m as far as C2-C3 but then remains free throughout the spinal canal until it gains its final caudal attachments at the l e v e l o f $2. H e n c e these last authors conclude that every osteopathic cranial lesion has an influence on the p o s i t i o n o f the sacrum, this physiologic craniosacral unity being given the name "core link".
The double endochondral and membranous origin of the bones of the skull and face is sufficiently wellknown to need no emphasis. It need only be recalled that, at birth, there are 4 s y n c h o n d r o s e s . T h r e e are single and frontal: the frontoethmoidal and sphenoethmoidal synchondroses, completely synostosed between the ages of 7 and 8 years and the b a s i s p h e n o i d - b a s i o c c i p i t a l (or spheno-occipital) synchondrosis united at the end of adolescence. A
168 sagittal pair joining the greater wings to the body of the sphenoid bone is synostosed from the age of 3 years. Thus, it is logical to assert that movements of the bones belonging to the anterior and middle cranial fossae are impossible from the age of 8 years, and that movement is only possible - and that theoretically for those constituting the posterior cranial fossa. For the same reason, the progressive plication of the skull base due to m e c h a n i c a l stresses acting on the spheno-occipital synchondrosis is no longer possible after the end of adolescence. As regards the sutures and their anatomy, the reader is referred to the classic works (the edition by D h e m of the Anatomy of Feneis (1985), Rouvi~re and Delmas (1985) or Testut (1896)). These refer to the increase in size of the c r a n i u m under the influence of mechanical stresses associated with the development of the brain. Once this has been completed, the sutures come to a progressive standstill beginning with the internal table and ending with their progressive synostosis. Anatomists consider that this phen o m e n o n takes place in parallel with the disappearance of the growth cartilages of the long bones, though the metopic suture in man is synostosed before the end of the second year (Fig. 2) whereas it does not close in the anthropoid apes, for reasons unknown. Certainly, as long as any teeth remain, the lateral part of the calvarial sutures may exhibit a degree of activity, though limited. Again, it is probable for mechanical reasons that the insertion of large m a x i l l a r y bridges may produce modifications of the outer table at these same sutures. Nevertheless, we are dealing here with a p h e n o m e n o n of remodelling by opposition-absorption associated with a local modification of the distribution and intensi-
JC Ferr6 and JY Barbin : The osteopathiccranial concept: factor fiction? ty of the constraints in a specific zone, i.e. with a phenomenon analogous to the thickening of the medial cortex of the femur observed in relation to the lower end of the stem of an implanted hip prosthesis. In any case, there is no question of a restoration of activity of the sutures, which has generally long disappeared by the time that major loss of teeth requires a remedy. In sum, the calvarial sutures are well and truly synostosed and our 100 cranial sections (not including those e x a m i n e d at the a n a t o m y department of the UFR at Nantes) have, contrary to the osteopathic theory, c o n v i n c e d us that these nearly always exhibit a compact and resistant region (Figs. 3, 4, 5).
Flexion of the base of the skull: craniofacial biodynamics In effect, there occurs a progressive flexion of the base of the skull beginning in intrauterine life and completed at the end of adolescence in harmony with the synostosis of the spheno-occipital synchondrosis. The latter is thus subjected to major constraints, not only in the course of growth but also, as we shall see, during adult life. While in agreement with these authors in principle, we differ as regards the explanation given, for to acknowledge the dynamic role of the dural b r a c i n g a m o u n t s to p o s t u l a t i n g that the growth of the brain takes place amidst mechanical constraints. Yet it is known that the nervous system cannot develop under such conditions; the nerves, for instance, always occupy the neutral zone in a mechanically stressed bone. A good example is provided by the mandibular n e u r o v a s c u l a r bundle; the mandibular canal it occupies effectively corresponds to the neutral axis of this bone, around which moreover growth takes place (Ferr6 et al 1985). The role of the 5th cranial
nerve in facial morphogenesis is well-known. The meninges are in reality a support system whose role is to tether the brain to the cranium from which it is suspended, so as to protect it from kinetic accelerations and, within certain limits, during minor impacts. Nor do we believe (see Fig. 1) in the transmission to the meninges of the c o n s t r a i n t s g e n e r a t e d by contraction of the nuchal and sternocleidomastoid muscles, mediated by the galea aponeurotica. This is partly because these muscles are so powerful that their attachments are essentially bony (and also well-marked by outstanding ridges or hollowed n o t c h e s h a v i n g the s a m e mechanical significance) and also because, for the great part, the galea slides over the calvarium. To explain this flexion of the base of the skull we must resort to Sakka's theory of cranial externation. For this author, the growth of the brain is not uniform, but certain zones develop faster than others. The gradient of decrease of curvature associated with the growth in size of the cranial cavity is not equal e v e r y w h e r e ( p a r t i c u l a r l y at the squamous portion of the occipital bone). Thus, what is w i t n e s s e d during growth is first a straightening of the forehead and then a forward migration of the Euryons (the most pronounced point of the parietal bump), whereas the posterior part of the cranium does not exhibit a s e e - s a w p h e n o m e n o n . On the contrary, it is the site of a thrusting expansion in particular directions, guided and supported by the basicranial hammock.
Mechanical structure of the skull base and the calvarium In a series of studies devoted to the b i o m e c h a n i c s of the base of the skull and calvarium, we announced a biomechanical conception asser-
JC Ferr6 and JY Barbin : The osteopathiccranial concept: factor fiction? ting the synostosis of the synchondroses and the sutures at the same time as the disappearance of the growth cartilages of the long bones. We should bear in mind the concept of the biomechanical unity of the base of the skull and the face, and likewise that of the division of the skull base into two zones whose roles, and hence mechanical structures, are different. The anterior cranial fossa seems to have been "designed" to resist the constraints developed by mastication, whereas the posterior cranial fossa seems to have been intended to sustain those developed by the cervical statics and during movements of the head. The middle cranial fossa is rather special, a zone of transition assuming both mechanical functions at once, with the sphenoidal sinus assuming a role that we c o n s i d e r of m a j o r i m p o r t a n c e . Without going into b u r d e n s o m e detail, it should be noted that these constraints are considerable, that some of them involve the concept of moment (which amplifies them), while others, particularly during complex movements of the head, are asymmetric. Thus, at the base of the skull so mechanically stressed there arise flexion, torsion and shearing constraints. C o m m o n sense requires us to try to understand how it is organised to resist these. The anterior and middle cranial fossae rely on "caisson structures" reinforced peripherally by "frames" of such a nature that the forces boxed in by the alveolar plate are first distributed over almost the entire facial mass and then relayed to the base of the skull, where they are dispersed by the sphenoidal sinus, the latter p r o b a b l y also playing the part of a "circuit-breaker" of force b e t w e e n the constraints developed by mastication and those developed by cephalic statics and robotics. Acting as struts, the frontal crest and the dor-
169
sal margins of the lesser wings of the sphenoid relay part of the strains towards the calvarium, which may account for the bony remodelling observed after the placing of large maxillary bridges at its outer table. The inertia of the posterior cranial fossa relies on systems of solid beams with cellular filling and thin walls. There are two such systems: (1) The petromastoid system consists of the pyramidal petrous beams in continuity with the mastoid processes which resist the shearing forces localised to the lateral borders of the clivus, forces generated by the contraction of the sternocleidomastoid muscles. The squama of the occipital bone, by virtue of its nature as a composite prestressed material and because of the presence of bracers (the borders of the groove for the transverse sinus), probably also plays a part in the horizontal stability of this petromastoid V and in the maintenance of its angulation. Produced in the course of cranial externation, it remains so stressed t h r o u g h o u t life by the action of the nuchal muscles.
(2) The foraminoclival zone, which we have already stated to be subject to intense constraints in flexion and torsion, is reinforced by the solid clival beam, without any solution of mechanical continuity with the robust periforaminal ring. Two struts, the clivoforaminal struts described by us, further contribute to the solidity of the assembly. Thus, from the biomechanical and the engineering viewpoint, the base of the skull relies on mechanical aeronautical solutions (of the type used in the Airbus) combining strength with lightness. Such reinforcing arrangements are found only where major constraints exist and result in giving the cranium (base and calvarium) exceptional lightness but also great rigidity. Thus, the concept of free sutures allowing displacement of the cranial bones seems in total contradiction with its mode of construction. A final argument is that, when an anatomy teacher wishes to separate the cranial bones for purposes of description, he cannot do so without using a saw, even when the
:----._-. = :-31.__~ . ~
31
-.-
.,.. -
---
2423-.,~ 19-
Fig. 6
Cerebral membranes and spaces. 12 Dura mater 19 Subdural space 23 Arachnoid24 Subarachnoid space 31 Arachnoidalgranulations (From:Feneis: R6pertoire illustr6 d'anatomie humaine, French ed A Dhem) 12 Dure-m6rede rencrphale 19 Espace subdural 23 Arachnoidede rencrphale 24 Espace subarachno~'dien31 Granulations arachnoidiennes (In Heinz Feneis Rrpertoireillustr6 d'anatornie humaine 6ditionFrangaise : A Dhem. Medsi 6diteur )
170 sutures are clearly visible on the surface of the bone. To obtain an "exploded" skull, it is necessary to fill the cranial cavity with dry haricot beans and immerse the whole in water. The pressure developed by the progressive hydration of the beans b e c o m e s such that it is a necessary preliminary to reinforce the skull with numerous turns of thick cord, without which it would l i t e r a l l y e x p l o d e p r o v i d e d the sutures were still visible, for if this were not the case there would be random shattering. While the calvarial sutures may represent a weak zone under these extreme conditions, it is difficult to understand how a hypothetical "respiration" could separate such solid sutures. Again, apart from certain injuries, sutural disjunction is rare except occasionally for the parieto-occipital sutures.
Cranial pulsation and cerebrospinal fluid It is a matter of experience that when the cranium is opened in life the brain exhibits the phenomenon of pulsation. But what is its precise origin and is it transmitted to the calvarium, as asserted by the osteopaths, so becoming perceptible to palpation ? These authors refer to three different rhythms. The first is associated with "the inherent mobility of the brain and cord" as well as with the rhythmic pulsation of the cerebrospinal fluid. The second is r e l a t e d to the s y s t o l i c c a r d i a c rhythm, and the last with respiration. The " p r i m a r y r e s p i r a t o r y rhythm" of the osteopaths does not
JC Ferr6 and JY Barbin : The osteopathiccranial concept: factor fiction? correspond to respiration but to the contractions of the brain and the rhythmic pulsations of the CSF. It is obviously inadmissible that the brain and cord exhibit movements of a peristaltic nature like other v i s c e r a , for they are not contractile. It is equally difficult to believe in a hypothetical pulsation of the CSF since this, like all fluids, is incompressible and has a low pressure (of the order of 0.4 Newtons, around 400 g/m2). Such a pressure, even assuming cyclical variation, is situated in a much too feeble range to have any effect on the sutures. Moreover, the CSF is contained in the non-extensible suba r a c h n o i d space, t r a v e r s e d by fibrous strands contributing to the tethering of the brain and resistant to any expansion. Finally, the cerebrospinal fluid, secreted by the choroid plexuses and drained by the foramina of the 4th ventricle into the subarachnoid space (Fig. 6), enjoys its own security system. This consists of: (1) the subarachnoid cisterns, local enlargements of the subarachnoid space. This system functions in such a manner that dilatation of a channel slows the speed of fluid flow and reduces its pressure (loss of thrust); (2) the cerebello-medullary cistern, situated between the cerebellum and the medulla oblongata. (3) the arachnoid granulations, villous and avscular evaginations of the s u b a r a c h n o i d space into the superior longitudinal sinus and the diploic veins, drain the excess of CSF and function as safety valves (waste gate).
On the other hand, the movements that certainly affect the brain correspond to systolic expansion in pulsations synchronous with the heart rate. It is also undeniable that there are modifications of the intracranial pressure, and therefore of the cerebral volume, related to respiration. We have already mentioned that these are due to the effects of pressure changes during emptying of the jugular veins into the right heart cavities. Likewise, neurosurgeons confirm that vascular compression produces cerebral turgescence, a maneuver employed to demonstrate cerebrospinal rhinorrhea since compression of the CSF then leads to its evacuation through t r a u m a t i c b r e a c h e s of the skull base. However, these pulsations of the brain, real as they are, cannot be transmitted to the calvarium, which has long been well and truly synostosed in the adult. What the osteopath feels when palpating the skull are pulsations related to the vascular system of the scalp, with its known abundance and tendency to hemorrhage on injury, or else his own capillary pulsations. Conclusion It emerges from this objective and impartial recital of the facts that the theory of "primary respiration" has no s c i e n t i f i c basis and totally contradicts the findings of physics, anatomy, physiology, biomechanics and clinical experience.
Surg Radiol Anat (1991) 13 : 165-170
Journal of Clinical Anatomy
© Springer-Verlag 1991
The osteopathic cranial concept: fact or fiction ? JC Ferr6 and JY Barbin CNERB, 15, rue Charles Monselet, F-44000 Nantes, France
The osteopathic cranial concept, though long-known, seems to be currently attracting fresh attention and has been discussed or mentioned in numerous recent articles or books. It therefore seems useful to specify in this article the viewpoints of engineers, physicians, surgeons, anatomists, those concerned with biomechanics and others engaged in problems of functional morphology, whether of the skull or the axial and appendicular skeleton.
Offprint requests : JC Ferr6
The osteopathic cranial concept
Cranial rhythm This concept was first described by Sutherland in 1939 and has been revived by Karni and Upledger in 1979 as well as in m o r e r e c e n t works by cranial osteopaths such as Clauzade and Daraillans (1989). The consensus is that the brain is a biphasic fluid system enclosed by dural membranes. It has a double origin, with the cerebrospinal fluid in the subarachnoid space and interstitial fluid in the subpial space. These are subject to the pulsatile
movements of the arterial, nervous and p u l m o n a r y s y s t e m s , which transmit their stresses to the dura mater via vertebral connections over the cervical segments of the vertebral column. Although the pulsatile movements of the arterial system do seem to correspond to reality, and while neurosurgeons consider that there certainly exist modifications of intracranial pressure and hence of cerebral volume in relation to respiration (this arising from the repercussions of pressure changes during emptying of the jugular veins into the right side of the heart), it is also the case that the cerebrospinal and interstitial fluids, like all fluids, are incompressible while the calvarium and base of the skull, totally synostosed in adult life, constitute a closed system resistant to deformation. This incompressibility of fluids is a basic physical law admitting of no exceptions save in the field of very high pressures. H o w e v e r , the o s t e o p a t h s do regard them as compressible and have measured a "modular mass" which they define as the amount of increase in pressure due to their change in volume. The values indicate that these variations in the volume of the fluids cannot be totally compensated by their compressibility. Thus, part of the increase in volume of the cerebrospinal and
166
JC Ferr6 and JY Barbin : The osteopathic cranial concept: fact or fiction?
interstitial fluids would take place at the expense of displacement of the b o n e s c o n s t i t u t i n g the c a l v a r i u m a n d the b a s e o f the s k u l l s i n c e , a c c o r d i n g to Sutherland, the nonsynostosed calvarial and basicranial sutures, which are j o i n e d by "soft sutural tissues" remain mobile t h r o u g h o u t life. T h e s e d i s p l a c e m e n t s are not n e g l i g i b l e , and are given as 10 to 25 ].t in the mediolateral direction at the parietal bone by Karni and as 1 m m by Sutherland. They are perceptible to palpation, even in the adult. In short, changes in the internal pressure of the fluid system are supposed to produce shifts of each bony component, the sum of these leading to a r h y t h m i c d i s p l a c e m e n t of the whole of the calvarium. This "cranial rhythm", which is the essence o f c r a n i a l o s t e o p a t h y , o c c u r s in c o n j u n c t i o n w i t h the b r a i n , v e n tricles and intracranial membranes. Sutherland ascribes to it a frequency of 6 to 12 cycles per minute, a primarily "respiratory" rhythm which is palpable at the ends of the limbs, particularly in the thumbs. A n y cause capable of restricting this physiologic mobility constitutes the origin of a symptomatology hitherto consid e r e d as i d i o p a t h i c ; h e n c e the importance of cranial manipulations i n t e n d e d to free the bones of the skull and so to reestablish the primary respiratory rhythm.
1
The craniofacial skeleton, membranes of reciprocal constraint, craniosacral unity According to Delaire, Deshaye and Clauzade and Darraillans, the cran i o f a c i a l s k e l e t o n is in p e r p e t u a l dynamic evolution, due particularly to the m e m b r a n o u s s y s t e m of the dura mater (Fig. 1). This comprises a median sagittal system, consisting of the falx cerebri and falx cerebelli, and a horizontal system: the tentor i u m c e r e b e l l i , the w a l l s o f the cavernous sinus and the dura mater adherent to the anterior cranial fossa. These authors consider this dural system as responsible for the linearity of the anterior cranial fossa, the position and orientation of the foramen magnum, the positioning of the external and internal occipital protuberances, the orientation of the crista galli and hence of the perpendicul a r l a m i n a o f the e t h m o i d b o n e . Through its mediation, and that of the galea aponeurotica, the calvarium and the skull base are influenced by the constraints developed by the nuchal muscles and by the muscles attached on and around the mastoid processes (Fig. 1). Deshaye spells out the ideas of Delaire by indicating that the modifications of the neural tube precociously subject the primitive mesodermal sheet to constraints leading to a virtual endocranial bracing of
the calvarium. These constraints, in the midst of the membranous vault, demarcate the bony territories according to a system of plate tectonics by delineating lines of junction between the two mesodermal sheets which cover the neural vesicles. In these j u n c t i o n a l zones there intersect fibrous bundles which are later colonised by b o n y spicules. Thus, the orientation of the bony trabeculae is d e t e r m i n e d by the m e m b r a nous constraints. As a result of the f o r e g o i n g , the o s s i f i c a t i o n o f the b o n y v e r g e s r e s u l t s in b e v e l l e d e d g e s , first e n d o c r a n i a l and then e x o c r a n i a l , the b o n y e v i d e n c e o f t h e s e r e c i p r o c a l c o n s t r a i n t s , and each skeletal component, guided by its dural envelopes and attachments, possesses a functional capacity for a d a p t a t i o n to the p h e n o m e n o n o f flexion of the skull base. Craniofacial harmony, or c o n c o r d a n c e , w o u l d t h u s b e an equilibrium between this phenomenon of evolutional accommodation of the constituent elements of the calvarium and the increasing flexion o f the skull base, l i n k e d with the pull o f the s p h e n o - o c c i p i t a l sync h o n d r o s i s . T h e r e is a c l a s s i c a l explanation of the very real bevelring which is effected, sometimes at the e x p e n s e o f the o u t e r t a b l e , sometimes at that of the inner table. During delivery there develops an often very m a r k e d o v e r l a p p i n g of
Fig. 1
Action of the posterior and lateral cervical muscles on the occipital squama, petrous bones, skull vault (via the epicranial aponeurosis and the falxes of the cerebrum and cerebellum) and the base of the skull (via the tentorium cerebelli). The sternomaxillarystrip which connects the sternocleidomastoid to the angle of the mandible contributes to the morphogenesis of this bone (From: Functional, surgical and orthopedic rehabilitation of congenital labio-maxillo-palatine clefts, Delaire 1989, Vol. II, p 141) 1 Epicranial aponeurosis and scalp 2 falx cerebri 3 tentorium cerebelli 4 falx cerebelli 5 cervical muscles Action des muscles cervicaux postrrieurs et latrraux sur l'rcaille de l'occipital, les rochers, la vofite du cr~ne (par l'aponrvrose 6picr~nienne et les faux du cerveau et du cervelet) et base du crgme(par la tente du cervelet). La bandelette stemo-maxillaire qui unit le stemo-clrYdo-mastridien ~t l'angle de la mandibule contribue ~t la morphogrnrse de cet os (In J. Delaire 1989 La rrhabilitation fonctionnelle, chirurgicale et orhoprdique des fentes labio-maxillo-palatinescongrnitales, Tome IIP. 141) ALPS) 1 Apondvrose 6picranienne et cuir chevelu 2 faux du cerveau 3 tonte du cervelet 4 faux du cervelet 5 mm. cervicaux postrrieurs et latrraux
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JC Ferr6 and JY Barbin : The osteopathic cranial concept: factor fiction?
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Fig. 2 Microradiograph of a metopic suture: note the total synostosis of the suture (A Dhem, Department of Human Anatomy, UCL Louvain en Woluve, Belgium) Microradiographie d'une suture m&opique. Noter la totale synostose de la suture (A Dhem, Unit6 d'AnatomieHumaine UCL Louvain en Woluve - Belgique)
Fig. 3 Superior view of adult cranium: note total synostosis of sutures (A Dhem) Vue sup6rieure d'un cr~ne adulte. Noter ia totale synostose des sutures (A Dhem)
Figs. 4, 5 Thick frontal sections at level of coronal suture: note that these sutures, though completely synostosed, are still represented at the inner table in the form of low serrations. The inverted Y seen on the lower photograph represents the extremity of the coronal and lambdoid sutures Coupes frontales 6paisses au niveau de la suture coronale. Noter sur ces deux photographies que ces sutures, totalement synostos6es, subsistent au niveau de la lame interne sous forme de dentelures de faible profondeur. L'Y invers6 visible sur la photographie du bas repr6sente l'extr6mit6 de la suture coronale et la suture lambdofde
Discussion
The sutural system of the cranial container the bony components of the calvarium. This cranial adjustment during passage through the inferior part of the birth canal is evidently enhanced by t h i s a n a t o m i c a r r a n g e m e n t . C e r t a i n o s t e o p a t h s , s u c h as C l a u z a d e and D a r a i l l a n s f u r t h e r suggest that during each contraction of the neuroglia the neuraxis undergoes a m o v e m e n t of ascent towards the c r a n i u m , w h i l e the s a c r u m , a f f e c t e d by the s a m e m o v e m e n t , simultaneously becomes more verti-
cal. T h e y explain this by the fact that the i n t r a s p i n a l m e m b r a n e is attached cranially around the perimeter o f the foramen m a g n u m as far as C2-C3 but then remains free throughout the spinal canal until it gains its final caudal attachments at the l e v e l o f $2. H e n c e these last authors conclude that every osteopathic cranial lesion has an influence on the p o s i t i o n o f the sacrum, this physiologic craniosacral unity being given the name "core link".
The double endochondral and membranous origin of the bones of the skull and face is sufficiently wellknown to need no emphasis. It need only be recalled that, at birth, there are 4 s y n c h o n d r o s e s . T h r e e are single and frontal: the frontoethmoidal and sphenoethmoidal synchondroses, completely synostosed between the ages of 7 and 8 years and the b a s i s p h e n o i d - b a s i o c c i p i t a l (or spheno-occipital) synchondrosis united at the end of adolescence. A
168 sagittal pair joining the greater wings to the body of the sphenoid bone is synostosed from the age of 3 years. Thus, it is logical to assert that movements of the bones belonging to the anterior and middle cranial fossae are impossible from the age of 8 years, and that movement is only possible - and that theoretically for those constituting the posterior cranial fossa. For the same reason, the progressive plication of the skull base due to m e c h a n i c a l stresses acting on the spheno-occipital synchondrosis is no longer possible after the end of adolescence. As regards the sutures and their anatomy, the reader is referred to the classic works (the edition by D h e m of the Anatomy of Feneis (1985), Rouvi~re and Delmas (1985) or Testut (1896)). These refer to the increase in size of the c r a n i u m under the influence of mechanical stresses associated with the development of the brain. Once this has been completed, the sutures come to a progressive standstill beginning with the internal table and ending with their progressive synostosis. Anatomists consider that this phen o m e n o n takes place in parallel with the disappearance of the growth cartilages of the long bones, though the metopic suture in man is synostosed before the end of the second year (Fig. 2) whereas it does not close in the anthropoid apes, for reasons unknown. Certainly, as long as any teeth remain, the lateral part of the calvarial sutures may exhibit a degree of activity, though limited. Again, it is probable for mechanical reasons that the insertion of large m a x i l l a r y bridges may produce modifications of the outer table at these same sutures. Nevertheless, we are dealing here with a p h e n o m e n o n of remodelling by opposition-absorption associated with a local modification of the distribution and intensi-
JC Ferr6 and JY Barbin : The osteopathiccranial concept: factor fiction? ty of the constraints in a specific zone, i.e. with a phenomenon analogous to the thickening of the medial cortex of the femur observed in relation to the lower end of the stem of an implanted hip prosthesis. In any case, there is no question of a restoration of activity of the sutures, which has generally long disappeared by the time that major loss of teeth requires a remedy. In sum, the calvarial sutures are well and truly synostosed and our 100 cranial sections (not including those e x a m i n e d at the a n a t o m y department of the UFR at Nantes) have, contrary to the osteopathic theory, c o n v i n c e d us that these nearly always exhibit a compact and resistant region (Figs. 3, 4, 5).
Flexion of the base of the skull: craniofacial biodynamics In effect, there occurs a progressive flexion of the base of the skull beginning in intrauterine life and completed at the end of adolescence in harmony with the synostosis of the spheno-occipital synchondrosis. The latter is thus subjected to major constraints, not only in the course of growth but also, as we shall see, during adult life. While in agreement with these authors in principle, we differ as regards the explanation given, for to acknowledge the dynamic role of the dural b r a c i n g a m o u n t s to p o s t u l a t i n g that the growth of the brain takes place amidst mechanical constraints. Yet it is known that the nervous system cannot develop under such conditions; the nerves, for instance, always occupy the neutral zone in a mechanically stressed bone. A good example is provided by the mandibular n e u r o v a s c u l a r bundle; the mandibular canal it occupies effectively corresponds to the neutral axis of this bone, around which moreover growth takes place (Ferr6 et al 1985). The role of the 5th cranial
nerve in facial morphogenesis is well-known. The meninges are in reality a support system whose role is to tether the brain to the cranium from which it is suspended, so as to protect it from kinetic accelerations and, within certain limits, during minor impacts. Nor do we believe (see Fig. 1) in the transmission to the meninges of the c o n s t r a i n t s g e n e r a t e d by contraction of the nuchal and sternocleidomastoid muscles, mediated by the galea aponeurotica. This is partly because these muscles are so powerful that their attachments are essentially bony (and also well-marked by outstanding ridges or hollowed n o t c h e s h a v i n g the s a m e mechanical significance) and also because, for the great part, the galea slides over the calvarium. To explain this flexion of the base of the skull we must resort to Sakka's theory of cranial externation. For this author, the growth of the brain is not uniform, but certain zones develop faster than others. The gradient of decrease of curvature associated with the growth in size of the cranial cavity is not equal e v e r y w h e r e ( p a r t i c u l a r l y at the squamous portion of the occipital bone). Thus, what is w i t n e s s e d during growth is first a straightening of the forehead and then a forward migration of the Euryons (the most pronounced point of the parietal bump), whereas the posterior part of the cranium does not exhibit a s e e - s a w p h e n o m e n o n . On the contrary, it is the site of a thrusting expansion in particular directions, guided and supported by the basicranial hammock.
Mechanical structure of the skull base and the calvarium In a series of studies devoted to the b i o m e c h a n i c s of the base of the skull and calvarium, we announced a biomechanical conception asser-
JC Ferr6 and JY Barbin : The osteopathiccranial concept: factor fiction? ting the synostosis of the synchondroses and the sutures at the same time as the disappearance of the growth cartilages of the long bones. We should bear in mind the concept of the biomechanical unity of the base of the skull and the face, and likewise that of the division of the skull base into two zones whose roles, and hence mechanical structures, are different. The anterior cranial fossa seems to have been "designed" to resist the constraints developed by mastication, whereas the posterior cranial fossa seems to have been intended to sustain those developed by the cervical statics and during movements of the head. The middle cranial fossa is rather special, a zone of transition assuming both mechanical functions at once, with the sphenoidal sinus assuming a role that we c o n s i d e r of m a j o r i m p o r t a n c e . Without going into b u r d e n s o m e detail, it should be noted that these constraints are considerable, that some of them involve the concept of moment (which amplifies them), while others, particularly during complex movements of the head, are asymmetric. Thus, at the base of the skull so mechanically stressed there arise flexion, torsion and shearing constraints. C o m m o n sense requires us to try to understand how it is organised to resist these. The anterior and middle cranial fossae rely on "caisson structures" reinforced peripherally by "frames" of such a nature that the forces boxed in by the alveolar plate are first distributed over almost the entire facial mass and then relayed to the base of the skull, where they are dispersed by the sphenoidal sinus, the latter p r o b a b l y also playing the part of a "circuit-breaker" of force b e t w e e n the constraints developed by mastication and those developed by cephalic statics and robotics. Acting as struts, the frontal crest and the dor-
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sal margins of the lesser wings of the sphenoid relay part of the strains towards the calvarium, which may account for the bony remodelling observed after the placing of large maxillary bridges at its outer table. The inertia of the posterior cranial fossa relies on systems of solid beams with cellular filling and thin walls. There are two such systems: (1) The petromastoid system consists of the pyramidal petrous beams in continuity with the mastoid processes which resist the shearing forces localised to the lateral borders of the clivus, forces generated by the contraction of the sternocleidomastoid muscles. The squama of the occipital bone, by virtue of its nature as a composite prestressed material and because of the presence of bracers (the borders of the groove for the transverse sinus), probably also plays a part in the horizontal stability of this petromastoid V and in the maintenance of its angulation. Produced in the course of cranial externation, it remains so stressed t h r o u g h o u t life by the action of the nuchal muscles.
(2) The foraminoclival zone, which we have already stated to be subject to intense constraints in flexion and torsion, is reinforced by the solid clival beam, without any solution of mechanical continuity with the robust periforaminal ring. Two struts, the clivoforaminal struts described by us, further contribute to the solidity of the assembly. Thus, from the biomechanical and the engineering viewpoint, the base of the skull relies on mechanical aeronautical solutions (of the type used in the Airbus) combining strength with lightness. Such reinforcing arrangements are found only where major constraints exist and result in giving the cranium (base and calvarium) exceptional lightness but also great rigidity. Thus, the concept of free sutures allowing displacement of the cranial bones seems in total contradiction with its mode of construction. A final argument is that, when an anatomy teacher wishes to separate the cranial bones for purposes of description, he cannot do so without using a saw, even when the
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31
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Fig. 6
Cerebral membranes and spaces. 12 Dura mater 19 Subdural space 23 Arachnoid24 Subarachnoid space 31 Arachnoidalgranulations (From:Feneis: R6pertoire illustr6 d'anatomie humaine, French ed A Dhem) 12 Dure-m6rede rencrphale 19 Espace subdural 23 Arachnoidede rencrphale 24 Espace subarachno~'dien31 Granulations arachnoidiennes (In Heinz Feneis Rrpertoireillustr6 d'anatornie humaine 6ditionFrangaise : A Dhem. Medsi 6diteur )
170 sutures are clearly visible on the surface of the bone. To obtain an "exploded" skull, it is necessary to fill the cranial cavity with dry haricot beans and immerse the whole in water. The pressure developed by the progressive hydration of the beans b e c o m e s such that it is a necessary preliminary to reinforce the skull with numerous turns of thick cord, without which it would l i t e r a l l y e x p l o d e p r o v i d e d the sutures were still visible, for if this were not the case there would be random shattering. While the calvarial sutures may represent a weak zone under these extreme conditions, it is difficult to understand how a hypothetical "respiration" could separate such solid sutures. Again, apart from certain injuries, sutural disjunction is rare except occasionally for the parieto-occipital sutures.
Cranial pulsation and cerebrospinal fluid It is a matter of experience that when the cranium is opened in life the brain exhibits the phenomenon of pulsation. But what is its precise origin and is it transmitted to the calvarium, as asserted by the osteopaths, so becoming perceptible to palpation ? These authors refer to three different rhythms. The first is associated with "the inherent mobility of the brain and cord" as well as with the rhythmic pulsation of the cerebrospinal fluid. The second is r e l a t e d to the s y s t o l i c c a r d i a c rhythm, and the last with respiration. The " p r i m a r y r e s p i r a t o r y rhythm" of the osteopaths does not
JC Ferr6 and JY Barbin : The osteopathiccranial concept: factor fiction? correspond to respiration but to the contractions of the brain and the rhythmic pulsations of the CSF. It is obviously inadmissible that the brain and cord exhibit movements of a peristaltic nature like other v i s c e r a , for they are not contractile. It is equally difficult to believe in a hypothetical pulsation of the CSF since this, like all fluids, is incompressible and has a low pressure (of the order of 0.4 Newtons, around 400 g/m2). Such a pressure, even assuming cyclical variation, is situated in a much too feeble range to have any effect on the sutures. Moreover, the CSF is contained in the non-extensible suba r a c h n o i d space, t r a v e r s e d by fibrous strands contributing to the tethering of the brain and resistant to any expansion. Finally, the cerebrospinal fluid, secreted by the choroid plexuses and drained by the foramina of the 4th ventricle into the subarachnoid space (Fig. 6), enjoys its own security system. This consists of: (1) the subarachnoid cisterns, local enlargements of the subarachnoid space. This system functions in such a manner that dilatation of a channel slows the speed of fluid flow and reduces its pressure (loss of thrust); (2) the cerebello-medullary cistern, situated between the cerebellum and the medulla oblongata. (3) the arachnoid granulations, villous and avscular evaginations of the s u b a r a c h n o i d space into the superior longitudinal sinus and the diploic veins, drain the excess of CSF and function as safety valves (waste gate).
On the other hand, the movements that certainly affect the brain correspond to systolic expansion in pulsations synchronous with the heart rate. It is also undeniable that there are modifications of the intracranial pressure, and therefore of the cerebral volume, related to respiration. We have already mentioned that these are due to the effects of pressure changes during emptying of the jugular veins into the right heart cavities. Likewise, neurosurgeons confirm that vascular compression produces cerebral turgescence, a maneuver employed to demonstrate cerebrospinal rhinorrhea since compression of the CSF then leads to its evacuation through t r a u m a t i c b r e a c h e s of the skull base. However, these pulsations of the brain, real as they are, cannot be transmitted to the calvarium, which has long been well and truly synostosed in the adult. What the osteopath feels when palpating the skull are pulsations related to the vascular system of the scalp, with its known abundance and tendency to hemorrhage on injury, or else his own capillary pulsations. Conclusion It emerges from this objective and impartial recital of the facts that the theory of "primary respiration" has no s c i e n t i f i c basis and totally contradicts the findings of physics, anatomy, physiology, biomechanics and clinical experience.
