What is the Primary Respiratory Mechanism (PRM), foundation of Cranial Osteopathy ?
The cranial rhythmic impulse (CRI) refers to the palpatory sensation of the widening and narrowing of the skull.
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Normal rate: 8–14 times per minute
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A result of the PRM
The PRM is composed of five elements :
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Inherent motility of the brain and spinal cord
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Brain and spinal cord have an inherent wave-like motion.
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Described as coiling and uncoiling of the central nervous system (CNS).
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Fluctuations of the cerebrospinal fluid (CSF): volume of CSF changes in relation to the cranial rhythmic impulse (CRI).
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Mobility of the intracranial and intraspinal membranes
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The meninges surround the CNS and are made up of the dura, arachnoid, and pia mater.
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A continuous connection is present from the foramen magnum to the cervical vertebrae and second sacral segment.
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These membranes move due to the inherent motility of the brain and spinal cord and fluctuations of the CSF.
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Motion of these membranes causes the cranial bones and sacrum
to move in relation to one another.
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Articular mobility of cranial bones
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Although cranial sutures fuse shortly after birth, they contain small motions that cannot be felt individually.
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An amalgamation of the cranial bones and multiple sutures allow for palpable motion.
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Involuntary mobility of the sacrum between the ilia
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The dural connection between the cranium and S2 of the vertebral column causes sacral movement.
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This dural connection is termed the reciprocal tension membrane (RTM).
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The bones move in rhythm with the motion of the shifting tensions of the RTM.
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The primary physiologic motion is between the articulation of the sphenoid and the occiput called the sphenobasilar synchondrosis (SBS). It moves in a biphasic cycle (flexion and extension) in response to the pull of the reciprocal tension membrane and fluctuations of the CSF.