Dear Friends:
    Kermaline's question in response to Esther's observations about the
possibility of "baby whiplash" due to a precipitous labor was about TMJ
anatomy and function.
    The TMJ is two joints; one between the mandibular condyle and a disc, and
the other between that disc and the mandibular or temporal fossa. The
sticking out prominence of the mandible (jawbone)  fits in the hole or fossa,
cushioned by the disc. The mandible is one bone that articulates (or joins)
with two separate bones, the two temporal bones that don't connect with each
other, one on each side of the head. The temporal bones have a subtle rhythm
of motion (the cranio-sacral rhythym) which mimics the cranio-sacral rhythm
of the ilia.
    The TMJ allows for two motions: rolling forward, and dropping down.
    To open the jaw, the mandible begins to swing around the point of its
condyle as it also slides forward and down on the disc, which in turn slides
forward and down in the hole (fossa) of the temporal bone.
    There are many muscles, ligaments, and nerves that are part of TMJ
movement: the lateral pterygoid muscle, the masseter muscle, the medial
pterygoid muscle, the temporalis muscle, the trigeminal nerve system (which
is the largest sympathetic nerve in the body), the retrodiscal elastic
tissue, and the stylomandibular ligament.
    The retrodiscal elastic tissue keeps the disc in place; if this tissue is
pulled over the condyle, it gets stretched and holds things in a
non-physiologic position. The lateral pterygoid muscle is a key muscle to
open the mandible, and it comes off the sphenoid bone. The sphenoid bone is
connects with every other bone in the head. including the occiput. So what
happens to the sphenoid has impact on what happens in the TMJ
    When the occipital-cranial base is damaged, which can easily happen with
birth, there are many symptoms that can occur. In babies, this can be
clenching, colic, seizures, irritability, digestive problems.
    In addition, the sacrum influences the activity of the occiput, which
impacts on the function of the sphenoid which can impact on the function of
the TMJ. Trauma can go in either direction: a rough birth can damage the
cranial base or the sacrum, which affects all the related structures. Or the
mandible can be damaged from vigorous suctioning or intubation and this can
have impact on the function of the TMJ which can send the sphenoid out of
whack, and consequently shift the occiput and thence the sacrum.
    This is all written from a cranio-sacral therapy perspective. We are
wonderfully made and tremendously interconnected.
    How do other disciplines describe this?
    Warmly,
Nikki Lee RN, MSN, Mother of 2, IBCLC, ICCE, CSTP
Elkins Park (a suburb of Philadelphia, Pennsylvania,  northeastern USA)

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