Cranial Tightness: Myofascial & Neurological Causes
Introduction
Cranial tension is associated with various different conditions from headaches and migraines to temperomandibular joint dysfunction. Myofascial and neurological reflexes can provide an interesting insight into the pathology of these type of disorders. The main clinical points listed in this article are:
(1) A continuous myofascial chain from the cervical dura running anteriorly over the vertex to the dura of the optic nerve. Myofascially this can produce tightness and an entrapment neuropathy along its course.
Suboccipital fascia attaches to spinal dura and galea aponeurotica.
Frontalis muscle attaches to the corrugator supercilii and orbicularis oculi.
Entrapment of the supratrochlear nerve can occur in the corrugator supercilii.
Meningeal tension in the optic nerve from the muscular attachments of Muller's (supratarsal) muscle.
(2) Myofascial continuity of the cranium.
Each muscle intern has a seperate origin and insertion. Listed is both the anatomical connections of each muscle and the anatomy of the connecting fascia. Thereby force transmission from one muscle to another can occur across larger distances than any individual muscles origin and insertion.
(3) Neurological reflexes.
Tightening of certain muscles can not only occur from force transmission but also from neurological reflexes. The two neurological reflexes are:
Eyelid opening stimulates mechanoreceptors in Muller’s (supratarsal) muscle that causes reflex contraction of the levator palpebrae superioris and frontalis. It also stimulates a response in the sympathetic nervous system.
Tongue position: placing the tongue on the roof of the mouth causes reflex contraction of the temporalis and suprahyoid muscles. It also stimulates a response in decreasing vagal tone.
Stretching the suboccipital muscles has been postulated as modulating vagal tone.
(4) Embryological forces acting through the occipitofrontalis on the cranium and occipitoantlal joint.
A developmental model has been hypothesised whereby the occipitofrontalis and SMAS are initimately associated with cranial development. They found during late brain growth tension is created in the occipitofrontalis increasing tension in the SMAS. This model describes the occipitofrontalis/SMAS as being a conduit for a brain derived force directing craniofacial development and jaw rotation. This developmental cranial rotation occurs around the occipitoantlal joint.
Occipitofrontalis & Galea aponeurotica
Occipitofrontalis
Occipitalis: originates from lateral two thirds of the highest nuchal line and mastoid process and extends to the galea aponeurotica.
Frontalis: originates from the galea aponeurotica and extends to the superficial fascia and the skin above the eyes and nose. Muscular attachments are medial fibers attach to the procerus; intermediate fibers attach to the corrugator supercilii and orbicularis oculi; lateral fibers attach to the orbicularis oculi.
Kushima et al (2005) found the occipitalis becomes the galea aponeurotica. Galea aponeurotica is attached to the underside of the frontalis.
Bordoni & Zanier (2014) found the occipitofrontalis continuous posteriorly (via the occipitalis) with the superficial cervical fascia and anteriorly (via the frontalis) with Muller’s (supratarsal) muscle. Muller's (supratarsal) muscle is the smooth muscle fibers of the musculus levator palpebrae.
The superficial fascia envelopes the occipitalis. The temporoparietal fascia (the temporal part of the superficial fascia) envelopes the frontalis. Kim & Lee (2016) found the temporoparietal muscle continuous with the frontalis.
Standerwick and Roberts (2009) found the occipitofrontalis and SMAS initimately associated with cranial development. They hypothesised late brain growth creates tension in the occipitofrontalis increasing tension in the SMAS. This model describes the occipitofrontalis/SMAS as being a conduit for a brain derived force directing craniofacial development and jaw rotation. This developmental cranial rotation occurs around the occipitoantlal joint and is responsible for.
Enlargement of the airways.
Maxillomandibular rotation.
Asymmetric separation of the sphenooccipital synchondrosis (SOS): due to the weight of the brain and anteroposterior tension from the occipitofrontalis/SMAS a pivot point is created at the superior aspect of the SOS. This creates a greater separation of the pharyngeal side of the SOS relative to the endocranial aspect.
The frontalis muscle is attached to the corrugator muscle.
Galea aponeurotica
The Galea aponeurotica is a continuation of the occipitalis and is attached
Anteriorly: frontalis.
Posteriorly the galea aponeurotica transitions to the suboccipital neck fascia by dense fibrous attachments (Dacey et al 2018).
Laterally: the galea aponeurotica continues as the temporoparietal fascia (superficial temporal fascia). Both galea aponeurotica and temporoparietal fascia connect the occipitalis and frontalis despite belonging to the deep and superficial aponeurotic systems respectively (Kim & Lee 2016). The Galea also gives rise to the anterior and superior auricular muscles.
The deep mastoid fascia forms the subgaleal fascia in the temporoparietal region. It separates the temporoparietal fascia from the superficial layer of the deep temporal fascia. Its inferior attachments are posteriorly, with the superficial mastoid fascia it attaches on to the superior nuchal line; anteriorly it blends into the fascia and ligament of the sternocleidomastoid muscle (Hongo et al 2019).
Some authors class the temporoparietalis as part of the galea aponeurotica.
Deep and superficial musculoaponeurotic system
Deep musculoaponeurotic system (DMAS)
The DMAS is composed of the:
Occipitalis.
Galea aponeurotica.
Superficial musculoaponeurotic system (SMAS)
The SMAS is composed of the:
Frontalis.
Temporoparietal muscle.
Temporoparietal fascia.
Superficial fascia.
SMAS becomes continuous with:
Mimetic muscles (zygomaticus major, frontalis, periorbital fibers of the orbicularis oculi, corrugator supercilii and buccinator). The SMAS forms a zone of fusion with the buccinator muscle.
Superficial layer of parotid fascia.
Mandibulocutaneous ligament: fixes the inferomedial aspect of the SMAS (Holger et al 2008).
Superficial mastoid fascia (Hongo et al 2019).
The deep musculoaponeurotic system pulls back the superficial aponeurotic system.
Mimetic muscles
Zygomaticus Major
The Zygomaticus Major originates from the zygoma and inserts on the modiolus. The zygomaticus major interdigitates with the levator anguli oris (Shim et al 2008), buccinator (Shim et al 2008), orbicularis (Spiegal and DeRosa 2005)
Buccinator
The Buccinator originates from the alveolar processes of the maxilla, mandible and temperomandibular joint. It inserts on to the orbicularis oris. It has anatomical connections to the lateral deep slip of the platysma (Hur et al 2015), temporalis (Hur 207), incisivus labii inderioris (Hur et al 2011), zygomaticus major (Shim et al 2008) and parotid duct where it is associated with its function (Kang et al 2006).
Orbicularis Oculi
The Orbicularis Oculi occupies the eyelid spreading onto the temporal region and cheek. It attaches to the nasal part of the frontal bone, frontal process of the maxilla and lacrimal bone. It blends with the occipiofrontalis and corrugator muscle. It also blends with the medial palpebral ligament and forms the lateral palpebral raphe.
The orbicularis oculi acts as a sphincter of the eyelids (and draws them slightly medially), draws the skin of the forehead, temporal region and cheek towards the medial end of the orbit (causing crow's feet), creates a vertical furrowing above the bridge of the nose and can cause lacrimation.
Not only can myofascial trigger points create head pain but orbicularis oculi twitching has been associated with cluster headaches (Bagheri et al 2017) and abnormal blink reflexes have been associated with migraine sufferers (Unal et al 2016).
Metha and Sheshia (1976) found electrical stimulation of the supraorbital nerve (SON) evoked contraction of the orbicularis oculi. Could entrapment of the SON in the corrugator muscle and the fascia of the supraorbital notch cause trigger points in the orbicularis oculi?
Corrugator Supercilii
The corrugator supercilii, except the medial and superior portions, is loacted under the eyebrow (Isse & Elahi 2001).
The corrugator supercilii extends from the medial end of the eyebrow (deep to the occipitofrontalis and orbicularis oculi) attached to the supraciliary arch. It then pass laterally and superiorly to the skin above the middle of the supraorbital region ("corrugator dimple"). Contraction of the muscle causes elevation of the head of the brow and concurrent depression of the lateral aspect of the eyebrow.
The corrugator supercilli blends with the occipitiofrontalis and orbicularis oculi.
Janis et al (2013) found the supratrochlear nerve to pierce, and be compressed, by the corrugator muscle causing migraine headaches.
Superficial fascia & temporoparietal fascia
Superficial fascia posteriorly envelopes the occipitalis then continues with the superficial cervical fascia. The superficial mastoid fascia, which includes the posterior auricular muscle, is continuous with (i) the temporoparietal fascia; (ii) where it fuses at the superior nuchal line, with the superficial cervical fascia (Hongo et al 2019).
Superficial fascia in the neck provides a fascial sleeve for the platysma muscle.
Superficial fascia is bound inferiorly by the mandibulocutaneous ligament before ascending over the parotid fascia and zygomatic major to attach with fibrous consistency to the zygomatic arch (Holger et al 2008).
The modiolus is formed from a fusion of the zygomaticus major, orbicularis oris, SMAS and buccinator (Holger et al 2008).
In the temporal region the superficial fascia becomes the temporoparietal fascia.
The temporoparietal fascia is split into the superficial and deep laminae (Beheiry & Abdel-Hamid 2007).
The temporoparietal fascia envelopes the frontalis and orbicularis oculi.
The temporoparietal fascia is continuous with the superficial mastoid fascia (Hongo et al 2019).
The inferior temporal septum is formed by fusion of superficial (temporoparietal) and deep temporal fascia. It runs inferiorly along the temporalis originating from the lateral corner of the temporal ligament* extending posteriorly towards the superior crus of the helix (Huang et al 2017).
Temporoparietal fascia has tight fibrous fusions with the deep temporal fascia at their insertion into the zygomatic arch but splits from the superficial fascia at this insertion (Holger et al 2008).
Temporoparietal fascia has a thin muscle below the temporal line (Tellioglu et al 2000).
*temporal ligament: between middle and lateral third of eyebrow extending superiorly to the the superficial fascia at the junction of temporoparietal fascia and the galea on the deep surface of the frontalis muscle.
Cervical spine attachments to the dura and galae aponeurotica
The cervical spine attaches to the cervical dura and galae aponeurotica by:
Myodural bridges from the suboccipital fascia.
Meningodural ligaments.
Myodural bridges from the suboccipital fascia
Rectus Capitis Posterior Minor (RCPMi)
The RCPMi extends from C1 (tubercle on posterior arch) to the occiput (medial part of inferior nuchal line & between this and the foramen magnum).
Rectus Capitus Posterior Major (RCPMa)
The RCPMa extends from C2 spinous process to the occiput (lateral part of the inferior nuchal line and just below this line).
Obliqus Capitus Inferior (OCI)
The OCI extends from the C2 spinous process to the C1 transverse process.
Fascial extensions from the suboccipital muscles to the dura
Superiorly the suboccipital fascia runs, via dense fibrous attachments, into the galea aponeurotica (Dacey et al 2018). This gives a continuous fascial change from the scalp to the epidural space. Scaley et al (2015) found attachments of the suboccipital fascia to the dura:
RCPMi
Deep and lateral fascia of the RCPmi continuous with the PAO membrane and the vascular sheath of the vertebral artery.
Posterior Antlo-occipital (PAO) membrane attaches to the posterior border of the foramen magnum. The PAO membrane contains periosteum from the foramen magnum. Anteriorly, the periosteal tissue of the PAO membrane merges with the dura mater at the level just below the atlas. It becomes indistinguishable from the spinal dura at C3.
Deep fascia blends with the PAO membrane and is traversed anteroinferiorly to form the atlantooccipital myodural bridge. This bridging structure enters into the epidural space to fuse with the dorsal meningovertebral ligament of C1 sharing a common insertion site on the posterior surface of the dura mater.
RCPMa & OCI
The epimysium of the RCPma and OCI attaches to (1) in part the C2 lamina (2) but mainly they combined to form fibrous bands that traverses the atlantoaxial interspace.
These fibrous bands passed between two thin strips of the ligamentum flavum.
Once through the ligamentum flavum the fascial bands merges within the epidural space to become the atlantoaxial myodural bridge.
C2 spinal nerve pierces the antloaxial myodural bridge.
Atlantoaxial myodural bridge blends with (1) dorsal meningovertebral ligament of C2. (2) A structure extending from the inferior pole of the posterior arch of C1 and ligamentum flavum of C1/C2 to the antloaxial myodural bridge.
All these soft tissue structures that inserts into the dura were easily separable but maintained a common dural insertion point.
Janis et al (2010) found a tight fascial band surrounding the belly of the obliquus capitis inferior muscle near the spinous process that is potentially capable of compressing the greater occipital nerve.
Meningodural ligaments
Meningodural ligaments are connective tissue bands running mainly from the ligamentum nuchae but also the laminae to the dura. Most commonly from C5 up with the strongest attachments being at C2 (Shi et al 2014)
Soft tissue tightness in the muscles associated with the ligamentum nuchae (upper trapezius, rhomboideus minor, serratus posterior superior, and splenius capitis (Nan Zhen et al 2014)) has been linked to headaches.
Reflex tightening of the SMAS
Reflex muscle tightness in the SMAS can occur via myofascial continuity and neurological reflexes. The two facial structures involved in these reflexes are the:
Eye lid position.
Tongue position.
Suboccipital tightness.
Eye lid position
Mechanoreceptors in Muller’s (supratarsal) muscle is innervated by the trigeminal nerve that terminates in the mesencephalon. Eyelid opening stretches mechanoreceptors in the Müller (supratarsal) muscle to activate the proprioceptive fibers supplied by the trigeminal mesencephalic nucleus. This proprioception induces reflex contractions of the levator palpebrae superioris and frontalis muscles to sustain eyelid and eyebrow positions against gravity (Matsuo et al 2015) and the occipitofrontalis (Bordoni & Zanier, 2014).
There is a direct myofascial link whereby tension in the posterior superficial cervical fascia pulls on and stimulates mechanoreceptors in Muller’s (supratarsal) muscle via the occipitofontalis and levator palpebrae superioris (Bordoni & Zanier, 2014). Muller's (supratarsal) muscle is the smooth muscle fibers of the levator palpebrae superioris attached to the medial and lateral rectus muscle pulley (Kakizaki et al 2010).
This stimulation of mechanoreceptors in Muller’s muscle not only exerts a somatic neurological reflex in tightening muscles in the head but also an autonomic reflex via the locus coeruleus.
Based on these neural connections day to day activities of the eyes creates varying states of arousal and vigilance to facilitate our everyday activities.
Stimulating the mechanoreceptors in Muller's (supratarsal) muscle stimulates the locus coeruleus creating arousal just as not stimulating them can create sedation. For example opening and rubbing the eyes will stimulate mechanoreceptors in Muller's (supratarsal) muscle to evoke vigilance such as when opening our eyes on waking, rubbing our eyes to stay awake or evoking memory retrieval by an upward gaze. Closing our eyes or evoking a downward gaze can decrease stimulation in the mechanoreceptors in Muller’s (supratarsal) muscle to help with sedation of the locus coeruleus such as when meditating or sleeping (Matsuo et al 2015).
The Locus coeruleus is not just associated with day to day vigalence but in pain modulation via locus coeruleus-noradrenergic neuromodulatory system. When dysfunctional it has been associated with a range of chronic pain conditions such as temperomadibular dysfunction (TMD) associated with dysfunction of the noradrendergic arousal system (Monaco et al 2015).
The potential for stimulation of the locus coeruleus via trigeminal afferents is reflected in the sympathetically mediated sweat response in response to prolonged upward gaze (Matsuo et al 2015) a phenomena also associated with trigeminal autonomic cephalagia (Costa et al 2015).
To extend the myofascial chain from the superficial cervical fascia to the Levator Palpebrae Superioris further the Levator Palpebrae Superioris and rectus superior muscle is connected with Tenon’s capsule, where the eyeball is located; particularly, they share extraocular muscles; Tenon’s capsule surrounds the optic nerve where it terminates in the eye, blending with the meningeal tissue. Could it be that tension in the fascial area in the upper cervical spine affects the movement of the eyeball, altering the visual field and posture, or causing dysfunction related to the fascial traction on the optic nerve, with resultant alteration in the ocular reflexes? (Bordoni Zanier 2014).
Tongue position
Schmidt et al (2009) found placing the tongue on the roof of the mouth:
Increased muscle activity in the temporalis and suprahyoid muscles.
Reduction in cardiac vagal tone.
Because there is evidence that even small increases in muscle activity for extended periods can result in the development of pain and dysfunction, the importance of allowing the tongue to rest as frequently as possible seems self-evident.
Suboccipital tightness
The suboccipital fascia has a
Myofascial continuity with cervical dura posteriorly (Scaley et al 2015) coursing anteriorly around the head to Tenon's capsule where it blends with meningeal tissue of the optic nerve in the eye (Bordoni & Zanier, 2014).
Standerwick and Roberts (2009) found late brain growth creates tension in the occipitofrontalis increasing tension in the SMAS. This tension directs craniofacial development and jaw rotation that occurs around the occipitoantlal joint.
Suboccipital release has been hypothesised as affecting vagal tone (Kwan et al 2013 & Giles et al 2008). Could this work in concert with mechanisms affected by tongue and eyelid position?
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