Cranial Nerves Flashcards
What is the function of the olfactory nerve?
1 The olfactory nerve enables us to receive sensation of smell.
2 Olfactory sensations also stimulates responses the digestive function through connections of the brain with the vagus nerve.
3 Emotional responses and memories are also activated through connections with the lambic system and associated areas of the brain.
4 increases the sense of taste thanks to the capacity of the nose to distinguish hundreds of substances even in minute quantities.
Describe the pathway of the olfactory nerve
- receptors within the olfactory mucosa in the upper part of the nasal cavity receive sensation of smell
- fibres travel up through the cribriform plate of the ethmoid bone
- fibres emerge onto the surface of the ethmoid bone and enter the olfactory bulbs (extensions of the forebrain lying on the surface of the cribriform plate and they sinapse
- neurological impulses are transmitted posteriorly from the olfactory bulbs along the olfactory tracts to the forebrain
What could be the causes of anosmia?
^Fracture of the cribriform plate with damage of the olfactory fibres passing through it
^displacements or restrictions of the ethmoid or its adjoining bones, including frontal bone, sphenoid and vomer
^membranous tension impinging on the olfactory fibres as they pass through the dura on the superior surface of the cribriform plate
^congestion in the nasal cavity blocking receptors
^blockage of the nasal passage due to cold or nasal allergy can cause transient anosmia
^ eccessive dryness of the nose can also cause transient anosmia
What is another important function of the olfactory nerve pathway apart from carrying olfactory sensations?
It provides the most significant pathway for drainage of the cerebrospinal fluid.
Other outlets of cerebrospinal fluid are:
Arachnoid villi
Spinal nerve exit
Cranial nerve exit
What type of nerve is the olfactory nerve?
Purely sensory
What type of nerve is the optic nerve?
Purely sensory
What are the symptoms of vagal dysfunction?
Vagotonia and underactivity of the vagus
What are the symptoms of vagotonia?
Hypotension Bradycardia Cold hands and feet Cold and clammy skin Severe fatigue
What are the symptoms of under active vagus?
Reduced activity of stomach (gastroparesis)
Nausea
Heartburn
Abdominal pain
Stomach spasms
Disturbance of the awareness of hunger and digestion
and the symptoms of overactive sympathetic system:
Arrhythmia, increased heart rate, shortness of breath, difficulty with swallowing and speech
What is the effect of healthy level of vagal tone?
Lowering blood pressure Lowering heart rate Reduced risk of stroke and cardiovascular diseases Improved digestion Enhanced blood sugar regulation Enhanced stomach acid secretion Enhanced digestive enzymes production Reduced sympathetic stimulation
What is low vagal tone associated with?
Cardiovascular conditions and stroke Depression Diabetes Chronic fatigue Cognitive impairment Inflammatory conditions like: rheumatoid arthritis, inflammatory bowel disease, endometriosis Autoimmune thyroid conditions Lupus
What are the natural ways to stimulate the vagus nerve?
Deep breathing Relaxation Yoga Submerging the tongue Cold water face immersion Healthy diet Probiotics Social interaction Soft gentle contact to the eyeballs
With which other cranial nerve and part of the brain does the olfactory nerve connect?
With the vagus nerve, stimulating digestion
With the lambic area stimulating emotional responses and memories
How does the process of vision work?
The light enters the lens, the aqueous humour and the vitreous humour of the eyeball, is focused by the lens onto the receptors.
What are the receptors of the retina?
Rods for the light and dark vision 125 millions in the retina
Cones for the color vision 7 millions
Where are the central vein and central artery of the retina?
They travel through the centre of the optic nerve
How many fibres does an optic nerve have?
Around 1 million
What’s the pathway of the optic nerve?
The optic nerve travels posteriorly from the back of the eyeball
Passes through the optic canal (between the body and the lesser wing of the sphenoid) and emerges medial to the anterior chinois process of the sphenoid, anterior to the pituitary gland.
Here the 2 optic nerves come together to form the optic chiasm in which medial fibres from each optic nerve decussate (cross over to the other side) and continue posteriorly as the optic tract
With which cerebral structures does the optic tract connect?
It gives off branches to the geniculate body of the thalamus enabling visual reflexes
Continues as optic radiation to the visual cortex in the calcarone fissure of the occipital lobe
What is particular about the optic nerve?
The optic nerve is considered an extension of the brain as the eyeball is completely enveloped within the meninges, the sclera (white) of the eye being a continuation of the meningeal membrane
How do you know the site of neurological damage within the optic pathway?
Damage to the optic nerve, between the eyeball and the chiasma, would cause a loss of sight in the affected eye
Damage to the centre of the optic chiasma (ex: pituitary tumor)may lead to tunnel vision (dysfunction of medial fibres on both sides, which carry information from the lateral part of the visual field)
Damage in the optic tract would lead to loss of vision in the medial fibres of one eye and lateral of the other, reducing the visual field on the opposite side
What would a damage to the optic nerve cause?
If it’s located between the eyeball and the chiasma, would cause loss of vision in the affected eye
What would damage to the optic chiasma cause?
If the centre of the chiasma is affected, there will be tunnel vision, as the dysfunction will affect the medial fibres of both sides (ex: pituitary tumor) which perceive the lateral part of the visual field
What would be the effect of damage to the optic tract?
Loss of vision of the medial side of the eye and lateral vision of the opposite eye
What can be the source of disturbance of the optic nerve function?
Cranial bone displacement (particularly involving the sphenoid)
Nerve compression (particularly optic canal and sella turcica)
Membranous tension
Neuritis
Why are cranial nerve III IV and VI often described together?
Because their main function is the movement of the eyeball and they coordinate their activity when directing the gaze in different directions
What is the function of cranial nerve III oculomotor?
Movement of the eye (up, middle, down, up and out)
Rising of the upper eyelid
Control of intrinsic muscles of the eye for pupil constriction and lens accommodation
What’s the pathway of cranial nerve III?
Oculomotor nerve emerges from the anterolateral midbrain
Runs on the floor of the middle cranial fossa
Passes through the cavernous sinus
Enters the orbit through the superior orbital fissure
Passes through the tendinous ring and
Gives branches to the superior rectus, inferior rectus, medial rectus, inferior oblique muscles and to the levator palpebrae superioris muscle
The parasympathetic fibres branch away from the main nerve within the posterior orbit to synapse with the ciliary ganglion, and they continue into the eyeball as short ciliary nerves to control the intrinsic muscles of the eye for pupil constriction and lens accommodation.
What’s the pathway of cranial nerve IV?
The trochlear nerve emerges from the posterolateral midbrain
Runs along the floor of the middle cranial fossa
Passes through the cavernous sinus
Enters the orbit through the superior orbital fissure
Goes directly to the superior oblique muscle which directs the gaze down and out, without passing through the tendinous ring
What’s the pathway of cranial nerve VI?
The abducent nerve emerges from the anterolateral pons
Runs along the floor of the middle cranial fossa
Enters the orbit through the superior orbital fissure
Passes through the tendinous ring and goes to the lateral rectus muscle to control the moment of the eye in order to look laterally
What is the clinical effect of an injury to the Oculomotor nerve?
Injury may lead to strabismus (squints) and diplopia (double vision) on looking in whatever direction which involves the use of the superior, inferior and medial rectus muscles.
The affected eye can only move laterally and downward and will tend to be directed laterally since the lateral rectus muscle will now act unopposed.
Injury affecting the levator palpebrae superioris may lead to ptosis (drooping) of the eyelid, but because the eyelid is also supplied by the sympathetic fibres to the tarsal muscle, the effect will be only partial.
Injury affecting also the parasympathetic branch of the nerve will lead to a persistently dilated pupil on the affected side, potentially causing photophobia, and may affect accommodation of the eye to near and far vision
What is the effect of injury on the parasympathetic component of oculomotor nerve?
Injury affecting the parasympathetic branch of the nerve will lead to a persistently dilated pupil on the affected side, potentially causing photophobia, and may affect accommodation of the eye to near and far vision
What’s the clinical effect of injury to the trochlear nerve?
Injury may lead to strabismus (squint) and diplopia (double vision) on trying to look down and out to the affected side as one eye will move in that direction whilst the other will continue to look forward, up or down.
What’s the clinical effect of an injury to the abducent nerve?
Injury may lead to strabismus (squint) and diplopia (double vision) on trying to look laterally to the affected side as one eye will move in that direction whilst the other will not turn, but rather continue to look straight ahead, leading to transient diplopia, to the point that usually patient will adapt by turning the head instead of the eyes.
The eye will tend to be directed medically (convergent strabismus) since the medial pull of the medial rectus will now be unopposed by the paralysed lateral rectus muscle.
What would be the craniosacral treatment for squints?
Squints are often addressed through an operation at an early age. This may resolve the squints successfully, but will not address the other imbalances that may be contributing to the squint.
When there are clearly evident cranial or membranous distortions, the cases are very responsive to cranio sacral integration.
Craniosacral treatment involves:
Clear understanding of the nerves, muscles and other structures involved and identification of the dysfunction
Accurate diagnosis of the location and source of disturbance by tracing the nerve pathways with informed awareness
Craniosacral balancing of the orbit, cranium, membranes and any other structure involved
Identify and address patterns throughout the body that may be contributing to the disturbance in the eye
Addressing birth trauma
What are the functions of the Trigeminal nerve?
The Trigeminal nerve is primarily associated with receiving sensation from the face: skin of the face from the top of the head to the lower jaw and throat, eyeball, conjunctiva, lacrimal gland, ear, external auditory canal, nasal cavity, oral cavity, sinuses, teeth, TMJ, anterior tongue, nasopharynx, meningeal membranes of anterior and middle cranial fossa, including parts of the tentorium.
Proprioceptive input from the muscles of mastication, of facial expression, extrinsic muscles of the eye and eyeball.
The motor branch supplies the muscles of mastication enabling chewing and other movements of the lower jaw, and several small muscles:
Tensor tympani, tensor veli palatini, anterior belly of the digastric, mylohyoid.
Where il the Trigeminal nerve emerging?
It emerges from the pons
Where is the trigeminal ganglion located?
It bulges out of each side of the pons, and it is contained within the cavum Trigeminale, a membranous cave encapsulating the ganglion and its roots, at the apex of the petrous portion of the temporal bone.
What is the function of the trigeminal ganglion?
It is the site of synapse for sensory fibres travelling in from the periphery. Preganglionic fibres of the three sensory divisions of the trigeminal nerve: ophthalmic, maxillary and mandibular nerves pass into the ganglion, where they synapse before relaying their sensory input into the brain stem via postganglionic fibres.
What are the sensory divisions of the Trigeminal nerve?
Ophthalmic, maxillary, and mandibular division
What is the pathway of the ophthalmic division of Cr.V?
After emerging from the pons and synapsids in the trigeminal ganglion, the ophthalmic division
Travels along the floor of the middle cranial fossa together with CIII CIV and CVI,
Passes through the cavernous sinus together with CIII CIV and CVI,
Enters the orbit through the superior orbital fissure together with CIII CIV and CVI,
Within the orbit it gives off
a sensory branch to the lacrimal area (lacrimal branch)
a sensory branch to the cornea, iris, ciliary muscles and pupil dilator muscles, that travels further on to the nasal cavity and passes to the frontal, ethmoidal and sphenoidal sinuses (nasociliary branch)
a main sensory branch which emerges at the supraorbital notch and receives sensation from the frontal area: forehead and frontal sinuses.
Where does the ophtalmic division receive sensation from?
From the upper portion of the face, the forehead, the eyes, upper eyelids, lacrimal glands, nose, nasal cavity and frontal, ethmoidal and sphenoidal sinuses
What is the pathway of the maxillary division of the trigeminal nerve?
After emerging from the trigeminal ganglion,
It travels anteriorly along the floor of the middle cranial fossa
Turns inferiorly through the floor of the cranium via the foramen rotundum
Emerges to the inferior surface of the cranium and turns anteriorly to enter the orbit through the inferior orbital fissure
Passes along a groove on the floor of the orbit until it deepens to become a tunnel
It gives off an alveolar branch to the upper teeth
A branch to the maxillary sinus
And emerges at the surface of the face through the infraorbital foramen, below the inferior rim of the orbit
Where does the maxillary division of the Trigeminal nerve receive sensation from?
It receives sensation from the middle portion of the face:
From the lower eyelid to the upper lip, including the side of the nose
From the mucous membranes of nose and nasopharynx,
From the maxillary sinus
From the roof of the mouth and the upper teeth
What is the pathway of the mandibular branch of the trigeminal nerve?
After emerging from the trigeminal ganglion,
It turns downward through the foramen ovale
Gives off a recurrent meningeal branch which passes back up to the meninges of the middle and anterior cranial fossa through the foramen spinosum (together with the middle meningeal artery) as well as to the mastoid air cells
At the inferior surface of the cranium, the mandibular branch divides in 4 branches:
Auriculo-temporal branch to the skin of the external ear, external auditory canal, tympanic membrane and temporal area
Buccal branch to the buccinator muscle
Lingual branch to the anterior 2/3 of the tongue
Inferior alveolar branch which enters the mandibular foramen on the medial surface of the ramus of the mandible, travels inside the mandible giving off alveolar branches to the lower teeth and emerges at the mental foramen on the anterior surface of the mandible
The motor division also travels with the mandibular branch
Where does the mandibular branch receive sensation from?
From the lower portion of the face including the mandible,
From the lower teeth, gums and lip
The anterior 2/3 of the tongue
TMJ
Mastoid air cells
Skin of the ear, external auditory canal and tympanic membrane
Temporal area
What are the branches of the mandibular division?
Recurrent meningeal nerve Auriculo-temporal nerve Buccal nerve Lingual nerve Inferior alveolar nerve
Where does the auriculo-temporal nerve receive sensation from?
Auriculo-temporal nerve receives sensation from the skin of the external ear, external auditory canal, tympanic membrane and temporal area
Where does the buccal nerve receive sensation from?
Buccal nerve receives sensation from the buccinator muscle
Where does the lingual nerve receive sensation from?
Receives sensation of touch from the anterior 2/3 of the tongue
Where does the inferior alveolar nerve receive sensation from?
From the teeth, gums, lower lip, TMJ
Where does the recurrent meningeal branch ( Nervous spinosus) receive sensation from?
Anterior and middle cranial fossa
Mastoid air cells
What is the pathway of the motor division of the trigeminal nerve?
It emerges from the pons
Travels beneath the trigeminal ganglion
Passes out through the foramen ovale together with the sensory component of the mandibular branch of CV
Joins the sensory component of the mandibular division and gives off branches to the muscles of mastication and other small muscles, travelling together with the sensory fibres in the different nerves that carry both sensory and motor fibres
What are the muscles supplied by the motor component of the CV?
2 nerves to Temporalis muscle 1 nerve to Masseter muscle 1 nerve to Lateral pterygoid muscle 1 nerve to Medial pterygoid muscle 1 nerve to mylohyoid muscle and anterior belly of digastric muscle of the throat The nerve to the medial pterygoid muscle also gives off 2 branches to Tensor tympani muscle Tensor veli palatini muscle
What are the clinical considerations for a dysfunction of the motor component of the CV?
- The tensor veli palatini is involved in opening the Eustachian tube which drains the middle ear. Overstimulation of the mandibular division of CV (including teeth grinding) may be involved in recurrent middle ear infections and glue ear
- the tensor tympani dampens vibrations by tensing the tympanic membrane. Overstimulation could affect acuity of hearing, therefore hearing disorders and learning difficulties. And exposure to loud noises can lead to involuntary contraction of tensor tympani and stapedius which can be accompanied by earache, fluttering sensations or a sense of fullness of the ear. Hyperacusis may also be caused by tension of the tensor tympani muscle.
Craniosacral engagement with the trigeminal nerve and other associated structures including energy drive to the middle ear and the tensor tympani and stapedius muscles in particular, may be beneficial.
What is trigeminal neuralgia?
It consists in the intermittent recurrent episodes of extremely severe facial pain which come and go unpredictably in sudden shock like attacks, generally described as stabbing, shooting, excruciating, burning or strong electric shocks. It affects one or more of the three areas of the face, most commonly maxillary or mandibular area. It may occur only occasionally or frequently throughout the day and the night, lasting from a few seconds to a couple of minutes, for weeks, months or years.
Attacks can be triggered by the slightest stimulus.
What is the cause of trigeminal neuralgia?
The cause is unknown, there are theories …
- The most common medical theory is that the pain is caused by pressure on the trigeminal nerve, probably on the ganglion. Compression causes irritation, and irritation can cause damage to the myelin sheath. The nerve then becomes more excitable and erratically fires pain impulses
- compression along the pathway caused by injury, infection, a tumor or multiple sclerosis
- latent herpes virus, with the virus staying dormient in the ganglia
Trigeminal neuralgia is likely to be aggravated at times of stress or other causes of sympathetic stimulation
What’s the Craniosacral approach to trigeminal neuralgia?
- engage and see quality, shock, trauma and specific restrictions and allow the expression and resolution
- allow the inherent treatment process to address the system needs, enabling greater mobility and fluent function of the system as a whole and of the specific areas
- explore especially:
- area around trigeminal ganglion at the apex of the petrous portion, by ensuring free mobility of temporal bone and sphenoid
- membranes surrounding the trigeminal ganglion, check if there is tension, whether from contraction, inflammation, emotional tension or previous episode or meningitis
- trace back the pathways of the affected division of the nerve with informed awareness
- identify and address any trauma to the face and the cranium as a whole.
- enhance the immune system through usual progression of the craniosacral process
- address any other factor that may be relevant: virus, stress, injury, medications, toxicity.
What are the functions of the CVII Facial nerve?
Motor to the muscles of the face
Special sense of taste from anterior 2/3 of tongue
Sensory from external ear and mastoid region
Parasympathetic to the glands of the face
What is the pathway of the Facial nerve?
The facial nerve
Emerges from the lower pons
It immediately enters the petrous portion of the temporal bone at the internal auditory meatus together with CVIII
It then travels through the facial canal within the petrous portion of the temporal bone (we sort, motor and parasympathetic together)
At the geniculum, where the ganglion for the sensory fibres is, the canal turns 90 degree angle
Several branches separate from the main trunk within the facial canal
- parasympathetic division to the glands of the upper face
- motor branch to the stapedius
- sensory branch to the tongue for special sense of taste
- parasympathetic branch to glands of the lower face
The main trunk emerges at the stylomastoid foramen:
* gives off motor branches to the digastric and stylohyoid muscles of the throat
* gives of a motor branch to the muscles behind the ear (posterior auricolari nerve)
The main motor branch travels anteriorly across the angle of the jaw
Passes through the parotid gland, without supplying it
Within the parotid gland the nerve divides in two divisions:
Temporal-facial
Cervico-facial
And then in 5 main branches to the various muscles of the face:
Temporal branch
Zygomatic branch
Buccal branch
Mandibular branch
Cervical branch
What are the 5 main branches of the facial nerve? What is their function?
Temporal branch Zygomatic branch Buccal branch Mandibular branch Cervical branch
What is the frequent condition affecting the CVII?
Bell’s Palsy. It’s the flaccid paralysis of the muscles of the face, usually unilateral, due to damage or impingement of the facial nerve.
Can be transient in case of mumps (during parotitis there can be a compression of the motor branch of the facial nerve) and it usually recover spontaneously once the infection, inflammation and swelling of the parotid glad have passed.
What are the symptoms of Bell’s palsy?
- Flaccid paralysis of the muscles of the affected side of the face: the muscles droop and become expressionless
- one side of the face remains immobile
- the smile is crooked and one-sided
Tears tend to trickle from the affected side, as the lower lid no longer contains them
Saliva may dribble from the affected side of the mouth
Food tends to collect in the cheek
What are the causes of Bell’s palsy?
It’s by definition of unknown origins. With unilateral facial paralysis there is sometimes a clearly definable cause, involving damage within or around the cranium.
At other times it may arise spontaneously, maybe following a viral infection
Causes of damage include stroke, tumor, surgery (acoustic neuroma), parotid gland surgery, head injury, nerve inflammation, middle ear infections, latent herpes virus infection.
Transient episodes may be brought on by cases of mumps, through compression of the facial nerve passing through the swollen and inflamed parotid gland
What’s the craniosacral approach to Bell’s palsy?
- Engage with the system and allow to express and resolve any restriction or imbalance that may arise in the cranium, face or elsewhere
- identify the site of damage, through the symptom picture and tracing the nerve pathway with informed awareness and therapeutic attention
- engage with the muscles of the face, utilizing soft tissue stimulation and fascial unwinding to release and revitalize the muscles and helping to stimulate the nerve
- release restrictions within the parotid gland
- integration of the area and the matrix
Tracing the nerve pathway may lead to the internal auditory meatus in case of acoustic neuroma or nerve damage following an operation for acoustic neuroma
With which cranial nerves is the nucleus of the CVII connected?
CII CIII CIV CV CVI CVIII Coordinating movements of the eyelids and eyeballs, including blink reflex in response to bright light or loud sounds
What is the pathway of the parasympathetic division of the facial nerve?
The parasympathetic component arises from its own nucleus within the pons and travels with the main trunk as far as the geniculum (Nervus intermedius)
It then separates in two divisions:
1 - First division passes through the pterygoid canal together with sympathetic fibres as Vivian nerve to synapse with the pterygopalatine ganglion, the postganglionic fibres supplying the lacrimal gland and the mucus glands of nose, mouth and sinuses
2 - the second division joins the lingual nerve (branch of the mandibular nerve of CV) passes to the submandibular ganglion where it synapses with postganglionic fibres to the submandibular and sublingual glands (saliva and mucus)
What is the craniosacral approach to the dysfunction of the secretion of mucus and saliva in the sinuses, nose and submandibular and sublingual glands?
Overall integration of imbalances and tension in the whole body and in the cranium
Free mobility of the palatine bones
Maxillae
Vomer
Sphenoid
Especially in consideration that both sympathetic and parasympathetic fibres pass through the pterygopalatine ganglion
Where is the pterygopalatine ganglion located?
In the pterygopalatine fossa located between
Lateral pterygoid plates of the sphenoid posteriorly
Palatine bones medially
Maxilla anteriorly
What is the function of the sensory division of the CVII facial nerve?
Special sense of taste from the anterior 2/3 of the tongue
Sensory afference from the skin of the ear, external auditory canal, tympanic membrane mastoid and temporal areas behind the ear
What is the pathway of the sensory component of the CVII facial nerve?
The geniculate ganglion is located within the facial canal at the geniculum.
The sensory branch to the tongue (together with the second division of the parasympathetic fibres) diverges from the facial canal between the geniculum and the stylomastoid foramen and follows an intricate pathway, passing through the middle ear (chorda tympani nerve) and continuing through another bony canal emerging in the infratemporal fossa, between the mandible and the lateral pterygoid plates. It then joins the lingual nerve (CV mandibular division which carries general sensation from the tongue) through which it reaches the tongue.
During the portion of its pathway (together with parasympathetic fibres) from the geniculate ganglion and the lingual nerve it is known as chorda tympani
What are the principal consequences of facial nerve dysfunction?
Bell’s palsy and other disturbances of muscles of face
Disturbed secretion of the lacrimal glands and of the glands and mucous membranes of the eyes, nose, mouth, sinuses and face (parasympathetic division)
Disturbances in hearing and learning (nerve to stapedius muscle)
Disturbances to taste (chorda tympani)
Factors which may influence facial nerve function
Bony restrictions or imbalances, particularly involving the temporal and sphenoid bones
Membranous tension along the nerve pathway
Disturbance to the nerve root at the internal auditory meatus or at the pons
Acoustic neuroma or effect of surgery because of acoustic neuroma
How to detect the point of damage of the facial nerve?
If symptoms only involve the motor branches, this would suggest that the injury is outside the facial canal
If symptoms affecting the muscles of the face are accompanied by disturbance of taste and of the parasympathetic supply to the glands of the face (dry eye, facial secretion…) this would indicate damage proximal to the emergence of the relevant branches (acoustic neuroma, damage to the upper portion of CVII)
If only the parasympathetic supply to the glands is affected without disturbance of motor function, this might suggest disturbance to the pterygopalatine ganglion, perhaps involving the palatine bones, the relationship between palatines and sphenoid, or balances of the ANS
Symptoms affecting taste only, might involve middle ear infections
What is the function of CVIII?
The vestibulo-cochlear nerve enables us to hear and to maintain our balance.
What is the pathway of CVIII?
Emerging from the anterolateral pons,
The two divisions enter together into the internal auditory meatus to the inner ear
How does the cochlear division work?
Sound waves entering the external auditory canal cause vibration of the tympanic membrane
These vibrations are transmitted through the malleus, incus and staples of the middle ear to the oval window
Through which they are transmitted to the cochlea of the middle ear
Hair cells of the organ of corti within the cochlea convert those vibrations into neurological stimuli
Which are transmitted to the brain via the cochlear division of the vestibulo-cochlear nerve
How does the vestibular division work?
Vestibular sensations (balance and equilibrium) are picked up by tiny hair-like receptors within the vestibular system (located in the ampullae of the semicircular canals and the macula of the saccule and utricule). The movement of the fluid in these structures generates stimuli which are translate in neurological impulses and transmitted to the CNS through the vestibular division of CVIII
Where are ampullae of the semicircular canals and the macular of the saccule and utricule? What is their function?
They’re in the inner ear. They contain hair-like receptors who get stimulated by the movements of the fluid within the canal. These stimuli get converted in neurological impulses and reach the brain through the vestibular division of CVIII
What is the effect of dysfunction to the cochlear division?
Hearing problems, deafness and tinnitus
What is the consequence of dysfunction in the vestibular division of CVIII?
Dizziness, vertigo and motion sickness
What are the causes of damage to CVIII?
Inner ear infections, Ménière’s disease,meningitis, encephalitis, head injuries, prolonged exposure to loud noise, acoustic neuroma, ototoxic antibiotics (gentamicin, streptomycin)
What are the main functions of CIX glosso-pharyngeal nerve?
Special sense of taste from posterior third of tongue
General sensation of pain, temperature and touch from tongue, pharynx and middle ear
Parasympathetic to the parotid gland
Motor to stylopharyngeus muscle
With which nerves is the glosso-pharyngeal nerve mainly connected?
With CX and CXI . Their coordination plays an important role in swallowing and speaking
Where does the general sensory afferent fibres of the glosso-pharyngeal nerve receive their information from?
Posterior third of tongue Pharynx, tonsils and palate Middle ear cavity and Eustachian tubes Skin behind ears Meninges of the posterior cranial fossa Carotid sinus and carotid body
What nerve is responsible of the secretion of saliva from the parotid gland?
CIX - glosso-pharyngeal nerve
What’s the pathway of the glosso-pharyngeal nerve?
The glosso-pharyngeal nerve emerges from the anterolateral medulla
Passes down immediately through the jugular foramen (together with CX and CXI and jugular vein)
It has 2 sensory ganglia (superior and inferior) located within the Jugular Foramen
Below the inferior ganglion it gives off several branches to the periphery
What are the branches of the glosso-pharyngeal nerve?
Tympanic nerve
Sensory component: tympanic membrane, middle ear, external auditory canal, mastoid air cells
Parasympathetic component: continue through the middle ear as lesser petrosal nerve, passing through the temporal bone, through the middle cranial fossa, and out through the foramen ovale to the otic ganglion where they synapse with the postganglionic fibres to the parotid gland
Motor nerve to stylopharyngeal muscle (swallowing)
Carotid branch - visceral afference from the carotid artery and carotid body regarding blood pressure, carbon dioxide levels, pH levels from baroceptors and chemoceptors in the carotid sinus
Lingual nerve - special sense of taste
Sensory branches - general sensation of pain, temperature and touch from the posterior third of tongue, tonsils, pharynx and palate
What is the effect of disturbances to the glosso-pharyngeal nerve?
Problems with swallowing, speaking, saliva secretion, sensation of touch and taste especially from posterior third of tongue
What are the main functions of the vagus nerve?
The vagus nerve is vital for the body:
Parasympathetic to the thoracic and abdominal viscera (until ascending colon)
80% of it is composed by sensory fibres from the viscera
Special sense of taste and touch from epiglottis
Motor component to muscles of pharynx, larynx and palate
With which nerves is the vagus nerve connected?
It has connections with very many other neurological structures, including glosso-pharyngeal nerve and accessory for swallowing and speaking, but also facial nerve with a wide range of consequences both physical and psycho-emotional including mood and social interactions
What is the pathway of the vagus nerve?
Emerges from the anterolateral medulla
Has two sensory ganglia located within and immediately below the jugular foramen
Passes down immediately through the jugular foramen (with CIX CXI and jugular vein)
Provides branches to meninges, epiglottis, pharynx, larynx, palate and throat
Continues down the neck through the carotid sheath (with carotid artery and jugular vein)
Gives off branches to the organs of the thorax (heart and lungs)
Passes through the oesophageal opening in the diaphragm
Divides in an anterior trunk and posterior trunk supplying stomach, spleen, liver, pancreas, gall bladder, kidneys, small intestine, ascending colon
What are the ganglia of the vagus nerve?
Superior vagal ganglia is located within the jugular foramen and receives sensation from pharynx, larynx, palate, epiglottis, ears and meninges
Inferior vagal ganglion is located just below the jugular foramen and is the site of synapse for the fibres carrying sensation from the viscera
What are the branches of the vagus nerve in the neck and throat?
- Meningeal branch to the meninges of the posterior cranial fossa
- Auricular branch to the external auditory canal and tympanic membrane
- Sensory branch to the epiglottis for special sense of taste and general sensation of touch
- Parasympathetic branches to mucous membranes of pharynx and larynx
- Motor branches to different muscle of the neck and throat
- Superior laryngeal branch and recurrent laryngeal branch - motor to the larynx for speech
- parasympathetic branches to the heart
What is particular about the recurrent laryngeal nerve?
It travels down the throat and neck, hooking under the aortic arch on the left and the subclavian artery on the right, before returning all the way up to the larynx
What is the function of the recurrent laryngeal nerve?
Motor supply to the muscles of the larynx, it is involved in speaking
They pass between trachea and esophagus and speech may be affected by thyroid tumor or surgery, or by any restriction in the structures of throat and neck
Where is the site where fascial restrictions may affect particularly the vagus nerve?
Carotid sheath, a fascial tube within which the vagus nerve travels in the neck together with the carotid artery and the jugular vein
In which way the inner action of the colon is clinically significant?
The vagus nerve supplies only the ascending colon whilst transverse and descending colon are supplied by the pelvic splanchnic nerves coming from S2-4.
What is the consequence of vagal dysfunction?
A dysfunction fo the vagus can have a multitude of effects
It can be involved in
a range of heart conditions,
respiratory disorders including asthma
A wide variety of visceral dysfunction including colic, peptic ulcer, IBS, Chron’s disease, indigestion, diarrhea, constipation
Autism and freeze response
Where is the most susceptible site of functional disturbance for the vagus nerve?
Damage could occur anywhere along its pathway, but the most susceptible site of disturbance is at its emergence from the brain stem in the posterior cranial fossa around the foramen magnum and at the Jugular foramina (compression of occipital-mastoid suture is very common)
Another frequent site of restriction is the carotid sheath
What are the main means of disruption of vagus function?
Injury or restriction to the efferent supply
Sensory feedback from the viscera or other sources
Disturbance within the brain and brain stem
Toxicity
Psycho-emotional factors, including sympathetic overstimulation and ANS imbalance
What are the causes of injury or restriction of the vagus nerve?
Compressive and other traumatic forces on the brain stem or the cranial base
Inflammation sclerosis and contraction within the posterior cranial fossa around the brain stem
Impingement within the caroti sheath
Overstimulation at the passage through the cardiac, pulmonary and celiac sympathetic plexi
Overstimulation when passing through the diaphragm
Damage elsewhere along the pathway
How can the sensory feedback from the viscera and other sources affect the vagus nerve?
Auditory, visual, olfactory, emotional, physical and visceral stimulation can affect the vagus function.
A common source of vagus overstimulation is the feed back caused by an imbalance in the digestive tract
What are the toxins that block the actin of acetylcholine in the parasympathetic division and the vagus nerve?
Botox and mercury
How is the microbiome influenced by the vagus?
The vagus nerve can modulate a response and initiate inflammation when the organisms part of the microbiome are pathogenic, whilst the presence of healthy bacteria in the guts creates a positive feedback loop through the vagus nerve increasing its tone
What is know as poly vagal theory?
Stephen Porges
What are the factors of disturbance of the vagus nerve?
Birth trauma Compressive forces Structural injuries Meningeal inflammation Fascial restriction Feedback from the viscera or other sources Sympathetic overstimulation Toxins
What are the steps to go back to a healthy vagal function?
1 recognition of the vagal symptom picture
2 identify the underlying causes of vagal dysfunction (structural, inflammatory, digestive, emotional, traumatic, perinatal)
3 releasing restrictions (bones membranes) around the brainstem
4 release of carotid sheath ( fascial unwinding of the neck)
5 reducing stimulation of cardiac pulmonary and celiac plexi via heart centre and solar plexus
6 working with the viscera to reduce inappropriate sensory feedback and relieve visceral symptoms such as spasm, diarrhea, pain, constipation and poor digestion
7 Settling the sympathetic nervous system
8 Reducing stress factors, managing lifestyle
9 eliminating toxins
10 overall craniosacral integration
What are the functions of the CXI accessory nerve?
Motor to sternocleidomastoid muscle and trapezius
Motor to pharynx, larynx and palate, assisting the vagus
Why is the accessory nerve often clinically significant?
Because of the mechanism of interaction:
SCM muscle tension can cause jugular foramina compression
The jugular foramina compression can cause vagal impingement
The vagal impingement can cause tension of the SCM muscle
What are the main causes of disturbance to the CXI?
SCM muscle tension
Birth trauma and compression of the jugular foramina
Head and neck injuries that cause imbalances in the cranial base and upper cervical area
What are the 2 divisions of the CXI?
Cranial division emerging from the anterolateral medulla
Spinal division emerging from C1-C4
What is the pathway of the spinal division of the accessory nerve?
After emerging from the spinal chord at the level of C1-C4
The 4 roots join together as a single trunk that
Passes up inside the vertebral canal within the dural membrane
Enters the cranium through the foramen magnum
Joins the cranial division for a short tract
Passes out of the cranium through the jugular foramen
Provides motor supply to SCM and trapezius muscles
What is the pathway of the cranial division of the vagus nerve?
After emerging fro the medulla
Joins the spinal division briefly
Passes out through the jugular foramen
Separates from spinal division and merges with the vagus nerve travelling to the pharynx, larynx and palate
What is the most relevant portion of the accessory nerve in clinical practice?
The spinal portion: the SCM muscle attaches on both the occipital and the temporal sides of the occipitomastoid suture, so tension in the muscle will tend to compress the suture and the jugular foramen.
Tension and contraction of SCM muscle is very common, when unilateral it’s most commonly attributable to birth trauma, when bilateral it may be attributable to stress and psycho-emotional tension held in the neck and shoulders
What is the main cause of infant torticollis?
Birth trauma: when a baby is born through the birth canal, the birth process involves a significant twisting of the head and neck as they negotiate the shape of the pelvic outlet. Combined with the compressive forces of the birth process, this frequently leaves some degree of twist embedded in the base of the skull and neck, compressing the occipitalmastoid suture and jugular foramen, the twist often extending throughout the whole body
What is a frequent find in autistic children?
Extreme rigidity in the upper cervical and cranial base area, which appears to be substantially contributing to their autistic tendencies. The symptoms will often improve steadily as the rigidity on the neck and the pressure on both vagus nerves is released
What is the function of the hypoglossal nerve CXII?
It is a purely motor nere supplying the intrinsic and extrinsic muscles of the tongue, with a small contribution to the suprahyoid muscle of the throat
What is the pathway of the hypoglossal nerve?
After emerging from the anterolateral lower medulla
It passes through the hypoglossal canal, located within the medial wall of the foramen magnum, in the conciliar portion of the occiput
Emerges at the inferior surface of the base of the cranium, immediately anterior to the occipital condyles
And passes forward below the angle of the mandible to provide motor supply to the extrinsic and intrinsic muscles of the tongue
It also provides a small branch to the ansa cervicalis, a cervical nerve loop which together with C1-4 provides motor supply to the suprahyoid muscle of the throat.
What is the most common cause of dysfunction in the hypoglossal nerve?
Distortions, imbalances or compression of the condylar area (often due to the twisting and compressing forces of birth process
Is tongue tie a neurological condition of the hypoglossal?
No, it’s a condition involving the frenulum
What are the neurological causes of speech and language problems?
Cerebral Neurological: Compression of the hypoglossal nerve Dysfunction of CX CXI Structural Muscular Motor function Sensory Auditory Psychological
What nerves provide the sensory innervation of the tongue?
CV sense of touch temperature and pain from anterior 2/3
CIX sense of touch temperature and pain from posterior third
CX laryngeal branch sense of touch temperature and pain from epiglottis
CVII chorda tympani special sense of taste from anterior 2/3
CIX special sense of taste from posterior third
CX special sense of taste from epiglottis
