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I kind of know where the hypoglossal nerve is located when I look at the diagram, but I'd like to know how far is the nerve from the skin and where is the closest area to the skin before and right after it's branching?
Is there any video or schema showing the location of the Hypoglossal nerve relative to skin and not the skeleton?
From this pic. I can't really tell the closest location of being able to detect the nerve near the skin.
The following image of a cadaver shows the hypoglossal highlighted:
You can see the flap of skin/muscle that has been removed to get an understanding of the thickness of tissues separating the nerve from outside the body.
Additionally, here is an image showing a person receiving an operation. You can see the relative depth of the nerve fairly well:
Source: Cambridge University Press
When it comes to the innervation of the head and neck, we know it’s all about the cranial nerves. Explaining all of them at once would mean too much complex information and facts, so in this particular article, we will be focused on the anatomy and the clinical importance of the last, but certainly not the least, 12th cranial nerve called the hypoglossal nerve (CN XII).
The hypoglossal nerve is purely motor nerve, which innervates extrinsic tongue muscles and geniohyoid muscle. It originates from it motor nucleus found in the ventral medulla oblongata.
|Type||General somatic efferent (GSE) (motor)|
|Origin||Hypoglossal nucleus in medulla oblongata|
|Branches||Meningeal branch, superior root of the ansa cervicalis, and terminal lingual nerves|
|Field of innervation||The intrinsic muscles of the tongue |
Three extrinsic muscles of the tongue:
- the genioglossus muscle
- the hyoglossus muscle
- the styloglossus muscle
This article will discuss the anatomy and function of the hypoglossal nerve.
Jahangir Moini , Pirouz Piran , in Functional and Clinical Neuroanatomy , 2020
Hypoglossal nerves (XII)
Hypoglossal nerves (XII) is only motor, controlling tongue movements. These nerves originate in the motor nuclei of the medulla, passing through the hypoglossal canals of the occipital bone, to reach the tongue muscles. Each hypoglossal nerve exits the cranium and curves, reaching the skeletal tongue muscles. It provides voluntary motor control of tongue movements. Normal function of CN XII is verified by having a patient stick out the tongue. If there is damage to these nerves, the tongue will move toward the side of the lesion.
Name the cranial nerves that are mostly involved in each of the following: a.
Regulating the heart rate and digestive activity
List the cranial nerves that are exclusively sensory and state their functions.
Which cranial nerve is the only one that extends beyond the head and neck areas?
Which cranial nerve carries sensory signals from the largest area of the face?
Research on Hypoglossal Nerve Stimulation
Studies have shown that patients with sleep apnea who respond best to Upper Airway Stimulation share similar characteristics. One,their body mass index is no greater than 32 kg/m2. Two, they all share certain findings on a short evaluation procedure called drug-induced sleep endoscopy.
Body mass index is a measure reflecting body weight and height, and a value of 32 is approximately 235 pounds for someone who is 6 feet tall. Drug-induced sleep endoscopy is performed in the operating room, with the goal of learning more about what is causing blockage of breathing in the throat in someone with obstructive sleep apnea.
While more research needs to be done on hypoglossal nerve stimulation , the newest obstructive sleep apnea treatment , this first system (Upper Airway Stimulation) seems to be worth considering. If you are looking for a new sleep apnea treatment , consult your doctor to find out whether hypoglossal nerve stimulation could be the right option for you.
Dr. Eric Kezirian
Inspire and Upper Airway Stimulation are trademarks of Inspire Medical Systems, which is not affiliated with this website.
Though it is a rare occurrence that any damage can be caused to the Hypoglossal Nerve, it is mostly gunshot wounds and compression caused by tumors can result in damage to this nerve. Also, surgical damage, medullary stroke, multiple sclerosis, Guillain-Barre syndrome and infections like sarcoidosis can be a root cause of damage of the Hypoglossal Nerve.
Since this nerve shares a close proximity with nerves, arteries, and veins, the damage outcome is not isolated. For example, when damage occurs to any of the facial and trigeminal nerves from a clot of the vertebrobasilar artery, it could faintly affect the hypoglossal nerve too, hence resulting in complexities of speaking, eating and chewing. A motor neuron disease is a common disease that can have a harmful impact on the Hypoglossal Nerve.
During any injuries caused to the Hypoglossal Nerve, the tongue will be wasted away and will not stick out straight. A doctor will examine the tongue and its movements, if found to be protruding to one side, it could be because of fasciculation (bag of worms) or wasting (atrophy). If the tongue appears to be weak it may result in slurred speech, alveolar stops, velar nasals, dental stops etc. sometimes the tongue strength by an examiner by feeling the tongue from pressing of the cheek, this is done by poking the tongue from inside the cheek.
While a surgeon is attempting to restore the function of a facial nerve, the Hypoglossal Nerve comes in use to be connected to the facial nerve. In case of trauma or cancer (focal facial nerve damage), there are attempts made to repair the connecting nerve fibers from the Hypoglossal Nerve to the facial nerve.
Hypoglossal nerve (CN XII)
The hypoglossal nerve (twelfth cranial nerve, CN XII, latin: nervus hypoglossus) is a motor nerve that supplies general somatic efferent fibers to all intrinsic skeletal muscles of the tongue and to three of the four extrinsic tongue muscles.
The general somatic efferent neurons of the hypoglossal nerve originate in the hypoglossal nucleus, which is a cluster of motor neurons located in the medulla oblongata, in the hypoglossal trigone (a raised area in the rhomboid fossa).
The axons of these motor neurons traverse the reticular formation, pass medial to the inferior olivary nuclei, and loop laterally. Ten to fifteen bundles of fibers exit the brainstem and collect to create the hypoglossal nerve.
The hypoglossal nerve appears on the ventral surface of the brainstem between the pyramid and the olivary eminence in the anterolateral sulcus. The hypoglossal nerve passes through the hypoglossal canal and exits the canal through the hypoglossal foramen, and descends medially to the internal jugular vein and internal carotid artery.
After exiting the hypoglossal canal, the hypoglossal nerve is joined by the superior root of the cervical plexus, which is formed by the anterior root of 1st cervical spinal nerve (C1). These fibers are distributed before the hypoglossal nerve reaches the tongue.
As the hypoglossal nerve descends it passes caudally posterior to the vagus nerve in the neurovascular bundle behind the pharynx. At the level of the angle of the mandible the nerve emerges from behind the posterior belly of the digastric muscle. Then in an arch-shaped bend of 90 degrees, the nerve turns rostrally and medially. The hypoglossal nerve runs forward at the upper edge of the carotid triangle, traverses the external carotid artery at the level of the division of the lingual artery and reaches the tongue between the hyoglossus and mylohyoid muscles.
In the tongue, the hypoglossal nerve distributes into the lingual branches, which innervate all the intrinsic tongue muscles and three of the four extrinsic tongue muscles: the genioglossus, styloglossus, and hyoglossus muscles.
A cranial foramen allows important nervous and circulatory tissue to travel throughout the head and neck region.
The following headings list the singular or paired name, location, and the structures that pass through each aperture.
Some foramina are the result of mirrored notches in multiple bone articulations that, when put together, form a circular hole in this case, the information is repeated.
Foramina of the Frontal Bone
- Paired supraorbital foramen (or supraorbital notch) inferior rim of the upper orbit supraorbital nerve, artery, and vein.
- Single foramen cecum shared between the frontal crest of the temporal bone and the ethmoid bone, between the cranium and nasal cavity emissary veins.
Parietal Bone Foramina
- Paired parietal foramen at the back of the parietal bone, close to where the parietal bones meet parietal emissary vein and occasionally a branch of the occipital artery.
Foramina of the Temporal Bones
- Paired stylomastoid foramen between the styloid and mastoid processes of the temporal bone facial nerve (CN VII) and stylomastoid artery.
- Paired jugular foramen shared between the temporal and occipital bones, close to the foramen magnum inferior petrosal and sigmoid sinusus, glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), and arterial branches of the meningial blood supply.
- Paired internal acoustic meatus close to the ear facial nerve (CN VII), acoustic nerve (CN VIII), and branch of the basilar artery.
- Paired carotid foramen opens into a channel (carotid canal) through which the internal carotid artery and internal carotid plexus pass. The carotid canal ends at another aperture (f. lacerum) in the sphenoid bone.
Foramina of the Occipital Bone
- Singular foramen magnum large hole at the skull base that connects the brain stem to the spinal cord spinal and vertebral arteries, meninges, and accessory nerve (CN XI).
- Paired jugular foramen shared between the temporal and occipital bones, close to the f. magnum glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), inferior petrosal and sigmoid sinuses, and arterial branches of the meningial circulation.
- Paired anterior condyloid foramen above the f. magnum hypoglossal nerve (CN XII) and branch of the ascending pharyngeal artery.
- Singular posterior condlyar foramen close to the f. magnum occipital emissary vein. This text includes photographs that show where several occipital foramina are located.
Foramina of the Sphenoid Bone
- Paired optic foramen back of the eye socket optic nerve (CN II) and ophthalmic artery. In the image, this aperture is labelled as number 2 (1 = ethmoid foramen 3 = superior orbital fissure 4 = sulcus for lacrimal sac 5 = infraorbital sulcus 6 = inferior orbital fissure 7 = infraorbital foramen).
- Paired superior orbital fissure between the lesser and greater wings of the sphenoid bone oculomotor nerve (CN III), trochlear nerve (CN IV), branches of the opthalmic nerve, abducens nerve (CN VI), and ophthalmic veins.
- Paired foramen rotundum greater wings of the sphenoid bone maxillary nerve.
- Paired foramen sphenopalitinum shared between the sphenoid and palatine bones nasopalatine nerve, greater palatine nerve branches, and the sphenopalatina artery and vein.
- Paired inferior orbital fissure shared with the maxilla bone (the opening into the maxilla is called the infraorbital f.) below the lower ridge of the eye socket on either side of the nose infraorbital nerve, artery, and vein.
- Paired foramen ovale greater wing of the sphenoid bone mandibular nerve, accessory meningeal artery, and emissary vein.
- Paired foramen Vesalius not always present vein of Vesalius.
- Paired foramen spinosum greater wing of the sphenoid bone branch of the mandibular nerve and middle meningeal artery.
- Paired foramen lacerum the end of the shared carotid canal that begins at the carotid f. (temporal bone) located next to the sella turcica nerve and artery of the pyterygoid canal, internal carotid artery, and emissary vein.
Foramina of the Ethmoid Bone
- Cribriform plate foramen most of us have around 20 of these small holes that form the sieve-like portion of the ethmoid bone above the nasal cavity multiple fibers of the olfactory nerve (CN I).
- Paired anterior ethmoidal foramen back of the eye socket anterior ethmoidal nerve, artery, and vein.
- Paired posterior ethmoidal foramen back of the eye socket posterior ethmoidal nerve, artery, and vein.
Nasal Bone Foramen
Foramina of the Palatine Bones
- Paired greater palatine foramen palatine nerve, artery, and vein.
- Paired foramen sphenopalitinum shared between the palatine and sphenoid bones nasopalatine nerve, nasal branches of the greater palatine nerve, and the sphenopalatina artery and vein.
- Lesser palatine foramen set of four foramina shared between the palatine and maxilla bones at the back of the hard palate lesser and greater palatine nerves, and the lesser palatine artery and vein.
Foramina of the Zygomatic Bones
- Paired zygomatico-orbital foramen orbital processes of the zygomatic bones – from here, a single canal splits to exit via two holes (see below image). These two holes are the paired zygomaticotemporal and zygomaticofacial foramina that convey similarly-named facial nerves and vessels.
Foramina of the Maxillae
- Paired infraorbital foramen part of the inferior orbital fissure shared with the sphenoid bone that ends at the infraorbital f. of the maxilla infraorbital nerve, artery, and vein.
- Lesser palatine foramen set of four foramina shared between the maxilla and palatine bones at the back of the hard palate lesser and greater palatine nerves, and the lesser palatine artery and vein.
Foramen of the Mandible
- Paired mandibular foramen ramus of the mandible (lower jaw) inferior alveolar nerve and vessels.
- Paired mental foramen chin (body of mandible) mental nerve and vessels.
Anatomy of the nerve
Nerves are filamentary structures, that is, cables or bundles of nerve fibers formed by axons (motor fibers) and dendrites (sensitive fibers).
Its covering is made of connective tissue , which are classified as follows:
- Epineuro : corresponds to the fibrous layer and helps to fill the spaces between the fiber bundles.
- Perineuro : corresponds to a sheath of cells that lines the bundles of fibers.
- Endoneuro : located inside the perineurium, it is another layer of fibers.
They are considered appendages of the axons of nerve cells, which make the connections between the nervous system and the human body.
Structure and Location
The hypoglossal nerve is the twelfth cranial nerve (XII) and innervates all extrinsic and intrinsic muscles of the tongue, except for the palatoglossus. The hypoglossal nerve emerges from the medulla oblongata in the preolivary sulcus where it separates the olive (olivary body) and the pyramid (medullary pyramid).
It goes on to traverse the hypoglossal canal and, upon emerging, it branches and merges with a branch from the anterior ramus of C1. It passes behind the vagus nerve and between the internal carotid artery and internal jugular vein which lies on the carotid sheath. After passing deep to the posterior belly of the digastric muscle it proceeds to the submandibular region to enter the tongue.
Hypoglossal nerve: Schematic image of the hypoglossal nerve and the structures it innervates.
Origin of the Cranial Nerves
The first two cranial nerves such as olfactory nerve I and the optic nerve II originate from the cerebrum while the cranial nerves III – XII arise from the brain stem.
12 pairs of cranial nerves, their nature, distribution and functions are described below:
Nature: Pure Sensory nerve
Origin and Distribution: It is originated from the olfactory lobe of cerebrum and extended to the mucus membrane of the nazal cavity. It is capable of regeneration.
Functions: It transmits the sense of smell from the nasal cavity.
Nature: Sensory nerve
Origin and Distribution: It is originated from the optic lobe of the midbrain and extended to the retinal wall of the eye.
Functions: It carries visual information from the retina of the eye to the brain.
Nature: Motor nerve
Origin and Distribution: It is originated from the ventro-lateral side of the midbrain and innervates the eye muscles.
Functions: It controls the movements of eye muscles. It also helps the constriction of the pupil, and regulates an open eyelid
Nature: Motor nerve
Origin and Distribution: It is originated from the dorso-lateral side of the midbrain and innervates the eye muscles.
Functions: It controls the rotational movements of eye muscles.
Origin and Distribution: It is originated from lateral side of the medulla obolongata and divides into the following three branches and extended to the different organs.
(i) Opthalmic: It innervates the eye lid and the mucus membrane of the nazal cavity. It is sensory in nature.
Functions: It transmits senses from the eye-lid and the mucus membrane to the brain.
(II) Maxillary: It is extended to eye-lid, upper and lower jaws. It is sensory in nature.
Functions: It transmits senses from the eye-lid, upper and lower jaws to the brain.
(III) Mandibular: It is extended to the the muscles of the ventral buccal cavity. It is a mixed type nerve.
Functions: It controls the movement of lower jaw and transmits heat, pressure and touch senses to the brain.
Origin and Distribution: It is originated from lateral side of the medulla obolongata and innervates the lateral rectal eye muscle.
Nature: It is mixed type nerve.
Functions: It is responsible for lateral movement of the eye.
Origin and Distribution: It is originated from the lateral side of the medulla obolongata and having two branches for different organs.
(i) Palatine: It is extended to the roof of the buccal cavity.
Nature: It is sensory in nature.
Functions: It is responsible for taste of food.
(ii) Hyomandibular: It is extended to the buccal cavity and lower jaw.
Nature: It is mixed in nature.
Functions: It is responsible for the taste of food and controls nick membrane.
VIII. Auditory/ Vestibulocochlear
Nature: Sensory nerve
Origin and Distribution: It is originated from lateral side of the medulla obolongata and extended to the inner ear.
Functions: It is responsible for hearing and maintains balance of the body.
Nature: It is mixed nerve
Origin and Distribution: It is originated from the lateral side of the medulla obolongata and extended to the tongue and pharynx.
Functions: It is responsible for taste and movment of the pharynx.
Origin and Distribution:It is originated from the lateral side of the medulla obolongata and it divides into the following four branches:
(i) Laryngeal: It is extended to the larynx.
Nature: It is mixed in nature.
Functions: It regulates the activities of the larynx.
(ii) Cardiac: It is extended to the heart.
Nature: It is mixed in nature.
Functions: It regulates the activities of the heart.
(iii) Gastric: It is extended to the wall of the stomach.
Nature: It is mixed in nature.
Functions: It regulates the activities of the stomach.
(iv) Pulmonary: It is extended to the lungs.
Nature: It is mixed in nature.
Functions: It regulates the activities of the lungs.
XI. Spinal Accessory
Origin and Distribution: It is originated from the floor of the medulla obolongata and extended to the pharynx, larynx and neck.
Functions: It maintains the muscle movement of related organ such as shoulder and neck.
Origin and Distribution: It is originated from the lateral side of the medulla obolongata and innervates the tongue and neck.