Inion
Citation, DOI, disclosures and article data
Citation:
Hacking C, Thibodeau R, Dmytriw A, et al. Inion. Reference article, Radiopaedia.org (Accessed on 24 Jan 2025) https://doi.org/10.53347/rID-40397
Permalink:
rID:
40397
Article created:
Disclosures:
At the time the article was created Craig Hacking had no recorded disclosures.
View Craig Hacking's current disclosures
Last revised:
Disclosures:
At the time the article was last revised Ryan Thibodeau had no financial relationships to ineligible companies to disclose.
View Ryan Thibodeau's current disclosures
Revisions:
9 times, by
7 contributors -
see full revision history and disclosures
Systems:
Sections:
Synonyms:
- External occipital protuberance
- Inia
- Inions
The inion (plural: inia/inions) is the tip of the external occipital protuberance (EOP), the midline bony prominence in the occipital bone from which the ligamentum nuchae and trapezius muscle attach. It is usually easily palpable 1.
Clinical importance
The inion the surface marking of the internal attachment of the tentorium cerebelli. It is one of the skull landmarks, craniometric points for radiological or anthropological skull measurement.
Enthesopathic change of this insertion typically occurs due to flexion at the ligamentum nuchae and trapezius.
In a contemporary context, this finding is thought to develop from postures assumed when viewing mobile phones and other similar devices, although there are numerous occupational and biomechanical possibilities 2.
References
- 1. Clinically Oriented Anatomy. Lippincott Williams & Wilkins. ISBN:1451119453. Read it at Google Books - Find it at Amazon
- 2. Shahar, D., Sayers, M.G.L. Prominent exostosis projecting from the occipital squama more substantial and prevalent in young adult than older age groups. Sci Rep 8, 3354 (2018). https://doi.org/10.1038/s41598-018-21625-1
Incoming Links
Articles:
- Skull landmarks
- Trapezius muscle
- Tuberculum sellae - occipital protuberance line
- Occipital spur
- Superficial layer of the deep cervical fascia
- Temporal bone (modified Stenvers view)
- Galea aponeurotica
- Ligamentum nuchae
- Cervical spine ligaments
- Axial plane for imaging of the brain
- Craniocervical fixation
- Occipital bone
Related articles: Anatomy: Head and neck
- skeleton of the head and neck
-
cranial vault
- scalp (mnemonic)
- fontanelle
-
sutures
- calvarial
- facial
- frontozygomatic suture
- frontomaxillary suture
- frontolacrimal suture
- frontonasal suture
- temporozygomatic suture
- zygomaticomaxillary suture
- parietotemporal suture (parietomastoid suture)
- occipitotemporal suture (occipitomastoid suture)
- sphenofrontal suture
- sphenozygomatic suture
- spheno-occipital suture (not a true suture)
- lacrimomaxillary suture
- nasomaxillary suture
- internasal suture
- basal/internal
- skull landmarks
- frontal bone
- temporal bone
- parietal bone
- occipital bone
- skull base (foramina)
-
facial bones
- midline single bones
- paired bilateral bones
- cervical spine
- hyoid bone
- laryngeal cartilages
-
cranial vault
- muscles of the head and neck
- muscles of the tongue (mnemonic)
- muscles of mastication
-
facial muscles
- epicranius muscle
- circumorbital and palpebral muscles
- nasal muscles
-
buccolabial muscles
- elevators, retractors and evertors of the upper lip
- levator labii superioris alaeque nasalis muscle
- levator labii superioris muscle
- zygomaticus major muscle
- zygomaticus minor muscle
- levator anguli oris muscle
- malaris muscle
- risorius muscle
- depressors, retractors and evertors of the lower lip
- depressor labii inferioris muscle
- depressor anguli oris muscle
- mentalis muscle
- compound sphincter
-
orbicularis oris muscle
- incisivus labii superioris muscle
- incisivus labii inferioris muscle
-
orbicularis oris muscle
- muscle of mastication
- modiolus
- elevators, retractors and evertors of the upper lip
- muscles of the middle ear
- orbital muscles
- muscles of the soft palate
- pharyngeal muscles
- suprahyoid muscles
- infrahyoid muscles
- intrinsic muscles of the larynx
- muscles of the neck
- platysma muscle
- longus colli muscle
- longus capitis muscle
- scalenus anterior muscle
- scalenus medius muscle
- scalenus posterior muscle
- scalenus pleuralis muscle
- sternocleidomastoid muscle
-
suboccipital muscles
- rectus capitis posterior major muscle
- rectus capitis posterior minor muscle
- obliquus capitis superior muscle
- obliquus capitis inferior muscle
- accessory muscles of the neck
- deep cervical fascia
-
deep spaces of the neck
- anterior cervical space
- buccal space
- carotid space
- danger space
- deep cervical fascia
- infratemporal fossa
- masticator space
- parapharyngeal space
- stylomandibular tunnel
- parotid space
- pharyngeal (superficial) mucosal space
- perivertebral space
- posterior cervical space
- pterygopalatine fossa
- retropharyngeal space
- suprasternal space (of Burns)
- visceral space
- surgical triangles of the neck
- orbit
- ear
- paranasal sinuses
- upper respiratory tract
- viscera of the neck
- blood supply of the head and neck
-
arterial supply
-
common carotid artery
- carotid body
- carotid bifurcation
- subclavian artery
- variants
-
common carotid artery
- venous drainage
-
arterial supply
- innervation of the head and neck
-
cranial nerves
- olfactory nerve (CN I)
- optic nerve (CN II)
- oculomotor nerve (CN III)
- trochlear nerve (CN IV)
-
trigeminal nerve (CN V) (mnemonic)
- trigeminal ganglion
- ophthalmic division
- maxillary division
- mandibular division
- abducens nerve (CN VI)
- facial nerve (CN VII)
-
vestibulocochlear nerve (CN VIII)
- vestibular ganglion (Scarpa's ganglion)
- glossopharyngeal nerve (CN IX)
- vagus nerve (CN X)
- (spinal) accessory nerve (CN XI)
- hypoglossal nerve (CN XII)
- parasympathetic ganglia of the head and neck
- cervical sympathetic ganglia
- greater occipital nerve
- third occipital nerve
-
cervical plexus
- muscular branches
- longus capitis
- longus colli
- scalenes
- geniohyoid
- thyrohyoid
-
ansa cervicalis
- omohyoid (superior and inferior bellies separately)
- sternothyroid
- sternohyoid
- phrenic nerve
- contribution to the accessory nerve (CN XI)
- cutaneous branches
- muscular branches
- brachial plexus
- pharyngeal plexus
-
cranial nerves
- lymphatic drainage of the head and neck
- embryological development of the head and neck
Unable to process the form. Check for errors and try again.