Anatomy of the orbit of the orbit... · Anatomy of the orbit Prof. Pia C Sundgren MD, PhD Department of Diagnostic Radiology, Clinical Sciences, Lund University, Sweden Lund University

Lund University / Faculty of Medicine / Inst. Clinical Sciences / Radiology / ECNR Dubrovnik / Oct 2018

Anatomy of the orbit

Prof. Pia C Sundgren MD, PhD

Department of Diagnostic Radiology, Clinical Sciences, Lund University, Sweden


Lay-out

• brief overview of the basic anatomy of the orbitand its structures

• the orbit is a complicated structure due to its embryological composition

• high number of entities, and diseases due to its composition of ectoderm, surface ectoderm andmesoderm

Recommend you to read for more details


3 layers: - neuroectoderm (retina, iris, optic nerve) - surface ectoderm (lens)- mesoderm (vascular structures, sclera, choroid)

3 spaces: - pre-septal

extraconal

- post-septal

intraconal

3 motor nerves: - occulomotor (III)

- trochlear (IV)

- abducens (VI)

3 x 3




• CT and / or MR

• IOM plane

• thin slices

• axial and coronal projections

• CT: soft tissue and bone windows

• MR: T1 pre and post, T2, STIR, fat suppression, DWI (?)

Imaging technique



Rooffrontal bonelesser wing of the sphenoid bone

Floormaxillazygomatic bone

Medial wallethmoid bone (lamina papyracea)lacrimal bonemaxilla

Lateral wallgreater wing of the sphenoid bonezygomatic bone


Orbital fissures and optic canal

Superior orbital fissure: lesser and greater wingof the sphenoid bone

Inferior orbital fissure: greater wing of sphenoid the maxilla and palatine bone

Optic canal: at the apex of the orbit in the sphenoid bone


Superior orbital fissure

• cranial nerves (CN) III, IV, and VI

• lacrimal nerve

• frontal nerve

• nasociliary nerve

• orbital branch of middle meningeal artery

• recurrent branch of lacrimal artery

• superior orbital vein

• superior ophthalmic vein


Mnemonic of the order in which the nervespassing through the Sup. orbital fissure

”Lazy French tarts sit naked in anticipation”

Lacrimal nerve (branch of CN V1)Frontal nerve (branch of CN V1)Trochlear nerve (CN IV)Superior division of the oculomotor nerve (CN III)Nascociliary nerve (branch of the CN V1)Inferior division of the oculomotor nerve (CN III)Abducens nerve ( CN VI)

Courtesy Dr C Romanovski


Inferior orbital fissure

• infraorbital nerve

• zygomatic nerve

• parasympathetics to lacrimal gland

• infraorbital artery

• infraorbital vein

• inferior ophthalmic veinbranch to pterygoid plexus


The infraorbital sulcus (SIO) crosses the floor of theorbit and carries • infraorbital artery• infraorbital vein• infraorbital nerve from the inferior orbital fissure to the infraorbital foramen

NOTE this is a route of spread for infection or maxillary tumors to the orbit and the skull base

Infraorbital sulcus and foramen


Optic canal

• optic nerve

• ophthalmic artery

• central retinal vein

• dural sheath

www.clinicalgate.com

Annulus of Zinn


Optic nerve

• cranial nerve II

• transmits visual information from the retina to the brain

• composed of retinal ganglion cell axons and support cells



Courtesy Dr A.I Ranchod, SA

Calcifications of optic nerve


optic n. glioma

optic n. meningioma


- preseptal

- postseptal intraconal extraconal

“septum”

“retrobulbar space”- clinical term


Mnemonic intraconal lesions of the orbita

”Mel met Rita mending hems on poor Charlies grave”

Melanoma Meningeoma pseudotumor

Metastasis Hemangioma cellulitis

Retinoblastoma Optic glioma Graves disease

Courtesy Dr P Maly, Malmoe


Postseptal extraconal

Postseptal intraconal


preseptalsoft tissue/edema

”Septum”- med.palpebral lig.

Courtesy M Annertz/Lund


Episcleral infiltration

Preseptal infiltration

Chemosis of the eyeswelling of the tissue that lines the eyelids and surface of the eye (conjunctiva)



lens anterior chamberchoroid

sclera retina

Scleritischronic, painful, inflammatory diseasecharacterized by edema and cellularinfiltration of the scleral and episcleraltissues (outermost coat of the eye)


Cryptophthalmos

A rare congenital anomaly in which the skin is continuous over the eyeball, with absence of eyelids. Eye might benormal or abnormal.


Retinal detachment

occurs when the intraretinal space persists


Buphthalmos enlargement of the globe due toincreased intraocular pressure

• secondary to obstruction of the Schlemm canal

• isolated / associated - Sturge Weber - NF type 1- cobblestone lissencephaly

Buphthalmos and coloboma




Courtesy Dr. S Andronikou, SA


Buphthalmos and coloboma

Coloboma congenital fissures in the globe due to incomplete closure of the embryonic optic fissure

0.5 to 0.7 per 10,000 births

iris coloboma: defect in anterior portion of the embryonic fissure cleft in the iris pigment epithelium

retinochoroidal coloboma: arise from the wall of the globe

optic nerve coloboma: insertion of the optic disc


Courtesy Dr A Rossi, IT


protrusion of the uveal tissue through a thinningof the sclera - weak point in the eyeball

Staphyloma

severe axial myopia, more common posteriorlyanteriorly more common after infection or trauma

M Tsatsos and T Eke Eye (2007) 21, 857–858



Retinoblastoma

Clinical findings

• leukoaria (white pupillary reflex) “cat eye reflex”due to replacement of vitreous humor by a white mass

• reduced vision, eye pain, strabismuswww.retinoblastoma.com


Persistent hyperplastic primary vitreous



Bulb laceration


www.pinterest.com

Annulus of Zinna fibrous ring formed by the common origin of the 4 rectus muscles

Extra ocular muscles

• develop in situ

• input from respective cranial nerve (III, IV,VI) 1 month gestation

• fully developed at 6 months gestation


Muscle Action Cranial Nerve

Lat. rectus moves eye laterally VI ( n.abducens)

Med. rectus moves eye medially III (n. oculomotorius)

Sup. rectus elevate, turns it medially III

Action of the extra-ocular muscles


Muscle Action Cranial Nerve

Inf. rectus depresses, turns medially III

Inf. oblique elevates turns laterally III

Sup. obligue depresses, turns laterally IV (n. trochlearis)

Action of the extra-ocular muscles


Thyroid ophthalmopathy

m. rectus inferior > med >sup > lat


The major nerves

Cranial nerves – motor III oculomotor nIV trochlear nVI abducens n

II optic nerve

Cranial - sensory nervesV trigeminal n – ophthalmic n V1 (the upper eyelid, the conjunctiva and cornea of the eye) and its branches




Ophthalmic nerve

nasociliary nervefrontal nervelacrimal nerve

branches


The ophthalmic artery enters the orbit on the inferolateral side of the optic nerve and gives off the central retinal arteryand posterior ciliary arteries near the orbital apex

The ophthalmic artery

http://www.retinareference.com/anatomy/first branch of the a. int car.


Involvement of the ophthalmic artery in giant cell arteritis

Copyright © 2016 British Society for Rheumatology


Kumar JB et al EyeNet Magazine May 2015

The orbital veins

NOTE the superior ophthalmic vein is a communicationbetween facial vein and cavernous sinus “Danger Zone”


Ophthamology.standford.edu

T1 weighted, without fat suppression, showing bilateral enlarged superior ophthalmic veins in carotid cavernous stula


Orbital phlebograhy

showing left-sided venousfistula

Courtesy Dr. P Maly, Malmoe


Take home message

complicated anatomy and embryology

high number of possible diseases

For correct diagnosis

important to differentiate between the preseptal andpostseptal space

important to differentiate between extraconal andintraconal

Lund University / Faculty of Medicine / Inst. Clinical Sciences / Radiology / ECNR Dubrovnik / Oct 2018PC Sundgren, Spine Infect… ASSR’ 12

Thank you

Documents

Anatomy of the orbit of the orbit... · Anatomy of the orbit Prof. Pia C Sundgren MD, PhD Department of Diagnostic Radiology, Clinical Sciences, Lund University, Sweden Lund University