Show Menu
Cheatography
  1. Home >
  2. Cheat Sheets >

Cranial Nerves Cheat Sheet (DRAFT) by

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Olfactory Nerve (CNI)

General Type
Special sense of smell or olfaction
Course
1. From olfactory receptor neurons in nasal olfactory epithelium in roof of nasal cavity.
2. Olfactory nerves pass via foramina of cribriform plate of ethmoid.
3. Olfactory bulbs (L+R) and olfactory tracts (L+R) enter cerebrum directly- synapse in olfactory cortex.
Nerve Lesion
Can no longer smell (anosmia), decreased sensit­ivity of smell (hypoo­smia), exagge­rated sensit­ivity (hyper­osmia) or distorted smell (dysos­mia).
Test for Integrity
Scent tests (eg. coffee).

Optic Nerve (CNII)

General Type
Special sense of vision
Course
1. Optic nerves (L+R) formed by axons of retinal ganglion cells- via optic disk enter the optic nerve- course via the orbit within the dural sheath.
2. Exit the orbit via the optic canal- into the middle cranial fossa to form the optic chiasm.
3. Optic tracts (L+R) proceed to terminate in the lateral geniculate bodies of the thalamus- axons arising from here form the optic radiations to the primary visual cortex in the occipital lobes.
Nerve Lesions
Parts of fields of vision are gone (anopia) or no pupillary light reflex as light is not regist­ered.
Test for Integrity
Pupillary light test, vision test (eg. looking at something in the distance).

Oculomotor Nerve (CNIII)

General Type
Motor:
Somatic motor-all extrao­cular muscles (except SO
4
LR
6
) and levator palpebrae superi­oris.
Visceral motor (PS)- via ciliary ganglion to sphincter pupillae and ciliary muscles.
Course
1. Emerges from midbrain- via posterior and middle cranial fossae- travels via superior part of lateral wall of cavernous sinus.
2. Enters orbit via superior orbital fissure within common tendinous ring.
3. Divides into 2 divisions:
Superior- for SR + LPS
Inferior- for IR, MR + IO
4. Superior division runs on lateral side of the optic nerve and on inferior surface of SR piercing it to end up in LPS.
5. Inferior division breaks up into terminal branches immedi­ately after entering orbit, carries PS (presy­naptic) fibres to ciliary ganglion (synapse)- postsy­naptic fibres via short ciliary nerves to ciliary body and the sphincter pupillae.
Distri­bution
All extrao­cular muscles (except SO
4
LR
6
), LPS, sphincter pupillae and ciliary muscles.
Nerve Lesions
No accomo­dation or light reflex (unila­teral), eye deviated laterally, drooping of eyelid (ptosis) or pupil constantly dilated.
Test for Integrity
Accomo­dation or light reflex.

Trochlear Nerve (CNIV)

General Type
Motor:
Somatic motor- to superior oblique muscle (abducts, depresses and medially rotates eyeball).
Course
1. Only cranial nerve that emerges on dorsal side of brainstem.
2. Travels via lateral wall of cavernous sinus, inferior to CNIII.
3. Enters orbit via superior orbital fissure supero­lateral to tendinous ring- runs above the LPS to SO muscle.
Distri­bution
Exclus­ively SO muscle.
Nerve Lesion
Cannot look down.
Test for Integrity
Look at tip of nose.
 

Trigeminal Nerve (CNV)

General Type
Mixed:
Somatic sensory- principal sensory nerve of head, all 3 divisions.
Somatic motor- 3rd division.
Course
1. Large sensory root and a small motor root emerge from lateral aspect of pons.
2. Sensory trigeminal ganglion located within trigeminal cave lateral to cavernous sinus.
3. Peripheral processes of ganglionic (sensory neurons) form 3 divisions
Ophthalmic (V1)
Maxillary (V2)
Mandibular (V3)
4. Motor root fibres bypass trigeminal ganglion and blends with V3.
Extra Note
Sensory and motor branches are used by all 4 PS ganglia to carry postga­ngl­ionic fibres to their destin­ation.

Ophthalmic Nerve (CNV1)

General Type
Sensory
Course
From trigeminal ganglion traverses the lateral wall of the cavernous sinus and divides into 3 terminal branches via superior orbital fissure into the orbit.
Branches
1. Lacrimal- passes laterally close to orbital plate of frontal bone to enter lacrimal gland; innervates conjun­ctiva and skin above lateral canthus; also carries postga­nglion PS fibres from CNIII- via CNV2 to lacrimal gland.
2. Frontal- runs above LPS, divides into suprao­rbital (to frontal scalp skin) and suprat­roc­hlear (to skin above medial canthus.
3. Nasoci­lilary- runs on medial side of orbit:
Infrat­roc­hlear- terminal branch to skin adjacent to medial canthus.
Ethmoidal (anterior + poster­ior)- via anterior and posterior ethmoidal foramina to ethmoidal and sphenoidal sinuses, dura in anterior cranial fossa and nasal mucosa.
External nasal- to skin of nose.
Long ciliary- sensory to ciliary body, iris, cornea, carry S fibres to dilator pupillae.
Short ciliary- carry sensory, S fibres and PS fibres from ciliary ganglion to sphincter pupillae and ciliary muscles.
Distri­bution
Sensation from cornea, upper conjun­ctive, dura mater, mucosa of antero­-su­perior nasal cavity, frontal, ethmoidal paranasal sinuses, skin of face and upper eyelid.
Corneal Reflex
Afferent- from CNV1.
Efferent- from CNVII.
Nerve Lesions
No corneal reflex or cannot feel area V1 supplies on face.
Test for Integrity
Touch area on face that V1 supplies or perform the corneal reflex.

Maxillary Nerve (CNV2)

General Type
Sensory
Course
From trigeminal ganglion traverses lateral wall of cavernous sinus and exits cranial cavity via foramen rotundum in greater wing of sphenoid to enter pteryg­opa­latine fossa. Terminal part enters orbit via inferior orbital fissure and terminates as infrao­rbital nerve.
Branches
1. Meningeal.
2. Ganglion branches to PPG.
3. Infrao­rbital-