Oculomotor nerve palsy
Encyclopedia
Oculomotor nerve palsy is an eye condition resulting from damage to the third cranial nerve or a branch thereof. As the name suggests, the oculomotor nerve
supplies the majority of the muscles controlling eye movements. Thus, damage to this nerve will result in the affected individual being unable to move their eye normally. In addition, the nerve also supplies the upper eyelid muscle (Levator palpebrae superioris) and the muscles responsible for pupil constriction (sphincter pupillae) . The limitations of eye movements resulting from the condition are generally so severe that the affected individual is unable to maintain normal alignment of their eyes when looking straight ahead, leading to strabismus
and, as a consequence, double vision (diplopia
).
It is also known as "Oculomotor neuropathy".
(innervated by the fourth cranial or trochlear nerve), is unantagonized by the paralyzed superior rectus
and inferior oblique
and displaced outward, because the lateral rectus
(innervated by the sixth or abducens cranial nerve) is unantagonized by the paralyzed medial rectus
. The affected individual will also have a ptosis
, or drooping of the eyelid
, and pupil dilation.
It should be borne in mind, however, that the branched structure of the oculomotor nerve means that damage sustained at different points along its pathway, or damage caused in different ways (compression versus loss of blood supply, for example), will result in different muscle groups or, indeed, different individual muscles being affected, thus producing different presentation patterns.
Ischemic insult selectively affects somatic fibers over parasympathetic fibers, while traumatic insult affects both types more equally. Therefore, while almost all forms cause ptosis
and impaired movement of the eye, pupillary abnormalities are more commonly associated with trauma than with ischemia.
Oculomotor nerve
The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...
supplies the majority of the muscles controlling eye movements. Thus, damage to this nerve will result in the affected individual being unable to move their eye normally. In addition, the nerve also supplies the upper eyelid muscle (Levator palpebrae superioris) and the muscles responsible for pupil constriction (sphincter pupillae) . The limitations of eye movements resulting from the condition are generally so severe that the affected individual is unable to maintain normal alignment of their eyes when looking straight ahead, leading to strabismus
Strabismus
Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...
and, as a consequence, double vision (diplopia
Diplopia
Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other...
).
It is also known as "Oculomotor neuropathy".
Eye Position
A complete Oculomotor nerve palsy will result in a characteristic down and out position in the affected eye. The eye will be displaced downward, because the superior obliqueSuperior oblique muscle
For the abdominal muscle see: Abdominal external oblique muscleThe superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit which abducts, depresses and internally rotates the eye...
(innervated by the fourth cranial or trochlear nerve), is unantagonized by the paralyzed superior rectus
Superior rectus muscle
The superior rectus muscle is a muscle in the orbit. It is one of the extraocular muscles. It is innervated by the superior division of the oculomotor nerve...
and inferior oblique
Inferior oblique muscle
The Obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit.-Action:Its actions are lateral rotation, elevation and abduction of the eye....
and displaced outward, because the lateral rectus
Lateral rectus muscle
The lateral rectus muscle is a muscle in the orbit. It is one of six extraocular muscles that control the movements of the eye and the only muscle innervated by the abducens nerve, cranial nerve VI....
(innervated by the sixth or abducens cranial nerve) is unantagonized by the paralyzed medial rectus
Medial rectus muscle
The medial rectus muscle is a muscle in the orbit.As with most of the muscles of the orbit, it is innervated by the inferior division of the oculomotor nerve ....
. The affected individual will also have a ptosis
Ptosis (eyelid)
Ptosis is a drooping of the upper or lower eyelid. The drooping may be worse after being awake longer, when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers to amblyopia...
, or drooping of the eyelid
Eyelid
An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily...
, and pupil dilation.
It should be borne in mind, however, that the branched structure of the oculomotor nerve means that damage sustained at different points along its pathway, or damage caused in different ways (compression versus loss of blood supply, for example), will result in different muscle groups or, indeed, different individual muscles being affected, thus producing different presentation patterns.
Congenital Oculomotor Palsy
The origins of the vast majority of congenital oculomotor palsies are unknown, or idiopathic to use the medical term. There is some evidence of a familial tendency to the condition, particularly to a partial palsy involving the superior division of the nerve with an autosomal recessive inheritance. The condition can also result from aplasia or hypoplasia of one or more of the muscles supplied by the oculomotor nerve. It can also occur as a consequence of severe birth trauma.Acquired oculomotor palsy
- 1. Vascular disorders such as diabetes, heart diseaseHeart diseaseHeart disease, cardiac disease or cardiopathy is an umbrella term for a variety of diseases affecting the heart. , it is the leading cause of death in the United States, England, Canada and Wales, accounting for 25.4% of the total deaths in the United States.-Types:-Coronary heart disease:Coronary...
, atherosclerosisAtherosclerosisAtherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
and aneurysmAneurysmAn aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
, particularly of the posterior communicating arteryPosterior communicating arteryIn human anatomy, the posterior communicating artery is one of a pair of right-sided and left-sided blood vessels in the circle of Willis. It connects the three cerebral arteries of the same side. Anteriorly, it connects to the internal carotid artery prior the terminal bifurcation of the ICA... - 2. Space occupying lesions or tumours, both malignant and non-malignant
- 3. InflammationInflammationInflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
and InfectionInfectionAn infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease... - 4. TraumaPhysical traumaTrauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
- 5. Demyelinating disease (Multiple sclerosisMultiple sclerosisMultiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
) - 6. Autoimmune disorders such as Myasthenia gravisMyasthenia gravisMyasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...
- 7. Post operatively as a complication of neurosurgeryNeurosurgeryNeurosurgery is the medical specialty concerned with the prevention, diagnosis, treatment, and rehabilitation of disorders which affect any portion of the nervous system including the brain, spine, spinal cord, peripheral nerves, and extra-cranial cerebrovascular system.-In the United States:In...
- 8. Cavernous sinus thrombosisCavernous sinus thrombosisCavernous sinus thrombosis is the formation of a blood clot within the cavernous sinus, a cavity at the base of the brain which drains deoxygenated blood from the brain back to the heart. The cause is usually from a spreading infection in the nose, sinuses, ears, or teeth. Staphylococcus aureus...
Ischemic insult selectively affects somatic fibers over parasympathetic fibers, while traumatic insult affects both types more equally. Therefore, while almost all forms cause ptosis
Ptosis
Ptosis refers to droopiness of a body part. Specifically, it can refer to:* Ptosis * Ptosis * Enteroptosis * Gastroptosis...
and impaired movement of the eye, pupillary abnormalities are more commonly associated with trauma than with ischemia.
External links
- Animation at mrcophth.com
- Video on youtube.com
- Pituitary Apoplexy Presenting as Acute Painful Isolated Unilateral Third Cranial Nerve Palsy on ams.ac.ir