Ocular Palsies Flashcards
When do you get triad of symptoms?
lesions of ocular motor nuclei
nerves weaken
paralyse of the EOM
What is strabismus?
Deviation of the eye from the primary gaze position in the opposite directions of the muscle’s normal action
What is diplopia?
Double vision
What is external Ophthalmoplegia?
Limitation of eye movements in the muscles normal directions of action
How do you get classical nerve palsies?
Complete (all nerves function effected)
Isolated ( no other brain or nerve involvement)
Unilateral (1 nerve and one eye only )
Who gets 3rd nerve palsies?
Adult more
Who gets 4th nerve palsies
Children more
Who gets 5th Nerve palsies ?
Adult more
Who gets mixed nerve palsies?
Equal in children and adults
What are the potential acquired causes?
Nuclei in the brainstem
Intra cranial nerve (classical cause)
Intra cranial nerve (mixed multiple involvement)
How does nuclei in the brainstem cause problems?
Other brainstems structures are involved
vascular infarct, tumors, inflammation
How does classical intra cranial cause problems?
trauma, tumours, arterial aneurysms, subarachnoid space ischemic micro - vascular neuropathy
How does mixed intra cranial nerve cause problems?
In or near cavernous sinus,
inflammation
How is acquired classical adult palsies caused?
Vascular - common in type 2 diabetes in older px
25% idiopathic
Why does each muscle have an action ?
contributions of their anatomy to this
Origins, orbital paths and scleral insertions
What are the medial walls of orbits ?
Medial walls formed by ethmoid bones and are parallel to visual axis
What is the angle of medial walls and lateral walls?
45 degrees
What is the angle between the visual axis and orbital axis of each eye?
22.5 degrees
Where does the 4 rectus and the superior oblique originate?
common tendon (the annulus of zinn) attached to the bone at the orbital apex, and encircling the optic canal and adjoining part of the superior orbital fissure
Where do the 4 rectus insert?
insert near the limbus anterior to the equator
What do SR and IR do?
SR & IR run parallel to the orbital axis 23 degrees to the visual axis in primary gaze and have a convex insertion
Where does the SO pass?
The SO passes backwards through the trochlear pulley at 45 degrees to the visual axis and insert posterior to the equator
Where does the IO originate from ?
From a short tendon attached to the anterior medial wall of the orbit just inferior to the rim of lacrimal fossa
Where does the IO run?
Runs parallel backwards at 51 degrees to the visual axis under the IR and inserts posterior to the equator
What are the three paths of the rectus muscles?
Equator of the globe
Mid orbital region
common annular tendon
What does the scleral to limbus distance of rectus muscles show?
How strong or weak the muscle is
The closer to limbus the stronger the muscle
Which rectus is the strongest?
Medial rectus - 5.5mm insertion distance sclera to limbus
What type of insertion does the superior oblique have?
Wide insertion by long tendon 20mm posterior and lateral to the equator under the SR muscle
What type of insertion does the inferior oblique have?
Wide insertion by short tendon
What are the key features of classical 3rd nerve palsy?
Ocular deviation
external ophthalmoplegia
Internal ophthalmoplegia
Complete or partial ptosis
What does complete deviation show in 3rd nerve palsy?
complete exotropia (abduction) and some depression (hypotropia)
What does external ophthalmoplegia show in 3rd nerve palsy?
limited no adduction or elevation eye movement
What does internal ophthalmoplegia show in 3rd nerve palsy?
dilated unreactive pupil and loss of accommodation
What does complete or partial potosis show in 3rd nereve palsy?
so no or little diplopia
Why do you get these features in 3rd nerve palsy?
All adductors (MR, IR, SR) and elevators (SR, IO) are paralysed with 2 abductors (LR, SO) and depressors(SO) unopposed
Why do you get undilated and unresponsive pupil?
Constriction sphincter muscle paralysed, dilator muscle unopposed
Why do you get ptosis?
levator palpebrae superioris muscle paralysed, orbicularis oculi unopposed
What is common cause of 3rd nerve palsy?
Posterior Communicating artery aneurysm
What does the 3rd nerve contain?
parasympathetic, nerve fibres cause pupil to constrict and run from superior to inferior
What does the 3rd nerve axons occupy?>
Superficial edge supplied by larger blood vessels
What problems do you get with spared pupillomotor axons in diabetic retinopathy?
PCoA aneurysm somewhere else non directly on the axons and spares the pupil
What is effected in diabetic retinopathy?
The deep micro vascular capillaries in the nerve
What are clinical key features of 6th nerve palsy?
External ophthalmoplegia - limited no abduction eye movements
ocular deviation - complete adduction
Horizontal diplopia - worsening with gaze towards the affected side and at far
What does the 6th nerve palsy have compared to 3rd nerve palsy?
No ptosis
What do you have to do for 6th nerve palsy and esotropia?
Compensatory strategy= abnormal head posture,
reduce diplopia
What are some causes of 6th nerve palsy?
Lateral head trauma to temporal bone
Arterial pathology
Non classical brainstem tumours
What is meant by lateral head trauma to temporal bone
inward movement of petrous portion crushes nerve against the clivus at the petro-sphenoidal ligament
What is meant by arterial pathology?
Hardening or aneurysm of the basilar artery or AICA near nerve exit from the brainstem
What is meant by non classical brainstem tumours?
Downwards pressure ruptures nerve in the same region
What are the clinical features of 4th nerve palsy?
Ocular deviations - exotorsion, hypetropia and exotropia
External ophthalmoplegia - limited no adduction especially on near gaze
Torsional and vertical diplopia- worse when looking down or near
When do patients complain of SO palsy?
Read , walk or down the stairs
What are the causes of 4th nerve palsy?
> Frontal head trauma- whiplash
Brainstem tumours that pushes brain back and forwards
Rupture nerve by displacement as long thin and unprotected by dura as it curves around the midbrain and into subarachnoid space
What do you do in 4th nerve palsy?
Compensation - head tilt away from affected eye to reduce vertical and torsional components of diplopia
What happens if you get a lesion in 6th nerve ?
Lesion in pons on abducens nerve - would be subarachnoid space - right eye esotropia
Cause: aneurysm in artery
