BV lab 2

How does someone with a SO palsy often present?

1. will have contralateral head tilt or contralateral head turn

2. may have increased vertical vergence ranges if long standing

what prism can be prescribed to tx a SO palsy?

R hyper → BD in R, BU in L

L hyper → BU in R, BD in L

how to measure torsion?

Maddox rod

Brown's syndrome is often mistaken for?

IO palsy

What is Brown's tendon sheath syndrome?

inflammation of trochlea or SO tendon causes tendon to get stuck in trochlea → overaction of SO and restriction of IO

what is the etiology of Brown's syndrome

1. congenital

2. inflammatory

3. trauma

How does Brown's tendon sheath syndrome present?

normal in primary and downward gazes

in up-gaze looks like an IO palsy

How can you tell if something is an IO palsy or Brown's?

forced duction test: manually push eye

if full with forced ductions → non-restrictive and is IO palsy

if restricted in force duction test → Brown's

How does a CN VI (LR) palsy present?

ipsilateral head turn

eso deviation in primary gaze

What are causes of a CN VI palsy?

1. change in intracranial pressure → pushes nerve against petrous portion of temporal bone

2. diabetes, HTN

what prism do you use to tx CN VI palsy?

BO prism

What is Duane's Retraction syndrome?

co-contraction of MR and LR causing retraction of the globe on adduction

What is Type 1 Duane's Retraction syndrome?

abduction impaired + retraction on adduction

What is type 2 Duane's Retraction syndrome?

adduction impaired + retraction on adduction

What is type 3 Duanes retraction syndrome?

abduction and adduction impaired + retraction on adduction

what is the tx for a SO palsy, Brown's syndrome, CN VI palsy and Duane's retraction syndrome when pt has no diplopia in primary gaze?

nothing

what is the tx for a SO palsy, Brown's syndrome, CN VI palsy and Duane's retraction syndrome when pt has diplopia in primary gaze?

prescribe prism

What type of muscle is ocular muscle?

striated muscle

What are the layers of the ocular muscles?

global layer

orbital layer

What are the two type of fibers in ocular muscle?

twitch fibers

slow muscle fibers

Which layer of ocular muscle does twitch movements?

global layer

Which layer of ocular muscle does prolonged contraction?

orbital layer

what does the global layer have a lot of?

glycolytic enzymes

what is the orbital layer rich in?

oxidative enzymes

What are muscle pulleys?

muscle tethered to orbit in area other than origin

what is the role of muscle pulleys?

1. keeps EOMs from slipping when eye is moved away from primary gaze

2. alters the non-primary gaze kinematics of classic theory

what is a saccade?

an abrupt voluntary shift in fixation from one point to another, as occurs in reading

what is the stimulus for a saccade?

target displacement on retina

What is the saccadic pathway for a right saccade?

left frontal cortex → right omnipause neurons → right PPRF → right CN VI (right eye turns to right) + left MLF → left CN III (left eye turns to right)

How do both the eyes move at the same time in a saccade, despite the neurons firing from one side of the brain?

the neurons going contralateral move via the MLF which is highly myelinated for fast transmission

What is the general saccadic pathway?

contralateral frontal cortex → ipsilateral omnipause neurons → ipsilateral PPRF → ipsilateral CN nucleus + contralateral MLF → contralateral CN nucleus

What is the PPRF?

paramedian pontine reticular formation

What happens if there is a lesion at the left MLF?

during a right saccade → the right eye turns but the left eye stays @ midline

during a left saccade → both eyes move (may have nystagmus)

What is inter-nuclear ophthalmoplegia?

damage to the MLF

What are the characteristics of inter-nuclear ophthalmoplegia?

1. lag on adduction

2. may have nystagmus of abduction

3. convergence unaffected

What causes inter-nuclear ophthalmoplegia?

1. MS

2. vertebrobasilar disease - poor vascular perfusion of the posterior brain

What does inter-nuclear ophthalmoplegia mimic?

partial III palsy (MR)

What is binocular inter nuclear ophthalmoplegia (BINO)?

damage to both MLF

What does BINO look like/get mistaken as?

binocular MR palsy

What are the characteristic of BINO?

during right saccade → right eye looks to right and left eye stays

AND

during left saccade → left eye looks left and right eye stays

AND convergence is normal