muscle sequelae Flashcards
define agonist
the agonist is the primary muscle moving the eye in a given direction
define antagonist
an extra ocular muscle whose action opposes the action of the contracting muscle
- pairs of muscles of the same eye that move the eye in the opposite direction
the agonist is the primary muscle moving the eye in a given direction
for example the right lateral rectus is the antagonist to the right medial rectus
what is a synergist
synergists are muscles of the same eye that move the eye in the same direction - e,g, right superior rectus and right inferior oblique
what are yoke muscles
contralateral extraocular msucles that work together
contralteral synergists
e.g. left so and right ir
define muscle sequelae
sequence of eom adaptation following muscle weakness
what is sherringtons law of reciporcal innervation
- uniocular law
when increased innervation is sent to a muscle to contract an equivalent decrease in innervation is recieved by the direct antagonist - e.g. right lateral rectus and right medial rectus
this means the direct antagonist muscle is relativley relaxed
what is herrings law of equal innervation
binocular law
- when an impulse goes to a muscle causing it to contract a simultaneous equal impulse is sent to its contralateral syngerist to contract
equal innervation is supplied to yoke muscles to move eyes into the same direction of gaze
e.g. left superior oblique and right inferior rectus
describe the pattern of muscle sequelae
- primary underaction
overaction of the contralateral synergist - herrings law of equal innervation
overaction/contracture of the ipsilateral antagonist - because of sherringtons law of reciprocal innervation
secondary inhibition of the contralateral antagonist because of
herrings law of equal innervation -
what pattern would you expect to see in a left lateral rectus muscle palsy
- underaction of the left lateral rectus
overaction of the right medial rectus
overaction of the left medial rectus
underaction of the left lateral rectus
what muscle sequelae sequence would you expect to see in a left medial rectus palsy
underaction of the left medial rectus
over action of the right lateral rectus
overaction of the left latera; rectus
underaction of the right medial rectus
what muscle sequelae process would you expect to see in a right superior oblique palsy
underaction of the right superior oblique
overaction of the left inferior rectus
overaction of the right inferior oblique
underaction of the left superior rectus
what muscle sequelae would you expect to see in a right superior rectus palsy
underaction of the right superior rectus
overaction of the left inferior oblique
overaction of the right inferior rectus
underaction of the left superior oblique
what factors affect muscle sequelae
- the expected pattern of muscle sequelae develops over time
the amount of muscle sequelae development will determine what you see on om
e..g in the beginning you mahy just see the overaction of the contralteral synergist
the degree of muslce sequelae can be determined by how affected the primary underacting muscle is e.g. is a slight primary underaction is present then the overaction of the contralteral synergist will be the same - however is the primary underacting muslce is completley paralysed and has no function then the overaction of the contralteral synergist will be much greater
- the patient will fix with their unaffected eye but not always - va , pre exisitng strabismus and other factors may mean that the patient fixates with the affected eye - contractture of the ipsilateral antagonist shpuld not develop as much in a patient that fixates with their affected eye
what happens when muscle sequelae develops
over time the deviation will look less incomitant and will become more concomitant
when a deviation is very incomitant the deviaition in primary position will measure a different amount fixing with either eye in primary position
the fixing eye is the eye behind the prism
define primary deviation and secondary deviation
a primary deviation is where the angle is measured when fixing with the unaffected eye
a secondary deviation is where the angle is measured when fixing with the affected eye
in a incomitant deviaiton what will you see with the priamry and secondary deviation
the secondary deviation will be greater than the primary deviation in a incomitant deviation i.e. the deviation will be greatest fixing with the affected eye in the primary position
what happens to the primary and secondary deviation as muscle sequelae develops
as muscle sequelae develops the difference between the primary and secondary deviation reduces and may become concomitant over time
as a result of these changes in the primary and secondary deviation it can be usedul in determing weather the palsy is long standing or recent onset
define restriciton
- abnormal ocular rotation where the movement does not improve fully when testing ductions and is often associated with mechanical ateiology
define underaction
reduced ocular rotation where the movement improves testing on ductions and is often associated with neurogenic palsy
define overaction
excessive action of a muscle caused by increased innervation as a consequence of a palsy or a limitation to the ipsilateral antagonist or contralteral synergist
