investigation of neurogenic palsies Flashcards
in general what type of palsy is a neurogenic palsy
inconstant - the angle of deviation varies depending on which eye is used for fixation and the direction of gaze - angle Varys depending on where you look
caused by neurogenic palsy
mechanical limitation - i.e. something physically stopping it i.e. mass
aniesmetropia- i.e. if you have a + 3 in one eye and a Plano in the other - when you cover the Plano eye you will have convergence in +3 eye
what is a concomitant deviaition
primary cause = esotropia/ exotropia
the angle of deviation is the same fixing either eye and in all positions of gaze
what are neurogenic palsies
where the nerve supply to a muscle is affected
may affect one individual muscle or a group of muscles
consider observations and determine further investigations required
recording of clinical picture to show evidence of recovery, regression and stability
what is visual acuity like in patients with a neurogenic palsy
normal acuity= usually
reduced acuity
previously present e.g. old amblyopia
traumatic mydriasis - i.e. they have had trauma to the eye and the pupil is dilated
related to neurogenic condition e.g. retrobulbar neuritis- affects optic nerve - in ms
if recent can contribute to decompensation of longstanding palsy - i.e. a patient may have had a 4th nerve palsy for a long time and they might be well compensated - however if they start to develop a cataract and the acuity reduces in one eye then fusion is challenged and then that can cause you to get diplopia because your vision and fusion ability is reduced
co- incidental pathological cause
what muscle are you testing when you look up and out
superior rectus
when you look up and in what muscle action are you testing
inferior oblique
when you are looking down and out what muscle are you testing
inferior rectus
when you look down and in what muscle are you testing
superior oblique
what are the actions of the superior rectus
elevation , intorsion , adduction
what are the actions of the inferior rectus
depression , intorsion , adduction
what are the actions of the superior oblique
depression intorsion abduction
what are the actions of the inferior oblique
elevation , extorsion , abduction
what does rad sin stand for
superior intort, recti adduct
what things need to be consdidred with a neurogenic palsy
deviation in the primary position
fixing with the unafffected eye (primary deviation)
fixing with with the affected eye (secondary deviation)
app (compensatory head posture) to avoid deviation- patients move their head away from the deviation in order to achieve bsv
primary deviation is usually smaller than secondary deviation
if you had a left lateral rectus palsy what deviation would you have in primary positon
a eso deviation
what should you observe with ahps
observe for
head turn
head tilt
head elevation / depression
observe during visual task
put head straight and observe return to app
look for facial asymmetry - suggests longstanding
how do head postures work
head turn to place eyes away from action of the affected muscle
head elevation or depression
vertical- as head tilts e.g. to the right
right moves up and the left eye moves down thus tilt to lower eye to use this
torsion - as head tilts e.g. to the right - right eye introits and left eye extorts
thus if left extortion is present , tilt right to match fellow eye to that position
what to record on cover test
record app
single cover removes reason for app
record first with app n and d then without app
record size and type of deviation
also note
degree of incomitance fixing either eye
difference in vertical deviation between n and d
obliques larger at near
recti larger at distance
what would you expect to see with a left superior rectus under action
- left superior rectus - moves the eye app, adducts the eye and introrts the eye
so the eye would be hypo , exo . and extortion
superior rectus is tested in laevoelevation so to avoid diplopia you would want your eyes to be dextrodepression
what general observations would you make during om
- smoothness of movement during pursuit
- ie, sherringtons and herrings law
- head movements in child may indicate avoidance of affected movement
pupils - i.e. third nerve palsy
lid positon - i,e., ptosis - due to elevator - third nerve
globe position changes- globe may move forward or back
nystagmus (oscillations of the eyes~)
what are underactions
reduced ocular rotation
which improves on testing suction
what are restrictions
abnormal ocular rotation where the movement does not improve when testing ductions
what are limitations
abnormal ocular rotation
what to check for ocular movements
check versions and ductions
interpret development of muscle sequelae
include different eye movement systems
smooth pursuit
saccades
OKN
VOR
what do you need to consider when assessing binocular function
most commonly normal bsv or potential for
may have previous deviation with suppression or ac , diplopia may occur with change of angle
traumatic loss of fusion
what do you have to measure
with or without ahp
with/without refractive correction
near/distance
nine positions of gaze
pct
synoptophore
torsion
synoptophore
torisonometer
double Maddox rod
Maddox rod
subjective where small vertical deviations
n.b expected deviation not always found due to a pre- existing deviation
what is the lees screen used for
measurement of deviation - up to 9 positions of gaze
compare 1 eye to fellow eye
aids identification of affected eye and muscle
aids differential diagnosis of neurogenic and mechanical limitations
illustrates degree of concomitance
used for monitoring patient
n.b torsion can only be measured with a special adaptation
not good for bilateral conditions
what is a field of bsv
records area in which bsv is maintained
excellent - records patients symptoms
what does the investigation determine
nerves affected (unilateral or bilateral)
possible causes
long standing or recently acquired
presence of a or v patterns
recovery, regression , stability
need for refferal
management plan
