investigation of neurogenic palsies

Question 1

in general what type of palsy is a neurogenic palsy

Answer 1

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

Question 2

what is a concomitant deviaition

Answer 2

primary cause = esotropia/ exotropia

the angle of deviation is the same fixing either eye and in all positions of gaze

Question 3

what are neurogenic palsies

Answer 3

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

Question 4

what is visual acuity like in patients with a neurogenic palsy

Answer 4

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

Question 5

what muscle are you testing when you look up and out

Answer 5

superior rectus

Question 6

when you look up and in what muscle action are you testing

Answer 6

inferior oblique

Question 7

when you are looking down and out what muscle are you testing

Answer 7

inferior rectus

Question 8

when you look down and in what muscle are you testing

Answer 8

superior oblique

Question 9

what are the actions of the superior rectus

Answer 9

elevation , intorsion , adduction

Question 10

what are the actions of the inferior rectus

Answer 10

depression , intorsion , adduction

Question 11

what are the actions of the superior oblique

Answer 11

depression intorsion abduction

Question 12

what are the actions of the inferior oblique

Answer 12

elevation , extorsion , abduction

Question 13

what does rad sin stand for

Answer 13

superior intort, recti adduct

Question 14

what things need to be consdidred with a neurogenic palsy

Answer 14

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

Question 15

if you had a left lateral rectus palsy what deviation would you have in primary positon

Answer 15

a eso deviation

Question 16

what should you observe with ahps

Answer 16

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

Question 17

how do head postures work

Answer 17

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

Question 18

what to record on cover test

Answer 18

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

Question 19

what would you expect to see with a left superior rectus under action

Answer 19

• 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

Question 20

what general observations would you make during om

Answer 20

• 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~)

Question 21

what are underactions

Answer 21

reduced ocular rotation

which improves on testing suction

Question 22

what are restrictions

Answer 22

abnormal ocular rotation where the movement does not improve when testing ductions

Question 23

what are limitations

Answer 23

abnormal ocular rotation

Question 24

what to check for ocular movements

Answer 24

check versions and ductions

interpret development of muscle sequelae

include different eye movement systems

smooth pursuit

saccades

OKN

VOR

Question 25

what do you need to consider when assessing binocular function

Answer 25

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

Question 26

what do you have to measure

Answer 26

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

Question 27

what is the lees screen used for

Answer 27

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

Question 28

what is a field of bsv

Answer 28

records area in which bsv is maintained

excellent - records patients symptoms

Question 29

what does the investigation determine

Answer 29

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