Characteristics of neurological palsies Flashcards
what is a third nerve palsie
Commonly known as the oculomotor nerve.
The impairment of the nerve is commonly associated with a down and out appearance of the ipsilateral eye, enlarged pupils and often sluggish reactions.
This reflects the presence of some depression and full abduction action of the globe, controlled by the superior oblique and lateral rectus which are innervated by the fourth cranial nerve and sixth cranial nerve respectively.
how to localise an isolated third nerve palsie
It is straightforward to localise an isolated third nerve palsy when complete ptosis is apparent as it involves the LPS.
Other factors involve complete paralysis of innervated extraocular muscles and pupil mydriasis. However, third cranial nerve palsies are often subtle and overlooked as they result from partial defects. The only reason for this is that third cranial nerve palsies are often incomplete
describe the course of a third nerve palsie
This nerve is in the brainstem within the midbrain and originates from the oculomotor nucleus. The point at which the nerve leaves the cranial cavity via the superior orbital fissure the nerve divides into two branches:
The superior branch innervates the superior rectus which elevates the eyeball and the Levator palpebrae superioris which raises the upper eyelid. The superior branch of the oculomotor nerve also travels with sympathetic fibres which innervate the superior tarsal muscle which keeps the eyelid elevated after the LPS.
The inferior branch provides innervation to the inferior rectus which depresses the eyeball, the medial rectus which is an adductor of the eyeball and inferior oblique which is responsible for elevation, abduction, and lateral rotation of the eyeball. This branch also innervates the sphincter pupillae and ciliary muscle.
what are the common aetiologies of a third nerve plasy
Most common cause of third nerve palsy:
Pressure on the nerve
Inadequate blood flow to the nerve (Low, 2020)
Third nerve palsy can be acquired or congenital. All acquired third nerve palsies should be investigated thoroughly to ensure there are no space occupying lesions.
Causes of third nerve palsy include:
Congenital: 43%
Local inflammation: 13%
Trauma: 20%
Aneurysm: 7%
Myasthenia Gravis
Migraines
what are the causes of a congenital third nerve palsieCauses of congenital third nerve palsy are following:
Causes of congenital third nerve palsy are following:
Oculomotor nucleus development aplasia or hypoplasia
Birth trauma during labour because of force on skull
Infection such as meningitis (eyewiki.aao.org, n.d.)
CN III palsy can also be either complete/ incomplete.
Incomplete palsies are most commonly associated with compressive aetiologies (tumours and aneurysms).
Incomplete → Abnormal pupil reaction, as well as lids not being fully involved.
Complete → Complete or near complete ptosis & involvement from all EOM innervated by CN III.
what are the actions of the muscles
Action of muscle(s):
· Controls the movement of 4 muscles
· Inferior rectus which depresses the eyeball
· Medial rectus which is an adductor of the eyeball
· Superior rectus which is responsible for elevation, adduction, and lateral rotation of the eyeball
· The Lavator palpabrae superioris which raises the upper eyelid.
what are the possible ahps for people with third nerve palsies
Patients with third nerve palsies may develop characteristic head postures. Usually when the palsy is mild or during recovery.
These head postures serve to avoid diplopia or, when fixation is with the paretic eye, to allow fixation of a target directly in front of the patient.
Temporary management of the abnormal head posture can be accomplished by patching one eye with a Fresnel prism or with Botulinum toxin. When spontaneous resolution of the paresis does not occur, surgical treatment is usually needed for permanent correction of the face turn. Surgical outcomes are usually satisfactory except in cases of complete or nearly complete third nerve palsy (Archer, 1995).
Significant abnormal head posture could cause permanent tightening of neck muscles that can lead to chronic neck ache or headache. An abnormal head posture may also cause the facial bones to grow abnormally leading to facial asymmetry.
what cover test findings are found with someone with a third nerve palsie
Complete 3rd nerve palsy
XT, HoT, incyclotropia
Divisional palsy
Superior division (SR, levator palpebrae superioris) = HoT
Inferior division (IR, MR, IO) = XT, HT
Single muscle palsy
SR = HoT
IR = HT
MR = XT
IO = HoT, ET, incyclotropia
what are the divisions of third nerve palsies
Divisions of 3rd nerve palsies:
Complete 3rd nerve palsy = ‘down and out’
Total paralysis
Partial paralysis (paresis)
A complete 3rd nerve palsy means that the SR (which elevates), the IR (which depresses), the MR (which adducts), and the IO (which elevates, abducts, and extorts) will be affected. This will cause the affected eye to have an exotropia, hypotropia, as well as an incyclotropia.
Incomplete 3rd nerve palsy
Divisional palsy
The superior division supplies the SR (which elevates) and the levator palpebrae superioris (elevates eyelids) and therefore if it is affected, the eye will have a hypotropia. The hypotropia may cause a pseudoptosis where the coexisting ptosis can be assessed with the eyes fixing in the primary position.
The inferior division supplies the IR (depresses), the MR (which adducts), and the IO (which elevates, abducts, and extorts) therefore if it is affected, the eye will present with an exotropia and a hypertropia
Single muscle palsy
SR elevates the eye therefore SR palsy will cause a hypotropia
IR depresses the eye therefore IR palsy will cause a hypertropia
MR adducts the eye therefore MR palsy will cause an exotropia
IO elevates, abducts and extorts the eye therefore IO palsy will cause an hypotropia, esotropia, and incyclotropia
what ocular movement findings are found in people with third nerve palsies
The superior branch supplies the levator muscle and superior rectus muscle. The inferior branch supplies the medial rectus, inferior rectus and inferior oblique muscles and carries the pupil reflex fibres”
On ocular motility testing of a third nerve palsy elevation, depression and adduction will all be limited and these limitations can be either partial or complete dependent on the seriousness of the palsy.
It is also likely that a ptosis will be present in the patient, in which case either the orthoptist performing ocular movements or a helper will need to elevate the eyelid
what is an example of a hess chart found in a patient with a third nerve palsy
Hess charts of patients suffering from a third nerve palsy will show a small squashed field on the chart of the afflicted eye and the other eye will demonstrate a hess chart showing overaction
what effect on bsv does a third nerve palsie have
A large aim of treatment is the restoration of BSV and steropsis - when the ptosis and deviation are corrected both usually can .
what tests need to be conducted for a third nerve palsie
Diplopia: People have double vision when they look in a certain direction(Rubin, 2022)Diplopia: People have double vision when they look in a certain direction(Rubin, 2022)
Pupil Reflex: Pupils may not narrow (constrict) in response to light.
Measure size of ptosis: measure distance between the
upper and lower lid margin whilst patient is in primary gaze.
( normal: 7-12mm) (Eyes On Eyecare, 2022)
Test presence of torsion on depression to check SO action
Look for Aberrant regeneration
The affected eye turns slightly outward and downward when the unaffected eye looks straight ahead, causing double vision.
Pupil reflex test - Pupils may not narrow (constrict) in response to light so will be widened (dilated)
The 3rd nerve allows movement of the upper eyelid so with a 3rd nerve palsy the affected eye will have ptosis which can be measured.
where does the fourth nerve originate from
It originates from the trochlear nuclei within the medial midbrain at the level of the inferior colliculus.
The nerve fibers decussate (cross-over) to the other side of the brain stem, before leaving the brain-stem at the junction of the midbrain and pons
*Only brainstem which leaves from the posterior surface of the brainstem
It runs anteriorly and inferiorly within the subarachnoid space before piercing the dura mater
The nerve then moves along the lateral wall of the cavernous sinus
Then enters the orbit of the eye via the superior orbital fissure.
what are the common aetiologies of a 4th nerve palsie
may have other health problems along with congenital fourth nerve palsy and may compensate for diplopia with variable head positioning at later stages in life.
TRAUMA - CN IV has the longest intracranial course and is vulnerable to damage, even with relatively mild trauma, patients typically report symptoms immediately after the injury.
Vascular disease e.g. diabetes (reduces blood supply to nerve), aneurysm (bulging area of an artery that can press onto nerve or burst subsequently decreasing blood supply to nerve)
Increased intracranial pressure -(pressure in skull can press on nerve)
Injury - The most common cause of fourth nerve palsy in adults. Most common causes of injury are whiplash or concussions. Another common cause is from poor blood flow which is related to diabetes. Fourth nerve palsies that are caused by injury may not go away.
Idiopathic- cause is unclear and not caused by injury. Idiopathic cases may improve or completely resolve over a matter of weeks on their own.
what are the muscle actions of superior oblique
depression
intorsion
abduction
what are symptoms and signs of a 4th nerve palsy
There are 2 types of 4th nerve palsy:
Isolated - this is the most common type of nerve palsy, and is congenital. (1)
Non isolated - this type of palsy is normally caused by trauma, infection and inflammation. (2)
Signs and symptoms.
Diplopia - different types can be present in a 4th nerve palsy, the most common are: Binocular, torsional and vertical diplopia.
Vision - problems can accrue when someone has been suffering with a 4th nerve palsy for a long period of time, things like: blurred vision, focussing problems and dizziness. In the end these vision can cause a person’s daily life to become very difficult.
Head posture - people can develop a head tilts in the opposite direction to the affected eye, this head posture occurs due to the 4th nerves affect on the superior oblique (intorsion and depression).
(3), (4)
what are fetatures are present in a congen trial 4th nerve palsy
unilateral
Facial asymmetry common - shallowing between lateral canthus & edge of mouth
Abnormal Head Position - Head depression with head tilt or turn to the unaffected side
First symptom of the palsy decompensating is intermittent diplopia
A large hyperphoria (usually exceeding 20 diopters) with AHP
Potential manifest vertical deviation without AHP
bilateral palsy
Abnormal Head Position - Chin depression with no head tilt or turn unless one side is affected more than the other
Non fixing eye may have V pattern esotropia and hypertropia
Associated inferior oblique overaction
No symptomatic torsion but can be seen objectively in fundus test.
how is a congenital 4th nerve palsy managed
Correct refractive error and treat any amblyopia if present.
Potential surgery for: Marked AHP, moderate/large angle deviations of decompensating cases, strabismus
If the patient has an abnormal superior oblique tendon a superior oblique tuck procedure may correct the palsy.
Also could have other surgeries to weaken the overacting muscles.
what ahp do people in 4th nerve palsies have
Abnormal head posture is where a patient will tilt their head at an angle that is away from the normal primary position, due to misalignment of the eyes. This is so the patient can avoid deviation, diplopia or relieve strain.
Someone with a 4th nerve palsy, with the superior oblique affected/weakened, will tilt their head away from the affected eye, so their eyes can become more straight or where the eyes are best aligned.
Because their superior oblique is affected, the affected eye will therefore not be able to turn ‘in and down’, as the action of the superior oblique is to abduct, depress and intort the eye. The patient will move their head, chin down to compensate diplopia.
For example, if it’s the right eye that’s affected, the patient would tilt their head to the left and with chin depressed (away from the affected eye), to avoid diplopia. If that patient tilts their head towards the affected eye, there would be an increase in hypertropia, and therefore vertical diplopia.
We can test if a patient has AHP by:
Observing them during a visual task, such as reading off a board
Put their head straight and observe if they return back to AHP repeatedly.
Look for facial asymmetry, where the ipsilateral side of face can look less developed
what cover test findings are found in a unilateral 4th nerve palsy
Unilateral 4th Nerve Palsy
Hypertropia in primary gaze (as SO depresses the eye)
Excyclotorsion (as SO intorts the eye)
Sometimes esotropia (as SO abducts the eye)
