Clinical Signs - Eyes Flashcards
What are the features of occulomotor nerve palsy?
Following findings in the primary gaze position:
- Hypotropia (eye deviated down)
- Exotropia (eye deviated out) - supressed elevation from lS and LO and unopposed abduction from LR
- Ptosis - CN3 inervates levator palpebrae superioris
- Mydriasis - loss of PNS function.
What eye movements are impaired in occulomotor nerve palsy?
- Elevation
- Depression
- Adduction
- Extorsion
Supressed elevation from LS and LO and unopposed abduction from LR
What nerve is affected in the following presentation?
Occulomotor nerve palsy (CNIII)
What nerve is affected in the following presentation?
Occulomotor nerve - Impaired elevation, depression, adduction and extorsion of the affected eye.
Why do those with occulomotor nerve palsy get hypotropia?
Unnopposed superior oblique muscle
What are the different severities of occulomotor nerve palsy?
- Complete
- Pupil Sparing
- Myadriasis only
Why do those with occulomotor nerve palsy get myadriasis?
Pupillary constrictor muscle weakness
What are the most common causes of occulomotor nerve palsy
- Midbrain pathology
- Diabetic mononeuropathy/microvascular infarction (hypertension)
- Uncal herniation
- Posterior communicating (PCOM) artery aneurysm
- Ophthalmoplegic migraine (transient)
- Mass lesion – tumour, abscess, AVM
- Demyelination
Why do those with occulomotor nerve palsy get Ptosis?
Levator palpebrae weakness
Why do those with occulomotor nerve palsy get exotropia?
Unnopposed Lateral rectus muscle
Why do those with occulomotor nerve palsy get impaired elevation?
Superior rectus muscle weakness
Why do those with occulomotor nerve palsy get impaired depression?
Inferior rectus muscle weakness
Why do those with occulomotor nerve palsy get impaired adduction?
Medial rectus muscle weakness
Why do those with occulomotor nerve palsy get impaired exotorsion?
Inferior oblique muscle weakness
What are causes of the following?
- Diabetic neuropathy
- Increased ICP - false localising sign
- Trauma to base of skull
- MS
- Wernicke’s encephalopathy
- Cavernous sinus syndrome
- Cavernous carotid artery aneurysm
- Giant cell arteritis
How do disorders of the subarachnoid space cause abducens nerve palsy?
The abducens nerve emerges from the brainstem adjacent to the basilar and vertebral arteries, and the clivus. Aneurysmal dilation of these vessels and/or infectious or inflammatory conditions of the clivus can compress the abducens nerve
What muscle does abducens nerve innervate?
Lateral rectus
Presentaion of abducens neve palsy
Eye cant abduct beyond midline - deflective abduction and horizontal diplooa
What is the main mechanism behind abducens nerve palsy?
Abducens nerve palsy is caused by a peripheral lesion of the abducens nerve. Lesions of the abducens nuclei typically result in horizontal gaze paresis (i.e. ipsilateral abduction paresis and contralateral adduction weakness) due to an impaired coordination of conjugate eye movements with the oculomotor motor nuclei, via the medial longitudinal fasciculus (MLF).
How does increased ICP cause abducens nerve palsy?
Due to the relatively fixed nature of the abducens nerve at the pontomedullary sulcus and at the point of entry into Dorello’s canal, it is vulnerable to stretch and/or compression injury secondary to elevated intracranial pressure.
Why is abducens palsy due to increased ICP known as false localising sign?
Referred to as a ‘false localising sign’ as the clinical findings are not solely due to an isolated peripheral lesion of the abducens nerve - due to course the nerve follows
How does diabetic neuropathy cause abducens nerve palsy?
Diabetic vasculopathy of the vasa nervorum (i.e. disease of the blood supply of the nerve) may result in microvascular infarction of the abducens nerve.
What are argyle robertson pupils?
Characterised by:
- Miosis (small pupils)
- Absence of the pupillary light response
- Brisk accommodation reaction
- Bilateral involvement.
What is the mechanism behind Argyll-Robertson pupils?
Caused by a pretectal lesion in the dorsal midbrain affecting the fibres of light reflex, which spare the fibres of the accommodation pathway that innervate the Edinger–Westphal nuclei
What conditions are argyll robertson pupils associated with?
- Multiple sclerosis
- Neurosarcoidosis
- Tertiary syphilis
What is an afferent cornreal reflex defect?
Absence of bilateral blinking, due to ophthalmic division of the trigeminal nerve (CNV V1) dysfunction
What nerve is implicated in an afferent corneal reflex deficit?
Opthalmic division of trigeminal nerve
What is an efferent defect of the corneal reflex?
Absence of unilateral blinking, due to facial nerve (CNVII) palsy.
What nerve is implicated in an efferent defect of the corneal reflex?
Facial nerve
What are causes of absent corneal reflex?
- Bell’s palsy (idiopathic facial nerve palsy)
- Facial nerve palsy
- Brain death
- Cerebellopontine angle tumour – acoustic schwannoma, glomus tumour
- Cavernous sinus syndrome
What is horners synrome?
Interrupted sympathetic innervation to the eye. Can occur at any level - central lesion to post gangliotic fibres.
What are features of horner’s syndrome?
- Miosis (fixed constricuted pupil due to loss of sympathetic function)
- Ptosis with apparent enopthalmos (eye lid lag with sunken eye)
- Anhydrosis (unilateral reduction in sweating)
Differentials of horners
Central lesions: anhidrosis of face, arm and trunk
- Stroke
- Syringomyelia
- Multiple sclerosis
- Tumour
- Encephalitis
Pre-ganglionic lesion: anhydrosis of face
- Pancoats tumour
- Thyroidectomy
- Trauma
Post gangliotic lesions: no anhidrosis
- Carotid artery dissection
- Carotid aneurysm
- Cavernous sinus thrombosis
- Cluster headache
What is Hutchison’s pupil?
Hutchinson’s pupil is a non-reactive dilated pupil caused by oculomotor nerve compression secondary to uncal herniation. Other signs of oculomotor nerve palsy (e.g. extraocular muscle weakness, ptosis) may also be present