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CN III palsy (Aetiology (Trauma
Increased ICP (tentorial herniation and…
CN III palsy
Aetiology
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Infection
Meningitis, encephalitis
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Diagnosis
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Investigations
Bloods
FBC, CRP, U+E, LFT, clotting
CSF
MCS, cytology,
oligoclonal bands
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History
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FH
Stroke, autoimmune disease,
cancers
PMH
Cancer, autoimmune disease, strokes,
medical conditions, surgical conditions
SH
Living arrangements, occupation,
smoking, alcohol
PC/HPC
Symptoms, recent illness
Pathophysiology
Mechanism
Lesion in CN III results in all muscles bar S oblique and lateral rectus being paralysed
S oblique moves eye down and in, lateral rectus moves it out
Overall eye is down and out
Normal eye movement
All eye muscles supplied by CN III, apart from lateral rectus (CN VI) and superior oblique (CN IV)
All muscles are pulling muscles; obliques in opp direction to name!
Medial rectus abducts the eye (moves medially)
Lateral rectus adducts the eye (moves lateral)
Superior rectus moves eye up and out (superolateral)
Inferior rectus moves eye down and out (inferolateral)
Superior oblique moves eye down and in (inferomedial)
Inferior oblique moves eye up and in)
Defect
Medical palsy: microvascular compromise so muscle is taken out but pupillary reflexes are spared
Surgical palsy: muscle and reflexes out by e.g. SOL
Clinical
presentation
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Eye down and out
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