Eye exam-pupils and HGP

hrhodes's version from 2015-10-20 00:33

Miosis and mydrisis

Question Answer
Causes of Bilateral miosis?Bilateral pontine lesion, Bilateral thalamic haemorrhage,(both due to disruption of desc sympathetic fibres), Opiate intoxication, Organophosphate poisoning, Barbiturate poisoning
Causes of unilateral miosis?Horner's syndrome, sympathetic damage at any level - ipsilateral pontine, thalamic or sump chain
Causes of bilateral mydraisis?Parasympathetic damage or sympathetic drive - Sympathetomimetics, anticholinergics, End point of brainstem herniation, bilateral CN3 injury - BOS#, bilateral midbrain injury
Unilateral mydriasis?Uncal herniation CN3, raised ICP CN 6, aneurysm compressing CN3, midbrain lesion (- parasympathetic tone disrupted)
For the purposes of memorising, brain levels causing sympathetic and parasympathetic disruption?pontine and thalamic lesions = > sympathetic disruption (mitosis), Midbrain => Parasympathetic disruption (mydriasis)

Eye pearls

Question Answer
What does the presence of spontaneous eye movements exclude? brainstem pathology as the cause of coma. The 3rd, 4th and 6th nerves are all engaged, and the medial longitudinal fasciculus coordinates conjugate eye movements.
Horizontal movements of the eyes are coordinated by which hemisphere and pons?The contralateral hemisphere, via the ipislateral pons.
If you have a right sided cortical lesion what direction will the eyes look towards?Right - the same direction
In cortical pathology, which way will the eyes will look?towards the lesion
In pontine pathology which was will the look?deviate away from it
Question Answer
Vertical movements of the eyes are coordinated by?both hemispheres.

CN3 - Occulomotor

Question Answer
Which muscles does occulomotor control?Medial rectus, Also superior rectus, inferior rectus, inferioir oblique, SPHINCTER PUPILAE
What does the eye look like if you have a CN3 lesion?Down and out, ptosis and mydriasis
Is CN 3 parasympathetic or sympathetic?PARASYMPATHETIC ( therefore, damage to CN3 => Sympathetic unappeased = > Dilated pupils)
CN 3 lesion also causes mydriasis, what causes of CN3 lesion can spare the pupil? Ischemia, means normal size pupil- i.e a diabetic neuropathy. Anything compressing CN3 causes dilatation - Compression of CNIII - uncal herniation, aneurysm compression, BOS#

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