Neurological Diseases of the Eye Flashcards
describe blindness (3)
- unilateral or bilateral
- retina/optic nerve/optic chiasm
-abnormal menace and PLR
-can’t see bc no info getting in
-cheaper to rule out! use menace and PLR - contralateral prosencephalon
-abnormal menace, normal PLR
-can’t see because can’t process info
describe blindness due to retina/optic nerve/optic chiasm (5)
- abnormal menace and PLR
- blind (most common owner complaint)
- mydriasis
- absent menace (with normal CN VII/palpebral)
- absent PLR
rule out retinal causes first! with fundic exam and electroretinogram
what are optic chiasm causes of blindness?
- MUE
- neoplasia
need an MRI for this but if bilateral, retina or optic nerves are much more commonly affected than optic chiasm
what are optic nerve causes of blindness?
- most common disease: optic neuritis
-typically non-infectious/immune-mediated (MUE)
-large breeds can get immune-mediated (NO MUE) - sometimes neoplasia
- as always, can’t easily tell these apart without MRI
describe presumptive diagnosis of optic neuritis
- compatible clinical presentation
-acute onset
-any breed
-median age: 6 years
-bilateral more common (80%) - optic nerve head elevation: can’t tell inflammation from neoplasia though
- infectious disease testing (very uncommon though)
describe definitive diagnosis of optic neuritis/retinal causes of blindness
retina: if fundic exam normal, electroretinogram before MRI
-ensure is not retina before go hunting for optic neuritis
optic neuritis:
1. MRI:
-swelling of optic nerve(s)/loss of CSF around nerves
-+/- multifocal, asymmetrical brain lesions in cases of MUE
- CSF: mononuclear pleocytosis
- negative infectious disease titers
describe treatment and prognosis of optic neuritis
- prednisone: 1-2 mg/kg/day, slow taper
- antimicrobials while waiting for titers?
-not if fungal suspect - dogs with MUE may need long term treatment
prognosis:
-14% regained partial vision
-16% regained complete vision
describe internal ophthalmoplegia
- disease of parasympathetic of CN III
-mydriasis
-abnormal PLR: cannot constrict affected pupil, unaffected pupil will constrict with light in either eye
-visual: normal menace
-don’t forget iris atrophy!
- unilateral: structural disease
- unilateral or bilateral: head trauma
- bilateral
-ivermectin toxicity
-thiamine deficiency
describe unilateral CN III lesion/parasympathetic/internal opthalmoplegia (2 etiologies, diagnostics, and treatment options) also what else might you see if CN III is affected?
etiologies:
1. neoplasia most common
2. rarely idiopathic/neuritis
diagnostic:
3. recommend MRI!
treatment options:
1. palliative
2. surgery
3. radiation: 18-28 month survival
if CN III affected, might also see
1. ispilateral ptosis: levator palpebrae superioris is innervated by CN III (NOT on exam)
describe strabismus/opthalmoplegia
- lesion of CN III innervates somatic extraocular eye muscles
-ipsilateral fixed ventrolateral strabismus
-lack of adduction/medial movement - lesion of CN 6: medial strabismus
- lesion of CN 4: extorsion of eye (rare)
- external opthalmoplegia
-paralysis of extraocular muscles
-lack of physiologic nystagmus - commonly affect all nerves together:
-no deviation of the eye
-no movement of the eye - cavernous sinus syndrome: tumor here affects 3, 4, 5 CN going to eye
- retrobulbar disease more common: neoplasia, abscess
describe extraocular myositis
- RARE
- immune-mediated inflammation of extraocular eye muscles
- young large and giant breeds
- exophthalmos +/- painful
- treat with immunosuppressive steroids
describe Horner syndrome
- loss of sympathetic innervation to the eye
- miosis, ptosis, enophthalmos, third eyelid elevation (passive due to enophthalmos)
-remember! if just have a miotic pupil, could just be pain! esp if don’t see other horner signs - common causes:
-otitis media/interna: sometimes Horner is the ONLY sign of OMI!!
-neoplasia anywhere along pathway
-idiopathic: golden retrievers esp
describe the pathway of sympathetics to eye (just for context)
pathway of sympathetics to the eye (for context, not memorize); disease anywhere along this pathway can cause Horner’s!
-cervical spinal cord
-T1-T3
-brachial plexus: in thoracic cavity for some time!!
-vagosympathetic trunk
-tympanic bulla
-eye
describe diagnostic workup of Horner syndrome
describe how to decide what eye is normal versus abnormal
