CN 4 Flashcards
What type of diplopia is most common with CN 4 defect?
Vertical diplopia
specifically:
- w/ torsional component
- worse in down gaze
Ocular management for patient w/ CN 4 defect (5)
- Fresnel Prism
- Ground-in Prism
- Vision Therapy
- Strab Surgery
- Alternate Occlusion
In a patient suspected to have a CN 4 palsy, when is imaging required?
- Patients 50+ (w/o Hx of DM/HTN/Trauma)
- Complicated cases
- Trauma
- Presumed vasculopathic that does not resolve in 3 months
Trochlear nucleus lies in the ____ (ventral/dorsal) part of the midbrain at the level of the _____.
Ventral; inferior colliculus
Most common cause of CN 4 Palsy
Head trauma
Most common lesion impacting the brainstem
Stroke
Deficits associated w/ Cavernous Sinus defect (5)
Affects chiasm, CN 2, 3, 4 ,V1, V2, 6, and sympathetic fibers:
- Ophthalmoplegia
- Horner’s
- Bitemporal VF defect
- Facial pain/numbness
- ON dysfunction
T/F: Orbital Syndrome in a CN 4 defect results in (+) APD
TRUE; CN 4 enters orbit near CN 2 —> (+) APD + vision loss
What location of the CN 4 tract is most susceptible to countercoup forces?
Subarachnoid Space
Dorsal Midbrain Syndrome: Signs/Symptoms (4)
- Bilateral lid retraction
- Upgaze palsy
- Fixed pupil
- Light near Dissociation
Signs/Symptoms of Nuclear/Fascicular CN 4 lesion (5)
- Contralateral Horner’s
- Increase in ICP
- Contralateral INO (near MLF)
- Cerebellar dysfunction
- Dorsal Midbrain Syndrome
Signs of bilateral CN 4 palsy? (2)
- Crossed hypertropia
- “v” Pattern ET
Why might a congenital SO palsy not present itself until years later?
Becomes decompensated as an adult (due to fatigue, stress, and old age)
Signs of Congenital SO Palsy (3)
- Chronic head tilt (look at old photos)
- Facial asymmetry
- Large compensating Vergence range
