Ch. 13 - Eye Movement & Pupillary Control Pathology

Diplopia (double vision) Causes

- mechanical problems (orbital fx w/ muscle entrapment)

- disorders of extra-ocular muscles (thyroid disease, orbital myositis)

- disorders of NMJ (myasthenia gravis)

- disorders of CN III, IV, VI & their nuclei

If blurriness goes away when patient closes one eye?

- indicates diplopia causes by Eye Movement Abnormality

- when extra-ocular muscle is not working correctly, dysconjugate gaze results, causing Diplopia

Exotropia

abnormal lateral deviation of one eye

Esotropia

abnormal medial deviation of one eye

Hypertropia

- vertical deviation

- one eye higher than the other

Cover - Uncover Test for Diplopia

- visual input usually keeps eyes yoked in same direction

- when an eye is covered while looking in the direction of a weak muscle, it may drift back toward neutral

What is the mild weakness noticeable during Cover-Uncover Test?

Ex- or Esphoria (not ex- or estropia)

Oculomotor Palsy (CN III)

disruption of CN III causes paralysis of all muscles except for Lateral Rectus & Superior Oblique

What are the only remaining movements in CN III Palsy?

some abduction, depression, & intorsion

Decreased tone in muscles affected by CN II results in?

"down & out" position of eye at rest

Paralysis of Levator Palpebrae (CN III Palsy)

Ptosis (droopy eyelid)

How does the pupil present in CN III Palsy?

dilated & unresponsive

What is a common report regarding Diplopia during CN III palsy?

Diplopia is worse when looking at near objects (convergence is impaired)

Common Causes of CN III Palsy

- Diabetic Neuropathy

- Head trauma w/ shear to CN III

- Compression of CN via intracranial aneurysms

Where does compression of CN via intracranial aneurysms usually occur?

most often arise from the junction of the Posterior Communicating Artery w/ ICA

CN IV Palsy

- Trochlear N. produces depression & intorsion of the eye

-Lesion causes hypertropia, extorsion & vertical diplopia

When will hypertropia & vertical diplopia worsen w/ CN IV Palsy?

- worsens when affected eye looks nasally

- worsens w/ downgaze

- improves w/ head tilt away from eye

When will patients reports improvement of diplopia w/ CN IV Palsy?

by looking up (chin tuck) & by tilting head away from affected side

Common Causes of CN IV Palsy

- most commonly injured nerve (shear injury) in head trauma

- pathology in Subarachnoid space

- vascular or neoplastic disease in the Midbrain or near the Tectum

What movement of the eye is CN VI responsible for?

- Abduction

- lesion leads to horizontal diplopia & esotropia (medial deviation) in some cases as well

When do CN VI patients report diplopia is better?

when they are viewing near objects (worse w/ far objects)

When do CN VI patients reports diplopia is worse?

when patient tries to abduct affected eye

Common Causes of CN VI Palsy

- susceptible to injury from downward traction caused by elevated ICP (due to course along clivus & ridge of Petrous Temporal bone)

- early sign of Supratentorial or Infratentorial Tumors & Hydrocephalus

CN III Lesion (Pupillary Abnormalities)

- affects efferent (pre- & post-ganglionic) pathway from Edinger-Westphal nucleus to pupillary constrictor muscle

- can cause impaired ipsilateral pupillary constriction, resulting in a dilated pupil

Complete CN IIII Lesion can result in?

very large or "blown" pupil

Why do CN III lesions cause Ipsilateral deficts?

due to lesion of motor component after bilateral contribution

Light in affected eye w/ CN III Lesion

- affected eye response is impaired, unaffected eye intact

- no constriction in affected eye, constriction of unaffected eye

Light in unaffected eye w/ CN III Lesion

unaffected eye response intact, affected eye response is impaired

Horner's Syndrome

- caused by disruption of sympathetic pathways to eyes & face

- Ptosis (upper eyelid drooping)

- Miosis (decreased pupillary size)

- Anhidrosis (decreased sweating of ipsilateral face & neck)

Ptosis cause

loss of innervation of Muller's smooth muscle in the upper eyelid

Miosis cause

loss of sympathetic innervation to pupillary dilators

Anhidrosis cause

loss of pre-ganglionic sympathetic innervation

Marcus Gunn Pupil

afferent pupillary defect, direct response to light in the affected eye is decreased or absent

Light in affected eye w/ Marcus Gunn Pupil

no constriction of affected or unaffected eye

Light in unaffected eye w/ Marcus Gunn Pupil

constriction of affected & unaffected eye

Cause of Marcus Gunn Pupil

- decreased sensitivity of affected eye to light

- lesion of optic nerve, retina, or eye affect; ipsilateral side only

Lesions at or after the optic chiasm...

would affect inputs from both sides & therefore do not generally produce a Marcus Gunn pupil

Ptosis (eye opening)

- Levator Palpebrae Striated Muscle (CN III)

- Muller's Smooth Muscle (Sympathetic)

- Frontalis Muscle of Forehead (CN VII)

Ptosis (eye closure)

Orbicularis Oculi muscle (CN VII)

Causes of Ptosis

- Horner's Syndrome (Muller's Smooth Muscle)

- CN III Palsy

- Myasthenia Gravis

Cavernous Sinus Syndrome

- can affected isolated nerves or all nerves

- all nerves (CN III, IV, VI) = total Opthalmoplegia

- Fixated, dilated pupil

- involvement of CN V1 & V2 (also travel thru Cavernous Sinus) causes sensory loss

Abducens N. (CN VI) Lesions

impaired abduction of ipsilateral eye

Abducens (CN VI)/PPRF Lesions

Ipsilateral Lateral Gaze Palsy (involved abduction of ipsilateral eye & adduction of contralateral eye via MLF)

MLF Lesion

- Internuclear Ophthalmoplegia

- Medial Rectus = decreased adduction ipsilaterally

- Nystagmus on opposite side (realigning?)

Parinaud's Syndrome

- impaired upward gaze (compression of dorsal pretectal area)

- large, irregular pupils

Common causes of Parinaud's Syndrome

- Pineal tumor

- Hydrocephalus

Right Way Eyes (lesions of Cerebral hemispheres)

- impaired eye movement in contralateral direction (gaze preference toward lesion)

- contralateral weakness & eyes gaze toward side w/o weakness (R lesion would see L hemiparesis & gaze to the R)

Wrong Way Eyes

- contralateral extremity weakness

- eyes look to the side of weakness

- not common (cannot be caused by Cerebral Hemisphere lesion)

Causes of Wrong Way Eyes

- seizure activity in cortex (activation of Frontal Eye Fields)

- Thalamic Hemorrhage (disrupt CST in Internal Capsule & causes weakness, eyes deviate towards weakness)

- Pontine Lesion (disrupt CST leading to contralateral weaknee, involvement of CN VI or PPRF = ipsilateral gaze weakness)