Control of Eye Movement Flashcards
What does the vestibuloocular reflex accommodate for?
Acceleration (via vestibular labyrinth)
What does the optokinetic reflex accommodate for?
Velocity (movement of the whole visual field)
What does the pupillary light reflex accommodate for?
Changes in ambient light (maintains level of retinal illumination)
What is the purpose of the blink reflex?
Keeping shit out of your eye.
What tract(s) coordinates(s) eye and head movements?
- Reticulospinal
- Interstitiospinal
What is strabismus?
Defect in which eyes are misaligned.
If not corrected, brain will ignore input from one eye and fail to focus it (amblyopia - if you need more info, ask Carly), and eventually not orient it
What is light-near dissociation?
Accommodation preserved within given eye, but no reaction to light within the pupil. Therefore, efferent/afferent limbs intact, but damage to pretectal projection to cortex (retinomesencephalic pathway) –> Argyll Robertson pupil, Pretectal Syndrome
What is Argyll Robertson pupil / Pretectal Syndrome associated with?
Neurosyphilis / tabes dorsalis and diabetes mellitus
Uncal herniation (uncus over edge of the tentorium) can compress…
CN III and CN IV, as well as the crus cerebri
What occurs during trochlear nerve palsy?
Patient tilts head AWAY FROM affected side to level the plane of each eye and avoid diplopia; this is the most commonly injured CN from trauma
Looking upward slightly (chin tuck) corrects _______
hypertropia (misalignment of the eyes)
What is the Adie’s pupil?
Lesion to ciliary ganglion or postganglionic psym fibers; thus NO Edinger-Westphal projection. Ability to constrict is impaired, so it’s dilated. Reacts slowly to light, but well to accommodation.
What is a blown pupil?
Mydriasis, or severe dilation of the pupil. Caused by lesion to the post-ganglionic psym input.
What is the Prostitute’s pupil (Argyll Robertson)?
Accommodates, but doesn’t react.
Walker said it, not me ¯_(ツ)_/¯
What has gone wrong to cause a prostitute’s pupil?
Lesion to olivary pretectal nuclei or a lesion of its projection (from something like tabes dorsalis) - weak/absent pupillary light reflex, but accommodation is gucci.
What is a Markus Gunn pupil?
An afferent (light) defect, such that light in one eye results in NO consensual or direct reflex
What is a disgruntled pupil?
Any med student
What is anisocoria?
Unequal pupil size
Cavernous sinus thrombosis can cause what?
Impingement upon CN III, IV, V1, V2, VI, and associated sympathetic fibers along the ICA. Caused by vascular lesions, tumors, infection, ischemia, inflammation, trauma.
What is internuclear ophthalmoplegia?
Lesion to internuclear neurons from abducens part of the MLF. LR contracts appropriately in horizontal gaze, but MR for opposite eye does not (no connection to CN III contralaterally). Nystagmus also occurs.
What is one-and-a-half syndrome?
Lesion to abducens nucleus and MLF fibers from contralateral abducens. Causes:
- Contralateral nystagmus
- Ipsilateral eye frozen in both horizontal directions
- Contralateral eye can only abduct
What is horizontal gaze palsy?
Lesion to PPRF (paramedian pontine reticular formation) or abducens nucleus/nerve
What is Horner’s syndrome (humor me plz)
Damage to sympathetics from superior cervical ganglion
- Ptosis
- Miosis
- Anhidrosis
Can also come from damage to pathway linking hypothalamus and brainstem to preganglionic neurons in IML (hypothalamospinal tract)
What is Parinaud’s Syndrome?
Lesions (pineal tumors) that compress dorsal midbrain and pretectal areas:
- Impaired vertical gaze
- Large, irregular pupils (not light reactive, disruption of optic fibers to EWN)
- Eyelid abnormalities (sym impingement)
- Impaired convergence (vergence center impaired)
What is the Near Response Triad?
- Eyes converge (medial recti)
- Lens becomes more round (ciliary m.)
- Pupil constricts (miosis, change focal length)
What is Balint syndrome?
- Optic ataxia (hard to track)
- Optic apraxia (saccades)
- Simultanagnosia (can’t focus on more than one thing)
Lesion in the “where” stream
Lesion to frontal eye fields:
Increase latency for saccades, hypometria of saccades, inability to suppress inappropriate saccades
Inability to suppress inappropriate remarks is something completely different, and you can ask Reuben about that.
Lesion to supplementary eye field:
Inaccurate memory-guided saccades, normal visual guided saccades
Lesion to dorsolateral prefrontal cortex:
Impaired predictive and memory-guided saccades
Lesion to posterior parietal cortex, parietal eye fields:
Increase latency of visually-guided saccades, ipsilesional gaze deviation
Lesion to primary visual cortex:
Impaired generation of saccades or smooth muscle pursuits to visual stimuli in blind hemifield
Lesion to MT:
Retinotopic defect of motion, decrease smooth pursuit speed, dysmetric saccades for contralateral hemifield
What is the optokinetic reflex?
Match velocity of retinal slip to attempt to track object the is moving too quickly for smooth pursuit.
Alternating slow (compensatory) and fast (saccadic) phases of movement (clinically-defined by fast phase).
What causes a vertical gaze palsy?
Lesion of midbrain-diencephalon junction, or vertical gaze center in riMLF (rostral interstitial nucleus)
A pinealomas impinging on the posterior commissure can cause:
Vertical gaze palsy (site of communication)
What is the afferent limb of the optokinetic reflex?
Wide-field retinal ganglion cells sensitive to slow movements of whole receptive field
What is optokinetic nystagmus?
Fast phase of saccades that bring eyes back to primary position, occurring when limit of smooth rotation is reached; alternating slow and fast
Pupillary light reflex is a ____ neuron arc
4
Briefly describe the pathway for the pupillary light reflex.
- Retinal ganglion cells detect light and project half to ipsilateral side and half contralateral (consensual)
- Go to pretectum (olivary pretectal nucleus)
- Project to EWN (some decussate via posterior commissure)
- Project along CN III
- Ciliary ganglion, sphincter pupillae m.
What do people with retinitis pigmentosa (blind) still have pupillary light reflex?
Melanopsin-containing ganglion cells
Where is the frontal eye field?
Brodmann area 6. Caudal parts of middle frontal gyrus.
What areas of the brain direct saccadic movements?
- Frontal/cortical eye fields (voluntary and memory-guided saccades)
- Superior colliculus (reflexive saccades)
Loss of either can be compensated for by the other.
What kind of nystagmus is seen in Arnold-Chiari malformation?
Downbeat nystagmus, worse on lateral gaze
Also present with:
- Saccadic dysmetria, impaired pursuits, VOR cancellation, impaired optokinetic nystagmus
What are some causes of ptosis?
- Myogenic
- Aponeurotic
- Neurogenic
- Mechanical
- Traumatic
In patients with Parkinson’s, there is death of neurons involved in the nigrotectal pathway, causing __________
Death of spontaneous eye movements
Lesion of the flocculus can cause:
Deficit in smooth pursuit eye movements from lack of cerebellar inputs for rate of movement and predicting trajectory
What is blepharospasm?
Disorder of rhythmic behavior causing bouts of high-frequency blinking
Is blepharospasm seen in Parkinson’s?
NO! The opposite - none of that high-frequency nonsense.
What cranial nerves are involved in the vestibuloocular reflex?
III, VI, VIII (largely driven by vestibular system)
Which vestibular nuclei contribute to which CNs in the vestibuloocular reflex?
- Lateral vestibular nucleus: CN III (MR, ipsilateral)
- Medial vestibular nucleus: CN VI (LR, contralateral)
What do opiates and barbiturates do to pupils?
Pinpoint pupils
What do anticholinergics (scopolamine, atropine) do to pupils?
Dilate them (used for exams); no muscarinic Ach activity
1% pilocarpine eyedrops do what to pupils?
Constriction them (muscarinic agonist)
What sympathetically-activated muscles keep the lids open?
Tarsal muscles
What normal physiological response causes drooping of the eyelids?
Psym activation relaxes mm. and causes “heavy eyelids”.
Boredom during Walker’s lectures is also an acceptable response.
Hit me with Weber Syndrome:
- Oculomotor nerve damage: Ipsilateral oculomotor palsy with muscle atrophy, ptosis, mydriasis
- Damage to crus cerebri: Contralateral hemiparesis of upper and lower extremities, contralateral paralysis of lower face, and deviation of tongue to contralateral side on protrusion
Claude Syndrome:
- Oculomotor nerve: Ipsilateral oculomotor palsy with muscle atrophy, ptosis, mydriasis
- Red nucleus and cerebellothalamic fibers: Contralateral tremor and ataxia (contralateral loss of position sense, vibratory sense, and discriminative touch if medial lemniscus involved)
Benedikt Syndrome:
Weber + Claude
In addition, these patients may have a contralateral rigidity due to damage to the substantia nigra.
