Neuro-ophthalmology Flashcards
Heavily based on Case-Based Neuro-Ophthalmolgy https://casebasedneuroophthalmology.pressbooks.com/chapter/fourth-nerve-palsy/
What are the cardinal features of typical optic neuritis?
Young (20-50yo), white woman
Pain with eye movements
Acute to subacute loss of vision
Unilateral
Absent or mild disc edema
Absence of intraocular inflammation
Absence of retinal hemorrhages, disc hemorrhages, or retinal vasculitis
Recovery of visiion with or without treatment
Approximately what percentage of patients with optic neuritis have pain?
Over 90% (ONTT 92.2%)
The pain was constant and worse with eye movements in 51.3% and present with eye movements only in 35.8%
Approximately what percentage of patients with optic neuritis have optic disc edema?
30-40%
In the ONTT, 35.3% of patients had optic disc edema. In optic neuritis, the disc edema is usually mild and without disc hemorrhages. Disc or peripapillary hemorrhages were found in only 5.6% of patients in the ONTT.
Severe disc edemas and the presence of hemorrhages are atypical features
What visual field deficits occur in optic neuritis?
Almost every type of visual pattern can be seen. ONTT found that most common were diffuse (48.2%), altitudinal (14.9%), three quadrant (7.1%), quadrant (6.0%), cecocentral (4.5%), and hemianopic (4.2%) defects.
If OCT of the retinal nerve fiber and ganglion cel complex were performed early in disease course, what would you expect?
Normal RNFL and GCC thickness. However, in patients with acute optic neuritis and no optic disc edema, the RNFL and GCC are approximately normal thickness assuming there is no prior history of an optic neuropathy. The RNFL and GCC will start to decrease in thickness a few weeks after the onset of vision loss. OCT of the RNFL and macular GCC from this patient with acute optic neuritis is shown below and shows an RNFL and macular GCC thickness within the normal range.
According to the revision of the 2017 McDonald criteria, dissemination in space is established by the presence of …
One or more T2-hyperintense lesions characteristic of multiple sclerosis in two or more of four areas in the central nervous system: - periventricular
cortical or juxtacortical
infratentorial brain regions
the spinal cord.
The optic nerve was not included as a site to determine dissemination in space in the 2017 revision of the McDonald criteria since it was felt that there was insufficient evidence for its value in predicting a second attac
According to the revision of the 2017 McDonald criteria, dissemination in time is established by the presence of …
Dissemination in time is essential for the diagnosis of multiple sclerosis and can be demonstrated either by:
1. the simultaneous presence of gadolinium-enhancing and non-enhancing lesions or
2. the appearance of a new T2-hyperintense of gadolinium-enhancing lesion on follow-up MRI, irrespective of the timing of the baseline MRI. Gadolinium enhancement indicates an active lesion and is usually observable for the first 4-6 weeks after formation. If there are enhancing (new) and non-enhancing (older) lesions, dissemination in time can be established.
3. Cerebrospinal fluid-specific oligoclonal bands may also be used to establish dissemination in time and were added to the 2017 revisions to the McDonald criteria.
What is the best treatment regimen for a patient with optic neuritis?
IVMP 1g daily for 3 days followed by oral prednisone taper
The Optic Neuritis Treatment Trial (ONTT) compared treatment with intravenous methylprednisolone to oral prednisone (1 mg/kg) and oral placebo and found that intravenous methylprednisolone hastened the recovery of vision by approximately 4-6 weeks if started within 8 days of onset. There was no difference in visual acuity at 6 months in the intravenous methylprednisolone compared to the placebo or oral prednisone group. Visual acuity improved to at least 20/40 in over 90% of patients at 6 months. Intravenous methylprednisolone also reduced the risk of developing clinically definite multiple sclerosis for two years in the intravenous methylprednisolone group. This beneficial effect appeared to lessen after the first two years of follow-up.
What is a tropia?
How does this compare to a phroia?
A tropia is a physical misalignment in one or both eyes that can also be called strabismus
A phoria is a deviation that may only be present when the eyes are not looking at the same object
Whether or not fusion is maintained or not (ie if in unilateral cover test there is no movement in uncovered eye then eyes were aligned with the target at patient has a phoria, if ther was movement then the patient has a tropia)
What extraocular muscles are involved in CN III?
Levator palpebrae superioris, medial rectus, superior rectus, inferior rectus
Elevation, abduction, depression
Describe oculomotor nuclear complex anatomy
There are 5 motor subnuclei with 1 subnucleu for levator palpebrae shared and 1 parasympathetic subnuclei aka Edinger Westphal nucleus
Key:
P = parasympathetic = Edinger-Westphal (EWN)
IO = inferior oblique
SR = superior rectus
IR = inferior rectus
MR = medial rectus
LP = levator palpebrae = central caudal (CCN)
Describe function of Edinger Westfall Nucleus
The EWpg nucleus receives input from the locus ceruleus in response to the light hitting the retina, which then prompts the nucleus to send a forward signal which synapses at the postganglionic cells of the ciliary ganglion (CG).[6] This synapse between the EWpg nerve fibers and the ciliary ganglion postganglionic cell bodies is a nicotinic synapse with acetylcholine as the neurotransmitter.[6]
In response to the signal from the EWpg, the postganglionic ciliary bodies relay the signal along their axons by way of the ciliary nerves towards the eye. This relay leads to the innervation of the sphincter pupillae (causing miosis) and ciliary muscles (ocular accommodation). The constriction of the pupil moderates the amount of light the retina is exposed to, which is the efferent limb of the pupillary light reflex. Additionally, the contraction of the ciliary muscles leads to the relaxation of the zonular fibers, allowing for increased convexity of the lens and, subsequently, an increase in refractive power and accommodation
Describe function of Edinger Westfall Nucleus
https://www.ncbi.nlm.nih.gov/books/NBK554555/
EDIT
The EWpg nucleus receives input from the locus ceruleus in response to the light hitting the retina, which then prompts the nucleus to send a forward signal which synapses at the postganglionic cells of the ciliary ganglion (CG).[6] This synapse between the EWpg nerve fibers and the ciliary ganglion postganglionic cell bodies is a nicotinic synapse with acetylcholine as the neurotransmitter.[6]
In response to the signal from the EWpg, the postganglionic ciliary bodies relay the signal along their axons by way of the ciliary nerves towards the eye. This relay leads to the innervation of the sphincter pupillae (causing miosis) and ciliary muscles (ocular accommodation). The constriction of the pupil moderates the amount of light the retina is exposed to, which is the efferent limb of the pupillary light reflex. Additionally, the contraction of the ciliary muscles leads to the relaxation of the zonular fibers, allowing for increased convexity of the lens and, subsequently, an increase in refractive power and accommodation
Since the discovery of the two cell populations of the EW nucleus, the function of the EWcp has been a subject of ongoing research. The EWcp is located medial and dorsal to the OCN in the midbrain and is comprised of a collection of peptidergic neuron cell bodies.[6][8][2] It is known that a large population of these cells are urocortinergic neurons, which are positive for the neuropeptide urocortin-1 (part of the corticotropin-releasing factor family) and negative for choline acetyltransferase.[4] These differ in immunohistochemistry from the cholinergic parasympathetic neurons of the EWpg, which are choline acetyltransferase positive. The EWcp nucleus is a significant contributor to the amount of urocortin-1 neuropeptide in the brain.[9] Studies have shown that this nucleus is involved in stress adaptation, anxiety, and pain.[10] However, the thought is that the response to stress by the EWcp nucleus is separate from that of the hypothalamic-pituitary-adrenal (HPA) axi
At what level of the brainstem is the third nerve? Why is that relevant?
At the level of the superior colliculus where visual information is incorporated with other environmental stimuli and works in coordinating eye movements (ie saccadic oculomotor and head movements such that it helps orient the head and eyes toward stimuli that are seen and heard)
What fundamental feature of your oculomotor/eye exam should prompt you to localize to the oculomotor nucleus?
BILATERAL 3rd nerve findings
Name the 4 recognized oculomotor fascicular syndromes and their mneumonics
- Weber - “weber is weak” - CN III fascicle + contralateral hemiparesis
- Benedikt - “benedikt is bouncy” - CN III fascicule + tremor (red nucleus)
- Claude - “claude is contralateral” - CN III fascicule + contralateral ataxia +/- tremor
- Nothnagel - most challenging to pin down - fascicular oculomotor palsy with ataxia (original described location superior and inferior colliculi)
Describe the trajectory of CN III
Describe CN III Fiber organization and how this relates to aneurysmal presentation
Parasympathetic fibers are located exterior, superior, and midline
The most common arteries to cause 3rd nerve palsy are posterior communicating artery aneurysms (at junction with ICA) because the CN III runs immediately below PCA
Note that ICA, SCA, and basilar artery aneurysms can also cause CN III palsy
Basilar artery aneurysms can compress the third nerve from below and SPARE the pupil since pupillary fibers run superior and medial on the outer part of the third nerve
What study should all CN III palsies have as part of workup?
CTA
What are the contents of the cavernous sinus?
Describe Wilbrand knee
Inferior optic nerve fibers moving anteriorly in the anterior chiasm on the opposite side before they go backwards such that one could get loss of vision in a single eye (ie left) and superior temporal vision loss in the opposite eye (ie right)
Not clear if this is really a “normal” anatomical structure…
It hasn’t been clearly demonstrated in normal animals or humans but like we were discussing in clinic has been seen in people with monocular injury, the leading theory that the knee develops after a chronic injury creating room for the inferior fibers to slip forward (nicely demonstrated in figure 4 of the Hoyt pap
What is the primary action of the superior oblique muscle? The secondary action?
Tertiary action?
Incyclotorsion
Depression
Abduction
Describe the direction of eye movement and muscles involved with a head tilt (example left vs right head tilt leads to … )
With a LEFT head tilt, to maintain fusion on an object, the left eye incyclotors and the right eye excyclotorts. Incyclotorsion of the left eye is done by the SR and SO and excyclotorsion of the right eye is done by the actions of IR and IO
What is the most pertinent finding in this patient’s fundus photos?
Left fundus is excyclotorted due to left CN IV palsy
How do you assess for a 4th nerve palsy in the presence of a complete 3rd palsy?
Assess for torsion of the eye during depression in abduction
A 4th nerve palsy may occur in conjunction with a 3rd nerve palsy since the 3rd and 4th nerves are in close anatomical proximity in the cavernous sinus. Since the eye cannot adduct in a 3rd nerve palsy, the limitation of depression in adduction that is normally seen in a 4th nerve palsy CANNOT be assessed. The patient should be asked to abduct the eye and look down, if there is incyclotorsion of the eye when looking down, then the 4th nerve is intact. Incyclotorsion can be assessed by using an anatomical landmark such as a conjunctival blood vessel.
A patient has a small bleed in the midbrain in the region of the right 4th nerve nucleus. This will manifest as a:
- Right 4th nerve palsy
- Left 4th nerve palsy
- Bilateral 4th nerve palsy
- Right 6th nerve palsy
Left 4th nerve palsy
The 4th cranial nerve nucleus is located in the midbrain at the level of the inferior colliculus and the 4th nerve exits the brainstem dorsally and innervates the contralateral superior oblique muscle. Because the 4th nerve fascicle travels a very short distance before exiting the brainstem, it is very difficult to differentiate a nuclear and fascicular lesion. The course of the 4th cranial nerve is illustrated in the diagram below.
Describe the ocular tilt reaction
Ie what would you expect if a normal individual was rolled to the left (in the roll plane) as below:
You would expect right compensatory ocular tilt reaction:
- Incyclotorsion of the L eye
- Excylotorsion of the right eye
Right head tilt
Upward rotation of left eye
Downward rotation of the right eye
Aka
Head tilt
Ocular torsion
Skew deviation
A patient presents with a left head tilt and has a right hypertropia in primary position. Dilated fundus examination shows right eye incyclotorsion and left eye excyclotorsion. What is the diagnosis?
Pathologic ocular tilt reaction
Right 4th nerve palsy
Left 3rd nerve palsy
Thyroid disease
Pathologic ocular tilt reaction
A pathologic ocular tilt reaction is caused by a lesion in the vestibular pathways and results in asymmetric vestibular input to the central nervous system and mimics a change in body position in the roll plane. This patient is acting as if her body was rolled to the right and has a left ocular tilt reaction. Note that the hypertropic eye is incyclotorted in this case, whereas it would be expected to be excyclotorted in a 4th nerve palsy (since the superior oblique muscle is an incyclotorter).
What are structures implicated in dorsal midbrain syndrome?
Posterior commissure
Rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF)
Interstitial nucleus of Cajal (INC)
