MT2 Flashcards
4 questions of double vision
- Does it go away when one eye is covered?
- Is it horizontal or vertical?
- Is it worse when you look in a certain direction?
- Greater at distance or near
Causes of monocular diplopia
Glasses prob
Bifocal seams
Astigmatism Polycoria
cataracts due to asymmetry
What muscles do you suspect are causing a horizontal or vertical diplopia?
Horizontal- 4 muscles. MR and LR
Vertical- 8 muscles. SO, IO, SR, IR
To narrow down further, ask if it gets worse when looking to the left or right. Can narrow down to 2 or 4 more muscles now.
Thermostat vs dinner plate muscles
Thermostat- IO
Dinner plate- SO
3 causes of diplopia and the most common one
- Optical causes (not common)
- VF defects
- Ocular motility issues (most common)
Hemifield Slide phenom
Dense bitemporal hemi. Causes a sensory diplopia.
Palinopsia
Homo hemi. Brain substitutes visual images from the temporal lobe- moose on car.
Fast and slow eye movements
Fast- saccades. 300-700 deg/sec
Slow- pursuits. 30-40 deg/sec
Reading card positions
- Held to extreme left or right?
- Card held down and tilted?
- Card held down and head leaned back?
- Card pushed away?
- Card held close?
- Held to extreme left or right? Abduction deficit. Held closer to the normal eye. or hemi.
- Card held down and head tilted?
SO palsy, held away from paretic muscle. - Card held down and head leaned back?
Low bifocal, ptosis, A or V, CL problem - Card pushed away?
Constricted field, presbyopia, hyperopia - Card held close?
Myopia
Red glass test. Ask pt to look in different gazes? How do you know which muscle is involved?
The muscle involved is always in the eye the corresponds with the color of the light that is further away from fixation.
When can you do the bielchowsky head tilt test?
With red glass test. Have the pt tilt their head and tell you when the spread of the colors increases.
Maddox rod is a very sensitive test for determining what type of diplopia
Vertical
___ is the best way to test for cyclodeviations
maddox rod in a trial frame. Determine whether its ex or in based on how the top of the eye lines are rotated
Pt has CN palsy and doing maddox rod testing
Imagery will shift as pt looks up and down. Because as the pt looks down, the good eye will depress more than the paralyzed eye.
Tell the patient to look left.
pathway in brain that lets this occur
Corticotectal –> pons –> left PPRF –> CN 6 to contract to the LLR
At the same time, the yoke muscle is directed to contract by a small signal from the left PPRF –> MLF –> contralateral CN III that serves RMR
If the patient can’t intort, how will it look on maddox rod testing?
Will show an excyclorotation bc pt can’t intort.
PPRF
MLF
Paramedian pontine reticular formation
Medial longitudinal fasiculus
What is the problem in a gaze palsy?
Information can’t leave the PPRF to go to the R and L subnuceli. Therefore, pt can’t look in a certain gaze.
What condition causes a gaze palsy?
Fovilles (Inferior medial pontine syndrome)
Fovilles (Inferior medial pontine syndrome) location of lesion and results
Corticospinal tract.
Left tract lesion? Right hemiplegia, left facial palsy. Inability to move eyes together to the ipsi side.
LSO palsy. Tilting head where helps?
Tilt head to the right.
Skew Deviation
Non localizable defect in the brainstem causing vertical deviation and neuro problems.
3 types of skew deviations
- Comitant (OD always higher than OS)
- Non-comitant (OD higher on right gaze, OS higher on left gaze)
- Alternating (OD higher on right, then OS higher on right)
2 studies looking at Skew deviation
(+) for upright-supine CT. (Vertical deviation decreases when supine)
Static ocular counteroll reflex is significantly reduced in skew deviation. Asymmetry provides evidence that disruptions ould be due to utriculo-ocular pathway.
Signs of INO
Cannot adduct one eye + abduction nystagmus of the other eye.
Can be subtle. Asymmetry in the saccadic movements. Use OKN to look at saccades during the catch up phase (swing flag the opposite direction)
INO. Where is the lesion?
MLF. Lesion on the right? Signal can still go from the PPRF to the LLR, but can’t go to the MFL –> RMR. Therefore, RMR cannot abduct. and will have OS left gaze nystagmus.
Anterior INO- lesion in midbrain. Cannot converge. Less common.
Posterior INO- lesion in pons. Can converge. More common.
INO vs bilateral INO
Unilateral: Due to vascular disease/brainstem infarction, older person, males, sudden onset, 43% also have skew deviation, convergence still present due to posterior (pons) type.
Bilat: Due to demyelinating disease, younger person, males = females, slowly progressive, few with skew, convergence still present due to lesion in pons
Bilat INO. Ask pt to gaze right and left. What happens?
- When asked to gaze right, LMR cannot adduct and OD abduction nystag.
- When asked to gaze left, RMR cannot adduct and OS abduction nystag.
Fisher one and a half syndrome on the right side
• Lesion involves PPRF and MLF on one side. Ex: on the right. When asked to gaze right, neither eye moves. When asked to gaze left, OD remains forward and OS has abduction nystag.
Another name for Paralytic pontine exotropia
Acute 1 & 1/2 syndrome
Acute onset of brainstem infarction involve PPRF and MLF. Eventually, exo eye will turn in.
Most common brainstem syndromes that cause diplopia
INO and BINO
Be careful, INO may look like MR weakness.
CN III palsy most likely due to aneurysm at
ICA and PCA
CN III palsy with pupil sparing vs pupil involving
Pupil sparing- Usually due to DM/ vascular disease. Pt will get diabetic work up. Sharp pain at first, then goes away.
Pupil involving- Usually due to aneurysm. 92% specific. Pt will get arteriogram. Much more severe pain with presentation and it persists.
*Watch the pupil for 1 week as it may become involved.
See someone 55+ years with pupil sparing CN III palsy. What do you think?
GCA. Check for elevated ESR. Medical emergency.
Main differences between aneurysmal and ischemic vascular CN III palsy
- Pain. More severe and persistent with the aneurysm.
- Pupil sparing or not? If spared, continue to monitor for a week. May evolve.
- Elevated ESR in a patient over 55+ with pupil sparing = GCA/AAION
CN III nuclei organization
most dorsal part- IR
Below the IR subnucleus is the SR
The most Inferior lateral subnucelus is the MR
Claude’s Syndrome (CN III palsy due to lesion at the nucleus)
Lesion of the superior cerebellar peduncle.
Midbrain infraction.
Occurs with involvement of red nucelus that catches the fasicular CN III fibers.
Pt will have CN III palsy with contra ataxia and a tremor.
Benedikt’s Syndrome (CN III palsy due to lesion at the nucleus)
Involvement of the red nucelus and cerebral peduncle and catching the CNIII fasciculus. Pt will have same as Claude’s (contra ataxia and tremor) + contra hemiparesis.
Nothnagel’s Syndrome (CN III palsy due to lesion at the nucleus)
Same as Benedikt’s + inability to look up with both eyes. Could be due to involvement of brachium conjunctivum.
Weber’s Syndrome (CN III palsy due to lesion at the nucleus)
Occurs if the lesion catches the fascular portion of CN III and the crus cerebri.
- Ipsi CN III palsy
- Contra Hemi
- Extrinsic lesions compress crus cerebri and CN III. Operable.
- Intrinsic disease, such as pontine glioma, is inoperable. Tx with radiation and chemo.
An isolated involvement of a muscle innervated by CN III means the lesion must be ____
In the orbit or CN III nucleus.
Ex: IR palsy OD
total ipsi CN III palsy without any involvement of the other eye means the lesion cannot be
in the CN III nuceli
If the lesion was in the nuclei, the pt would have bilateral ptosis, and contra SR involvement. Pretty rare.
Most common and most likely CN III palsy
Weber’s syndrome.
Occurs if the lesion catches the fascular portion of CN III and the crus cerebri. Causes Inspi CN III palsy and contra hemi. Can be intrinsic (inoperable) or extrinsic (operable)
Subarachnoid Space CN III Palsy
As CN III travels through subarachnoid space, it is subject to compression by the uncus.
Bleeding –> Shifts brain down –> Hutchinsons pupil –> CN III palsy
5 main causes of cavernous sinus CN III palsy
- pituitary apoplexy
- Sphenoid sinus infection due to mucomycosis, mucocoele, carcinoma
- Carotid rupture/GCA
- Meninge tumor. Meningioma/neurofibroma.
- Tolosa Hunt (Dx of exclusion)
What is a pituitary apoplexy
Infarction in a vessel of a pituitary tumor. If someone has a sudden onset of CN III palsy with pain, diplopia, and field cut, its pituitary apoplexy. Life threatening.
An enlarging pituitary tumor can compress the cavernous sinus on both sides + internal carotid arteries + chiasm above it, causing bilateral CN III palsy.
Difference between pituitary apoplexy and cavernous sinus fistula
Apoplexy is life threatening
Cavernous sinus fistula is sight threatening, not life threatening.
THS
Idiopathic granulomatous inflammation in the cavernous sinus and SOF. dx of exclusion. Painful, may have horners, recurrent attacks, proptosis. Do 48 hour prednisone test (usually get better and CN abnormalities improve)
-Contrast enhanced MRI is modality of choice
3 P’s of cavernous sinus syndrome
Pain, proptosis, paralysis
The pupil in cavernous sinus syndrome can be -
Dilated from CN III palsy
Small from Horners
Mid position
Normal (spared)
3 fates after CN III palsy
- Remains permanently fixed and dilated
- Returns to normal (aberrant regeneration)
- Becomes light-near dissociated pupil (pseudo AR)
Aberrant Regeneration of CN III 6 signs
- Pseudo VG (when pt looks down, the lids go up)
- Lid dyskinesis (when MR is stimulated, the lid will go up. When MR is inhibited, lid goes down)
- Light- near dissociation
- Retraction of the once paretic eye on vertical gaze
- Adduction of the once paretic eye on vertical gaze
- Monocular vertical OKN responses are suppressed iin the eye with former palsy
Etiology of Aberrant regeneration
Aneurysm, trauma, tumor
NEVER due to DM !!!!!!!!!!!!!!!
*reorganization of the motor pool on a brainstem basis
Appearance of someone with R SO palsy
Chin depressed
Right head turn
Left head tilt ** Most reliable
SO action
Intort, depress, abduction
When the head is tilted to the left, which muscles of the left eye cause intorsion and which muscles of the right eye cause extortion?
OS: LSO and LSR intort
OD: RIO and LIR extort
Right CN 4 palsy increases hyper when
On left gaze, right head tilt
Left CN 4 palsy increases hyper when
looking right
tilting head left
The most common cause of vertical diplopia that presents clinically
Due to CN 4 palsy
Tectum
A region of the brain. Dorsal part of the midbrain (mesencephalon)
Tegmentum
Region ventral to the ventricular system, responsible for auditory and visual reflexes
The most sensitive way to observe vertical deviations
Have the patient look left and right
Pathway of CN V
Leaves brainstem dorsally –> Circles cerebral peduncles –> passes between superior and posterior cerebral arteries –> Travels in the subarachnoid space –> enters tentorium and goes through can sinus and SOF to innervate SO
Most reliable sign in TED
Upper lid retraction
__% of graves pts have eyelid retraction
__% of pts with graves ophthalmopathy have eyelid retraction
50
90
When you see someone with an eyelid retraction, what do you do? How do you know its not a ptosis of the other lid ?
- Check for contraction of frontalis muscle
- Push in on the patient’s frontal muscle with thumb to eliminate input from CN 7. ??????
- Look at pupils
- Raise the ptotic lid and look at what happens with the retracted one
Grafe’s sign
Lid lag. Less reliable than UL retraction.
Ask pt to look up, then slowly follow your finger down for 10 seconds. When the patient looks down, the lids don’t follow the globes.
