brainstem disorders - neuro-ophthalmology meeting'/2018...brainstem disorders dan gold, do...
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Brainstem DisordersDan Gold, DO
Assistant Professor of Neurology, Ophthalmology, Neurosurgery, Otolaryngology – Head & Neck Surgery
The Johns Hopkins University School of Medicine
Relevant Financial
Disclosures
• I have no financial interests or relationships to
disclose.
Outline• 1) Lateral Medullary Syndrome
• Saccadic dysmetria
• Nystagmus
• Semicircular canal & utricle imbalance
• 2) Medial Longitudinal Fasciculus Syndrome
• Nystagmus
• Semicircular canal & utricle imbalance
• 3) Oculopalatal Tremor
1) Lateral Medullary
(Wallenberg)
Syndrome
Lateral Medullary
SyndromeSACCADIC DYSMETRIA & OCULAR
LATEROPULSION
Is the lateral medullary lesion on
the right or the left?
RIGHT
Is the lateral medullary lesion on
the right or the left?
LEFT
Left lateral medullary lesion
R L
R L
Disruption of
climbing fibers
(ICP)
Simple spike (inhibitory)
discharge of Purkinje cells
increases
R L
Increased Purkinje firing increased fastigial inhibition
Inhibition of
fastigial nucleus…
R L
…Decreased
excitation of
contra IBN
R L
Decreased inhibition of left VIth N & PPRF results in
overaction of these structures, bias towards the
left
PEARL: End result with L Wallenberg is L
hypermetria & L ocular lateropulsion
R L
Lateral Medullary
SyndromeNYSTAGMUS
Unidirectional Nystagmus
Is this right 8th nerve or right lateral medullary?
Peripheral SCC imbalance
Central SCC imbalance
Semicircular canals (SCC) – angular acceleration detectors
Unopposed L PC
+ L HC + L AC
Result is mixed left-beating mixed
horizontal-torsional nystagmus
PEARL: At the level of the labyrinth/8th N & medulla, nystagmus can be UNIDIRECTIONAL &
indistinguishable
Torsional Nystagmus
Is this right 8th nerve or right lateral medullary?
PEARL: Pure TORSIONAL nystagmus is
almost always central
Can you have pure torsional nystagmus
from a peripheral lesion?
Gaze-Evoked Nystagmus
PEARL: MVN-NPH responsible for horizontal
gaze-holding GAZE-EVOKED NYSTAGMUS
Wernicke’s encephalopathy
Lateral Medullary
SyndromeVESTIBULO-OCULAR REFLEX
Is this vestibular neuritis or lateral medullary?
Abnormal Head Impulse Test (HIT) to the RIGHT
RIGHT Vestibular neuritis
Damage to horizontal SCC fibers in 8th nerve
Is this vestibular neuritis or lateral medullary?
Abnormal Head Impulse Test (HIT) to the LEFT
LEFT Wallenberg
Damage to horizontal SCC fibers synapsing in the MVN
PEARL: While an abnormal (+) HIT
is almost always indicative of a
peripheral etiology, certain central
localizations (vestibular nucleus)
can cause this finding
Lateral Medullary
SyndromeUTRICULAR-OCULAR REFLEX
Utricle – linear acceleration detector, responds to
translation & head tilt
Physiologic Ocular Tilt Reaction (OTR)
1) Head tilts right
2) Right eye elevates &
Left eye depresses
3) Ocular counter-roll
towards left ear
Skew Deviation
Pathologic OTR from Wallenberg on LEFT(PEARL: caudal to decussation of utricle-ocular motor fibers, ipsi-
hypotropia)
PEARL: Although a “peripheral” skew is possible, it is rare and usually
small. Presence of a skew should be
considered central until proven otherwise.
2) Medial Longitudinal
Fasciculus (MLF)
Syndrome
Left INO due to left MLF injury
What we won’t talk about
MLF SyndromeNYSTAGMUS
MLF lesions – PEARL: Torsional nystagmus is ipsiversive &vertical components can be dissociated
Why?
Most common patterns• Ipsiversive torsional component &…
• 1) UBN OU, more in the contralateral eye
• 2) DBN OU, more in the ipsilateral eye
• 3) Jerky (or hemi-) seesaw nystagmus with dissociated vertical components
• UBN in the contralateral eye
• DBN in the ipsilateral eye
How can the ipsiversive torsional
nystagmus be explained?
Semicircular Canal Pathways
Slow (contraversive) torsional phase towards right ear & Fast (ipsiversive) torsional phase toward left ear
PEARL: Left MLF injury damages PC & AC pathways originating in Right Labyrinth
R L R L
PEARL: Ipsiversive torsional nystagmus can be generated by
vertical (posterior & anterior) SCC asymmetry
Skew deviation with Left hypertropia(PEARL: rostral to decussation of utricle-ocular motor fibers,
ipsi-hypertropia)
What produces dissociated
vertical components?
1) Semicircular Canal Pathways
Stimulate R PC (BPPV) activate R SO, L IR
Slow phase down/towards left earFast phase up/towards right ear
Torsional towards left ear; more DB OS
Weaker L IR
Stronger L SR upward slow phase more DB OS (ipsilesional to MLF)
Torsional towards left ear; more UB OD
Weaker R SR
Stronger R IR downward slow phase more UB OD (contralesional to MLF)
What produces dissociated
vertical components?
2) Utricle-ocular motor
Pathways
Left MLF lesion causes Left hypertropia &
Right hypotropia
Skew (OS) – slow phase
up; fast phase down
Skew (OD) – slow phase
down; fast phase up
PEARL: Fast phases UB OD, DB OS
“Jerky see-saw”
MLF SyndromeVESTIBULO-OCULAR REFLEX
3 pathways for
anterior SCC
1 pathway for
posterior SCC
PEARL: PC VOR more affected
than AC VOR with MLF lesions
May experience oscillopsia from
vertical SCC weakness
PEARL:Abnormal HIT (VOR) in the planes of the posterior
canalsNormal HIT (VOR) in the planes of the anterior canals
MS patient with bilateral MLF lesions
3) Oculopalatal
Tremor (OPT)
Central tegmental tract
Guillain-Mollaret’s triangle
CTT normally inhibits IO
CTT injury IO hypertrophy & spontaneous discharges
Take Home Points• 1) Lateral Medullary Syndrome
• Ipsilesional hypermetria and ocular lateropulsion
• Ipsilesional hypotropia
• Can have an abnormal VOR
• Can have unidirectional nystagmus
indistinguishable from “peripheral” nystagmus
• Or, gaze-evoked nystagmus, torsional nystagmus
Take Home Points• 2) MLF Syndrome
• Ipsilesional hypertropia
• Dissociated torsional (ipsiversive)-vertical
nystagmus
• Most common is more UB in contralesional eye
• VOR abnormality in the planes of the posterior
canals
Take Home Points
• 3) OPT
• Guillain Mollaret’s triangle
• Commonly seen with horizontal gaze palsies,
related to central tegmental tract pathology
• Don’t forget to look at the palate when pendular
nystagmus is present!