Brainstem Disorders Dan Gold, DO Assistant Professor of Neurology, - - PowerPoint PPT Presentation

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Brainstem Disorders Dan Gold, DO Assistant Professor of Neurology, - - PowerPoint PPT Presentation

Nov 03, 2023 492 likes •1.14k views

Brainstem Disorders Dan 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

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Brainstem Disorders

Dan Gold, DO Assistant Professor of Neurology, Ophthalmology, Neurosurgery, Otolaryngology – Head & Neck Surgery The Johns Hopkins University School of Medicine

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Relevant Financial Disclosures

  • I have no financial interests or relationships to

disclose.

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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
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1) Lateral Medullary (Wallenberg) Syndrome

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Lateral Medullary Syndrome

SACCADIC DYSMETRIA & OCULAR LATEROPULSION

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Is the lateral medullary lesion on the right or the left?

RIGHT

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Is the lateral medullary lesion on the right or the left?

LEFT

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Left lateral medullary lesion

R L

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R L

Disruption of climbing fibers (ICP)

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Simple spike (inhibitory) discharge of Purkinje cells increases

R L

Increased Purkinje firing  increased fastigial inhibition

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Inhibition of fastigial nucleus…

R L

…Decreased excitation of contra IBN

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R L

Decreased inhibition of left VIth N & PPRF results in

  • veraction of these

structures, bias towards the left

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PEARL: End result with L Wallenberg is L hypermetria & L ocular lateropulsion

R L

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Lateral Medullary Syndrome

NYSTAGMUS

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Unidirectional Nystagmus

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Is this right 8th nerve or right lateral medullary?

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Peripheral SCC imbalance Central SCC imbalance

Semicircular canals (SCC) – angular acceleration detectors

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Unopposed L PC + L HC + L AC Result is mixed left- beating mixed horizontal-torsional nystagmus

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PEARL: At the level of the labyrinth/8th N & medulla, nystagmus can be UNIDIRECTIONAL & indistinguishable

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Torsional Nystagmus

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Is this right 8th nerve or right lateral medullary?

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PEARL: Pure TORSIONAL nystagmus is almost always central Can you have pure torsional nystagmus from a peripheral lesion?

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Gaze-Evoked Nystagmus

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PEARL: MVN-NPH responsible for horizontal gaze-holding  GAZE-EVOKED NYSTAGMUS Wernicke’s encephalopathy

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Lateral Medullary Syndrome

VESTIBULO-OCULAR REFLEX

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Is this vestibular neuritis or lateral medullary?

Abnormal Head Impulse Test (HIT) to the RIGHT

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RIGHT Vestibular neuritis

Damage to horizontal SCC fibers in 8th nerve

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Is this vestibular neuritis or lateral medullary?

Abnormal Head Impulse Test (HIT) to the LEFT

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LEFT Wallenberg

Damage to horizontal SCC fibers synapsing in the MVN

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PEARL: While an abnormal (+) HIT is almost always indicative of a peripheral etiology, certain central localizations (vestibular nucleus) can cause this finding

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Lateral Medullary Syndrome

UTRICULAR-OCULAR REFLEX

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Utricle – linear acceleration detector, responds to translation & head tilt

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Physiologic Ocular Tilt Reaction (OTR)

1) Head tilts right 2) Right eye elevates & Left eye depresses 3) Ocular counter-roll towards left ear

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Skew Deviation

Pathologic OTR from Wallenberg on LEFT (PEARL: caudal to decussation of utricle-ocular motor fibers, ipsi- hypotropia)

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PEARL: Although a “peripheral” skew is possible, it is rare and usually small. Presence of a skew should be considered central until proven

  • therwise.
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2) Medial Longitudinal Fasciculus (MLF) Syndrome

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Left INO due to left MLF injury

What we won’t talk about

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MLF Syndrome

NYSTAGMUS

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MLF lesions – PEARL: Torsional nystagmus is ipsiversive & vertical components can be dissociated

Why?

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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
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How can the ipsiversive torsional nystagmus be explained? Semicircular Canal Pathways

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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

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PEARL: Ipsiversive torsional nystagmus can be generated by vertical (posterior & anterior) SCC asymmetry

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Skew deviation with Left hypertropia (PEARL: rostral to decussation of utricle-ocular motor fibers, ipsi-hypertropia)

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What produces dissociated vertical components? 1) Semicircular Canal Pathways

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Stimulate R PC (BPPV)  activate R SO, L IR

Slow phase down/towards left ear Fast phase up/towards right ear

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Torsional towards left ear; more DB OS

Weaker L IR Stronger L SR  upward slow phase  more DB OS (ipsilesional to MLF)

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Torsional towards left ear; more UB OD

Weaker R SR Stronger R IR downward slow phase  more UB OD (contralesional to MLF)

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What produces dissociated vertical components? 2) Utricle-ocular motor Pathways

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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”

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MLF Syndrome

VESTIBULO-OCULAR REFLEX

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3 pathways for anterior SCC 1 pathway for posterior SCC

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PEARL: PC VOR more affected than AC VOR with MLF lesions

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May experience oscillopsia from vertical SCC weakness

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PEARL: Abnormal HIT (VOR) in the planes of the posterior canals Normal HIT (VOR) in the planes of the anterior canals

MS patient with bilateral MLF lesions

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3) Oculopalatal Tremor (OPT)

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Central tegmental tract

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Guillain-Mollaret’s triangle

CTT normally inhibits IO

CTT injury  IO hypertrophy & spontaneous discharges

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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
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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

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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!