Brainstem StrokeAnnegret Dahlmann-NoorConsultant in Paediatric Ophthalmology and Strabismus

Wales and West Vision Conference

26 June2015

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BackgroundIncidence:

Each year in England, approximately 110,000 people have a first or recurrent stroke and a further 20,000 people have a transient ischaemic attack

Wales: 11,000 have a first or recurrent stroke per year, of which 6,000 new stroke events

More than 900,000 people in England are living with the effects of stroke, with half of these being dependent on other people for help with everyday activities

Eye movement problems after stroke

Eye movement problems after stroke

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Vision and eye movement problems after stroke1. Sensory (afferent): visual field

defects

2. Ocular motility (efferent):double vision from limitation of eye movementsjumping images from nystagmushead turns to compensate for gaze palsy

3. Processing: Charles Bonnet, palinopsia

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BackgroundMost strokes are ischaemic (80-85%), some are haemorrhagic

Two main blood supplies to the brain:

1) Carotid

2) Vertebral/basilar arteries

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Background27% of ischaemic strokes affect the vertebral/basilar arteries

Symptoms of brainstem stroke: vertigo - dizzinessdouble vision/binocular visual disturbance generalised weakness

Eye movement problems after stroke

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Blood supply to brainstem and cerebellum

Posterior cerebral artery

Superior cerebellar artery: IV ncl/fasc

Anterior inferior cerebellar artery: VI ncl/fasc

Posterior inferior cerebellar artery

Vertebral artery

Branches of bifurcation of basilar artery: III ncl/fasc

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Superior cerebellar artery

Branches of basilar artery

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Paramedian branches of basilar artery

Branches of basilar artery and of anterior inferior cerebellar artery

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Eye movements• Smooth pursuit: eyes follow a moving target

• Saccades: gaze rapidly jumps from one fixation point to another

• Vergence eye movements: eyes do not move in parallel, but in relation to each other: convergence: when looking at something close up

• Vestibulo-ocular reflex (VOR): the signal triggering eye movements comes from the balance organ (labyrinth), which keps the image of the visual surroundings stable on the retina during head movements

• Optokinetic reflex: triggered by moving visual targets, consists of smooth pursuit and saccades

• Gaze holding: ability to keep the eyes in an eccentric position

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The players: the team on the ground• Six muscles on each eye

• Move eye horizontally, vertically, and tilt it in- and outwards

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The players: the middle managementVertical eye movements

• Interstitial nucleus of Cajal (INC)

• Rostral interstitial nucleus of the MLF (riMLF)

Horizontal eye movements

• Parapontine reticular formation (PPRF)

• Abducens nucleusThe runner:

Medial longitudinal fasciculus (MLF)

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The playersVertical eye movements

• Interstitial nucleus of Cajal

• Rostral interstitial nucleus of the MLF

Horizontal eye movements

• Paramedian pontine reticular formation

• Abducens nucleus

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The players: the supreme controls• Frontal eye field: sends signals to the

third nerve nucleus on the same side, and the paramedian pontine formation on the opposite side: horizontal saccades, and to the rostral interstitial nucleus of the MLF (riMLF) for vertical saccades

• Parietal eye field: production of smooth pursuit eye movements, also participates in the production of saccades (more to novel visual stimuli rather than to remembered targets)

• Paramedian pontine reticular formation: excitatory burst neurons that start the “pulse”

From: Oculomotor Dysfunction in Amyotrophic Lateral Sclerosis:  A Comprehensive ReviewArch Neurol. 2011;68(7):857-861. doi:10.1001/archneurol.2011.130

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The action: midbrain• Oculomotor nucleus• Trochlear nucleus• Rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF)

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Fourth cranial nerve

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Fourth cranial nerve

MRI courtesy of Dr Indran Davagnanam

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Third cranial nerve infarct

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Oculomotor nerve paresis• lack of adduction: eye deviated outwards• lack of elevation: eye deviated downwards• lid droop (ptosis)

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Midbrain• Control of vertical and torsional eye movements• Input from cortex (vertical and torsional saccadic commands and vertical gaze-holding signal)• Input from lower brainstem (vestibular and pursuit signals)• Generation of vertical saccades: rostral interstitial nucleus of the MLF (riMLF): projects bilaterally for eye elevation (superior rectus and inferior oblique), ipsilaterally for eye depression, also projects to the interstitial nucleus of Cajal (INC) From: T.C. Frohman et al. Neurology 2008;70:e57-e67

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Midbrain• Example: left head tilt

• Otoliths (balance organ) trigger signal to extorters (inferior oblique and inferior rectus muscles) in the right eye (cross midline) and to intorters of left eye (superior oblique and superior rectus muscles) in the left eye (double crossing)

• plus: torsional fast phases mediated by riMLF

• INC: neural integration of vertical and torsional gaze, eye-head coordination during roll movements, and inhibitory burst neurons for vertical eye movements

• lesions: intorsion and elevation of the right eye and extorsion and depression of the left eye = skew deviation From: T.C. Frohman et al. Neurology 2008;70:e57-e67

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Lesions of vestibular nucleiLesions of vestibular nuclei, for example lateral medullary infarction (Wallenberg syndrome):• Vestibular imbalance: nystagmus or skew deviation and impairment of gaze holding for all types of conjugate eye movement• Ocular tilt reaction (OTR): skew deviation, hypotropia on same side, lower eye extorsion and head tilt towards side of lesion • Lateropulsion: eyes deviate conjugately towards the side of the lesion if lids are closed, or with saccades Top: isolated vestibular nucleus infarct.

Bottom: different patient - marked skew deviationT.C. Frohman et al. Neurology 2008;70:e57-e67

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Dorsal midbrain syndromeLesions of the riMLF: • loss of upward gaze (vestibulo-ocular reflex and Bell phenomenon may be spared)• slowing of vertical saccades below the horizontal meridian, • convergence weakness, • convergence-retraction nystagmus, • light-near dissociation of pupils,• lid retraction

Patient with dorsal midbrain syndromeT.C. Frohman et al. Neurology 2008;70:e57-e67

Eye movement problems after stroke

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Stop and recap• 1. Strokes affecting the basilar artery or its brances can affect eye movements, causing double vision and jumping images• 2. There are different types of eye movements – smooth pursuit, saccades, vergences, and eye movements in response to changes in head or body position• 3. Areas in the cortex trigger saccades (fast eye movements) and pursuits.• 4. Centres in the midbrain forward signals to the cranial nerves which innervate the eye muscles that move the eyes vertically and in torsion.• 5. Lesions in these pathways can cause loss of saccades and vertical eye movements, and a complex change in vertical and torsional eye movements (skey deviation)

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Now the easy stuff: horizontal eye movements• Abducens nucleus

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Horizontal eye movements

1. Two types of nerve fibres in the abducens nerve:a) motoneurons to lateral rectus muscle on the same sideb) internuclear neurons, which project up the contralateral medial longitudinal fasciculus to contact medial rectus motoneurons of the oculomotor nucleus

=> Conjugate, horizontal eye movements

. Details of the descending projection involved in the volitional control of horizontal saccadic eye movements. Excitatory pathways are shown in orange and the reciprocal inhibitory pathways are shown in blue. T.C. Frohman et al. Neurology 2008;70:e57-e67

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Abducens nucleus

1. Inputs: vestibular and optokinetic inputs from vestibular nuclei

2. Saccadic commands originate from burst neurons of the pontine and medullary reticular formation

3. Descending smooth pursuit pathway via cerebellar nuclei to abducens nucleus

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Projections involved in the activation of the left lateral semicircular canal. This figure illustrates the projections involved during the activation of the left lateral semicircular canal. T.C. Frohman et al. Neurology 2008;70:e57-e67

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Stop and recap

1. From the abducens nucleus, signals go the lateral rectus muscle on the same side and medial rectus on the opposite side

2. Those signals are triggered by messages from the vestibular nuclei (tilting head), cerebellar nuclei (moving body), burst neurons in the PPRF, and the frontal and parietal eye fields.

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How things can go wrong in brainstem stroke1. Abducens nucleus lesions

2. Medial longitudinal fasciculus lesions

3. Combined lesions of MLF and abducens nucleus

4. PPRF lesion

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How things can go wrong in brainstem stroke1. Abducens nucleus lesions: paralysis of lateral rectus muscle on the same side and medial rectus muscle on the opposite side (vergence spared)

Usually associated with involvement of adjacent structures: facial nerve fascicle, MLF, paramedian pontine reticular formation

Eye movement problems after stroke

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How things can go wrong in brainstem stroke1. Abducens nucleus lesions: paralysis of lateral rectus on same side and medial rectus muscle on opposite side, vergence spared

Usually associated with involvement of adjacent structures: facial nerve fascicle, MLF, paramedian pontine reticular formation

MRI courtesy of Dr Indran Davagnanam

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MLF2. MLF lesions: Internuclear ophthalmoplegia (INO): • paresis of adduction on the side of the lesion,• abduction overshoot of the contralateral eye

Often accompanied by • skew deviation (disruption of the otolithic-ocular connections), • gaze-evoked vertical nystagmus,• impaired vertical pursuit, • decreased vertical vestibular responses, • small-amplitude saccadic intrusions

Volitional saccadic pathway with a lesion in the right medial longitudinal fasciculus (MLF) that results in an internuclear ophthalmoparesis (INO). Volitional saccadic pathway with a lesion in the right MLF that results in an INO during an attempted saccade to the patient's left. T.C. Frohman et al. Neurology 2008;70:e57-e67

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INOINO continued:

Usually orthotropic (straight eyes) or exophoric (latent outward drift) in primary position, except when associated with skew deviation

Occasionally exotropia (manifest outward strabismus) in bilateral INO (wall-eyed bilateral INO, WEBINO)

T.C. Frohman et al. Neurology 2008;70:e57-e67

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One and a half3. Combined lesion of one MLF and the adjacent abducens nucleus, or its inputs: • paresis of all conjugate movements except for abduction of the eye on side opposite the lesion: one and a half syndrome• If acute, may present with marked exotropia• Deviated eye (opposite the side of the lesion) may show marked nystagmus

Right internuclear ophthalmoparesis (INO) upon attempted gaze to the left. T.C. Frohman et al. Neurology 2008;70:e57-e67

Eye movement problems after stroke

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PPRF lesions4. Lesions of the PPRF

Loss of saccadic burst neurons: loss of saccades and quick phases of nystagmus to the side of the lesion

Pontine lesions may cause unilateral defect of smooth pursuit

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Stop and recap

1. Abducens nucleus lesions: loss of abduction same side, loss of adduction opposite side; often involve PPRF as well, so horizontal gaze palsy

2. Medial longitudinal fasciculus lesions: impaired adduction on the side of the lesion, abduction overshoot of the opposite eye

3. Combined lesions of MLF and abducens nucleus: affects all horizontal eye movements except for abduction on the side opposite the lesion

4. PPRF lesion: loss of saccades to the side of the lesion

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The last part of the talk: cerebellum and cortex stroke

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Cerebellar infarct• Three arteries from the posterior circulation:• Posterior-inferior cerebellar artery• Anterior-inferior cerebellar artery• Superior cerebellar artery

Infarcts often associated with brainstem infarcts, so mixed clinical picture

Superior cerebellar artery

Anterior inferior cerebellar artery

Posterior inferiorcerebellar artery

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Cerebellar infarct

• Posterior-inferior cerebellar artery: acute vertigo and nystagmus, possibly gaze-evoked nystagmus

• Anterior-inferior cerebellar artery:vertigo, vomiting, hearing loss, facial palsy, ipsilateral limb ataxia

• Superior cerebellar artery: ataxia of gait and limbs and vertigo, saccadic contrapulsion (overshooting of contralateral saccades, undershooting of ipsilateral saccades; attempted vertical saccades are oblique)

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Cerebral hemispheric lesions • acute lesion: eyes often deviated conjugately toward the side of the lesion; often after large stroke involving right post-rolandic cortex; associated with visual hemineglect

Eye movement problems after stroke

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Cerebral hemispheric lesions • chronic lesion: no resting deviation; persistence of gaze deviation• Small-amplitude nystagmus• Deficit of horizontal pursuit when tracking targets moving towards the side of the lesion (OKN)

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Bilateral Frontoparietal lesions • Acquired Ocular Motor Apraxia• Loss of voluntary control of eye movements• Preservation of reflex movements, including vestibulo-ocular reflex and quick phases of nystagmus• Can be associated with difficulty in lid opening• Balint syndrome: loss of voluntary eye movements plus disturbance of visual attention

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Management of ocular motility problems

1. Prism treatment

2. Occlusion

3. Ptosis props

4. Surgery/botulinum toxin

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Principles of surgery

Eye movement problems after stroke after Stroke

1. Enhance muscle action by shortening a paretic muscle, or by transposing a different muscle towards the insertion of a paralytic muscle

2. Create a matching defect by weakening a muscle, to reduce double vision

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Thank you