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BRAIN STEM, CEREBELLUM and NEURO-OPTHALMOLOGY PowerPoint PPT Presentation


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BRAIN STEM, CEREBELLUM and NEURO-OPTHALMOLOGY. Submitted to AskTheNeurologist.Com in 2007. GROSS ANATOMY . LATERAL VIEW. LOCATION OF CRANIAL NERVE NUCLEI WITHIN BRAINSTEM. CRANIAL NERVE 5. - PowerPoint PPT Presentation

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BRAIN STEM, CEREBELLUM and NEURO-OPTHALMOLOGY

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Brain stem cerebellum and neuro opthalmology l.jpg

BRAIN STEM, CEREBELLUM and NEURO-OPTHALMOLOGY

Submitted to AskTheNeurologist.Com

in 2007

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Gross anatomy l.jpg

GROSS ANATOMY

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Lateral view l.jpg

LATERAL VIEW

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Location of cranial nerve nuclei within brainstem l.jpg

LOCATION OF CRANIAL NERVE NUCLEI WITHIN BRAINSTEM

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Cranial nerve 5 l.jpg

CRANIAL NERVE 5

Note that although all fibres enter the brainstem at the level of the pons, those concerned with pain and temperature descend as low as C3

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Pathways involved in horizontal gaze l.jpg

PATHWAYS INVOLVED IN HORIZONTAL GAZE

LEFT FRONTAL

EYE FIELD

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Internuclear opthalmoplegia ino l.jpg

INTERNUCLEAR OPTHALMOPLEGIA ( INO)

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The facial nerve l.jpg

THE FACIAL NERVE

Therefore a lesion at or distal to the facial nucleus will result in weakness of the upper as well as the lower part of the face:- this is what is know as a “ peripheral facial palsy ”

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The Long Tracts

Note sites of decussation of major tracts :

Spinothalamic

Cuneate / Gracile

Corticospinal

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LONG TRACT DECUSSATION

  • Spinothalamic

Spinal cord

  • Gracile / Cuneate

Medulla

Medulla

  • Corticospinal

Therefore:- Lesions at medulla and below can result in dissociated sensory syndromes

- Lesions above the medulla will result in a contralateral upper motor neuron syndrome

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The corticobulbar tract l.jpg

The Corticobulbar Tract

  • Accompanies the corticospinal tract: can assume decussation occurs at level of nucleus

  • Connects with the brain-stem motor nuclei

  • Each tract connects bilaterally with most cranial nerve motor nuclei

EXCEPT:

Part of VII dealing with lower face is innervated unilaterally

Sometimes XII innervated unilaterally

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Bulbar palsy l.jpg

Lower motor neuron therefore signs of denervation present

Tongue wasting and fasciculation

Upper motor neuron therefore bilateral damage necessary

Inappropriate spells of crying / laughing

Jaw jerk and gag reflex increased

Bulbar Palsy

Pseudobulbar Palsy

Dysarthria, dysphagia, weight loss, risk of aspiration pneumonia present in both cases

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Lateral medullary wallenberg s syndrome l.jpg

LATERAL MEDULLARY (WALLENBERG’S) SYNDROME

LESION SITE IN

LATERAL MEDULLARY

SYNDROME

( BLUE)

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VERTIGO, NYSTAGMUS

VESTIBULAR NUCLEI

CLINICAL FEATURES OF LMS I

  • IPSILATERAL HORNER’S SYNDROME

  • DESCENDING SYMPATHETIC TRACT

  • IPSILATERAL CEREBELLAR SIGNS

  • INFERIOR CEREBELLAR PEDUNCLE

  • DYSPHONIA AND DYSPHAGIA

  • NUCLEUS AMBIGUUS

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CLINICAL FEATURES OF LMS II

  • LOSS OF IPSILATERAL FACIAL PAIN AND TEMPERATURE SENSATION

  • SPINAL TRACT AND NUCLEUS OF TRIGEMINAL NERVE

  • LOSS OF IPSILATERAL VIBRATION AND PROPRIOCEPTION IN LIMBS AND TRUNK

  • GRACILE AND

    CUNEATE NUCLEI

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CLINICAL FEATURES OF LMS III

  • LOSS OF CONTRALATERAL PAIN AND TEMPERATURE SENSATION IN LIMBS AND TRUNK

  • SPINOTHALAMIC TRACT

  • HICCUPS

  • UNKNOWN

  • NUCLEUS AND

    TRACTUS

    SOLITARIUS

  • LOSS OF TASTE

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Blood supply of Brainstem and Cerebellum

  • Ant. cerebral

  • Internal carotid

  • Middle cerebral

  • Post. communicating

  • Sup. cerebellar

  • Basilar

  • Ant. Inf. cerebellar

  • Vertebral

  • Ant. Spinal

  • Post. Spinal

  • Post. Inf. Cerebellar

  • Post cerebral

  • Mesencephalic

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Somatotopy of cerebellum

  • Midline lesions:

    • nystagmus

    • Titubation

    • Trunk / gait ataxia

  • Hemispheric lesions:

    • nystagmus

    • ipsilateral limb signs

posterior

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Basic Plan of Cerebellar connections

DN= Dentate nucleus

T = Thalamus

RN = Red nucleus

Each cerebellar cortex controls ipsilateral side of body

Efferents to cortex leave cerebellum via superior cerebellar peduncle

Note: red nucleus is present in midbrain and ultimately controls contralateral half of body

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DSCT= dorsal spinocerebellar tract

VSCT= ventral spinocerebellar tract

VSCT is crossed in the cord but crosses back within cerebellum

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Fronto-ponto Cerebellar tract

Right Cerebral cortex

Note that right side of cortex ultimately controls left cerebellar hemisphere

Fronto-ponto-cerebellar fibres enter cerebellum via middle cerebellar peduncle

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Symptoms and signs of cerebellar disease (VANISH’D)

  • Vertigo

  • Ataxia - usually falls towards lesion

  • Nystagmus – increased with gaze towards lesion

  • Intention Tremor

  • Scanning speech

  • Hypotonia

  • Dysdiadochokinesia + Dysmetria

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Approach to differential diagnosis of cerebellar dysfunction

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Approach to localisation within brainstem

A combination of long-tract and brainstem signs may allow accurate location of a brainstem lesion

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Case 1*

  • Right facial paralysis affecting upper and lower face + diplopia + left hemiparesis ( arm and leg)

  • What is the likely cause of the diplopia and where is the lesion?

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Answer 1

  • Diplopia likely to be due to a right VIth nerve lesion – the VIIth nerve passes around the nucleus of VI just below the 4th ventricle in the pons

  • Right pons

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Case2

  • A 72 year old man with a right hemiplegia. On examination in addition to the hemiplegia with pyramidal signs his tongue deviates to the left and is atrophic and fasciculating on the left side

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Answer 2

  • Left medulla

  • Combination of XII LMN lesion on left, and

    right UMN hemiplegia places lesion in the

    left medulla above the decussation of the

    pyramidal tract

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Case 3*

  • A 26 year old woman with horizontal diplopia on looking to left and right. On examination impaired adduction of both eyes on attempted lateral gaze with relative preservation of convergence. In addition dysmetria and intention tremor of right hand.

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Answer 3

The patient has features of

-a lesion of the medial longitudinal

fasciculus bilaterally

-a lesion of the right cerebellum ( or its connections)

  • A bilateral MLF lesion is almost pathognomonic of MS and the addition of cerebellar signs strengthens the diagnosis

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Case 4 *

  • A 24 year old woman with vertical diplopia maximal on looking up and horizontal diplopia maximal on looking right, difficulty swallowing, ptosis more pronounced on left, facial weakness more pronounced on right. Sensation in tact.

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Answer 4

  • No single brainstem lesion can account for all these features.

  • Myaesthenia gravis may present in this way with a combination of pure motor signs attributable to NMJ dysfunction of muscles innervated by various brainstem nuclei.

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Case 5*

  • A 65 year old lady with a right sided ptosis, right pupil dilatation, diplopia, left sided cerebellar and pyramidal signs

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Answer 5

  • Right Midbrain

  • Eye signs are due to right III palsy.

  • Contralateral cerebellar signs due to damage to right Red Nucleus

  • Contralateral pyramidal signs due to damage to corticospinal tract

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Case 6*

  • A 84 year old lady with sudden onset of a left hemiparesis and deviation of both eyes to the left side

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Answer 6

  • Right pons

  • The combination of gaze deviation and hemiparesis usually occurs with large hemispheric CVA’s; in such a case the eyes deviate to the side of the lesion ( due to destruction of the frontal gaze centre)

  • In case 8 the eyes deviate away from the lesion (left) due to the destruction of the right pontine paramedian reticular formation (PPRF)

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What is Nystagmus?

  • Rhythmic oscillation of the eyes

  • Fast phase ( saccade)

  • Slow phase ( smooth-pursuit – like)

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Describing nystagmus

  • Position of gaze in which occurs or is most prominent

  • Direction ( of FAST phase)

  • Precipitating / exacerbating factors

  • Fatiguing / persistent

  • Associated symptoms

    - Vertigo

    - Oscillopsia – feeling that vision is jerky

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Example vestibular neuronitis left side l.jpg

Example:- Vestibular neuronitis left side

  • Most prominent on gaze towards right

  • Horizontal right – sided nystagmus with a rotatory component

  • Exacerbated by quick head movements

  • Associated with severe vertigo + / - vomiting

  • Persistent / may fatigue

Illustrates following rule:

Nystagmus is always most prominent on gaze towards the direction of the fast phase

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Nystagmus may be l.jpg

Nystagmus may be………

  • Physiological

  • Pathological

Central

Peripheral

this is THE most important distinction to be made in assessing nystagmus!

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Is it normal l.jpg

IS IT NORMAL??

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Central vs Peripheral ( guidelines)

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Diplopia

“ The subjective feeling of seeing double”

May be:

  • Monocular ( present even when one eye open)

  • Binocular ( present only when 2 eyes open)

Monocular diplopia is either due to a local (ocular) process, “non-organic” in origin or very rarely from visual cortical dysfunction

Therefore almost all neurological causes of diplopia are “ binocular ”

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Binocular diplopia…questions

  • Horizontal vs Vertical ?

  • Worse on looking in which direction?

  • Worse on focussing near or far ?

  • RULES

  • Diplopia is maximal on gaze in the direction of action of the weak muscle.

  • The false image is projected towards the direction of action of the weak muscle

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Anatomical sites which may cause diplopia

  • Internuclear ( INO )

  • Nucleus

  • Fascicle

  • Cranial nerve

  • Neuromuscular junction (NMJ)***

  • Muscle

  • Local distortion of orbit

*** ANY type of diplopia or gaze disturbance may be due to a problem at the NMJ….usually Myaesthenia Gravis …and often with ptosis

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Example of a patient with Myaesthenia Gravis

The examiner is lifting the patient’s eyelids for 2 reasons:

- Good examination technique!

- In this case the patient has bilateral ptosis

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Which of the following patients cannot have MG?

  • Right eye totally paralysed, left eye moves freely but with ptosis

  • Inability of both eyes to move to left with no diplopia

  • Bilateral inability to look up with bilateral ptosis

  • Left eye deviated down and laterally with ptosis on left and left pupil larger than right

Myaesthenia Gravis NEVER causes pupil asymmetry ( anisocoria)

…..which brings us onto the next subject…..

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Anisocoria l.jpg

Anisocoria

“ Inequality between the 2 pupils”

Pupils may be :

- equal ( to within 1mm)

- unequal due to surgery / trauma usually irregular)

- unequal due to a neurological condition

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The 2 neurological causes of anisocoria

  • One pupil too big

  • One pupil too small

Parasympathetic---------------------------------------Sympathetic

Constricts (Ach)

Travels in III

Dilates (Nad)

Symp fibres

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Anisocoria rules l.jpg

Anisocoria rules

  • Darkness exaggerates failure of dilation

  • Bright light exaggerates failure of constriction

  • If unilateral ptosis is present assume that the eye with the ptosis is sick!

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Patient with a left IIIrd nerve palsy:

- Left sided ptosis

- Left pupil > Right

- Medial rectus weakness seen on attempted gaze to right

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Right – sided Horner’s Syndrome

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Horner’s syndrome

  • Due to interruption of sympathetic input to eye

    -Ptosis

    • Miosis ( constriction )

    • Anhidrosis ( lack of sweating on side of face)

Lesion sites - hypothalamus, brainstem, cervical cord

- cervical sympathetic chain and ganglion

- fibres running next to carotid artery

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Sphincter pupillae muscle

Pathways involved in the pupillary light reflex

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Left RAPD ( relative afferent pupillary defect)

AKA Marcus-Gunn pupil

For example a patient with multiple sclerosis who is suffering from acute left sided optic neuritis

Step 1

small reaction of BOTH pupils to light on L

Step 2

Normal (large) reaction of BOTH pupils to light on R

Step 3

Dilatation of BOTH pupils with light on L when compared to Step 2

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A lesion here would cause RAPD

A lesion beyond the chiasm would NOT cause RAPD

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Case 7*

  • Right facial paralysis with sparing of the forehead, right hemiparesis affecting arm>leg, diplopia maximal on looking right, left ptosis, left pupil larger than right, tongue deviation to right side

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Answer 7

  • Left midbrain

  • The UMN facial weakness places lesion above pons; remember that supra-nuclear innervation of each XIIth nerve nucleus is often unilateral therefore tongue deviation may occur

  • The IIIrd nerve palsy places lesion in midbrain

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Question 8*

  • A 23 year old obese woman with acne with a 3 month history of headaches vomiting and transient visual symptoms. Over last 3 days horizontal diplopia maximal on looking left and into distance; except for the diplopia and one other abnormality the neurological examination is normal.

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Answer 8

  • The “other abnormality” is papilloedema

  • This woman is exhibiting classical features of raised intracranial pressure (likely in this case to be due to pseudotumour cerebri). A VIth nerve palsy may occur as a false localising sign in any case of raised intracranial pressure.

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THE END

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