Neuro 2.1

Question 1

Internuclear Ophthalmoplegia

Answer 1

• Lesion of the Medial Longitudinal Fasciculus (MLF)
• Palsy of the MR
• With dissociated gaze evoked nystagmus of the abducting eye (Ataxic Nystagmus)
• Unilateral or bilateral

Question 2

INO - Pathways Involved

Answer 2

• To look to the left, the right frontal eye field sends a signal to the left PPRF
• The left PPRF innervates the left VI (abducens) nucleus, which controls the left LR and causes the LE to abduct (Gaze left)
• Also, the left VIN nucleus innervates the right IIIN (oculomotor) nucleus, which controls the right MR muscle, causing the RE to adduct (Gaze left)
• PPRF - paramedian pontine reticular formation - horizontal gaze centre
• The MLF is the tract connecting the R LR and L MR and the same on the opposite side where it is connecting the L LR and R MR
• In INO there is damage to the MLF giving a deficit in adduction
• Convergence is usually still intact
  
  • No convergence - lesion higher up the MLF
  • Convergence intact - lesion lower down MLF

Question 3

INO - Causes

Answer 3

• MS (most common)
• Stroke - basilar artery occlusion
• Tumour (rarely)

Question 4

INO - Signs

Answer 4

• Exophoria/tropia
  
  • If exotropia, px will tell you of diplopia when reading
  • Any exo deviation will be greater at near than at distance
• Deviation will increase on attempted adduction
• Impaired/slowed saccades useful when differentiating unilateral INO from asymmetric Bilateral INO
• Ataxic nystagmus on lateral gaze (bobbing effect - only when nystagmus is in one eye - not a true nystagmus hence why ataxic)

Question 5

INO - Differential Diagnosis

Answer 5

• Myasthenia Gravis
  
  • Look for fatigue, variability, ptosis, Cogan’s lid twitch, involvement of the vertical muscles
• Medial Wall BO fracture
  
  • History of trauma, enophthalmos, mechanical restriction of abduction
• Duane’s Retraction Syndrome
  
  • Looking for restriction of abduction and characteristic palpebral fissure changes
  • Infranuclear MR palsy (partial 3rd nerve palsy)
  • Very rare

Question 6

INO - Brief Summary

Answer 6

• Ipsilateral MR palsy (MR palsy in one eye e.g. R MR palsy - R INO, lesion in R MLF)
• Saccades more affected than smooth pursuit
• Convergence may be intact
• Ataxic nystagmus
• Skew Deviation - ipsilateral hypertropia
• Bilateral has gaze evoked vert nystagmus and impaired vert smooth pursuit

Question 7

INO - Recovery

Answer 7

• Adduction can recover quite quickly in MS patients
• Ataxic nystagmus may take longer
• This can be a sign when examining a px with previous episodes of INO

Question 8

One and a half Syndrome

Answer 8

• Unilateral INO and ipsilateral horizontal gaze palsy

Question 9

One and a half Syndrome - Causes

Answer 9

• Extensive lesion of the lower Pons
• Affecting the horizontal gaze centre and the adjacent MLF
• Bilateral MR Palsy and one LR Palsy (Gaze palsy + INO)
• MS, stroke, tumour

Question 10

One and a half Syndrome - Signs

Answer 10

• Unilateral INO
• Ipsilateral gaze palsy
• Preserved abduction of contralateral eye
• Ataxic nystagmus
• Intact vertical motility and convergence
• VOR (vestibulo-ocular reflex) usually intact - if px’s head is moved their eyes move in the opposite direction

Question 11

Parinaud’s Syndrome

Answer 11

• Also known as ‘Dorsal Midbrain Syndrome’
• Posterior Commissure Syndrome
• Sylvian Aqueduct Syndrome
• Nystagmus Retractorius Syndrome

Question 12

Parinaud’s Syndrome - Clinical Features

Answer 12

• Loss of upward saccadic movement with normal vertical pursuit
• Convergence Retraction ‘Nystagmus’ – best seen using OKN drum on downward rotation, characteristic rhythmical convergence movement of both eyes with retraction of the globe
• Light/near dissociation - dilated pupils that react only to accommodation and NOT to light
• Collier’s sign - bilateral upper eyelid retraction with lid lag (eyes have come down but lag of lids coming down)
• Papilledema - children more likely to have hydrocephalus (swelling in the brain) but can be present in adults too
• Convergence insufficiency
• Accommodative insufficiency
• Skew deviation

Question 13

Parinaud’s Syndrome - Extensive Lesions

Answer 13

• Pineal mass will compress superior colliculi restricting upward saccades
• Edinger-Westphal Nucleus (rostral portion of 3rd nerve) causing light near dissociation of the pupils

Question 14

Progressive Supranuclear Palsy

Answer 14

• Degeneration of the Brainstem Reticular Formation
• Disease of later life (px’s are older when they come and see you)
• Also known as Steele-Richardson Syndrome
• The vertical gaze palsy differentiates the condition from other Parkinsonian disorders

Question 15

Progressive Supranuclear Palsy - Ophthalmic Signs

Answer 15

• Impaired/slowing of vertical saccades
• Different to Parinaud’s as instead of losing upgaze saccades you lose downgaze saccades
• Usually affecting downgaze initially then complete loss of vertical saccades
• Late stages may have horizontal gaze disorders, with complete Ophthalmoplegia (unable to move eyes at all)
• Frequent square-wave jerks have been noted/saccadic intrusions
• Difficulty in voluntary opening the eyelids (Apraxia of lid opening)

Question 16

Progressive Supranuclear Palsy - Neurological Signs

Answer 16

• History of early falls
• Dysphagia with choking
• Symmetrical akinetic rigidity
• Absence of tremor
• Frontal lobe deficits (will affect personality)
• Difficulty seeing food on their plate
• Trouble walking downstairs
• Combination of vertical gaze palsy and axial rigidity limiting neck movement
• Dementia and death approx. 10yrs after onset

Question 17

Myasthenia Gravis

Answer 17

• Myogenic disorder of the muscles

Question 18

Myasthenia Gravis - Causes

Answer 18

• Autoimmune disorder
• Formation of acetylcholine receptor site antibodies
• The antibodies prevent acetylcholine from binding and reduce effectiveness of neurotransmitter, hence minimal muscle contraction
• Acetylcholine continues to be released
• This maintains the striated muscle contracture until the stores are drained.
• This then shows the classic early muscle fatigue

Question 19

Myasthenia Gravis - Types

Answer 19

• Systemic - eyes also affected
• Ocular - won’t have generalised systemic problem, only EOM’s affected

Question 20

Myasthenia Gravis - Signs

Answer 20

• Characterised by excessive fatiguability of striated muscle
• EOM, facial (can’t contain a smile), bulbar, neck, limb girdle, distal limb and trunk muscles
• When the respiratory muscles are severely affected can be fatal
• EOM’s - mostly affected as they have a very high concentration of receptors and increased sensitivity of the Neuromuscular junction
• May be associated with other autoimmune diseases such as diabetes, Graves’ Orbitopathy and rheumatoid arthritis

Question 21

Myasthenia Gravis - Systemic Signs

Answer 21

• Dependant on which muscle groups are affected
• Ensure that you ask for signs of general MG in case history
• Difficulty chewing/swallowing (jaw muscles)
• Difficulty speaking (bulbar muscles)
• Breathlessness (respiratory muscles)
• Fatigue climbing stairs or holding arms up high shows a weakness of the (limb girdle muscle)
• Lack of facial expression (facial muscles)

Question 22

Myasthenia Gravis - Symptoms

Answer 22

• Symptoms increase as day goes on (fatigue on muscles has not kicked in yet)
• May be symptom free in morning and only complain of fatigue by the evening

Question 23

Myasthenia Gravis - Ocular Symptoms

Answer 23

• Ptosis
• Diplopia (may not have in morning)
• Inadequate lid closure

Question 24

Myasthenia Gravis - Assessment of Ptosis

Answer 24

• Ptosis should increase on continued elevation or repeated up and down gaze
  
  • Extreme cases - lids may drop on continued gaze in the primary position
• Positive Cogan’s Lid Twitch
• Px look down for 15 secs, then refixate in primary position, twitch seen in upper lid as it overshoots the midline and returns to ptotic position
• “Flutter type” upper lid movements due to lid twitches
• If you hold the most affected eyelid open, innervational drive to both upper eyelids is reduced and the ptosis on the other, less affected eye increases
• Frontalis overaction in an attempt to raise the eyelids - apparent upperlid retraction

Question 25

Myasthenia Gravis - Assessment of Diplopia

Answer 25

- Dip can be hor/ver/both, and will vary throughout the day - MG can cause any type of muscle palsy - Limited elevation is the most common - Pseudo INO - Isolated IR palsy - Pseudo gaze palsy (can't look to the right) - Pseudo 3rd, 4th, 6th nerve palsies - Can mimic any EOM condition - Orbicularis weakness - Ask px to close eyes tightly, examiner tries to open them whilst they keep them shut

Question 26

Myasthenia Gravis - Classification

Answer 26

- Neonatal - rare - Congenital - infants may be affected with both ocular and systemic MG - Juvenile - from Birth to Puberty similar to the adult cases - Adults - most common - Ocular - if doesn’t become generalised within 2 yrs, will likely remain ocular

Question 27

Myasthenia Gravis - Investigations

Answer 27

- Ice pack test - Lowering temp can improve symptoms - Ice pack applied to eyelid can improve ptosis - Sleep test - Ask px to nap - lid position will improve if MG - Serum blood testing for acetylcholine receptor site antibodies - 80-90% seen in General MG - 40-50% seen in Ocular MG - Do not exclude MG if negative blood result - Electromyography - To record electrical activity of skeletal muscles - Single or multiple muscle fibres may be tested - Nerve supply to the muscles electronically stimulated and muscle activity recorded

Question 28

Myasthenia Gravis - Management

Answer 28

- The Ophthamologist may trial a longer acting antichoinesterase drug - CT scan of the thymus gland (can be enlarged in MG) - If gland is enlarged (Thymoma), can be removed

Question 29

Myasthenia Gravis - Ocular Management

Answer 29

- Fresnel prisms (change prisms frequently) - Ptosis props (allow lid to be lifted in evening, no need in morning) - Occlusion (to prevent diplopia) - Strabismus surgery under local anaesthesia with adjustables (only when things are very stable)

Question 30

Chronic Progressive External Ophthalmoplegia (CPEO)

Answer 30

- Mitochondrial disorder characterised by ptosis and slowly progressive bilateral ocular immobility - Associated with 'Kearns Sayre Syndrome'

Question 31

CPEO - Clinical Features

Answer 31

- Progressive symmetrical loss of motility - Upgaze usually first affected - Ptosis and orbicularis weakness - Normal pupils and accommodation - Diplopia not commonly complained of as symmetrical and very slowly progressive - Final stages have virtually no eye movements with positive FDT (force duction test? - eye is physically moved with callipers holding the conj anf if unable to move eye this is) due to secondary fibrosis

Question 32

CPEO - Kearns Sayre Syndrome

Answer 32

- CPEO (n childhood)/child with extreme ptosis or palsies etc - Fine pigmentary retinopathy - Mild visual impairment - Can be connected with a heart conduction block

Question 33

CPEO - Differential Diagnosis

Answer 33

- Myasthenia gravis - Graves' disease (TED) - Supranuclear gaze palsy - Multiple nerve palsies

Question 34

CPEO - Management

Answer 34

- Fundoscopy - ECG - Orthoptic assessment to include UFOF - Ptosis Props/Fresnels