Myasthenia and Myopathies An Ocular Perspective'

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Myasthenia and Myopathies - An Ocular
Perspective.

• Dr. V. Natarajan.
• Additional Professor of Neurology
• Institute of Neurology
• Government General Hospital and Madras Medical
  College

Presentation at CME on Neuro-ophthalmic
Disorders. at Regional Institute of
Ophthalmology and Government Ophthalmic Hospital,
Chennai. September 16, 2006.
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MYASTHENIA

• Ptosis or Diplopia
• Initial symptom in 2/3
• Fluctuation
• Spontaneous improvement
• Restricted weakness 10-40
• Progression in 2 years

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Findings

• One or more ocular muscle
• Pupils spared
• Variable weakness, fatigability
• Shift of ptosis Pathognomonic
• Ocular quiver Superfast saccades

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• Lid Twitch
• Lifting ptotic lid may cause the other lid to
  fall
• Covering of ptotic lid relieves contraction of
  opposite frontalis
• Ice pack test

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Investigations

• Anti Ach R antibody titre
• False positive is rare
• 50 of OMG Antibody negative
• 15 of GMG Antibody negative
• Anti Musk Ab 50 sero negative Ach R

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Edrophonium (Tensilon) Test

• Superseded
• Small risk of respiratory arrest, cardiac
  arrhythmias
• Resuscitation facilities
• Pre dose with Atropine

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Edrophonium (Tensilon) Test

• Ideal dose cannot be predetermined escalating
  dose 2mg, 3mg, 5mg IV
• IM Neostigmine
• Positive in MND and OMN lesions
• Negative test does not exclude MG

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Neurophysiologic Tests

• RNS
• Supra maximal 3 Hz decrement
• SF-EMG
• More sensitive
• 2 muscle fibers in 1 unit
• Inter potential interval variability
• Jitter / Block

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Treatment

• Ach EI Symptom relief
• Steroids Individualized
• Thymectomy
• Debatable
• Young patients
• Recent onset
• Poor response to Ch EI

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OCULO PHARYNGEAL MUSCULAR DYSTROPHY

• Same age group as MG 5th 6th decade
• EOM Ptosis asymmetrical
• Swallowing difficulty
• Facial limb weakness
• EMG Muscle biopsy

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Myotonic Dystrophy

• Ptosis, no EOM involvement
• Facial appearance wasting
• Associated features
• Cardiac
• Cataract
• Endocrine Testicular atrophy
• Myotonia on percussion
• EMG

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Mitochondrial myopathy

• Progressive external ophthalmoplegia with or
  without limb weakness
• RP, heart block, endocrinopathies
• Lactate, Pyruvate
• CSF proteins
• Muscle biopsy

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Congenital Myopathies

• Centro muscular or myotubular myopathy X linked
  recessive- infantile AD- in later life
• Ptosis, EOM, facial and limb muscles
• EMG Spontaneous activity
• Muscle biopsy

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Tolosa Hunt Syndrome

• Inflammatory pathology in anterior cavernous
  sinus, SOF
• Usually painful
• EOM paresis, asymmetrical
• Steroid responsive
• Recurrent
• Associated V, II helpful

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Partial III Nerve

• Superior branch
• Ptosis, Superior rectus
• Pupil spared
• Idiopathic, viral, aneurysm of IC, PCom

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Congenital Myasthenic Syndromes (CMS)

• Heterogenous group
• Genetic defects affecting NMT
• Presynaptic, synaptic and post synaptic defects
• Muscle weakness Increases by exertion

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• Early onset
• Opthalmoplegia, ptosis, bulbar
• Amyotrophy, tendinous retraction facial
  malformation
• Family history

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