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Myasthenia and Myopathies -

An Ocular Perspective.

Dr. V. Natarajan.

Additional Professor of NeurologyInstitute of NeurologyGovernment General Hospital and Madras Medical College

Presentation atCME on Neuro-ophthalmic Disorders.

at Regional Institute of Ophthalmology andGovernment 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Superseded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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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

Edrophonium (Tensilon) Test

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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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