Myopathies

Acquired myopathies like TED are much more common than inherited Always consider in patients with bilateral ptosis

Chronic progressive external ophthalmoplegia

Mutations in mitochondrial DNA Progressive failure of eye movements

Clinical features

• Bilateral ptosis

• Loss of smooth pursuits, saccades and reflex eye movements

  • NB: diplopia is rare as the ophthalmoplegia is symmetrical
  • Upgaze affected first then lateral movements

• Weakness of facial muscles

• Kearns-Sayre syndrome:

  • Ragged red fibre seen in skeletal muscle histologically due to accumulation of mitochondria
  • Presents in 1st or 2nd decade
  • Ptosis
  • External ophthalmoplegia
  • Heart block
  • Diabetes
  • Deafness
  • Short stature
  • Pigmentary retinopathy (‘salt-and-pepper’ appearance at the macula)
  • Peripapillary atrophy

• MELAS syndrome: CPEO, hemianopia and cortical blindness with

  • Mitochondrial encephalopathy
  • Lactic acidosis
  • Stroke-like episodes

Tests

• ECG
• Skeletal muscle biopsy: ragged red fibre
• Serology for mitochondrial DNA analysis
  • + elevated creatine kinase
• MRI
• EMG

Management

Cautious lid surgery as it risks corneal exposure

Oculopharyngeal dystrophy

Autosomal dominant inheritance: expanded GCG repeats. Mutation in PABN1 Recognised to affect a large French-Canadian pedigree Onset is in adulthood: mean of 48 years old for ptosis Progressive myotonia with selective involvement of the eyelid and pharyngeal muscles:

• Delay in muscle relaxation
• Dysphagia
• Pooling of saliva leading to ‘wet’ voice: tongue atrophy in 82%
• Bilateral ptosis
• External ophthalmoplegia: typically limitation of upgaze, but diplopia is not usually a feature (the ophthalmoplegia tends to be more mild than in CPEO)
• Orbicularis weakness

Life expectancy is normal

Myotonic dystrophy

Autosomal dominant with anticipation: triplet expansion increases with successive generations. Also associated with French-Canadians Expanded CTG repeat on chromosome 19q

Clinical features

• Bilateral ptosis
• Cataracts: polychromatic ‘Christmas tree’ or PSCO
• Orbicularis weakness
• Pigmentary retinopathy
• EOM myotonia
• Mournful facies
• Dysphasia
• Dysphagia
• Myotonic grip
• Testicular atrophy
• Frontal balding
• Cardiac myopathy and conduction deficits

Tests

• Genetic testing
• ECG