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Chronic Progressive External Ophthalmoplegia

CHRONIC — Neuro

Symptoms

  • Slowly progressive, symmetric drooping of the eyelids (ptosis).
  • Gradually reduced eye movements (ophthalmoplegia) over many years.
  • Diplopia is RARE because the progression is symmetric (distinguishes it from Myasthenia Gravis).
  • Chin-up head posture due to severe bilateral ptosis.
  • No diurnal variation or fatigability.
  • Possible systemic features: hearing loss, dysphagia, exercise intolerance, or ataxia.

Clinical Findings

Cardinal clinical pattern

  • Bilateral, symmetric ptosis and external ophthalmoplegia.
  • "Fixed" character: No fluctuation or fatigability (negative ice-pack and rest tests).
  • Eyes may become essentially "frozen" in advanced disease.

Ptosis features

  • Chronic chin-up head posture with prominent forehead rhytids from sustained frontalis over-action.
  • Functional disability is often modest because downgaze is typically preserved.

Muscular & pupil signs

  • Orbicularis oculi weakness is usually present (indicates a generalized myopathy).
  • Pupils are NORMAL (smooth muscle is spared); abnormal pupils should prompt an alternative diagnosis.
  • VOR (doll’s head) and Bell’s phenomenon are lost as the disease progresses.

Kearns–sayre syndrome (KSS)

  • Triad: CPEO + pigmentary retinopathy + cardiac conduction defect.
  • Onset before age 20; usually sporadic.
  • Retinal sign: Diffuse "salt-and-pepper" RPE mottling in the mid-periphery (vision usually remains good).
  • Mandatory finding: Heart block (first-degree to complete) can be silent and fatal.

Mitochondrial histology

  • Muscle biopsy (orbicularis or deltoid) shows "ragged-red fibers" on modified Gomori trichrome staining.
  • Cytochrome-c-oxidase (COX) negative fibers.

Etiology

Mitochondrial genetics

  • Caused by mitochondrial DNA (mtDNA) deletions or point mutations affecting muscle energy metabolism.
  • Inheritance: Often maternal (mtDNA), but autosomal dominant forms (e.g., POLG mutations) exist.

Pathophysiology

  • Chronic energy failure leads to progressive degeneration of the extraocular muscles.

Red Flags

  • Kearns–Sayre Triad: CPEO + pigmentary retinopathy + heart block. Sudden death can occur from complete heart block.
  • EKG is MANDATORY: Every CPEO patient requires an initial EKG and cardiology referral, regardless of age or symptoms.
  • Surgical risk: Aggressive levator resection is contraindicated; poor lid closure and impaired Bell’s phenomenon lead to severe exposure keratopathy.
  • Mitochondrial toxicity: Avoid Valproate (fatal liver failure risk in POLG disease), Metformin (lactic acidosis), and statins.

Investigations

Clinical & screening

  • Mandatory EKG: Screen for AV block or bifascicular block immediately at diagnosis.
  • Dilated fundus exam: Check for salt-and-pepper retinopathy.
  • Orbicularis strength test: Weakness strongly supports CPEO over Myasthenia Gravis.

Laboratory & metabolic

  • Serum lactate and pyruvate levels.
  • CSF analysis: Elevated protein (>100 mg/dL) is characteristic of Kearns–Sayre syndrome.

Genetic & histologic

  • mtDNA analysis: Large single deletions or point mutations.
  • Muscle biopsy: To identify ragged-red fibers if genetic testing is inconclusive.

Exclusion of myasthenia

  • Order anti-AChR and anti-MuSK antibodies; consider ice-pack or rest tests.

Treatment

Surgical management

  • Frontalis sling: For severe ptosis limiting vision; must be conservative to prevent exposure keratopathy.
  • Leave 1–2 mm of residual ptosis to protect the ocular surface.
  • Aggressive overnight lubrication is required postoperatively.

Supportive care

  • Prism glasses or strabismus surgery: For the rare cases of primary-gaze diplopia.
  • Coenzyme Q10 and ubiquinol supplementation (may have limited benefit).

Systemic coordination

  • Multidisciplinary care involving cardiology, endocrinology (screen for diabetes/hypoparathyroidism), and genetics.

Clinical Pearl

Symmetric, "frozen" eyes with bilateral ptosis and no diplopia is CPEO. Because heart block can be silent and fatal, an EKG is a mandatory part of the eye exam.

Differential Diagnosis

  • Myasthenia Gravis (fluctuating, fatigable, asymmetric)
  • Oculopharyngeal muscular dystrophy (dysphagia + ptosis; older onset)
  • Progressive Supranuclear Palsy (axial rigidity, vertical gaze palsy)
  • Thyroid Eye Disease (retraction, proptosis, restrictive motility)
  • Abetalipoproteinemia (Bassen–Kornzweig syndrome)

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