Chronic progressive external ophthalmoplegia (CPEO) is a rare mitochondrial ocular disorder.
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Clinical presentation
Patients present with slowly progressive bilateral ophthalmoplegia (limitation of eye motion) and blepharoptosis 4. Diplopia is uncommon 4.
The entity can manifest in isolation or as a syndrome with other neurological deficits, the latter of which is referred to as CPEO+ (or CPEO plus). One specific syndromic variant of CPEO is Kearns-Sayre syndrome, which additionally has a pigmentary retinopathy and may have cardiac conduction abnormalities or ataxia 4.
Pathology
Genetics
Typically, patients have a large deletion in mitochondrial DNA (mtDNA), but autosomal dominant or recessive forms due to mutations in nuclear genes that affect mitochondrial DNA (mtDNA) repair or replication have also been reported (e.g. POLG-related disorders) 1,4. It is sporadic in a majority of cases 4.
Radiographic features
MRI
Patients show variable levels of mild to moderate extraocular muscle atrophy (25-60% volume loss compared to normal controls) 1-3. The findings should be bilaterally symmetric.
Some affected patients show extraocular muscle signal abnormalities, including T1 hyperintensity and very occasionally STIR hyperintensity 3. The T1 hyperintensity appears spongiform or like streaks within the muscle 2,3.
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