Chronic progressive external ophthalmoplegia

A mitochondrial disorder affecting eye muscles

Chronic progressive external ophthalmoplegia (CPEO) is a rare neuromuscular disorder characterized by slowly progressive paralysis of the extraocular muscles, which are responsible for controlling eye movements. This condition leads to ptosis (drooping of the eyelids) and limited eye movement, often resulting in diplopia (double vision). CPEO is primarily associated with mitochondrial myopathy, a type of mitochondrial disease.

Pathophysiology

CPEO is caused by defects in the mitochondria, the energy-producing structures within cells. These defects can result from mutations in nuclear DNA or mitochondrial DNA (mtDNA). The mutations lead to impaired energy production, particularly affecting tissues with high energy demands, such as the muscles controlling eye movement. The accumulation of dysfunctional mitochondria in these muscles results in their progressive weakness and paralysis.

Clinical Features

The hallmark of CPEO is the gradual onset of ophthalmoplegia, which typically begins in adulthood. Patients often present with:

• Ptosis: Drooping of one or both eyelids, which may be the initial symptom.
• Ophthalmoplegia: Limited movement of the eyes in all directions, leading to difficulty in tracking objects and diplopia.
• Facial Weakness: Some patients may experience mild weakness of the facial muscles.
• Muscle Weakness: In some cases, CPEO may be associated with generalized muscle weakness, particularly in the limbs.

Diagnosis

The diagnosis of CPEO is based on clinical examination, family history, and specialized tests. Key diagnostic tools include:

• Ophthalmologic Examination: To assess the extent of eye movement limitation and ptosis.
• Muscle Biopsy: May reveal characteristic "ragged-red fibers," indicative of mitochondrial myopathy.
• Genetic Testing: To identify mutations in mtDNA or nuclear DNA associated with CPEO.
• Electromyography (EMG): To evaluate muscle function and detect abnormalities.

Management

There is currently no cure for CPEO, and treatment is primarily supportive. Management strategies include:

• Ptosis Surgery: To improve eyelid function and vision.
• Prism Glasses: To alleviate diplopia by correcting eye alignment.
• Physical Therapy: To maintain muscle strength and function.
• Genetic Counseling: For affected individuals and their families to understand the inheritance patterns and risks.

Prognosis

CPEO is a progressive condition, but the rate of progression can vary widely among individuals. While the disorder primarily affects eye muscles, some patients may develop additional symptoms related to mitochondrial dysfunction, such as cardiac conduction defects or sensorineural hearing loss.

Related Pages

• Mitochondrial disease
• Ophthalmoplegia
• Ptosis
• Diplopia
• Mitochondrial myopathy