31 Progressive Myogenic Ptosis: Evaluation and Management
Abstract
This chapter introduces the approach to and management of different forms of progressive myogenic ptosis. In this ptosis category, there is usually localized or diffuse intrinsic muscular disease that results in poor levator excursion. These ptoses are rare, usually inherited, and bilateral, and may have associated ocular or systemic abnormalities. There may be poor extraocular motility and orbicularis muscle function. The amount of levator function indicates the extent of the disease and helps inform the surgeon’s choice for corrective surgery.
31.1 Introduction
Progressive myogenic ptoses consist mostly of genetic diseases that are intrinsic to the levator muscle. The levator, orbicularis, and extraocular muscles are often affected. Understanding the common presentations and physical findings observed in this ptosis group makes diagnosis and treatment straightforward. 1 When suspected, it is important to obtain a thorough family history even though variable penetrance may obscure a hereditary pattern or mutations may be sporadic.
Management of progressive myopathic ptosis depends upon the degree of upper eyelid ptosis, measurement of levator excursion, and intactness of corneal protective mechanisms (lagophthalmos, intact Bell’s phenomenon, and extent of dry eye).
31.2 Causes of Progressive Myopathic Ptosis
Progressive myopathic ptosis may occur in children and adults. Those seen in children are rare, frequently fatal, and discussed in Chapter 32. Below, we discuss the most common disorders seen in adulthood. Appropriate workup may include referral to other specialists and systemic testing to evaluate potentially life-threatening issues.
31.2.1 Oculopharyngeal Muscular Dystrophy
Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant muscle disorder, usually of late onset. 2 Patients become symptomatic by the fifth and sixth decades. It is characterized by progressive bilateral ptosis of the eyelids, dysphagia, and proximal muscle weakness (Fig. 31.1). Although other extraocular muscles may become gradually involved, complete external ophthalmoplegia is rare and intrinsic eye muscles are not affected. The ptosis is progressive and symmetrical as a result of levator weakness. Patients have good orbicularis function and Bell’s phenomenon. There are different phenotypes. In early onset disease, there is usually rapid progression of symptoms and severe disease. In late onset disease, there is slower progression and milder disease. OPMD occurs because of a stable mutation causing an expansion in the PABPN1 gene located on chromosome 14. Filamentous intranuclear inclusions in muscle fibers of OPMD patients are the pathological hallmark of the disease. 3
OPMD has a worldwide distribution with the largest cluster in Quebec followed by Bukhara Jews in Israel. 4 Also, an unexpected large OPMD population of Hispanic offspring living in New Mexico have been revealed. 5 To confirm the diagnosis in patients clinically suspected of having OPMD, molecular genetic testing is performed. The most common ptosis treatment options include levator resection and advancement in mild or moderate cases and frontalis suspension of the eyelids in more advanced cases. 6
31.2.2 Chronic Progressive External Ophthalmoplegia
Chronic progressive external ophthalmoplegia (CPEO) is a progressive myopathy affecting the external eye muscles bilaterally and usually occurs sporadically (Fig. 31.2). CPEO usually results from genetic defects that affect mitochondrial function. It is the most common manifestation of mitochondrial myopathy. Patients usually present in young adulthood. Progressive paralysis of the extraocular muscles is seen. The phenotype is varied due to the number of mitochondria involved. The ptosis develops and is associated with an extreme loss of ocular motility, to the point of no motility of lids and eyebrows. 7 The orbicularis is usually weak as well and therefore there is poor eyelid closure. Pupillary muscle fibers are spared and the ptosis may precede the motility problem.
Kearns–Sayre syndrome is a variant of CPEO, often called CPEO Plus. 8 It is associated with other tissue changes including heart block, pigmentary retinopathy, and sometimes peripheral muscle weakness. These patients should have a neurologic workup. 9 In both CPEO and Kearns–Sayre syndrome, hearing loss and diabetes mellitus can precede the onset of muscle involvement by years. 10
Ptosis associated with CPEO is one of the most difficult to manage. Due to weakness of the orbicularis oculi muscles and poor eyelid closure, the lids should not be raised in excess. Conservative frontalis sling procedures are useful to elevate the lids. 11 , 12 Due to poor Bell’s phenomenon, incomplete blink and lack of eye movements, exposure keratopathy can be common postoperatively. Additional procedures are often required to minimize the dryness.
31.2.3 Myotonic Dystrophies
Myotonic dystrophy is a disease that affects muscles and other body systems, characterized by progressive muscle loss and weakness (Fig. 31.3). It is the most common form of adult-onset muscular dystrophy. Myotonic dystrophy is inherited in an autosomal dominant pattern. 13 It is characterized by unstable mutations. The mutations occur when a piece of DNA is abnormally repeated a number of times, which makes the gene unstable. The phenotype varies depending on variation of the genotype.
Unlike OPMD, myotonic dystrophy is associated with abnormalities in other organ systems. Almost any other tissue or organ can be involved including the crystalline lenses (Christmas tree cataract), the brain, testicles, and hair. 13
The ptosis can be mild to severe and is known to progress slowly. Unlike CPEO, motility loss is usually mild. Severity of disease pattern varies based on the genotype. Ultimately, a conservative frontalis sling is required to elevate the lids. The repair can be complicated by facial weakness.
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