Myogenic ptosis is designated by the following codes in accordance with the International Classification of Diseases (ICD) nomenclature:
- 374.3 Ptosis of eyelid
- H02.4 Ptosis of eyelid
- H02.42 Myogenic ptosis of eyelid
- H02.421 Myogenic ptosis of right eyelid
- H02.422 Myogenic ptosis of left eyelid
- H02.423 Myogenic ptosis of bilateral eyelids
- H02.429 Myogenic ptosis of unspecified eyelid
Myogenic ptosis refers to a droopy upper eyelid, characterized by limited elevation due to levator muscle weakness.   The condition can be categorized as either congenital ptosis or acquired ptosis, depending on age of onset of disease.
Levator muscle weakness associated with myogenic ptosis can be caused by systemic disorders including myotonic dystrophy, oculopharyngeal muscular dystrophy (OPMD), and chronic external ophthalmoplegia (CPEO).  Weakness of the levator muscle in myogenic ptosis can also be caused by myasthenia gravis, facioscapulohumeral muscular dystrophy, congenital myopathies, and mitochondriopathy.
As systemic disorders that cause levator muscle weakness and thus myogenic ptosis are genetic disorders, the main risk factor associated with myogenic ptosis is having a family history of genetic mutations associated with those disorders, although sporadic disease may rarely occur.
Prevalence and Incidence
The true prevalence/incidence of myogenic ptosis is unknown but is typically rare.
Myogenic ptosis results from systemic disorders that cause weakness of the levator palpebrae superioris muscle.  The disorder can present itself in varying degrees and at varying ages. Congenital myogenic ptosis from birth or manifesting in the early ages is due to maldevelopment/dysgenesis of the levator palpebrae superioris muscle. In the non-pediatric population, weakness of the levator muscle in myogenic ptosis is most commonly a result of myotonic dystrophy, oculopharyngeal dystrophy (OPMD), and chronic external ophthalmoplegia (CPEO) but can also be caused by myasthenia gravis, facioscapulohumeral muscular dystrophy, congenital myopathies, mitochondriopathy, aromatic L-amino acid decarboxylase deficiency, congenital fibrosis of the extraocular muscles, glycogenosis, myositis, myasthenic syndrome, and orbital rhabdomyosarcoma although less common.   
Most myogenic ptosis cases result from myotonic dystrophy, oculopharyngeal dystrophy (OPMD), and chronic external ophthalmoplegia (CPEO) which are all documented to be the result of genetic mutations.Therefore, it is important to test the patient for these disorders if myogenic etiology is suspected or refer the patient to a neuromuscular disease specialist and a geneticist.
Myotonic dystrophy is the result of mutations in the DMPK gene. Mutations in the DMPK gene are associated with a lengthened noncoding CTG repeat. This expansion of the nucleotide repeat can increase further in subsequent generations.
Chronic external ophthalmoplegia (CPEO) is the result of mutations in genes associated with mitochondrial function. Mutations in the following genes have been linked to CPEO: TYMP, POLG, ANT1, C10orf2, POLH2, RRM2B, and DNA2.
Myotonic dystrophy, oculopharyngeal dystrophy (OPMD), and chronic external ophthalmoplegia (CPEO) all display an autosomal dominant inheritance pattern.Chronic external ophthalmoplegia (CPEO) has also been shown to display an autosomal recessive inheritance pattern.
There are currently no known ways to prevent myogenic ptosis.
Obtaining a careful family history may present an invaluable resource in determining if any of the causative disorders of myogenic ptosis have been documented in other family members. But a family history with no report of myotonic dystrophy or chronic external ophthalmoplegia (CPEO) does not rule out the presence of the disorders in the patient due to the varying degree of expression that these disorders may present (family members may have gone undiagnosed due to lack of signs and symptoms). Determining a patient’s ethnic origin may assist in the diagnosis of oculopharyngeal dystrophy (OPMD) due to its high presentation rate in individuals of French Canadian and Hispanic New Mexican descent. Family photographs may also be helpful in recognizing a familial inheritance.
Physical examination of patients with suspected myogenic ptosis typically involves evaluation of levator function, margin reflex distance 1 (MRD1), palpebral fissure height (PF), lid crease, orbicularis strength, extraocular motility, visual fields, and eyelid velocity when patient looks from a downgaze to an upgaze position.
Myogenic ptosis patients typically present with drooping of the upper eyelid, a tired appearance, decreased levator muscle function, and limited motility of extraocular and facial muscles.  Patients also report disturbance in their visual field that may range from mild to severe depending on the degree of upper lid droopiness. Myogenic ptosis may present in one or both eyes. In severe cases, patients may report the need to tilt their heads back or rely on forehead muscles and their fingers to lift their eyelids to improve their visual field.
- Myotonic Dystrophy
- Arm weakness
- Poor Bell’s phenomenon
- Cardiac conduction abnormalities
- Myotonia (difficulty relaxing the hand when gripping, such as after a handshake)
- Polychromatic “Christmas tree” cataracts or pigmentary retinopathy
- Oculopharyngeal Dystrophy (OPMD) 
- Dysphagia (trouble swallowing; coughing or choking when eating/drinking)
- Dysphonia (difficulty in speaking; abnormal/hoarse voice)
- Intact Bell’s phenomenon
- Female infertility
- Chronic Progressive External Ophthalmoplegia (CPEO)
Myogenic ptosis should be suspected in patients that present with ptosis in conjunction with levator muscle weakness and muscle weakness of other body muscles, facial muscles, and extraocular muscles (ophthalmoplegia). Criteria for clinical diagnosis of myogenic ptosis includes ptosis, possible evidence of levator muscle weakness, an evident decrease in velocity of the eyelid when the patient moves from a downgaze to an upgaze, and any of the following systemic disorders: myotonic dystrophy, oculopharyngeal dystrophy (OPMD), chronic external ophthalmoplegia (CPEO), myasthenia gravis, facioscapulohumeral muscular dystrophy, congenital myopathies, mitochondriopathy, aromatic L-amino acid decarboxylase deficiency, congenital fibrosis of the extraocular muscles, glycogenosis, myositis, myasthenic syndrome, and orbital rhabdomyosarcoma. 
Levator Muscle Function
Levator muscle function is determined by measuring the maximal distance in millimeters (mm) that the upper eyelid elevates when looking upward as far as possible without moving the head.  Care should be taken to negate flexion of the forehead frontalis muscle which could falsely elevate the levator muscle excursion.Normal levator muscle function is 15 mm.Levator function may not present below normal levels in all cases of myogenic ptosis. Measuring the velocity of the patient’s eyelid movement from a downward to an upward gaze may assist in myogenic ptosis diagnosis when levator function appears normal.
Images of the patient’s face are typically taken to assess degree of eyelid drooping and to allow for continued monitoring of disease progression. The ptosis often eventually blocks the pupillary axis and thus necessitates surgical repair. In myasthenia gravis, myotonic dystrophy, or OPMD, photographs are also helpful to document the limited motility of extraocular muscle movements.
Testing of Visual Fields
To evaluate the patient’s visual impairment, the patient’s visual field is evaluated with the eyelids in a natural position (untaped) and in a simulated elevated position (taped to show what the position of the eyelid should be in/would be with corrective surgery).
Biopsy and Genetic Testing
Biopsy of muscle tissue and genetic testing allows for the diagnosis of systemic disorders associated with myogenic ptosis. Therefore, consultation with a geneticist and neuromuscular disease specialist are indicated.
Diagnosis of myotonic dystrophy typically involves genetic testing in which the genome is analyzed for the presence of an expanded triplet repeat in the DMPK gene. Electromyography may also be utilized in diagnosis of myotonic dystrophy.
Diagnosis of oculopharyngeal dystrophy (OPMD) involves genetic testing which looks for mutations in the PABPN1 gene.
Diagnosis of chronic external ophthalmoplegia involves biopsy of muscles such as the orbicularis oculi, vastus lateralis, and deltoid. Biopsy samples are then evaluated for the presence of ragged-red fibers and partial cytochrome C oxidase deficiency.Diagnosis may also involve the use of MRI to evaluate the patient for reduced extraocular muscle size. Genetic testing is not standard practice for the diagnosis of CPEO due to the variety of associated genes and mutations.
Diagnosis of these diseases also typically involve family counseling for other involved members with perhaps incomplete penetrance, as well as to understand the risks of future family planning.
- Aponeurotic Ptosis 
- Most common in elderly patients
- Usually related to aging
- Associated with the levator aponeurosis
- Neurogenic Ptosis 
- Associated with damage or dysfunction of nerves and the central nervous system (i.e.. Third nerve palsy) 
- Mechanical Ptosis 
- Associated with increased eyelid weight (such as from a mass, lesion, brow/forehead ptosis, significant redundant/heavy skin tissues)
- Traumatic Ptosis 
- Associated with levator muscle weakness caused by trauma 
- Associated with contralateral retracted eyelid, brow ptosis, upper eyelid swelling, decreased orbital volume. 
Surgical options available for myogenic ptosis include frontalis (sling) suspension (most common surgical option), levator advancement/resection, blepharoplasty, and posterior approach surgery including MMCR and Fasanella-Servat.   Most clinical evidence and documentation highly recommend the use of a sling procedure or ptosis crutches due to the progressiveness and high recurrence rate of the condition. Frontalis sling suspension may be performed with a variety of materials, including sutures, silicone rods, autologous fascia lata, Gore-Tex, amongst others. Using a dissected flap from the ipsilateral frontalis muscle, that is pulled inferiorly into the eyelid and secured to the tarsal plate, is an excellent option that avoids the use of synthetic materials and their associated complications.
Other Treatment Options:
Ptosis crutches may also be recommended due to the progressive and recurrent nature of myogenic ptosis.Ptosis crutches were an option to treat myogenic ptosis in patients that did not want to have or could not have surgery but are rarely used now.
Complications associated with surgical options for myogenic ptosis may include asymmetry, sling breakage, sling exposure or infection, under-correction of the eyelid, need for additional surgery, and keratopathy.These complications can typically be resolved through sling revision/replacement and topical/eye drop medications. The patient should be aware that increased lagophthalmos (inability to close the eye) is common after elevation of the eyelid with myogenic ptosis.
Other complications associated with myogenic ptosis are typically related to the systemic disorders associated with levator muscle weakness. Patients with levator muscle weakness due to myotonic dystrophy or chronic external ophthalmoplegia (CPEO) may experience problems related to cardiac conduction and individuals with weakness due to oculopharyngeal dystrophy (OPMD) may experience dysphagia. 
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