Neuro-ophthalmologic Manifestations of Mitochondrial DNA Disorders: Chronic Progressive External Ophthalmoplegia, Kearns-Sayre Syndrome, and Leber’s Hereditary Optic Neuropathy

MRNA Transcription, Translation, and Defects in Developmental Cognitive and Behavioral Disorders

The growth of expertise in molecular techniques, their application to clinical evaluations, and the establishment of databases with molecular genetic information has led to greater insights into the roles of molecular processes related to gene expression in neurodevelopment and functioning. The goal of this review is to examine new insights into messenger RNA transcription, translation, and cellular protein synthesis and the relevance of genetically determined alterations in these processes in neurodevelopmental, cognitive, and behavioral disorders.

Strabismus surgery for diplopia in chronic progressive external ophthalmoplegia

BACKGROUND

To report midterm outcomes of strabismus strategy for management of diplopia in chronic progressive external ophthalmoplegia and specific surgical planning rationale.

DESIGN

Retrospective interventional case series.

RESULTS

Two patients, a 26-year-old male and a 36-year-old female, diagnosed with chronic progressive external ophthalmoplegia presented with blepharoptosis and intermittent diplopia. Ocular motility examination was significant for bilateral profound impairment of adduction with relative preservation of abduction, infraduction and elevation. Control of intermittent exotropia gradually worsened over 3 and 1.5 years of follow-up, respectively, in the presence of documented stability of the angle of exodeviation. Strabismus surgery involving modest amounts of bilateral medial rectus resection and lateral rectus recessions was undertaken. Surgical intervention was successful in controlling alignment in primary position and alleviating diplopia and asthenopia after 9 and 8 years of follow-up time, respectively, despite slow progression of ophthalmoplegia.

CONCLUSION

Bilateral selective impairment of adduction and intermittent exotropia may be the presenting ocular motility disturbance in chronic progressive external ophthalmoplegia. Properly designed strabismus surgery may provide sustainable, in the midterm, control of alignment and symptomatic relief in selected patients with CPEO.

The eye as a window to rare endocrine disorders

The human eye, as an organ, can offer critical clues to the diagnosis of various systemic illnesses. Ocular changes are common in various endocrine disorders such as diabetes mellitus and Graves' disease. However there exist a large number of lesser known endocrine disorders where ocular involvement is significant. Awareness of these associations is the first step in the diagnosis and management of these complex patients. The rare syndromes involving the pituitary hypothalamic axis with significant ocular involvement include Septo-optic dysplasia, Kallman's syndrome, and Empty Sella syndrome all affecting the optic nerve at the optic chiasa. The syndromes involving the thyroid and parathyroid glands that have ocular manifestations and are rare include Mc Cune Albright syndrome wherein optic nerve decompression may occur due to fibrous dysplasia, primary hyperparathyroidism that may present as red eye due to scleritis and Ascher syndrome wherein ptosis occurs. Allgrove's syndrome, Cushing's disease, and Addison's disease are the rare endocrine syndromes discussed involving the adrenals and eye. Ocular involvement is also seen in gonadal syndromes such as Bardet Biedl, Turner's, Rothmund's, and Klinefelter's syndrome. This review also highlights the ocular manifestation of miscellaneous syndromes such as Werner's, Cockayne's, Wolfram's, Kearns Sayre's, and Autoimmune polyendocrine syndrome. The knowledge of these relatively uncommon endocrine disorders and their ocular manifestations will help an endocrinologist reach a diagnosis and will alert an ophthalmologist to seek specialty consultation of an endocrinologist when encountered with such cases.

Optimizing muscle biopsy for the diagnosis of mitochondrial myopathy

PURPOSE

To establish a reliable technique for harvesting the orbicularis oculi muscle to facilitate diagnosis of chronic progressive external ophthalmoplegia, a mitochondrial myopathy.

METHODS

In this retrospective observational case series, 10 patients clinically suspected to have chronic progressive external ophthalmoplegia underwent surgery for upper eyelid ptosis. A protocol for orbicularis biopsy was developed. Initial cases of levator muscle biopsy yielded inadequate, unorientated skeletal muscle with significant contraction artifact that prevented the study of morphologic features. To improve yield and quality, orbicularis oculi muscle biopsy was performed in the later patients following a standard muscle biopsy protocol used for limb muscles. This involved suturing a third of the muscle on a wooden stick, to keep it at isometric length. The specimen was sent fresh in saline-moistened gauze to the pathologist who then divided the muscle for various studies.

RESULTS

The biopsies of orbicularis muscle performed using this protocol resulted in adequate skeletal muscle with an acceptable level of artifact. Mitochondrial myopathy was diagnosed in 9 of 10 cases.

CONCLUSIONS

The orbicularis oculi muscle is a good source of skeletal muscle for investigating muscle disorders, and it is easily collected during blepharoplasty or ptosis surgery. This has avoided the need for a standard proximal limb muscle biopsy, thereby reducing morbidity and cost to the patients.

Spinocerebellar ataxia type 7 mimicking Kearns–Sayre syndrome: A clinical diagnosis is desirable

Spinocerebellar ataxias are a group of autosomal dominant cerebellar degenerative disorders, which are characterized by clinical and genetic variability. Spinocerebellar ataxia type 7 (SCA7) is less variable in clinical presentation than other SCAs. We present a pediatric patient with 13 and 70 trinucleotide CAG repeats within SCA7 gene and no family history, whose presentation mimicked Kearns-Sayre syndrome (KSS). We review the differential diagnosis of cerebellar ataxia with vision loss secondary to retinal pigmentary dystrophy. This paper supports concept of a desirable clinical diagnosis to avoid multiple genetic or invasive testing in children with neurodegenerative disorders.

Unusual presentation of Kearns-Sayre syndrome in early childhood

Congenital glaucoma and insulin-dependent diabetes mellitus were the predominant presenting signs in a patient with Kearns-Sayre syndrome. Thereafter, he developed short stature, pigmentary retinopathy, progressive external ophthalmoplegia, and ataxia. The diagnosis was confirmed by detecting a deletion of mitochondrial DNA in muscle, thus demonstrating that Kearns-Sayre syndrome can have the unusual presenting signs described above.

Surgical management of strabismus associated with chronic progressive external ophthalmoplegia

PURPOSE

The purpose of the study is to describe the clinical characteristics and surgical management of strabismus associated with chronic progressive external ophthalmoplegia.

METHODS

The authors present four patients with chronic progressive external ophthalmoplegia and strabismus requiring extraocular muscle surgery, with attention to presenting symptoms, patterns of misalignment, results of surgical and nonsurgical therapies, and associated ocular or systemic conditions or both.

RESULTS

Three patients reported diplopia before surgery. One patient presented with an esotropia, one with an exotropia, and two with hypertropia. Three patients required only one strabismus surgery, and one patient required multiple surgeries.

CONCLUSIONS

Chronic progressive external ophthalmoplegia may have clinical characteristics similar to those of myasthenia gravis or thyroid ophthalmopathy. Patients with chronic progressive external ophthalmoplegia and strabismus frequently have diplopia in primary position and may benefit from extraocular muscle surgery to improve alignment. In addition, because these patients typically have poor motor fusion, prisms often are useful adjuncts to surgery.

The ophthalmologic manifestations of mitochondrial disease

The cardinal eye manifestations of mtDNA diseases are ophthalmoplegia, optic neuropathy, and pigmentary retinopathy. A number of other eye structures may also be affected in these disorders and the ophthalmologist is in a unique position to detect and interpret these findings. The presence of these ophthalmologic manifestations may be the first clue that the patient has an underlying mitochondrial disease with the eye as the initial or most prominently affected organ. The phenotypic manifestations of mitochondrial disease are protean and variable, and there are no clear-cut, minimal features that define these disorders. The possibility of a mitochondrial disorder should be raised when any of the mitochondrial eye manifestations (Table 1) are present, either alone or in concert with the neurological and systemic (Table 2) manifestations of mitochondrial disease. A maternal family history of an ophthalmologic, neurological, or systemic illness is also compatible with a mitochondrial disorder. The ophthalmologist should not loose sight of the fact that mitochondrial disorders have systemic manifestations and implications, even when the primary manifestations are ocular. Detection of and proactive intervention into comorbid features (eg, diabetes mellitus, hearing loss, heart block) is an important component.

Mapping a gene for congenital fibrosis of the extraocular muscles to the centromeric region of chromosome 12

Congenital Fibrosis of the Extraocular Muscles (CFEOM) is an autosomal dominant, ocular disorder characterized by congenital, nonprogressive, bilateral ptosis and external ophthalmoplegia. The pathophysiology of this disorder is unknown and it is unclear if it has a primary neurogenic or myopathic etiology. We report linkage of this disorder, in two unrelated families, to markers in the pericentromeric region of human chromosome 12. D12S59 does not recombine with the disease giving a two-point lod score of 12.5 (theta = 0.00). D12S87 and D12S85 flank the CFEOM locus with two-point lod scores of 8.9 (theta = 0.03) and 5.4 (theta = 0.03) respectively, defining a region of 8 cM. These data establish a map location for CFEOM and demonstrate that this may be a genetically homogeneous disorder.