Ocular motor signs in an infant with carbohydrate-deficient glycoprotein syndrome type Ia

Inborn Errors of Metabolism with Ataxia: Current and Future Treatment Options

A number of hereditary ataxias are caused by inborn errors of metabolism (IEM), most of which are highly heterogeneous in their clinical presentation. Prompt diagnosis is important because disease-specific therapies may be available. In this review, we offer a comprehensive overview of metabolic ataxias summarized by disease, highlighting novel clinical trials and emerging therapies with a particular emphasis on first-in-human gene therapies. We present disease-specific treatments if they exist and review the current evidence for symptomatic treatments of these highly heterogeneous diseases (where cerebellar ataxia is part of their phenotype) that aim to improve the disease burden and enhance quality of life. In general, a multimodal and holistic approach to the treatment of cerebellar ataxia, irrespective of etiology, is necessary to offer the best medical care. Physical therapy and speech and occupational therapy are obligatory. Genetic counseling is essential for making informed decisions about family planning.

Eye motor manifestations in children with neurometabolic disorders

Neurometabolic diseases are complex group of rare neurogenetic disorders, which are difficult to diagnose. Patients may have toxic metabolite accumulation, inadequate energy supply, or neurotransmitter deficiency, resulting in a variety of clinical manifestations and severity with enzyme activity or transporter function defects. Multiple organ involvement is frequently seen, among which neurological symptoms and signs are one of the most encountered problems. Ocular motor problems deserve special attention for it occurs in some inborn error of metabolism. Furthermore, some are early signs or characteristic findings of certain diseases, such as the gaze palsy in Niemann-Pick disease type C and Gaucher disease or oculogyric crisis in neurotransmitter diseases. Early recognition and intervention are important for better prognosis in treatable neurometabolic disorders. In addition, ways to evaluate and describe eye movement problems also help to demonstrate the severity or clinical progression for those diagnosed with certain neurometabolic diseases. However, the complexity of eye movement and ocular motor control renders our clinical observation, recording and even anatomic localization of abnormal eye movements. Clinicians are more likely to detect early signs and unravel problems by gaining awareness of abnormal eye movement. This study amied to approach neurometabolic diseases in children via eye motor manifestations.

Eye movement disorders and neurological symptoms in late-onset inborn errors of metabolism

Inborn errors of metabolism in adults are still largely unexplored. Despite the fact that adult‐onset phenotypes have been known for many years, little attention is given to these disorders in neurological practice. The adult‐onset presentation differs from childhood‐onset phenotypes, often leading to considerable diagnostic delay. The identification of these patients at the earliest stage of disease is important, given that early treatment may prevent or lessen further brain damage. Neurological and psychiatric symptoms occur more frequently in adult forms. Abnormalities of eye movements are also common and can be the presenting sign. Eye movement disorders can be classified as central or peripheral. Central forms are frequently observed in lysosomal storage disorders, whereas peripheral forms are a key feature of mitochondrial disease. Furthermore, oculogyric crisis is an important feature in disorders affecting dopamine syntheses or transport. Ocular motor disorders are often not reported by the patient, and abnormalities can be easily overlooked in a general examination. In adults with unexplained psychiatric and neurological symptoms, a special focus on examination of eye movements can serve as a relatively simple clinical tool to detect a metabolic disorder. Eye movements can be easily quantified and analyzed with video‐oculography, making them a valuable biomarker for following the natural course of disease or the response to therapies. Here, we review, for the first time, eye movement disorders that can occur in inborn errors of metabolism, with a focus on late‐onset forms. We provide a step‐by‐step overview that will help clinicians to examine and interpret eye movement disorders. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Recognizable phenotypes in CDG

Pattern recognition, using a group of characteristic, or discriminating features, is a powerful tool in metabolic diagnostic. A classic example of this approach is used in biochemical analysis of urine organic acid analysis, where the reporting depends more on the correlation of pertinent positive and negative findings, rather than on the absolute values of specific markers. Similar uses of pattern recognition in the field of biochemical genetics include the interpretation of data obtained by metabolomics, like glycomics, where a recognizable pattern or the presence of a specific glycan sub-fraction can lead to the direct diagnosis of certain types of congenital disorders of glycosylation. Another indispensable tool is the use of clinical pattern recognition-or syndromology-relying on careful phenotyping. While genomics might uncover variants not essential in the final clinical expression of disease, and metabolomics could point to a mixture of primary but also secondary changes in biochemical pathways, phenomics describes the clinically relevant manifestations and the full expression of the disease. In the current review we apply phenomics to the field of congenital disorders of glycosylation, focusing on recognizable differentiating findings in glycosylation disorders, characteristic dysmorphic features and malformations in PMM2-CDG, and overlapping patterns among the currently known glycosylation disorders based on their pathophysiological basis.

Do the clinical features in infantile-onset saccade initiation delay (congenital ocular motor apraxia) correlate with brain magnetic resonance imaging findings?

BACKGROUND

Infantile-onset saccade initiation delay (ISID) is a defect in saccade initiation. Other features may include impaired smooth ocular pursuit, developmental delay, hypotonia, and ataxia. Brain magnetic resonance imaging (MRI) can be normal or show supratentorial or infratentorial abnormalities. Our aim was to correlate the clinical features of ISID with brain MRI findings.

METHODS

Detailed review of the English medical literature between 1952 and 2012 revealed 67 studies with possible ISID. Patients without a brain MRI or with inadequate information, Joubert syndrome, neurodegenerative disorders, and acquired saccade initiation delay were excluded. Ninety-one patients (age range, 3 months to 45 years) met the inclusion criteria and were divided into 3 groups based on their brain MRI findings: normal (n = 55), supratentorial abnormalities (n = 17), and infratentorial abnormalities (n = 19). The patients' clinical features including the direction of head thrusts, smooth pursuit, optokinetic response (OKR), tone, development, and coordination were compared and analyzed among the MRI groups using χ test.

RESULTS

Horizontal head thrusts were significantly more common in patients with infratentorial abnormalities or normal brain MRI, whereas vertical head thrusts were more common among patients with supratentorial abnormalities (P < 0.0001). The slow phases of the OKR were significantly more likely to be impaired in patients with supratentorial or infratentorial abnormalities than in those with a normal MRI (P = 0.011). Other neuro-ophthalmological, neurological, and developmental features were similar among patients in the 3 neuroimaging groups.

CONCLUSION

The direction of head thrust and the integrity of the slow phases of the OKR are useful clinical indicators of possible sites of abnormality on brain MRI in patients with ISID.

Ophthalmic manifestations of congenital disorder of glycosylation type 1a

PURPOSE

To present the ophthalmic manifestations of patients with congenital disorder of glycosylation type Ia (CDG-Ia) due to the frequent R141H/F119L PMM2 genotype.

METHODS

Ophthalmic records of 23 patients (age: 10 months to 20 years) were evaluated. They had had at least one ophthalmic reexamination.

RESULTS

Measurements of refractive error showed that 18 patients were myopic, two were hypermetropic, and three could not be measured. Serial measurements in 12 patients indicated a progression towards myopia of 0.80 diopters (D) per year. Congenital esotropia and delayed visual maturation (DVM) were consistent findings. Two children developed good visual acuity (VA), 16 had low vision, and five were legally blind. Pallor of the optic disc was noted in five patients. Electroretinography (ERG) performed in nine patients showed reduced rod responses, while cone responses were only slightly reduced.

CONCLUSIONS

The present study illustrates the difficulties in examining severely disabled children. Consistent ophthalmic manifestations of CDG-Ia patients due to the R141H/F119L genotype were congenital esotropia, DVM, and a reduced rod response in ERG-examined patients. The vast majority of patients had reduced VA and developed myopia. We speculate that there is a relationship between the glycosylation defect in CDG-Ia and the development of myopia. We recommend that CDG-Ia patients be followed annually by an ophthalmologist.

Nystagmus

This article reviews the recent literature on nystagmus and various aspects of the pathophysiology of congenital idiopathic nystagmus and nystagmus treatment. One paper shows a new classification of latent/manifest latent nystagmus based on eye movement recordings. Nystagmus associated with complex syndromes and with onset in childhood represents the subject of several important recent articles, as does acquired nystagmus. Nystagmus as a manifestation of the toxicity of pharmacological agents is becoming increasingly recognized. Important contributions have been made to the genetics of various forms of nystagmus that represent an essential feature of retinal diseases, such as congenital stationary night blindness, albinism, blue cone monochromatism, and achromatopsia.