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Mysterious Optic Nerve Defects: How to Recognize and Treat Optic Nerve Dysplasia?
Septo-optic dysplasia (SOD), also known as Demercier syndrome, is a rare congenital malformation syndrome. Key features of this syndrome include hypoplasia of the optic nerve, pituitary gland dysfunction, and loss of the septum, a portion of the midline of the brain. According to medical standards, clinical diagnosis requires the presence of more than two of these three characteristics, however, only about 30% of patients have all three characteristics simultaneously. The condition was first described in 1956 by the French-Swiss doctor Georges de Morcier, who identified a correlation between hypoplasia of the cerebral septum and the optic nerve and chiasm.
Symptoms and signs
Symptoms of SOD can be divided into conditions related to optic nerve hypoplasia, pituitary hormone abnormalities, and midline brain abnormalities, and the severity of these symptoms can vary greatly.
Optic nerve hypoplasia
About a quarter of SOD patients have significant visual impairment in one or both eyes, primarily due to underdevelopment of the optic nerve. Developmental delays are more common in children with bilateral optic nerve hypoplasia than in children with unilateral optic nerve hypoplasia; bilateral cases are indicative of a more severe disease course.
Abnormal pituitary hormone
In SOD, hypoplasia of the pituitary gland often results in hypopituitarism, most commonly in the form of growth hormone deficiency. In some severe cases, panpituitary insufficiency may occur.
Midline brain abnormalities
In SOD, midline brain structures such as the corpus callosum and septum may fail to develop properly, which can lead to neurological problems such as epilepsy or developmental delays. Patients with epilepsy are more likely to display other neurological abnormalities such as cortical dysplasia, polymicrogyria, and schicephaly.
In fact, neurological symptoms are often considered late onset of SOD, with common initial manifestations including epilepsy, developmental delay, and limb weakness.
Intellectual abilities vary widely, ranging from normal to severe intellectual disability. Some early studies suggested that intellectual disability occurred in 71 percent of cases, cerebral palsy in 57 percent, and behavioral problems in 20 percent; but subsequent studies have suggested that these symptoms may be less common and caused by other neurological conditions.
Cause
SOD results from abnormal development of the embryonic forebrain during 4 to 6 weeks of gestation. Although a single cause has not been identified, it is thought that genetic and environmental factors may potentially influence the disease.
Rare reports of familial recurrence suggest the existence of at least one inherited form (HESX1), and five homozygous and eight heterozygous pathogenic HESX1 mutations have been identified.
Patients with homozygous mutations generally develop a typical SOD phenotype, while patients with heterozygous mutations have mild effects. In addition, mutations in OTX2, SOX2 and PAX6 are also related to SOD. The typical presentation of patients with SOX2 mutations shows severe bilateral ocular abnormalities such as microphthalmia and anophthalmia. These patients may also suffer from developmental delay, esophageal atresia, short stature, and sensorineural hearing loss.
Diagnosis
SOD is usually diagnosed at birth or in childhood and can be diagnosed when at least two of the following three characteristics are present: optic nerve hypoplasia, pituitary hormone abnormalities, and midline brain abnormalities, and can be diagnosed by MRI scan Confirm clinical diagnosis.
Treatment
There is currently no cure for SOD, and treatment focuses on symptom management, which usually requires a multi-professional team including neurologists, ophthalmologists, and endocrinologists. Hormone deficiencies can be treated with hormone replacement therapy (HRT), but visual impairment generally cannot be treated.
Epidemiology
According to a European survey, the incidence of SOD is approximately 1.9 to 2.5 cases per 100,000 live births, with reports in the UK being particularly high, and young mothers being at increased risk.
History
As early as 1941, Dr. David Reeves of Children's Hospital of Los Angeles first described the link between optic nerve hypoplasia and loss of the cerebral septum. Fifteen years later, French physician Georges de Morcier reported his theory, which he named optic coloboma. In 1970, American doctor William Hoyt linked these three characteristics of SOD and named the syndrome after Demercier.
Reflections in popular culture
British model and TV personality Katie Price's son Harvey suffers from the condition.
This mysterious and complex condition seems to be a neglected medical phenomenon. However, public awareness and research still need to be further promoted and explored. Have you had similar experiences and can you recognize and understand these rare diseases? What about the challenges faced by patients?
