Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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February 3, 2022
Septo-Optic Dysplasia Syndrome
- Background:
- Septo-optic dysplasia (SOD) is a rare, phenotypically variable developmental disorder in which the prosencephalic ventricle fails to expand normally into 2 telencephalic ventricles, resulting in a single, anterior midline ventricle.
- The estimated prevalence based on a European population study is between 1.9 and 2.5 per 100,000 births.
- Yield of genetic testing is quite low, but it can be caused by mutations in HESX1 and SOX2 genes.
- Clinical Presentation:
- Common presentation includes visual impairment, pituitary hormone deficiencies (most common - growth hormone deficiency), and developmental delay. Patients may have seizures, precocious puberty, and obesity.
- The age of presentation ranges from birth to the first 2 decades of life. Most cases are sporadic, but rare familial cases have been observed.
- May be referred to as SOD-plus when associated with cortical malformations, most commonly schizencephaly
- Key Diagnostic Features:
- Two or more features from the triad, which includes:
- 1. Optic nerve hypoplasia
- 2. Endocrine abnormalities
- 3. Midline brain defects such as agenesis of the septum pellucidum and/or corpus callosum
- Therefore, note that absence of the septum pellucidum is not mandatory for diagnosis of this syndrome. Also, isolated findings from the above criteria do not fulfill the diagnostic criteria for SOD.
- When reporting MRI studies, comment on the size of the anterior pituitary gland, infundibulum - presence and thickness, and presence and location of the posterior pituitary bright spot. Look for associated cortical malformations such as heterotopias and schizencephaly, which can be present. The latter is a transmantle CSF cleft lined by gray matter. If cleft walls are separated by CSF, it is classified as open lip. If cleft walls are in apposition, it is classified as closed lip and may be associated with a ventricular dimple to aid diagnosis.
- MRI provides the best visualization of optic pathways and the hypothalamic-pituitary axis; however, our patient had an interesting appearance on CT, which was able to detect multiple features of this syndrome.
- Two or more features from the triad, which includes:
- Differential Diagnoses:
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Lobar holoprosencephaly (HPE): Unlike more severe forms of holoprosencephaly, cerebral hemispheres are present and can present with several features of SOD such as absence of the septum pellucidum. Distinguishing features of HPE are a lack of optic chiasm hypoplasia and contiguity of the frontal lobes and of the fornices.
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Agenesis of the corpus callosum: Parallel lateral ventricles, colpocephaly, and absence of the cavum septum pellucidum
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Isolated absence of the septum pellucidum can occur, though rarely; always check for associated malformations.
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Perforation of septal leaflets: In chronic hydrocephalus
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Treatment:
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Treatment is based on symptoms.
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This patient with seizures and panhypopituitarism is being managed with antiepileptics and hormone replacement with regular follow-up.
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