Specific Imaging Findings

The wide spectrum of imaging findings in septo-optic dysplasia (SOD) includes variable combinations of defects involving the midline brain structures, pituitary gland, optic nerves and eyes, olfactory bulbs, as well as other brain structures. Midline brain defects classically consist of complete or partial absence of the septum pellucidum with fused midline fornices (60% of cases) and/or corpus callosum abnormalities, such as agenesis, dysplasia or hypoplasia. The presence of a normal septum pellucidum does not rule out SOD. Pituitary gland malformations include anterior pituitary hypoplasia and/or ectopic posterior lobe and/or thin or interrupted pituitary stalk. Another characteristic feature is the hypoplasia of the optic nerves and chiasm, more commonly bilateral than unilateral. Frequently associated ocular anomalies include coloboma, anophthalmia, and microphthalmia. The olfactory bulbs may be absent or hypoplastic. Other brain malformations commonly associated with SOD are schizencephaly (so-called SOD-plus), polymicrogyria, gray matter heterotopia, and hippocampal malformations.

Pertinent Clinical Information

The diagnosis of SOD is clinical and made when two or more features of the classical triad of optic nerve hypoplasia, pituitary hormone abnormalities and midline brain defects are present. Only a third of patients present with all cardinal features of SOD. Visual deficits (nystagmus, diminished visual acuity, color blindness) due to optic nerve hypoplasia and ocular malformations are usually the first presenting feature of the condition, while endocrine dysfunction may become apparent later on. The extent of pituitary–hypothalamic dysfunction (60–80% of cases) is highly variable, ranging from isolated pituitary hormone deficit (in particular growth hormone deficiency) to panhypopituitarism.