Incidental discovery: Two adult cases of septo-optic dysplasia

The first patient, a woman aged 56, presented to the ER following a fall, where an incidental frontal meningioma was detected during a CT exam. As a result, she was recommended to undergo a brain MRI. Since childhood, she has had no vision in her right eye.

The second patient, a 48-year-old woman, was diagnosed with cervical cancer and was recommended to undergo a CT scan for neoplastic staging. In childhood, she was diagnosed with anophthalmia and subsequently fitted with an ocular prosthesis in her right eye. She has hyperopia and presbyopia in the left eye.

Neither patient has had other skull imaging yet.

The brain MRI examination revealed enlarged lateral ventricles with pointing down frontal horns on coronal images and absent septum pellucidum, alongside a thinned-out corpus callosum. The pituitary gland exhibits reduced dimensions. Unilateral hypoplastic optic nerve and globe is also seen on the right side.

At the contrast-enhanced CT scan of the head, enlargement of the lateral ventricles with absence of the septum pellucidum was also highlighted, along with a “point down” appearance of the lateral ventricular frontal horns on coronal images, together with a hypoplastic right optic nerve and eyeball. Additionally, the ocular prosthesis is also observed.

Background

Septo-optic dysplasia (SOD), also known as de Morsier syndrome, is a rare congenital malformation syndrome with an estimated prevalence of ~1:10,000, having no gender predilection recognition. SOD is a result of abnormalities in the embryonic forebrain development occurring between 4 to 6 weeks of pregnancy, involving both genetic and environmental factors [1]. The syndrome is characterised by uni or bilateral optic nerve hypoplasia, hypothalamic-pituitary dysfunction and midline brain defects such as the absence of the septum pellucidum and/or thinning or agenesis of the corpus callosum. For a diagnosis to be made, at least two of these characteristics must be present [2,3].

Clinical Perspective

Some individuals present with SOD at birth, while others may manifest symptoms characterised by growth failure and/or visual abnormalities during childhood [4]. The manifestations of SOD can be categorised into symptoms associated with underdevelopment of the optic nerve (visual impairment in one or both eyes), abnormalities in pituitary hormone function (growth hormone deficiency and other endocrine dysfunctions), and anomalies in midline brain structures (neurological problems such as seizures, developmental delay or intellectual disability) [5]. The clinical presentation also depends on whether there is an association with schizencephaly (in approximately 50% of cases). This association, known as septo-optic dysplasia plus, is characterised by a less severe impairment of the optic apparatus and cortical anomalies (polymicrogyria and cortical dysplasia) [6,7].

Imaging Perspective

Imaging plays a critical role in diagnosing SOD. A CT scan may reveal the absence of the septum pellucidum, enlarged ventricles and hypoplastic optic nerve/globe. MRI is the preferred imaging method because, in addition to CT, it can better characterise the optic pathway, but it can also provide information about potential anomalies of the corpus callosum (hypoplasia/agenesis), pituitary gland (small pituitary gland with hypoplastic or absent infundibulum and ectopic posterior pituitary seen as a focus of T1 high signal intensity in the median eminence of the hypothalamus), and can highlight the absence of olfactory bulbs (arhinencephaly). The MRI findings eliminate the necessity for additional investigations to confirm the diagnosis [8].

Outcome

The clinical examination is more than important, but the complete diagnosis cannot be formulated without an MRI examination. The impact of imaging is evident, as it is essential for the patient to be treated appropriately. Symptomatic treatment for SOD requires oversight by a multidisciplinary team and ongoing monitoring. The prognosis varies depending on the severity of the condition. Early diagnosis significantly improves outcomes by facilitating the timely management of hormone deficiencies.

Take Home Message / Teaching Points

Radiologist awareness and recognition of characteristic features of SOD on MRI imaging, are crucial for accurate diagnosis and proper management of these patients.