Neuroradiology Case of the Week

Case 15

Ryan K. Lee, MD, Christopher Bang, DO,
Per-Lennart Westesson, MD, PhD, DDS, and Sven Ekholm, MD, PhD

Clinical Presentation: Patient is a 6-month-old infant girl with bilateral optic disc hypoplasia and nystagmus

Radiographic Findings: Axial images demonstrate markedly thinned optic tracts (Fig.1). Coronal images reveal an absent septum pellucidum (Fig. 2), which give the anterior horns a boxlike appearance. There is marked thinning of corpus callosum (Fig. 3) noted on the sagittal views.

Figure 1: The optic tracts are thinned bilaterally on this axial T2 image.
Figure 2: The absent septum pellucidum on this coronal T2 image results in a boxlike configuration of the anterior horn of the lateral ventricles. Also note the thin optic tracts.	Figure 3: Coronal T1 image demonstrates a thin corpus callosum.

Diagnosis: Septo-optic dysplasia (DeMorsier’s Syndrome)

Discussion: Septo-optic dysplasia is an anterior midline congenital anomaly, affecting females more than males (M:F=1:3), that consists of hypoplasia of the optic nerves, along with absence (64%) or hypoplasia (34%) of the septum pellucidum. The absent septum pellucidum causes a boxlike or squared off appearance of the frontal horns of the lateral ventricles on coronal MR sequences. When the septum pellucidum is only hypoplastic, usually the anterior portion is still present. It is because of this agenesis or hypoplasia of the septum pellucidum that many consider this entity to be classified as a type of holoprosencephaly. As such, it may represent the mildest form of the holoprosencephalies.
    Along with the hypoplastic optic nerves, tracts, and chiasm, there is also optic disc hypoplasia. The dysplastic optic pathways can result in a range of visual dysfunctions, from mildly diminished visual acuity to complete blindness. Visual nystagmus is also not uncommon. Nevertheless, despite these abnormalities, some patients may have no visual changes.
    Agenesis or hypoplasia of the corpus callosum as well as other white matter hypoplasia, manifested as enlarged ventricles and cisterns, are often associated with this abnormality. Science is classically described in 50% of patients with this disorder.
    Clinically, in addition to the visual disturbances, patients with septo-optic dysplasia often present with seizures. There is also an association with hypothalamic hypopituitarism (66%). This may be manifested as diabetes insipidus or as growth retardation due to diminished growth hormone.

References:

1. Osborn A: Diagnostic Radiology. St. Louis, MO: Mosby, 1994, pp 42.
2. Barkovich AJ: Pediatric Neuroimaging. New York: Williams & Wilkins, 2000, pp 324-27.
3. Grossman, RI, Yousem, DM. Neuroradiology The Requisites. 1st edition. Philadelphia, PA: Mosby, 1994, pp 253.
4. Dahnert W: Radiology Review Manual. 3rd edition. Baltimore, MD: Williams & Wilkins, 1996, pp 240.