This 29-year-old female presents with headache. Look at the first four images and try to determine the answer before looking at the latter four duplicate images with arrows.
Q1 – What is the most likely diagnosis?
(a) Alobar holoprosencephaly
(b) Dandy Walker variant
(c) Septo-optic dysplasia
(d) Kallman syndrome
A1 – (c) Septo-optic dysplasia
Q2 (Advanced) – MRI in septo-optic dysplasia may be associated with any of the following, except:
(a) Absence of midline cleavage involving the falx cerebri
(b) Hypoplasia of the optic apparatus
(c) CMV infection
(d) Ectopic neurohypophysis
A2 – (a) Absence of midline cleavage involving the falx cerebri
Septo-optic dysplasia (SOD) is characterized by optic nerve hypoplasia and absence of the septum pellucidum. Unlike alobar holoprosencephaly, midline cleavage of the falx and thalami is preserved though it may be considered on the low end of the holoprosencephaly spectrum. CMV infection has been described as a risk factor for SOD, as have maternal diabetes and exposure to quinidine antiepileptics. SOD is associated with schizencephaly (50 percent) as well as aqueductal stenosis, rhombencephalosynapsis, Chiari II and ectopic neurohypophysis.
Absence of the olfactory bulbs can also occur as a feature which may be shared with Kallmann’s syndrome. However, without a history of hypogonadism with anosmia, that diagnosis is unlikely.
Dandy-Walker (DW) variant is a continuum of posterior fossa abnormalities including at least partial inferior vermian hypoplasia. In it’s more classic forms, DW may include enlargement of the posterior fossa, cephalad rotation of the vermian remnant, loss of the fastigial point, torcular-lambdoid inversion and cystic dilation of the fourth ventricle with obstructive hydrocephalus.
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1. Barkovich AJ et. al. Septooptic Dysplasia: MR Imaging. Radiology 1989: 171 (1): 189-192.