Optimal prenatal diagnosis of CNS anomalies requires integration of sonographic, prenatal / postnatal / and sometimes post mortem MRI, laboratory and genomic test results. This requires a multidisciplinary approach inclusive of team meetings to discuss and reconcile findings and provide a single source of integrated and aligned information to the pregnant patient and her family. This process also facilitates judicious selection of patients for the offer of prenatal genomic testing which continues to be costly and limited by national laboratory capacity in Australia.

Using case based illustration , how this multidisciplinary approach to contemporary fetal CNS diagnosis and counselling works in practice will be explained and demonstrated.

Title: Prenatal Ultrasound Diagnosis of Partial Callosal Dysgenesis

Background
Partial callosal dysgenesis (PCD) represents a challenging prenatal diagnosis, beyond the well-established findings associated with agenesis of the corpus callosum (ACC). Prenatal diagnosis can be difficult because of the subtlety of the appearances and that there are limited descriptions of this finding. Accurate diagnosis will support counselling and management acknowledging that there is a paucity of evidence in this area.

Method
This presentation considers sonography the fetal corpus callosum, focusing on identifying and differentiating PCD from normal variations and complete agenesis. The sonoanatomy and embryology of the corpus callosum will be described to provide a foundational understanding. Key imaging includes acquisition of the midsagittal plane, assessment of callosal length, and evaluation of associated structures such as the cavum septi pellucidi & septal leaflets. The importance of looking for other associated anomalies will be emphasized.

Discussion
Understanding PCD requires a good understanding of fetal neuroanatomy. This presentation will describe a framework to classify sonographic findings of a shortened or incomplete corpus callosum. Major challenges, such as limited understanding of the clinical significance of a short corpus callosum, will also be addressed. The role of MRI and genetic testing (Whole Exome Sequencing) will be briefly considered discussed.

Conclusion
Diagnosis of PCD prenatally requires an awareness of the ultrasound appearances. Similarly, it is also very important to be aware of the pitfalls. The proposed framework has the potential to improve a sonographers description of PCD and stratify this finding when predicting outcome.
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