Diencephalic syndrome (DS) is a disorder of childhood that causes failure to thrive in the absence of malnutrition. In contrast, linear growth remains within normal ranges. DS is a result of several central nervous system (CNS) tumors.
Diencephalic syndrome is a condition that affects children in the first years of life . Its etiology lies in the presence of central nervous system (CNS) tumors. It has both major and minor features, the former being emaciation, failure to thrive, hyperkinesia, and euphoria. Minor features typically entail visual impairment, nystagmus, strabismus, hyperemesis, headache, pallor, and hypoglycemia . Visual changes affect over half of children with DS.
There are several brain tumors that can cause DS, exemplified by astrocytoma of the hypothalamus and optic tract (most common), craniopharyngioma, suprasellar ependymoma, suprasellar germinoma, and hypothalamic spongioblastoma .
Because of the vague nature of symptoms, diagnosis is challenging and often delayed for several months, as other, more common causes of failure to thrive tend to be investigated initially. Furthermore, there is no clear understanding of how DS causes failure to thrive despite adequate caloric intake.
Another characteristic feature of DS is that affected children have a low weight for an age while maintaining normal linear growth . Failure to thrive usually begins within the first year of life. Hydrocephalus is a common feature.
A few cases presenting in late childhood or adulthood have been reported. Gliomas associated with DS are more aggressive and have an earlier onset that their non-syndromic counterparts. DS may be associated with obesity, blindness, and mental impairment, although these are rare manifestations.
Despite advancements in radiological techniques and availability, diagnosis of diencephalic syndrome is still delayed as it is often not considered in the differential diagnosis for children with failure to thrive in the context of normal linear growth . It is generally agreed that the emaciation is not due to an imbalance in energy input and expenditure  . Imaging diagnostic modalities include:
Non-radiological diagnostic tools include:
When the suspicion exists, imaging should be carried out even in the absence of neurological signs.