ESPE Abstracts

Introduction: Diencephalic syndrome (DS) is a rare condition characterised by weight loss despite adequate calorie intake in association with other signs and symptoms such as hyperalertness, hyperactivity, visual field defects, nystagmus and vomiting. DS occurs in the presence of hypothalamic lesions, but its exact mechanism remains unclear. The diagnosis is often delayed due to the absence of specific clinical and biochemical features.

Case Description: The index case is a boy diagnosed with NF1 at five years of age with a large neurofibroma of the optic chiasm. Despite first- and second-line chemotherapy sight deterioration proceeded to almost complete blindness; after two years a pilocytic astrocytoma developed in close proximity to the neurofibroma and was deemed unresectable. A wait-and-see approach was adopted due to the slow progression. From an endocrine point of view, he displayed early puberty, growth hormone deficiency and progressive weight gain leading to obesity and insulin resistance. Metformin treatment and lifestyle changes were started with good effect. After three years, at the age of 15, he started to complain of lethargy, dizziness, loss of appetite and absence-like episodes. MRI demonstrated only a slight increase of the cystic component of the tumour with a stable appearance of a previously reported mild ventriculomegaly. In the following months the lethargy increased as well as the weight loss (10.5 kilograms in 1 year). He attended the emergency department for rapid deterioration of his general condition, ongoing weight loss, vomiting and increased frequency of seizure-like episodes. An urgent CT was performed and evidence of a slight increase of the ventriculomegaly and signs of obstructive hydrocephalus were found. He therefore underwent urgent decompression with endoscopic septal fenestration and cyst and tumour fenestration. After surgery his appetite improved with a significant increase in weight (7 kilograms in 4 months).

Discussion: Sporadic DS is typically diagnosed in early childhood and only few cases, mainly in NF1 patients, were reported in older children. The identification of signs and symptoms associated with this condition is difficult, particularly in the presence of multiple confounding factors: in this case the boy was already registered blind, was previously obese and was asked to lose weight. He presented with lethargy and fatigue instead of the more typical hyperactivity. It is still argued if DS is a result of tumour hormonal production/imbalance or of compression on the hypothalamus; our case supports the latter since the sole fenestration led to the resolution of symptoms.