GNRH1 and arachnoid cyst: The GnRH-dependent causes seen on imaging included: hypothalamic hamartoma (n = 10), hydrocephalus (n = 3), astrocytoma/glioma (n = 6), pineal gland tumour (n = 4), arachnoid cyst (n = 2) and 1 case each for pituitary microadenoma, myelin vacuolation in neurofibromatosis Type 1 (NF-1) and suprasellar germ cell tumour with cerebral metastases (Figures 2–5).