A 63-year-old man presented to the hospital accident and emergency department with an episode of syncope. He also gave a history describing several weeks of leftsided facial pain, which was initially thought to be secondary to a tooth abscess. On systemic enquiry the patient also reported having intermittent episodes of night sweats and mild anorexia, but he was otherwise well. Physical examination revealed the patient to have significant postural hypotension, allodynia affecting all three divisions of the trigeminal nerve and a palpable liver edge. Laboratory biochemistry investigations revealed profound panhypopituitarism.An MRI with gadolinium contrast of the brain subsequently revealed a hypothalamic mass sitting posterior to the optic chiasm and wrapping around the floor of the third ventricle with extension into the infundibulum. A second mass was also observed within Meckel's cave extending towards the foramen ovale. The masses appeared radiologically similar but anatomically separate (Figures 1 and 2).What is the differential diagnosis? What further investigations are indicated? DiagnosisRadiological assessment of the lesions initially suggested the possibility of (a) metastatic lesions including lymphoma; (b) two coincidental lesions, e.g. hypothalamic astrocytoma and trigeminal schwannoma; or (c) granulomatous pathology such as neurosarcoidosis. There is a 15612 mm hypothalamic mass that wraps around the floor of the third ventricle. The mass lateral to the cavernous sinus is situated within Meckel's cave and is likely to account for the left trigeminal nerve symptoms.