Lhermitte-Duclos disease associated to Cowden syndrome: de novo diagnosis and management of these extremely rare syndromes in a patient.

A 36-year-old woman, with history of cutaneous papilomatosis and thyroid carcinoma presented with headache, transitory visual blurring and nausea. Funduscopy showed papilloedema. MRI showed a tumour of the right cerebellar hemisphere with a striated, tigroid pattern, typical of Lhermitte-Duclos disease (LDD). Significant clinical and perimetric improvements were noted after surgery and the follow-up did not reveal recurrences of the tumour. LDD is an extremely rare differential diagnosis of posterior fossa tumours. LDD and the history of thyroid carcinoma permitted us to diagnose Cowden syndrome (CS). We present a clinical case that supports the possibility of performing a preoperative diagnosis of LDD based on MRI features. We review the diagnosis and management of LDD and CS. This report highlights the importance of excluding CS after LDD diagnosis, of monitoring the optic nerve postoperatively using optical coherence tomography and of prompt treatment that can potentially prevent visual function loss.