A 72 year-old woman is hospitalized and explored in the neurological department because of dementia discovered after a vitrectomy performed to treat a relapsing chronic uveitis. MRI examination shows atypical hyperintense white matter lesions on T2 weighted images related to
Lyme disease. Worsening of clinical status, despite appropriate medical treatment and apparition of enhanced nodules MR images rules out the diagnosis of
lyme disease and is attributed to brain metastases. The search for primitive tumor is not contributive and a brain biopsy is performed. It discloses a B cells non-hodgkin lymphoma. This case report stresses two points: first, a lymphoma must be one of the diagnosis to evocate if imaging shows an enhancing nodule, or extensive hypersignal of the white matter, second: it emphasizes the value of vitreous analysis searching for lymphoma during chronic uveitis associated to neurological symptoms.