In 1989, Tournier-Lasserve joined the
Institut national de la santé et de la recherche médicale (Inserm), the French National Institute of Health and Medical Research, as a researcher. She then became research director at the
Necker-Enfants Malades Hospital and, in 1999, formed the Inserm "Genetics of vascular diseases" unit at the Molecular Genetics Laboratory at
Lariboisière Hospital, which is a teaching hospital of the Faculty of Medicine of
Paris Diderot University. She is now head of the Molecular Genetics Laboratory, which provides a diagnostic service for hereditary neurovascular diseases for all French hospitals. With the geneticist
Marie-Germaine Bousser, she discovered a genetic disease, designated by the acronym CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), which is an adult-onset disorder characterized by recurrent
ischemic strokes,
dementia, and premature death. Bousser had first researched the condition in 1976, when a patient with signs of
Binswanger's disease suffered a stroke. She found that the condition was hereditary and in 1993 she showed, together with Tournier-Lasserve, that the condition was caused by a mutation on
chromosome 19. The discovery was published in 1993 in the scientific journal
Nature Genetics. Tournier-Lasserve's main research interest over the past 25 years has been hereditary neurovascular disorders. After the identification of the gene involved in CADASIL, her team identified several other genes involved in cerebral small-vessel diseases and cerebral cavernous malformations (CCM) and developed diagnostic tools for these conditions to improve clinical care and genetic counselling for patients and families. Recently, she has been involved in researching
moyamoya disease. ==Honours and awards==