Infantile null cell acute lymphoblastic leukaemia (ALL) presenting with cerebellar tonsillar herniation.

We report a child with ALL who presented with acute neurological collapse and coning of the cerebellar tonsils as a result of massive brain infiltration by leukaemic cells. Such severe involvement of cerebral parenchyma by leukaemic cells is rare and cerebellar tonsillar herniation has not been reported. CNS parenchymal involvement with leukaemia is demonstrated using MRI and, for the first time, cranial US.