Biogen Idec ( BIIB) and Elan ( ELN) said Monday that their Tysabri review found no new instances of a rare brain disease in patients taking the drug for Crohn's Disease and rheumatoid arthritis.

The last leg of the review resulted in no new confirmed cases of progressive multifocal leukoencephalopathy, or PML. On Aug. 9, the companies said they found no new confirmed cases of PML among multiple sclerosis patients.

Eighty-eight percent of more than 1,500 Crohn's and rheumatoid arthritis patients in Tysabri clinical trials participated in the safety evaluation. In total, 98% of the patients participating in the evaluation had a neurological exam by a consultant neurologist and an MRI, Elan and Biogen said.

The companies pulled Tysabri from the market on Feb. 28 following a report of PML linked to the drug. Subsequently, they said Tysabri was linked to PML in two MS patients and in one patient receiving the drug during a clinical trial for Crohn's Disease, an inflammatory gastrointestinal ailment. Two of the patients died.

Biogen and Elan filed on Sept. 26 to reinstate the drug as a treatment for MS.

Tysabri had been approved for relapsing-remitting MS, the most common form of the disease at the time of diagnosis. It is characterized by acute symptoms or a worsening of neurological functions that can occur intermittently. These symptoms can weaken or disappear for months or years between relapses.