BRUSSELS (AP) — The lawyer of a Frenchman accused of shooting dead four people at a Jewish Museum in Belgium said Thursday his client may have a brain tumor and is being denied medical treatment.

Mehdi Nemmouche is suspected of gunning down the four with an assault weapon in the Brussels museum in May 2014. He was charged with terrorism offenses but has been in solitary confinement without trial for three years.

Lawyer Sebastien Courtoy said Thursday that a medical expert believes Nemmouche should have medical tests and scans.

Courtoy said his client is going blind and deaf and may have a tumor, and his prison is refusing treatment. So far, a doctor has only given him cursory checks through a trap door, he said.

Nemmouche appeared in court Thursday and was ordered to be held in custody for another two months. The detention of suspects is often reviewed every month or two in Belgium in terror-related cases.

Courtoy said Nemmouche is incapable of attending or following a trial. The case has taken so long to come to trial because investigations are still ongoing, he said, and no trial is likely before September 2018.

"Mr. Nemmouche is only asking for one thing: treatment," said the lawyer, who insists that his client is not guilty, and that he has been an exemplary inmate.

Nemmouche was arrested at a bus station in Marseille, France days after the 2014 attack carrying weapons resembling those used in the killings. The shooting reinforced fears that Europeans who join radical fighters in Syria could return to stage attacks at home.

Later that year, Nicolas Henin, a French journalist held hostage for months by extremists in Syria, said Nemmouche was one of his captors and that he took sadistic delight in mistreating prisoners.