Schu was seriously injured in February fall
While testing for this year's German Superbike series at the Cartagena track in Spain, the retired seven time world champion fell at high speed and was hospitalized.
Schumacher, 40, claimed that hospital checks showed no significant injuries, but Blick insists the German sustained severe concussion and two broken ribs.
On his latest visit to the F1 paddock last weekend, meanwhile, it was rumored that Schumacher – still unable to ride a bike or even fully turn his head due to a stiff neck – may also have fractured a vertebrae in the fall.
His spokeswoman Sabine Kehm said: "We do not take part in speculation."
It is rumored that Schumacher still receives treatment for his injuries in the Bad-Nauheim hospital, but the Sportklinic's Dr Johannes Peil also refused to comment.
And spokeswoman Kehm insisted: "Once he is again fully fit, he would like to ride motorcycles again."