"They said it was borderline whether he needed surgery or not," says the source, "but they've taken some scans and see no further damage."
Aldridge, the father of Spears's 10-month-old daughter Maddie, has been hospitalized with a head injury that he suffered when he flipped his F-250 pickup truck on the driver’s side on a two-lane road in Louisiana at 1:30 a.m. Sunday.
The accident – during which three of the five occupants, including Aldridge, were ejected from the truck – occurred after a bachelor party for Aldridge's cousin at nearby Lake Bruin on Saturday, according to the source. The two other passengers thrown from the truck suffered less serious injuries.
Spears in Good Spirits"Jamie Lynn has been at the hospital, and all indications are that she is holding up well," the family source tells PEOPLE.
After his head injury was diagnosed at a small hospital in Vidalia, La., close to the crash site, Spears, 18, accompanied Aldridge during the two-hour ride to the Jackson, Miss., medical center.
"[Jamie Lynn] was in the ambulance with Casey, and Casey's sister followed in the car," says the source.
Given the nature of the incident, the police are surprised that Aldridge and his four passengers are faring as well as they are.
"It's an anomaly that no one was injured more seriously," says Louisiana State Police spokesman Mark Dennis. "Usually in that kind of accident, you see serious injuries or fatalities."
The family source agrees.
"Only one of them was even wearing a seat belt," says the source. "There had to be angels all around them."