Spinal injuries such as those that led to Freddie Gray's death while in police custody require "significant force" akin to the impact from a car accident and can fatally impair the body's ability to regulate blood flow and breathing, according to medical experts.
Deputy Commissioner Jerry Rodriguez said Monday that the 25-year-old Gray died of "a very tragic injury to his spinal cord," the bundle of nerves that carries messages between the brain and the rest of the body. Gray died Sunday, one week after his arrest in West Baltimore.
Details about Gray's injury and what caused it remain unknown. Police did not release results of an autopsy conducted Monday.
Police Commissioner Anthony W. Batts said investigators were searching for any evidence of abuse by officers or other trauma that might have occurred during a 30-minute ride in a police van. Gray was angry and having difficulty walking when placed in the van and then unable to talk or breathe when he was removed, Rodriguez said.
Gray's family has said he underwent surgery at Maryland Shock Trauma Center for three fractured neck vertebrae and a crushed voice box — injuries doctors said are more common among the elderly or victims of high-speed crashes.
Medical experts said it takes powerful blunt force, and often damage to the vertebrae that surround the spinal cord, to tear or sever it.
"You have to apply a significant amount of force in order to break somebody's neck," said Dr. Ali Bydon, an associate professor of neurosurgery at the Johns Hopkins University School of Medicine.
The spinal cord passes through a series of 33 vertebrae that protect it from trauma, surrounding it with bone. But around the neck, there is less space between the bone and the nerves, said Dr. Steven Newman, a neurologist with William Beaumont Health System in Michigan. That can make it more susceptible to injury, he said.
When the body undergoes trauma such as a car accident, the intense forces on the body can shift the vertebrae out of place. And if they move too far out of alignment with one another, they can tear or sever the spinal cord, Newman said. In many cases, spinal cord tears can cause paralysis even though the vertebral column may bounce back into place undamaged, he said.
In other cases, hyperextension of the neck either forward or backward can cause vertebrae to fracture, crushing the spinal cord.
Bydon cited the case of a 57-year-old Alabama man who was paralyzed in February after being handcuffed and thrown to the ground, suffering a severe neck injury. Handcuffs prevent a person from being able to brace themselves in a fall, placing pressure on the head and neck when they land, he said.
Bydon said spinal cord injuries also could be self-inflicted, including in cases in which the person is under the influence of alcohol or drugs.
While injuries to lower portions of the spinal column can often lead to some degree of paralysis, trauma to the neck can have the most serious consequences, including quadriplegia, the need for a ventilator to breathe, or death as a result of an inability to breathe.
Spinal cord injuries also can lead to what is known as spinal shock, when the nervous system is overcome by the injury and unable to maintain control of blood pressure or oxygenation of vital organs, Bydon said.
If neck trauma tears ligaments that help support the neck, it takes far less force to cause spinal cord damage, he added. But it wouldn't make vertebrae any more susceptible to fracturing.
To break vertebrae, "it's usually got to be a pretty forceful trauma," Newman said.