Common side effects to smoking synthetic marijuana include bloodshot eyes, disturbed perceptions and a change in mood, said Dr. Melinda Campopiano, a medical officer with the Substance Abuse and Mental Health Services Administration.
"People can become very agitated or can be come unresponsive -- conscious but not reacting normal to situations," she said. They may also appear paranoid or describe hallucinations. Some of the more potentially serious effects include an elevated heart rate and elevated blood pressure.
Campopiano said she had never heard of a patient having a stroke in these circumstances, but she described how high blood pressure could lead to one.
"Generally, strokes are caused by restricted circulation, or a blood clot that blocks circulation. What we would be looking at with Spice, or K2, is the restrictive circulation model," she said.
Bryant told CNN that doctors diagnosed his daughter with vasculitis, which is an inflammation of the blood vessels. The vessels going into Emily's brain were constricting, limiting blood and oxygen flow. Campopiano confirmed that vasculitis is one of the causes of strokes of this type.
"One of the difficulties is that there's no existing toxicology screen that can reliably detect these substances," said the physician. "There could very well be harms out there that we don't know about yet."
'She was literally just a shell'
Emily complained of a migraine and took a nap at her house after allegedly smoking Spice with friends on December 7, said Bryant. She woke up a different person.
Stumbling and slurring her words, she morphed into a psychotic state of hallucinations and violent outbursts, her family said.
They called 911 after they realized she had "done something," some drug, said her stepfather. The Harris County Sheriff's Office confirmed they visited the house but declined to provide details.
When paramedics arrived, they restrained her and rushed her to a Houston-area hospital, where she was admitted to the ICU.
She bit guardrails and attempted to bite those trying to help her. Hospital staff strapped Emily down in the bed, said her sister.
"We thought once she comes down off the drug, we'd take her home and show her the dangers of this drug," said the 22-year-old. "We didn't think it was as big of a deal until 24 hours later she was still violent and hurting herself. We realized you're not supposed to stay high this long."
To keep Emily safe, doctors put her in an induced coma.
After days in the sedated state, an MRI revealed she had suffered several severe strokes, said Bryant.
"In four days' time, we went from thinking everything is going to be OK and we'll put her in drug rehabilitation to now you don't know if she's going to make it," he said.
The doctors at North Cypress Medical Center told the family there was nothing more they could do. She was sent to Children's Memorial Hermann Hospital. Citing patient privacy, doctors at Children's Memorial declined to be interviewed.
No consistency, no way of knowing
Knowing how different people will react to fake weed is impossible. There are a few reasons that explain why.
"You're hearing some pretty bad things with the synthetic cannabinoids -- part of that has to do with the potency. It can be 100 times more potent than marijuana," said U.S. Drug Enforcement Administration spokeswoman Barbara Carreno.
"Anything that was truly a fake pot wouldn't be making your heart race. I've heard of palpitations with marijuana, but not tachycardia."
Carreno explained there's no consistency or quality control from one time to the next. The people making these products can be anyone from a college kid wanting to make extra cash to an operation blending large quantities in a cement mixer, she said. Two batches made by the same person could have different doses.
CNN showed Carreno a picture of the packets of potpourri Emily reportedly used -- the teen's friends gave her family the pouches after the incident. One black wrapper adorned with marijuana leaves reads "KLIMAX potpourri" and both labels read "KUSH TM."
"It's definitely a synthetic cannabinoid," Carreno said after seeing the photo.
The potpourri displays at stores also include a label that reads "not for human consumption."