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As Aria Long struggled to lift a star to a stacking ring, her parents watched wearily but hopefully — their eyes tracking the progress, their dreams for their first child rising and falling with each attempt.

Just a few weeks ago, the rosy-cheeked toddler was pulling herself up on furniture, scooting after the family pets, standing and attempting steps. But that was before a rare and mysterious affliction, called acute flaccid myelitis, or AFM, paralyzed her limbs and left her struggling to eat and breathe.

Now the question is: Just how much can she get back?

"It's not fair that she has to go through all this," said her father, Dylan Long, as Aria was wheeled from speech therapy to occupational therapy to physical therapy on Monday at Gillette Children's Specialty Healthcare in St. Paul. "But you have to play the hand you're dealt, right?"

Six or seven Minnesota children have been diagnosed this year with AFM, a polio-like disorder that attacks the spongy core of the spinal cord. The local cluster has renewed national attention to the disorder, which federal officials started tracking in 2014 after outbreaks in California and Colorado, while forcing parents to confront the realities of prevention and treatment.

The U.S. Centers for Disease Control and Prevention has reported 155 suspected cases in the nation so far this year, but it hasn't isolated the viral, genetic or environmental causes. While only one in a million children suffers the disorder, health officials don't know who is at risk. They also don't know why cases have peaked in September every other year since 2014 and who will recover the most.

"Recovery is a long, slow process," said Janet Dean, a pediatric nurse practitioner specializing in spinal cord injuries at the Kennedy Krieger Institute in Baltimore, a top AFM treatment center.

"We don't know how far kids are going to recover. We know that all kids make some improvement, some more than others, and that it's difficult to predict which kids are going to end up in which group."

The good news is that traditional rehab methods, used for all kinds of spinal cord injuries, appear effective for AFM despite its mysteries.

Step one is to stop the progression of the disease, which can be fatal if it paralyzes the stomach muscles that support breathing and eating. Step two is restoring muscle and nerve function with strength-building therapies. Step three is assessing how much damage is permanent and whether more extreme options such as nerve replacement surgeries can help.

"Rehab as much as you can, and then learn to live with it," said Aria's mother, Haley Spicer.

'Progress'

Aria came down with strep throat in September and was hospitalized near the family's home in Iron Junction, Minn. Shortly after she returned home, her parents found her scooting across the floor but with her left leg dragging behind. She was flown on Sept. 22 to Children's Hospital in Minneapolis and rapidly lost function in all four limbs.

Doctors put her on a feeding tube because she was struggling to eat and warned the family that she might need a ventilator to breathe.

Some but not all cases of AFM start with common viral illnesses. Doctors aren't sure whether the virus itself assaults the spinal cord or whether the damage results from an overreaction by the immune system. Several patients have shown progress with a drug known as IVIG, which boosts the body's production of antibodies and fights infections.

The drug seemed to help Aria, and by Oct. 4 she was stable enough to transfer to Gillette to begin rehab.

As hard as they found it to watch Aria struggle, her parents reminded themselves on Monday how far she has come. A week ago, she couldn't lift her arms over her head or sit upright.

"Up, up, up, up!" physical therapist Amy Schulz said during a session with Aria, encouraging her to use her weaker left arm to push herself into a sitting position.

Every day, Schulz has sat Aria upright and worked with her on hand strength and coordination. Last week, she was holding Aria around the chest to keep her stable. On Monday, the therapist's hands were down at her waist.

"You are sitting so much straighter than you were last week!" she said excitedly.

"Progress," her dad said.

All of the Minnesota cases involve children age 10 and younger, but Aria presents a challenge because she is 17 months old and can't describe her feelings. AFM can cause neuropathic pain — a feeling of being pricked by many needles — but the nerve medication gabapentin helps manage that so she can participate in three hours of daily therapy.

Aria's left leg hasn't recovered like her arms or right leg. She can feel it, though, because she hollers when it is pinched, her father said.

Like other children with severe AFM, Aria will be re-evaluated within six to nine months. Doctors don't want to consider riskier therapies until her nerves have had ample chance to heal on their own.

"[The healing] moves down from where they were injured," said Dr. Angela Sinner, Gillette's co-director of inpatient rehabilitation. "Nerves heal so slowly. Traditionally, we say a millimeter per day."

Nerve transfer surgery?

Recovery from AFM varies. A study of eight children in Colorado who suffered AFM in 2014 found one year later that two had fully recovered but six still had impairment.

Recovery of arm function, for example, depends on the nerves. Five nerves extend from a junction to the spinal cord, known as the brachial plexus, and control arm and hand movements. If AFM causes irreparable damage to all five, then patients would be unlikely to regain function and would receive adaptive devices to compensate. If healing occurs over time in all five, then full recovery is possible.

All or nothing hasn't been the norm, though. Some Minnesota children with AFM have regained control of their fingers and wrists but not yet of their upper arms — reflecting strength in some nerves but not others.

Electrical stimulation during therapy can kick-start nerves into faster healing and muscle movement, but Gillette doctors said some children might end up needing nerve transfer surgeries.

Doctors can measure patients' functioning nerves and transfer segments of them, if they're strong enough, into the dormant nerves to take over limb function.

Gillette has treated six patients in the current cluster. One Minnesota child is now at Kennedy Krieger.

None have undergone transfer surgery yet, because their nerves are still trying to heal, said Dr. Ann Van Heest, a Gillette surgeon. But waiting a year or more can be problematic, she said, because muscles can atrophy before the nerve recovers.

Considering the lack of recovery in Aria's left leg, her parents anticipate surgery for her. Progress in her other limbs means she will likely be discharged Nov. 1 and start outpatient therapies back home.

Aria was named after "Game of Thrones" character Arya Stark, a feisty warrior in the wilderness. Watching their own warrior princess in therapy, trying to push a tiny wheelchair with both arms, Aria's parents were encouraged. Grateful as they are, though, the wait can be tough.

"It's kind of hard," her father said, "to know if the nerves are dead or if they're going to come back on, or what."