After Brain Surgery, U.K. Gradeschooler Can't Stop Giggling After brain surgery, a young U.K. girl can't stop laughing for the life of her.

Aug. 9, 2011 -- Seven-year-old Enna Stephens is facing a daunting 16 months of chemotherapy and radiation after doctor's removed a tumor from her brain, but thanks to a bizarre side effect of the surgery -- all she can do is laugh about it.

Enna suffers from pseudobulbar affect (PBA), a neurological disorder brought on by nerve damage that makes it difficult to control one's emotional response. Some patients with PBA cry uncontrollably, others get angry, but for Enna, it has manifested as frequent bouts of the giggles.

'We were told by doctors that most patients who have a brain tumor removed feel depressed or angry afterwards. But when Enna came round she was giggling and it just carried on. She would giggle all the time – anything would set her off," Enna's mother Vana Stephens told the U.K. press.

While PBA can cause normal reactions, such as a chuckle following a joke, to become exaggerated, the emotional responses sometimes run contrary to the actual emotion the patient is feeling, or have nothing to do with it at all.

"Different patients suffer it in different ways," says Dr. Brian Greenwald, medical director of brain injury rehabilitation at the Mount Sinai Rehabilitation Center in New York City, who did not treat Enna. "Sometimes they'll be hysterically crying but not actually feel upset. Sometimes they are angry but it comes out as laughter. It can be incredibly frustrating to live with because it starts to interfere with one's social and professional life," he says.

In cases of traumatic brain injury, PBA can be a sign of damage to the brain and will often subside with time as the brain heals. For those with degenerative conditions, such as Parkinson's or Alzheimer's, however, PBA tends to worsen over time.

Though PBA is certainly not something one would wish for and Enna's PBA is expected to diminish, the little girl's parents note that this particular side effect has its silver lining:

"We'd visit Enna in hospital and try to put on a brave face but inside we were crushed. But once she started giggling we found ourselves doing the same. It was so infectious, and just a great way of releasing our emotions," Stephens told the U.K. press.

And according to Enna's doctors, there is something to smile about: they believe the cancer was completely removed and there is an 80 percent chance it won't return, doctors told the U.K. press.

Inappropriate Reactions: A Life with PBA

Though Enna's case of pseudobulbar affect was glaringly obvious, this neurological disorder occurs to varying degrees in many cases of brain injury or degeneration, brain experts say.

It's believed that about 2 million Americans suffer from PBA, says Dr. Erik Pioro, a Cleveland Clinic neurologist who specializes in ALS and related disorders.

Though the exact areas of the brain that controls for emotional expression are not known, it's thought that injuries to the prefrontal cortex, the area at the front of the brain and behind the eyes, may be more likely to produce PBA, as this region is thought to control, in part, for the regulation of our emotions.

Because PBA is a disorder of controlling and regulating emotions, Greenwald says it makes sense that children might experience stronger symptoms because they are just learning to control their behavior for social reasons.

"When you're kid, it's hard to have a poker face, because that control of emotions is something you learn throughout childhood and adolescence. There's already less of a filter," he says.

But this doesn't necessarily mean that the outbursts, whether of laughter or tears, are signifying an exaggerated version of what a patient like Enna is actually feeling.

"For example, people with PBA manifest primarily by crying are often mistaken as being depressed. In a similar way, the young girl with the continuous giggling probably does not feel happy or joyful 'inside' when she has these episodes," says Pioro.