Medical Mystery: What caused young athlete’s recurring ‘absence’ seizures?

Sean Carroll was an active and energetic 17-year-old athlete, a quarterback for his football team, when he started to experience debilitating symptoms that puzzled his family and the many doctors who evaluated him.

It was during his Christmas break in 2012 that he realized something was very wrong. He lost feeling in his feet and had to cling to his dad to avoid falling. His mother gave him some juice, and he immediately felt better. At the time, his family thought the symptoms were due to dehydration. Then, on a shopping trip a few months later, his family noticed that he was acting oddly, pushing a shopping cart and talking, but not making any sense.

His parents were very concerned; he went from being an excellent student and athlete to having to miss school and practice due to frequent episodes characterized by blurry vision, bizarre behavior, and unintelligible speech. Under the advice of his primary-care physician, Sean went to see the first of what would be a string of neurologists. The specialist ordered a sleep-deprived electroencephalogram (EEG), which detects abnormal electrical brain activity. The test showed a small spike in his left temporal lobe, so he was diagnosed with epilepsy and prescribed an anti-seizure medication. However, the episodes continued despite treatment, prompting other medications to be added to his anti-seizure treatment plan.

In fall 2013, Sean was playing quarterback for the College of New Jersey's football team when during a practice he started getting confused, calling plays from high school, not college, and stumbling around on the field. His coach and teammates were aware of his epilepsy diagnosis and noted that his symptoms made it appear as if he were inebriated. The symptoms resolved after the training staff gave him Pedialyte. During another incident, Sean found himself across campus without any memory of how he got there, almost as if he were sleepwalking.

For the next 2½ years, his "absence" seizures — brief, sudden lapses of consciousness — became more frequent and increased in duration. He also experienced increased hunger and gained 35 pounds in the course of a year. With great effort, Sean continued with his classes, majoring in civil engineering.

In May 2016, when he was home after finishing his junior year, he had a particularly bad episode in the evening and again the next morning. When his parents had trouble waking him that morning and noticed he was in and out of consciousness, they drove him to the hospital. In the emergency room, clinicians drew blood and found his blood sugar was dangerously low at 30 mg/dL. (Normal levels are 70 to 120.) They gave him sugar-containing fluids, and he woke up.

Why was Sean's glucose so low, and how did it relate to his symptoms?

Sean's response to sugar led doctors to reconsider his epilepsy diagnosis. He was admitted to the hospital, where intravenous dextrose and medication stabilized his glucose levels. An endocrinologist considered the possibility that the low glucose levels were due to excessive insulin and referred him to Children's Hospital of Philadelphia and its Congenital Hyperinsulinism Center.

The HI Center is equipped with a team of experts, including pediatric endocrinologists, surgeons, radiologists, pathologists, anesthesiologists, advanced practice nurses, nurses, social workers, researchers, speech and feeding therapists, and dietitians — all working together to provide specialized care for children with congenital HI and their families.

A comprehensive evaluation at the HI Center confirmed that Sean's hypoglycemia (low blood sugar level) was indeed caused by excessive insulin.

Insulin-induced hypoglycemia, also known as hyperinsulinism, is the most common cause of persistent hypoglycemia in children and adults. While the condition is common in patients with diabetes receiving treatment with insulin, hyperinsulinism is very uncommon in the general population. In children, hyperinsulinism is more commonly the result of genetic defects affecting insulin secretion. In older children and adults, an insulin-producing tumor, or insulinoma, is the more common cause.

An MRI revealed a small tumor (an insulinoma) in Sean's pancreas. Fortunately, most insulinomas, like Sean's, are benign and can be cured by surgical removal.

Sean underwent surgery to remove the tumor, and repeat testing confirmed complete resolution of hypoglycemia. Sean was back to his former healthy and active self, four years after he first experienced symptoms.

It's not surprising it took a while for Sean to receive the proper diagnosis. Insulinomas are rare — one to four new cases per one million people per year — and are more common in people 40 and older. As in Sean's case, 20 percent of patients are initially diagnosed with a neurologic or psychiatric disorder before the insulinoma is recognized. A simple blood test at the time of symptoms would have solved this mystery. Sean had many blood tests in the course of his disease, but they were performed when he had eaten and showed no symptoms. Because hypoglycemia comes and goes and is triggered by fasting, timing of the blood sample is important.

This case illustrates how critical it is for physicians (and patients) to continue searching for answers when things just do not make sense.

Diva D. De León-Crutchlow, M.D., MSCE, is chief of the division of endocrinology and diabetes and director of the Congenital Hyperinsulinism Center at Children's Hospital of Philadelphia.