A teen thought he was just short. He discovered he had a brain tumor stunting his growth after having a seizure.

• Jamie Connolly was diagnosed with a brain tumor when he was 16 after he had a seizure.
• The tumor had grown on a part of his brain responsible for development and growth.

A teenager who thought he was "small for his age" as a child was diagnosed with a brain tumor that had stunted his growth.

Jamie Connolly, now 35, was diagnosed with a low-grade astrocytoma — a slow-growing type of brain tumor that tends to be common in children and teenagers — when he was 16.

The tumor was growing on a part of his brain responsible for important functions, including development and growth, he told the charity Brain Tumour Research.

Astrocytoma brain tumors develop from astrocytes — a normal type of brain cell. When the cells don't die as they're supposed to, they can grow into a brain tumor, Brain Tumour Research said.

Symptoms of an astrocytoma can include headaches, difficulty speaking, double vision or blurriness, cognitive difficulties — such as trouble thinking or remembering, — and seizures.

Connolly had a grade one astrocytoma tumor which meant it was slow growing, compared to grade two and three tumors, which are cancerous and aggressive, according to The Brain Tumor Charity.

He told Insider that he'd experienced the odd headache as a teenager, but put them down to stress studying for his exams at school. Connolly also knew he was "small for his age" but didn't think much of it.

It wasn't until he was 16 years old that he had a seizure while playing a video game.

He told Insider that he woke up in the hospital with two big black eyes from where he passed out. He was then diagnosed with a brain tumor.

"I was really scared. A lot of things were going through my head and the added pressure of my GCSEs as well," Connolly said, referring to the exams students take aged 15 to 16 in the UK.

Connolly grew after he had part of his tumor removed

Connolly had his first operation on his tumor in 2004. Following this initial surgery, he grew from 4 feet 11 inches to 5 feet 7 inches.

He had three further operations over the following years, with the last in 2013, he told Insider.

Since the operations, his life has been full of hospital appointments, check-ups, and MRI scans, he said, as well as his work as a mental health care assistant where his employers have always been supportive.

He told Brain Tumour Research: "Despite multiple surgeries to remove the slow-growing tumor, it has left me with changes in my vision and as a result, I have to wear glasses.

"Part of the tumor is still there as removing it all could have left me with paralysis."

Now he has brain scans once a year to monitor what's left of his tumor.

Connolly told Insider he's shared his story to raise awareness of the "horrific disease," and said that signs of a brain tumor are often hidden and they are often not caught early enough.

He said he was lucky his tumor wasn't cancerous, but not everyone is as lucky.