Helen Leigh, 25, of Rotherham, South Yorkshire, was diagnosed with Non-Epileptic Attack Disorder (NEAD) before her death in May 2018.

Her mother Deborah Leigh is seeking to raise awareness of the condition.

Sheffield Teaching Hospitals NHS Foundation Trust said Helen's treatment was carefully considered by seizure specialists.

In September last year Mrs Leigh settled a clinical negligence claim with the trust, which did not admit liability.

Helen was diagnosed with epilepsy and prescribed medication in November 2014 after a seizure.

But in September 2015, Royal Hallamshire Hospital neurologists changed her diagnosis to NEAD, which causes attacks similar to epilepsy but with no physical cause.

Helen was taken off her medication and assured her seizures could not be fatal, her mother said.

Mrs Leigh, a GP practice manager, said: "The frequency and severity of her seizures were increasing over time, and this was reported to the neurologist who repeated that Helen did not have epilepsy."

In May 2018, Helen suffered a fatal seizure at home.

After her death, a neurologist told her family "in retrospect, Helen probably had both epileptic and NEAD seizures," Mrs Leigh said.

She added: "I was so angry - and still am. I think Helen's death was avoidable."

'Devastated'
Mrs Leigh said: "Not once before Helen died were we told that you can have both epilepsy and NEAD.

"Had we known this, we would have been able to have different conversations with those treating her."

Dr Jennifer Hill, the NHS trust's medical director, said several investigations were carried out into Helen's condition and changes to her treatment were only made after discussions with her and after "careful consideration by specialists in seizure disorders".