ONE of the star performers to get their GCSE results last week has to be Joanna Williams-Durkin. Despite undergoing four brain operations 12 months before sitting her exams, the St Peter's School pupil achieved seven A stars, three As and four Bs and came top of her class. Joanna, 16, has hydrocephalus, a condition in which excess fluid accumulates in the ventricular system of the brain. She had a tube (shunt) surgically inserted at the age of nine to drain the fluid from her brain into her heart. This year she missed 15 weeks of schooling after undergoing six operations at Addenbrooke's Hospital - the most recent in March. She also collapsed at school and had to be taken to hospital. Opening her results on Thursday Joanna said: "I never expected to do so well, I'm absolutely thrilled. I can't believe it and I can't stop shaking." Joanna's mum, Jaqui added: "I'm so proud of her. I would have been happy with Es, Fs and Gs but the grades she achieved are absolutely fantastic." And Martin Williams-Durkin, Joanna's father, said: ""We are just glad she was able to sit her exams. At times we thought she wouldn't be well enough. "At the time we were more concerned about her health. I'm still in shock about the grades because they are so fantastic. She made a huge effort to catch up and she worked so hard. "She does occasionally feel dizzy but when everything is working okay she is fine. Her shunt broke down a lot this year so we have been in and out of hospital to have an operation to fix it." In July the family moved from Hartford to Chesterton in Cambridge. Joanna plans to study maths, physics, chemistry and biology at Long Road Sixth Form College in Cambridge, and hopes to go to university to study medicine.