Doctors who treat sciatica pain (išijas)

My mum has had sciatica (išijas) pain for almost 3 months now and it's not getting any better even with all the exercises and treatments she's been getting. I'm just wondering if anyone has any experience with this and treatment available in Zagreb. Maybe a doctor who specialises in that area? A chiropractor? We don't really know what to do about it anymore so ANY advice/clinic recommendations are greatly appreciated.