Adhesive arachnoiditis is a rare disease with insidious course. It causes damage of the spinal cord and nerve roots. The causes of adhesive arachnoiditis include earlier traumatic injury of the spinal cord, surgery, intrathecal administration of therapeutic substances (e.g. anaesthetics, chemotherapy) or contrast media, bleeding, and inflammation. It can also be idiopathic or iatrogenic. We present the case of a 42-year-old patient with fulminant adhesive arachnoiditis which was provoked by spinal surgery and caused severe neurological disability with profound, progressive, flaccid paraparesis and bladder dysfunction. The electromyography (EMG) showed serious damage of nerves of both lower limbs at the level of motor roots L2-S2 and damage of the motor neuron at the level of Th11-Th12 on the right side. Magnetic resonance imaging of the lumbosacral and thoracic part of the spinal cord demonstrated cystic liquid spaces in the lumen of the dural sac in the bottom part of the cervical spine and at the Th2-Th10 level, modelling the lateral and anterior surface of the cord. Because of the vast lesions, surgery could not be performed. Conservative treatment and rehabilitation brought only a small clinical improvement.