Various ideas and hypotheses have been brought forward to explain the development of syringomyelia in the past two centuries. None of them offers a sufficient basis to serve as a concept for the treatment of all affected patients. Apart from a discussion of the different hypotheses this paper proposes a new pathophysiological concept based on clinical, experimental and literature studies. Syringomyelia is understood as a state of chronic interstitial edema of the spinal cord due to accumulation of extracellular fluid (ECF). This accumulation is caused by a cascade of events starting with obstruction of cerebrospinal fluid (CSF) flow and/or spinal cord tethering which ultimately alter ECF flow and increase ECF volume. Treatment should be targeted against the pathological process which causes CSF flow obstruction and cord tethering to inhibit this pathophysiological process at a decisive point.