A retrospective case report.To raise the issue of DuraSeal for dural tear repair; to raise the issue of the potential for fatal consequences, if not considered to be an issue around and after surgery; and to illustrate this with a case.Cerebrospinal fluid leak is a potential complication of spinal, and posterior fossa surgery. Leakage may be caused by inadvertent dural tears during decompressive laminectomy or extradural spinal approaches, for spinal surgery. We present the case of a complication as a result of repair for dural tear with hydrogel.History, focused neurologic examination with pre- and postoperative magnetic resonance scan images.C5-C6 anterior cervical discectomy, and fusion with a standard commercial PEEK space cage. Intraoperatively there was a small cerebrospinal leak when excising the posterior longitudinal ligament. Surgicel and DuraSeal were used to seal this. The patient developed a quadriparesis after surgery which was a result of expansion of the hydrogel seen on MRI and at re-exploration.Hydrogel is now described for the second time to cause potentially fatal expansion.