In the case of primary epilepsy, the seizures have no apparent underlying cause, resulting from an abnormal nidus in the brain that fires autonomously. (web-dvm.net)
Monitoring CT scan also supported the thesis of an osteoid osteoma given the absence of a «nidus» [9]. (wjon.org)
The scanner showed an indented humeral head with incisions in the front cortical bone at two points, without a «nidus». (wjon.org)