Epidural injections are routinely used for short-term management of radicular pain and chronic low back pain. Prescription of this intervention, in the presence of intracranial abnormalities, is a topic of debate. Intracranial arachnoid cysts are cerebrospinal fluid-filled spaces, which are usually asymptomatic despite being a formidable size. As far as the authors know, there have been no cases depicted in indexed literature regarding asymptomatic supratentorial arachnoid cysts becoming symptomatic post undertaking of spinal epidural injections. We depict this phenomenon in a 53-year-old woman, who ultimately required a craniotomy to address their symptoms. Asymptomatic supratentorial arachnoid cysts can become symptomatic post undertaking of spinal epidural injections. In cases of known cranial arachnoid cysts with mass effect, the small risk that the cranial arachnoid cyst may become symptomatic during or after epidural injections should be a consideration and the patients should be informed of the potential associated risks.