Background: Post-traumatic pseudomeningoceles are common findings after a brachial or lumbar plexus trauma, in particular after nerve root avulsion. Unlike meningoceles, pseudomeningoceles are CSF full-filled cysts confined by the paraspinous soft tissue, along the normal nerve course, in communication with the spinal subarachnoid spaces. Normally no more than a radiological finding at MRI, in rare instances they might be symptomatic due to their size or might constitute an obstacle during a reconstructive surgery. Methods: A review of the literature was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in a time span ranging from November 1972 to May 2024. A total of five articles were found meeting the inclusion criteria. A case report at our institution was added to the case history. Results: A 30-year-old man with complete right brachial plexus nerve roots avulsion and a voluminous pseudomeningocele at the C6-C7 level after a motorcycle incident in January 2023. The pseudomeningocele covered the entirety of the injured brachial plexus. Pre-operative external lumbar drainage was utilized to prevent relapse or worsening of the already existing cerebral spinal fluid collection, with good results at 6 months. The full case report is reported in detail. Conclusions: To date, no clear guidelines about the management of post-traumatic pseudomeningoceles are reported in the literature. The lack of symptoms or signs related to them does not usually require any surgical intervention. If not, a possible management strategy with the use of an external lumbar drainage is proposed, a solution already in use in other surgical contexts with successful results in preventing CSF fistula or its relapse.