Pseudomeningocele is a pathological condition deriving from cerebrospinal fluid leak throughout a fissure of the dura mater. The came out fluid is enclosed in a space delimited by the soft tissues. It can be congenital, iatrogenic or traumatic (mainly in brachial plexus injury) and can be often associated with root avulsion, a severe condition which should be aware as soon as possible. The incidence of traumatic pseudomeningocele of this type is 21–57 % [2, 3]. In brachial plexus injury, magnetic resonance (MR) is the gold standard to assess the damage, allowing the visualization of root avulsion and pseudomeningocele. Even high-frequency ultrasound (US) may be used as first line tool in brachial plexus injury, showing data that, in some cases, require a comprehensive assessment through MR.