Images below require Macromedia's Flash Player to view

Neuroradiology Case of the Week

Case 261

Brady Huang, MD, Cindy Zink, RPA-C, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 46-year-old male with lumbar postlaminectomy syndrome.

Imaging Findings:

Diagnosis: Postlaminectomy pseudomeningocele, with nerve root herniation

Discussion: A pseudomeningocele is an encapsulated CSF collection which can be a postoperative complication of laminectomy, and is the result of an inadvertent dural tear [1]. The true incidence of postlaminectomy pseudomeningocele is not known as many are thought to be asymptomatic. Some series report an incidence of less than 1% [2,3], but others as high as 2% [1].
     During surgery, if the dura is accidentally torn, but the arachnoid is intact, the arachnoid may herniate through the defect. More frequently however, both are torn, allowing CSF to leak into the paraspinal soft tissues. Subsequently, either the CSF is resorbed or it becomes encapsulated by fibrous tissue, thus resulting in a pseudomeningocele. It is possible for nerves to herniate through the defect which can lead to symptoms of lumbar radiculopathy. Nerve herniation also physically prevents healing of the dural defect. Neck and leg pain are the most common symptoms of nerve herniation. Headaches may be seen with large pseudomeningoceles. A palpable fluid collection may be found if it extends though the lumbosacral fascia [4]. The symptoms can be difficult to distinguish from persistent or recurrent symptoms after discectomy.
     Myelography is helpful in identifying the pseudomeningocele. However the actual communication between the thecal sac and meningocele sac may be difficult to visualize. CT myelography is considered the diagnostic procedure of choice for demonstrating the communication between the two, although MRI has been reported to demonstrate the communication [2,5,6]. One series reported that although pseudomeningoceles were well-demonstrated on CT and myelography, entrapped nerve roots were only identified intraoperatively [7]. There have been only a few case reports of calcified pseudomeningoceles [2,5,8,9].
     Asymptomatic pseudomeningoceles may be observed. Although as before, it may be difficult to distinguish symptoms from a pseudomeningocele from recurrent/persistent symptoms necessitating surgery in the first place. Treatments include cyst aspiration and fibrin patches. Definitive treatment consists of reduction of herniated roots and primary closure of the dural defect. The defect may be closed with a dural graft, the pseudomeningocele sac itself, or fibrin glue. The entire sac need not be removed.

References:

1. Teplick JG, Peyster RG, Teplick SK, Goodman LR, Haskin ME: CT identification of postlaminectomy pseudomeningocele. AJR Am J Roentgenol. 1983 Jun;140(6):1203-6. [Medline]
2. Schumacher HW, Wassman H, Podlinski C: Pseudomeningocele of the lumbar spine. Surg Neurol. 1988 Jan;29(1):77-8. [Medline]
3. Swanson HS, Fincher EF: Extradural arachnoidal cysts of traumatic origin. J Neurosurg 4:530–538, 1947.
4. Barron JT. Radiologic case study. Lumbar pseudomeningocele. Orthopedics. 1990 May;13(5):603, 608-9. [Medline]
5. Lee KS, Hardy IM. Postlaminectomy lumbar pseudomeningocele: Report of four cases. Neurosurgery. 1992 Jan;30(1):111-4. [Medline]
6. Murayama S, Numaguchi Y, Whitecloud TS, Brent CR: Magnetic resonance imaging of post-surgical pseudomeningocele. Comput Med Imaging Graph. 1989 Jul-Aug;13(4):335-9. [Medline]
7. Hadani M, Findler G, Knoler N, Tadmor R, Sahar A, Shacked I. Entrapped lumbar nerve root in pseudomeningocele after laminectomy: report of three cases. Neurosurgery. 1986 Sep;19(3):405-7. [Medline]
8. Rosenblum DJ, Derow JR: Spinal extradural cysts, with report of an ossified spinal extradural cyst. Am J Roentgenol Radium Ther Nucl Med. 1963 Dec;90:1227-30. [Medline]
9. Tsuji H, Handa N, Handa O, Tajima G, Mori K: Postlaminectomy ossified extradural pseudocyst. Case report. J Neurosurg. 1990 Nov;73(5):785-7. [Medline]