11.5.5\ Cerebrospinal Fluid Leak

11.5.5.1\ Discussion

Cerebrospinal fluid leakage occurs in about 2% of patients after spine surgery and results from dural and arachnoid defects, allowing cerebrospinal fluid to escape the thecal sac and infiltrate the paraspinal surgical bed. In particular, pseudomeningoceles represent a form of cerebrospinal fluid leak contained by a capsule of fibrous tissue and have been reported to occur in over 5% of discectomy cases (Fig. 11.98). Nerve roots can herniate into and become entrapped within pseudomeningoceles. Thus, patients typically present with orthostatic hypotension, but may also have associated focal neurological deficits. Imaging options for cerebrospinal fluid leakage after spine surgery include conventional MRI to delineate the presence of the fluid collections, although the exam can be limited by surgical hardware artifacts and there is a differential diagnosis for the extradural fluid, including abscess and seroma/ hematoma. Secondary findings that might be present on post-contrast images related to spinal hypotension include dilatation of the epidural venous plexus and diffuse dural thickening and enhancement. CT or MR myelography can provide a dynamic assessment that can help confirm the presence and site of cerebrospinal fluid leakage with high accuracy. Nuclear medicine spinal cisternograms are most suitable for detecting slow, intermittent leaks.

The diagnosis and localization of cerebrospinal fluid leak and pseudomeningoceles can be elusive. A variety of imaging techniques are available to evaluate the site of leakage, including MRI/MR myelography and CT myelography. MRI in spinal cerebrospinal fluid leak syndrome usually reveals cerebrospinal fluid signal intensity extradural fluid collections, spinal meningeal enhancement, and dilation of the epidural venous plexus. However, the actual site of cerebrospinal fluid leak is often not detectable with MRI. On the other hand, CT myelography can provide evidence delineate meningeal defects, the location of extradural collections, and their relationship to bony structures. However, CT myelography results in radiation exposure and it is a slightly invasive procedure.

Initial management of cerebrospinal fluid leak consists of cerebrospinal fluid diversion and epidural blood patch. If the leak or pseudomeningocele persists, dural repair and even flap reconstruction may be warranted.

11.5.6\ Postoperative Seromas

and Hematomas

11.5.6.1\ Discussion

Aseptic fluid collections are commonly found on early postoperative imaging along the surgical approach after spine operations, including seromas and hematomas. Seromas consists of plasma from disrupted vessels and inflammation from injured soft tissues. There is an increased incidence of sterile seromas and painful edema in the lumbar region after posterolateral fusion with rhBMP-2. Seromas typically appear as simple fluid collections on imaging (Fig. 11.99).

Postoperative spinal epidural hematomas are clinically significant in up to 1% of cases, attrib-

a

b

utable to mass effect upon the spinal cord or nerve roots. The majority of postoperative spinal hematomas occur at the operated level and rarely at a remote site. Prompt diagnosis and decompression of symptomatic epidural hematomas is important for averting an adverse outcome. Imaging diagnosis and assessment of the extent of spinal canal stenosis can be made via CT myelography or MRI. On MRI, epidural hematomas can be heterogeneous with a marbled appearance and of variable signal depending on the age of the hematoma. For example, hyperacute hematomas tend to have intermediate signal on T1 and bright on T2-weighted sequences (Fig. 11.100).

Fig. 11.100  Epidural hematoma. The patient underwent laminectomy and developed new lower extremity deficits caused by a large epidural hematoma confirmed on emergent decompression. Sagittal T2-weighted MRI shows a posterior epidural fluid collection (arrow) that severely narrows the spinal canal in conjunction with underlying degenerative disease