Correlation between balanced fast field echo sequence and intraoperative findings in the surgical treatment of an intradural spinal arachnoid cyst: illustrative case

Abstract

Background: Spinal arachnoid cysts can cause myelopathy through spinal cord compression. While MRI is the standard for diagnosis, traditional sequences may not clearly define cyst borders and septations, which are important for guiding surgical intervention. Balanced fast field echo (B-FFE) is an MRI sequence that highlights small arachnoid membranes within and at the borders of CSF spaces.

Observations: The authors report the case of a 13-year-old female who presented with progressive lower extremity paresthesias and weakness and urinary incontinence. MRI revealed an intradural cervicothoracic arachnoid cyst (C7-T3) dorsal to the spinal cord. B-FFE was used to identify the upper and lower borders of the intradural arachnoid cyst and its internal septations. These findings corresponded precisely with intraoperative findings and guided fenestration at the cyst's cranial, caudal, and internal septal ends. Postoperatively, the patient's symptoms resolved, and MRI confirmed the resolution of mass effect. At the 10- and 30-month follow-ups, there was no evidence of cyst recurrence clinically or radiographically.

Lessons: The authors raise awareness of the clinical utility of B-FFE imaging for intradural spinal arachnoid cysts. Due to its ability to demonstrate cyst borders and internal septations, it offers an alternative to more invasive tests, especially in the pediatric population. https://thejns.org/doi/10.3171/CASE25145.

Keywords: B-FFE; balanced fast field echo; balanced steady-state free precession; magnetic resonance imaging; pediatric neuroimaging; spinal arachnoid cyst.

FIG. 1.

Preoperative MR images. The superior pole (*) and internal septations (white arrows) of the intradural arachnoid cyst are clearly delineated on the sagittal T2 B-FFE sequence (A). The septations are less clearly visualized on a sagittal T2-weighted image without BFFE (B) and on a sagittal T1-weighted image with contrast (C). Axial B-FFE sequences show that the arachnoid cyst is located dorsal to the spinal cord and exerts mass effect along multiple levels including C6–7 (D) and T2–3 (E). The cyst extends slightly beyond the T3 level, as shown on an axial T1-weighted sequence with contrast (F).

FIG. 2.

Intraoperative view after laminectomy and opening of the dura. The left side of the images is caudal and the right side of the images is cranial. The dura is opened, and the dorsal arachnoid cyst is encountered (A). A Rhoton dissector is used to retract the cyst (B). The arachnoid cyst has been fenestrated and partial excision of the cyst wall has been performed revealing the underlying compressed spinal cord (C). On further caudal exposure, a septum is encountered that correlates with the location of the septum noted on preoperative B-FFE imaging (D).

FIG. 3.

Sagittal T2-weighted MR image of the cervical and thoracic spine obtained before surgery, showing an intradural arachnoid cyst and spinal cord displacement (A). Sagittal T2-weighted MR image of the cervical and thoracic spine obtained 10 months after laminectomy and arachnoid cyst fenestration, showing resolution of mass effect on the spinal cord at the upper thoracic levels (B).