Fatty filum terminale (FFT) as a secondary tethering element in children with closed spinal dysraphism

Classification of and individual treatment strategies for complex tethered cord syndrome

Objective

To study the classification, diagnosis, and treatment strategies of complex tethered cord syndrome (C-TCS) on the basis of the patients' clinical symptoms, imaging findings, and therapeutic schedule.

Methods

The clinical data of 126 patients with C-TCS admitted to our department from January 2015 to December 2020 were retrospectively analyzed. Classification criteria for C-TCS were established by analyzing the causes of C-TCS. Different surgical strategies were adopted for different types of C-TCS. The Kirollos grading, visual analogue scale (VAS), critical muscle strength, and Japanese Orthopaedic Association (JOA) scores were used to evaluate the surgical outcomes and explore individualized diagnosis and treatment strategies for C-TCS.

Results

C-TCS was usually attributable to three or more types of tether-causing factors. The disease mechanisms could be categorized as pathological thickening and lipomatosis of the filum terminal (filum terminal type), arachnoid adhesion (arachnoid type), spina bifida with lipomyelomeningocele/meningocele (cele type), spinal lipoma (lipoma type), spinal deformity (bone type), and diastomyelia malformation (diastomyelia type). Patients with different subtypes showed complex and varied symptoms and required individualized treatment strategies.

Conclusion

Since C-TCS is attributable to different tether-related factors, C-TCS classification can guide individualized surgical treatment strategies to ensure complete release of the tethered cord and reduce surgical complications.

Diagnostic Utility of 3D Gradient-Echo MR Imaging Sequences through the Filum Compared with Spin-Echo T1 in Children with Concern for Tethered Cord

BACKGROUND AND PURPOSE

Fatty intrathecal lesions are a cause of tethered cord, and detection of these on spinal MR imaging is paramount. Conventional T1 FSE sequences are the mainstay of detecting fatty elements; however, 3D gradient-echo MR images, volumetric interpolated breath-hold examination/liver acquisition with volume acceleration (VIBE/LAVA), are popular, given the increased motion resistance. We sought to evaluate the diagnostic accuracy of VIBE/LAVA compared with T1 FSE for detection of fatty intrathecal lesions.

MATERIALS AND METHODS

In this retrospective, institutional review board-approved study, 479 consecutive pediatric spine MRIs obtained to evaluate cord tethering between January 2016 and April 2022 were reviewed. Inclusion criteria were patients who were 20 years of age or younger who underwent spine MRIs containing both axial T1 FSE and VIBE/LAVA sequences of the lumbar spine. The presence or absence of fatty intrathecal lesions was recorded for each sequence. If fatty intrathecal lesions were present, anterior-posterior and transverse dimensions were recorded. VIBE/LAVA and T1 FSE sequences were evaluated on 2 separate occasions (VIBE/LAVAs first followed by T1 FSE several weeks later) to minimize bias. Basic descriptive statistics compared fatty intrathecal lesion sizes on T1 FSEs and VIBE/LAVAs. Receiver operating characteristic curves were used to determine minimal fatty intrathecal lesion size detectable by VIBE/LAVA.

RESULTS

Sixty-six patients were included, with 22 having fatty intrathecal lesions (mean age, 7.2 years). T1 FSE sequences revealed fatty intrathecal lesions in 21/22 cases (95%); however, fatty intrathecal lesions on VIBE/LAVA were detected in 12/22 patients (55%). Mean anterior-posterior and transverse dimensions of fatty intrathecal lesions measured larger on T1 FSE compared with VIBE/LAVA sequences (5.4 × 5.0 mm versus 1.5 × 1.6 mm, respectively; P values = .039 anterior-posterior; .027 transverse).

CONCLUSIONS

While T1 3D gradient-echo MR images may have decreased the acquisition time and are more motion-resistant than conventional T1 FSE sequences, they are less sensitive and may miss small fatty intrathecal lesions.

Surgical histopathology of a filar anomaly as an additional tethering element associated with closed spinal dysraphism of primary neurulation failure

Background:

Closed spinal dysraphism of primary neurulation failure could be associated with filar anomalies, such as filar lipoma or thickened and tight filum terminale (TFT), resulting from impaired secondary neurulation. Retained medullary cord (RMC) is a remnant of the cavitary medullary cord originating from the secondary neurulation failure. Some filar lipomas are known to contain a central canal-like ependyma-lined lumen with surrounding neuroglial tissues (E-LC w/NGT), that is, a characteristic histopathology of RMC. To clarify the embryological background of these filar anomalies, we evaluated the histopathological findings.

Methods:

Among 41 patients with lesions of primary neurulation failure who underwent initial untethering surgery, the filum including cord-like structure (C-LS) was additionally resected in 10 patients (five dorsal and transitional lipomas; five limited dorsal myeloschisis). We retrospectively analyzed the clinical, neuroradiological, intraoperative, and histopathological findings.

Results:

Among 10 patients, two patients were diagnosed with RMC based on morphological features and intraoperative neurophysiological monitoring. The diagnosis of filar lipoma was made in six patients, since various amounts of fibroadipose tissue were histopathologically noted in the filum. Two patients were diagnosed with TFT, since the filum was composed solely of fibrocollagenous tissue. E-LC w/NGT was noted not only in both C-LSs of RMCs but also in two out of six fila both with filar lipomas and fila with TFTs.

Conclusion:

These findings provide further evidence for the idea that entities, such as filar lipoma, TFT, and RMC, can be considered consequences of a continuum of regression failure occurring during late secondary neurulation.

Early- and long-term surgical outcomes in 109 children with lipomyelomeningocele

AIM

To determine the functional outcomes and risk factors for outcomes following surgery for lipomyelomeningocele (LMMC).

METHODS

Data from 109 children with LMMC who underwent surgery from January 2008 to December 2017 were retrospectively studied to evaluate functional outcomes and possible risk factors for early- (at discharge from hospital or within 1 month of surgery) and long-term outcomes after surgery.

RESULTS

There were 53 boys and 56 girls with median age of 36 months (IQR 12-90 months; range, 4 months to 18 years) at surgery. At presentation, neurological function was normal (asymptomatic group) in 28 (25.7%) children while there was neurological dysfunction (symptomatic group) in 81 (74.3%). Near total or radical excision of lipoma was done in 71 (65.1%) children. Six (5.8%) children had deterioration of neurological function in the post-operative period with recovery of function in three of them. There were no statistically significant risk factors for early outcomes. At a mean follow-up of 62.5 months (IQR 35-82 months; range, 12-146 months), 21 (27.6%) of the 76 symptomatic group children (including 59.3% with incomplete bladder dysfunction) showed improvement, 52 (68.4%) remained the same, while 3 (4%) deteriorated. In 31 children (symptomatic group) who developed symptoms after 1 year of age, early surgery after development of symptoms was associated with better chances of recovery (p = 0.0008). In the asymptomatic group, 23 (88.5%) had normal neurological function at mean follow-up of 57.5 months (IQR 30-77 months; range, 12-141 months) and 3 (11.5%) had neurological deterioration. The mean time to late deterioration (re-tethering) from surgery was 51.3 months (IQR 24-75 months; range, 24-84 months). Presence of syrinx on initial MRI (p = 0.008) and partial resection of the lipoma (p = 0.02) were independent risk factors for delayed deterioration.

CONCLUSION

Radical resection of LMMC probably helps in preserving neurological function in > 90% of children at long-term follow-up. Fifty-five percent of children > 2 years of age with incomplete bladder dysfunction regained normal function following surgery. In children who develop symptoms after birth, early surgical intervention can reverse the neurological deficits.

Real spinal cord injury without radiologic abnormality in pediatric patient with tight filum terminale following minor trauma: a case report

Background

Spinal cord injury without radiographic abnormality (SCIWORA) is defined as having “clinical symptoms of traumatic myelopathy with no radiographic or computed tomographic features of spinal fracture or instability”. The mechanism of pediatric SCIWORA following minor trauma is still unclear. Tight filum terminale (TFT) has been studied in the literature, but the information regarding the predisposing factor for SCIWORA is still being defined.

Case presentation

We report three cases of thoracic and lumber SCIWORA with TFT. The trauma was potentially mild in all cases but resulted in catastrophic damage of the cord. All patients had no signs or symptoms of tethered cord syndrome prior to the minor trauma. TFT was found during operation.

Conclusions

We suggest that TFT might be a predisposing factor for SCIWORA and chronic spinal cord traction play an important role in the mechanism of pediatric thoracic and lumber SCIWORA following minor trauma. Patients who never undergo treatment for TFT likely have an elevated risk of developing SCIWORA following minor trauma.