Filum terminale lipomas-the role of intraoperative neuromonitoring

Histological Characteristics of the Filum Terminale in Occult Tethered Cord Syndrome and Filum Terminale Lipoma

BACKGROUND

Tethered spinal cord syndrome is a neurological disorder characterized by pathological tethering of the spinal cord, leading to neurological, urological, and orthopedic dysfunction. Occult tethered cord syndrome (OTCS) presents with similar clinical manifestations but lacks definitive radiological evidence, whereas filum terminale lipoma (FTL) involves adipose infiltration of the filum terminale, contributing to spinal traction. The histopathological characteristics of the filum terminale in these conditions remain incompletely understood.

OBJECTIVE

To characterize the histological features of the filum terminale in OTCS and FTL.

METHODS

Filum terminale specimens were obtained from 17 patients with OTCS and 22 patients with FTL undergoing surgical untethering (April 2020-April 2024) and from six cadavers as reference samples. The histopathological evaluation included hematoxylin-eosin, Masson trichrome, and Elastica van Gieson staining. Immunohistochemistry assessed collagen types I and III.

RESULTS

OTCS cases showed reduced collagen type I, sparse and irregularly looped elastic fibers, capillary dilation, and hyaline-like degeneration. FTL specimens exhibited adipose infiltration, densely packed and elongated elastic fibers, and intense collagen type I staining, although some showed reduced elasticity. Cadaveric samples displayed normal histology without degeneration.

CONCLUSIONS

The observed decrease in collagen type I and elastic fibers in OTCS suggests compromised filum terminale elasticity, potentially contributing to pathological tethering. In FTL, adipose infiltration is the primary factor driving spinal cord traction, although some cases also showed reduced elastic fiber integrity. These findings emphasize the importance of further research into the relationship between histopathological changes and clinical presentations. Better understanding of this correlation is crucial for developing standardized management strategies.

Diagnosis and Treatment of Tethered Spinal Cord: A Systematic Review

CONTEXT

Tethered cord syndrome is associated with motor and sensory deficits.

OBJECTIVE

Our objective was to summarize evidence regarding the diagnosis, prophylactic surgery, symptomatic treatment, and repeat surgery of tethered spinal cord in a systematic review (CRD42023461296).

DATA SOURCES AND STUDY SELECTION

We searched 13 databases, reference-mined reviews, and contacted authors to identify diagnostic accuracy studies and treatment studies published until March 2024.

DATA EXTRACTION

One reviewer abstracted data, and a content expert checked the data for accuracy. We assessed the risk of bias, strength of evidence (SoE), and applicability.

RESULTS

The evidence base includes 103 controlled studies, many with risk of bias and applicability concerns, and 355 case series providing additional clinical information. We found moderate SoE for MRI diagnosing tethered spinal cord, with medium to high diagnostic sensitivity and specificity. A small number of prophylactic surgery studies suggested motor function benefits and stability of neurologic status over time, but also complications such as surgical site infection (low SoE). A larger body of evidence documents treatments for symptomatic patients; studies revealed improvement in neurologic status after surgical detethering (low SoE), but also postoperative complications such as cerebrospinal fluid leakage (moderate SoE). A small body of evidence exists for retethering treatment (low or insufficient SoE for all outcomes).

LIMITATIONS

There was insufficient evidence for key outcomes (eg, over- or undertreatment, clinical impact of diagnostic modalities, ambulation, quality of life).

CONCLUSIONS

This comprehensive overview informs difficult clinical decisions that parents and their children with tethered spinal cords, as well as their health care providers, face.

Application of neurophysiological monitoring during tethered cord release in children

OBJECTIVE

The objective of this study was to explore the effect of intraoperative neurophysiological monitoring (IONM) on tethered spinal cord release in children.

METHODS

The clinical data of 454 children with tethered cord syndrome who underwent surgery for tethered cord release were retrospectively analyzed. The children were divided into two groups: the non-IONM group and the IONM group. SPSS 26.0 software was used for statistical analysis. The evaluation indices included the effective rate and incidence of new neurological dysfunction.

RESULTS

The short-term results showed that the effective rate of the non-IONM group was 14.8%, while that of the IONM group was 15.2%. Additionally, the incidence of new neurological dysfunction was 7.8% in the non-IONM group and 5.6% in the IONM group. However, there was no significant difference between the two groups (P > 0.05). The medium- to long-term follow-up had significant difference (P < 0.05), the response rate was 32.1% in the IONM group and 23.7% in the non-IONM group, and deterioration rates regarding neurological dysfunction were 3.3% in the IONM group and 8.5% in the non-IONM group.

CONCLUSION

This study revealed that the use of IONM does not significantly improve the short-term treatment effect of patients undergoing surgery for tethered cord release or reduce the short-term incidence of postoperative new neurological dysfunction. However, the medium- to long-term prognoses of patients in the IONM group were better than those of patients in the non-IONM group.

Neurologic pathologies of the vertebral spine

At some institutions, musculoskeletal and general radiologists rather than neuroradiologists are responsible for reading magnetic resonance imaging (MRI) of the spine. However, neurological findings, especially intrathecal ones, can be challenging. Intrathecal neurological findings in the spine can be classified by location (epidural, intradural extramedullary, and intramedullary) or etiology (tumor, infection, inflammatory, congenital). In this paper, we provide a succinct review of the intrathecal neurological findings that can be seen on MRI of the spine, primarily by location and secondarily by etiology, in order that this may serve as a helpful guide for musculoskeletal and general radiologists when encountering intrathecal neurological pathologies.

The discrepancy in triggered electromyography responses between fatty filum and normal filum terminale

BACKGROUND

Functional role of filum terminale (FT) was not well studied though it contains structure basis for nerve impulse conduction. We aimed to explore the possible functions of the FT from the perspective of triggered electromyography (EMG) during surgery.

METHODS

We retrospectively reviewed intraoperative neurophysiological monitoring data from pediatric patients who underwent intradural surgeries at the lumbar level in Shanghai Children's. Hospital from January 2018 to March 2023. Altogether 168 cases with complete intraoperative neurophysiological recordings of the FT were selected for further analysis. Triggered EMG recordings of the filum originated from two main types of surgeries: selective dorsal rhizotomy (SDR) and fatty filum transection.

RESULTS

96 cases underwent SDR and 72 cases underwent fatty filum transection. Electrical stimulation of the FT with fatty infiltration did not elicit electromyographic activity in the monitored muscles with the maximum stimulus intensity of 4.0 mA, while the average threshold for FT with normal appearance was 0.68 mA, and 89 out of 91 FT could elicit electromyographic responses in monitored channels. The threshold ratio of filum to motor nerve roots at the same surgical segment was significantly higher in patients with fatty filum, and a cut-off point of 21.03 yielded an area under curve of 0.943, with 100% sensitivity and 85.71% specificity.

CONCLUSION

Filum with normal appearance can elicit electromyographic activity in the lower limbs/anal sphincter similar to the performance of the cauda equina nerve roots. The threshold of fatty filum is different from that of normal appearing FT. Triggered EMG plays an important role in untethering surgeries.

The role of intraoperative neurophysiological monitoring in intramedullary spinal cord tumor surgery

Intramedullary tumors are a class of central nervous system tumors with an incidence of 2 to 4%. As they are located very deep and frequently cause postoperative neurological complications, surgical resection is difficult. In recent years, many surgeons have performed electrophysiological monitoring to effectively reduce the occurrence of postoperative neurological complications. Modern electrophysiological monitoring technology has advanced considerably, leading to the development of many monitoring methods, such as SSEPs, MEPs, DCM, and EMG, to monitor intramedullary tumors. However, electrophysiological monitoring in tumor resection is still being studied. In this article, we discussed the different monitoring methods and their role in monitoring intramedullary tumors by reviewing previous studies. Intratumorally tumors need to be monitored for a summary of the condition of the patient. Only by using various monitoring methods flexibly and through clear communication between surgeons and neurophysiological experts can good decisions be made during surgery and positive surgical results be achieved.

Minimal invasive interlaminar approach for untethering of fatty filum terminale in pediatric patients - how I do it

BACKGROUND

Fatty filum terminale is a form of spinal dysraphism and a third of all patients develop symptoms such as sensory, motor, and urinary impairment. Early surgery at 6 months has the advantage that the bone density is still soft, and the patients are not ambulatory yet, promoting faster healing.

METHOD

We present our minimal invasive surgical technique for FFT untethering.

CONCLUSION

Due to the low complication rate and the potentially high benefit of surgery, prophylactic untethering is recommended.