Spinal dural sac termination and internal filum terminale fusion: A Study from 80 Cadavers.

Surgery for tethered spinal cord caused by thickened filum terminale (FT) is frequently performed through S1 laminectomy based on the assumption that the internal FT (FTi) fuses with dura mater at S2 vertebral level. Literature on specific study for the site of its fusion and dural sac (DS) termination was rather limited. Moreover, there is no large anatomical study in Asian population. To determine the anatomy, examination of the FTi fusion site, as well as the region at which DS ended, was undertaken. From 80 embalmed cadavers, the majority of FTi fusion occurred at, or below, S1/S2 disk space (62.5%) which was less frequent than previous reports (70%-90%). In addition, there was 11.3% of the fila that fused above S1. Regarding the DS termination, it was found at, or below, S1/S2 disk space in 76.3% with one subject (1.3%) at L5/S1 disk space. With modest differences compared with non-Asian cadaveric data, our results offer pertinent information to surgeons performing tethered cord release. One ought to keep in mind that small, but not negligible, percentage of FTi can fuse with dura mater above S1 level; hence, more rostral laminectomy at L5 may be required. Clin. Anat. 33:558-561, 2020. © 2019 Wiley Periodicals, Inc.

Anatomical and Histological Analysis of a Complex Structure Too Long Considered a Simple Ligament: The Filum Terminale.

BACKGROUND: The intradural filum terminale (iFT) connects the conus medullaris (CM) with the dural sac (DS), and the extradural filum terminale (eFT) connects the DS to the coccyx. The aim of the present study was to update the description of the FT and integrate these data in a physiological and pathological context. METHODS: Anatomical measurements and histological investigations were performed on 10 human cadavers. RESULTS: The mean length of the iFT and eFT was 167.13 and 87.59 mm, respectively. The mean cranial diameter of the iFT was 1.84 mm. It was >2 mm in 2 specimens. The mean half and caudal diameter of the iFT was 0.71 and 0.74 mm, respectively. The cranial diameter of the eFT correlated with the caudal diameter of the eFT (ρ = 0.94; P = 0.02). The level of the CM-iFT junction correlated significantly with the iFT length (ρ = -0.67; P = 0.03). The mobilization of the iFT was not transmitted to the extradural elements and vice versa. The iFT contained axons and ependymal cells, which were dense in the first third and then randomly arranged caudally in islets. This could explain why ependymomas can occur all along the iFT. Ganglion cells were abundant around the junction with the DS. The eFT contained smooth muscle cells, adipocytes, and axons. A mechanoreceptor was identified in 1 specimen. CONCLUSIONS: Consistently with their common embryological origin, a real anatomical and histological continuum is present between the CM and FT. The FT should, therefore, no longer be considered a simple ligament but, rather, a complex fibrocellular structure.

Cauda Equina Syndrome Due to Lumbar Disc Herniation: a Review of Literature.

Cauda equina syndrome (CES) is a rare neurologic condition that is caused by compression of the cauda equina. Cauda equina consists of spinal nerves L2-L5, S1-S5 and the coccygeal nerve. The compression of these nerve roots can be caused mainly by lumbar disc herniation (45% of all causes). The diagnosis consists of two critical points: a) detailed history and physical examination and b) MRI or CT. The gold standard of the treatment of this syndrome is the surgical approach in combination with the timing of onset of symptoms. The surgery as an emergency situation is recommended in the fi rst 48 hours of onset of symptoms. Any delay in diagnosis and treatment leads to a poor prognosis of CES.

Histological structure of filum terminale in human fetuses.

OBJECT: The structure of the filum terminale (FT) is important in the development of tethered cord syndrome (TCS) in children. Although many studies have been performed on the histological structure of the FT in adults, there has been no detailed investigation for those of fetuses. The aim of this study was to examine the histological structure of the FT in normal human fetuses and to compare the results with those of previous studies. METHODS: The histological examination of the FT was performed in 15 normal human fetuses; 11 of them were female and 4 were male. The gestational age of the fetuses ranged between 14 weeks and 35 weeks, and they weighed between 180 g and 1750 g. The FT of each fetus was cut and examined for adipose tissue, fibrous tissue, peripheral nerve, ganglion, ependymal cells, gliosis, elastic fibers, and collagen types (Types I and III). RESULTS: Adipose tissue was observed in 2 specimens (13%), whereas fibrous tissue was found in 8 specimens. Peripheral nerve was detected in 11 (73%), ganglion in 6, ependymal cells in 5, and glial tissue in 7 FT samples. Type III collagen was present in 12 specimens (80%) with different concentrations, whereas Type I collagen and elastic fibers were not detected. CONCLUSIONS: The normal structure of the FT in fetuses is different from its structure in adults. The FT has no elasticity during intrauterine life because of the lack of elastic fibers. More detailed studies are needed to understand the histological basis of TCS in children.

Spinal cord bypass surgery with intercostal and spinal accessory nerves: an anatomical feasibility study in human cadavers.

OBJECT: Despite extensive study, no meaningful progress has been made in encouraging healing and recovery across the site of spinal cord injury (SCI) in humans. Spinal cord bypass surgery is an unconventional strategy in which intact peripheral nerves rostral to the level of injury are transferred into the spinal cord below the injury. This report details the feasibility of using spinal accessory nerves to bypass cervical SCI and intercostal nerves to bypass thoracolumbar SCI in human cadavers. METHODS: Twenty-three human cadavers underwent cervical and/or lumbar laminectomy and dural opening to expose the cervical cord and/or conus medullaris. Spinal accessory nerves were harvested from the Erb point to the origin of the nerve's first major branch into the trapezius. Intercostal nerves from the T6-12 levels were dissected from the lateral border of paraspinal muscles to the posterior axillary line. The distal ends of dissected nerves were then transferred medially and sequentially inserted 4 mm deep into the ipsilateral cervical cord (spinal accessory nerve) or conus medullaris (intercostals). The length of each transferred nerve was measured, and representative distal and proximal cross-sections were preserved for axonal counting. RESULTS: Spinal accessory nerves were consistently of sufficient length to be transferred to caudal cervical spinal cord levels (C4-8). Similarly, intercostal nerves (from T-7 to T-12) were of sufficient length to be transferred in a tension-free manner to the conus medullaris. Spinal accessory data revealed an average harvested nerve length of 15.85 cm with the average length needed to reach C4-8 of 4.7, 5.9, 6.5, 7.1, and 7.8 cm. The average length of available intercostal nerve from each thoracic level compared with the average length required to reach the conus medullaris in a tension-free manner was determined to be as follows (available, required in cm): T-7 (18.0, 14.5), T-8 (18.7, 11.7), T-9 (18.8, 9.0), T-10 (19.6, 7.0), T-11 (18.8, 4.6), and T-12 (15.8, 1.5). The number of myelinated axons present on cross-sectional analysis predictably decreased along both spinal accessory and intercostal nerves as they coursed distally. CONCLUSIONS: Both spinal accessory and intercostal nerves, accessible from a posterior approach in the prone position, can be successfully harvested and transferred to their respective targets in the cervical spinal cord and conus medullaris. As expected, the number of axons available to grow into the spinal cord diminishes distally along each nerve. To maximize axon "bandwidth" in nerve bypass procedures, the most proximal section of the nerve that can be transferred in a tension-free manner to a spinal level caudal to the level of injury should be implanted. This study supports the feasibility of SAN and intercostal nerve transfer as a means of treating SCI and may assist in the preoperative selection of candidates for future human clinical trials of cervical and thoracolumbar SCI bypass surgery.

Lumbosacral intrathecal nerve roots: an anatomical study.

BACKGROUND: The lumbosacral intrathecal anatomy is complex because of the density of nerve roots in the cauda equina. Space-occupying lesions, including disc herniation, trauma and tumor, within the spinal canal may compromise the nerve roots, causing severe clinical syndromes. The goal of this study is to provide spinal surgeons with a detailed anatomical description of the intrathecal nerve roots and to emphasize their clinical importance. METHOD: Ten formalin-fixed male cadavers were studied. They were dissected with the aid of a surgical microscope, and measurements were performed. RESULTS: The number of dorsal and ventral roots ranged from one to three. The average diameter of roots increased from L1 to S1 (0.80 mm for L1 and 4.16 for S1), respectively. Then their diameter decreased from S1 to S5 (4.16 mm for S1, 0.46 mm for S5). The largest diameter was found at S1 and the smallest at S5. The average number of rootlets per nerve root increased from L1 to S1, then decreased (3.25 for L1, 12.6 for S1, and 1.2 for S5), respectively. The greatest rootlet number was seen at S1, and the fewest were observed at S5. The average diameter of the lateral recess gradually decreased from L1 to L4 (9.1 mm for L1; 5.96 mm for L4) and then increased at L5 level (6.06 mm); however, the diameter of the nerve root increased from L1 to L5. The midpoint of distance between the superior and inferior edge of the intradural exit nerve root was 3.47 mm below the inferior edge of the superior articular process at the L1 level, while the origin of the L5 exit root was 5.75 mm above the inferior edge. The root origin gradually ascended from L1 to L5. CONCLUSIONS: The findings of this study may be valuable for understanding lesions compressing intradural nerve roots and may be useful for intradural spinal procedures.

A comparative study of histopathological analysis of filum terminale in patients with tethered cord syndrome and in normal human fetuses.

BACKGROUND: The structural changes in filum terminale (FT) may be responsible for tethered cord syndrome (TCS) in children. Although the histological changes in FT related to TCS are well-known, there is no comparative study of the changes which occur in TCS and normal fetal FT samples. The aims of this study are to compare the histological changes which occurred in FT samples of TCS and in fetuses, and to point out these changes. METHODS: During the last 2 years, 14 cases of TCS were operated on, the FT was cut and the spinal cord was released. Among them, 6 samples of FT were obtained for histopathological examination. Moreover, 1 FT from an adult cadaver and 4 samples from fetal FT were obtained for the same examination. RESULTS: While adipose tissue, fibrosis, hyalinization, and meningothelial proliferation were observed in FT samples of TCS, none of these findings were observed in fetal samples. Elastic fibers were present in all TCS specimens and the adult cadaver, but were not observed in fetuses. Peripheral nerves, ganglion cells and ependymal cells were observed in fetal FT samples. CONCLUSION: These changes probably begin at birth.

Primary carcinoid tumor of the filum terminale--a case report.

Carcinoid tumors with a primary site in the central nervous system have not been reported in literature yet. We report here about a 41-year-old patient with recurrent and progressive low back pain and bilateral S1 radiculopathy on admission. The patient underwent hemi-laminectomies of the vertebral bodies L5 and S1 and an en bloc resection of the tumor. Postoperative histopathological examination resulted in a well-differentiated intrathecal neuroendocrine tumor (carcinoid) of the terminal filum. Postoperative staging showed no pathological abnormalities and no tumor recurrence after 6 months. Even though rare, carcinoids should be considered as differential diagnosis of tumors occurring in the CNS.

Tethered cord syndrome: a review of the literature from embryology to adult presentation.

Tethered cord syndrome (TCS) is a clinical condition of various origins that arises from tension on the spinal cord. Radiographic findings may include the conus medullaris in a lower than normal position, fatty infiltration of the filum terminale, lipomyelomeningocele, myelomeningocele, myelocystocele, meningocele, split cord malformations, dermal sinus, anorectal malformations, and intraspinal tumors. The clinical constellation of signs and symptoms associated with TCS may include dermatologic, urological, gastrointestinal, neurological, and orthopedic findings. The current review focuses on TCS by age group of the more common causes of the condition, including myelomeningocele, lipomyelomeningocele, as well as the adult presentation of occult TCS. Pertinent review of the neuroembryology and normal anatomical position of the conus medullaris is included.

A new endoscopic spine system: the first results with "Easy GO".

PURPOSE: Endoscopy meets increasing interest by spine surgeons. However, endoscopic results are diverging and many spinal endoscopic systems are difficult to apply and handle. METHODS: A system for endoscopic spinal surgery was developed where the main goals were: (1) easy intraoperative handling with standard microsurgical techniques, and (2) avoidance of a prolonged learning curve. The system consists of various dilators, two different work sheaths, two different 30 degrees endoscopes, and an endoscope holder. RESULTS: Between August 2006 and April 2008, 80 spinal surgeries were performed in degenerative lumbar spine cases (mean age 52 years, range 22-85 years). Intraoperatively, the system was easy to handle. Standard microsurgical techniques were used. Mean surgical time scored 75 min (range 28-168 min). There was no intraoperative complication, no new postoperative deficit and no infection. In four cases, the endoscope was abandoned and the procedure microsurgically continued (5%). At the last follow-up (mean FU 10 months, range 2 weeks up to 21 months), 89% of the patient were pain free (71/80). Four patients suffered from recurrent disc prolapses (5%). Another five patients (6%) were not satisfied without evidence of re-prolaps. Of those who answered the questionnaire of patient satisfaction, 83% (45/54) considered their postoperative status as excellent, 13% as good (7/54), 4% were not satisfied (2/54). CONCLUSIONS: The Easy GO system was easy and safe to handle with the standard bimanual microsurgical technique and good postoperative results. Further studies are needed to show a significant advantage of the technique in comparison to the microsurgical standard procedure.

Study of the effects of flexion on the position of the conus medullaris.

BACKGROUND: Previous anatomic studies have shown the conus medullaris to terminate between T12 and L1 vertebral levels in adults with normal spinal anatomy. Prior anatomic and radiographic studies of conus position with flexion and extension of the spine have had conflicting results. We performed a cadaveric study with direct visualization of the conus during flexion and extension to further study this question and potentially determine if flexion and extension of the spine during magnetic resonance imaging may prove to be a diagnostic tool in such pathologies as occult tethered cord syndrome. MATERIALS AND METHODS: We performed T12 to L3 laminectomies in five fresh adult cadavers and exposed the conus and cauda equina. Cadavers were fully flexed at the waist and neck and the conus position observed. RESULTS: In all specimens, the conus terminated between T12 and L1 in the prone position. During flexion, the conus position remained stable with no ascent. However, flexion produced stretching and medial displacement of the cauda equina. CONCLUSIONS: Flexion of the spine does not cause the conus medullaris to change position in fresh human cadavers; however, flexion does cause the cauda equina to stretch and displace medially over the conus. Therefore, it is unlikely that the conus would change position during spine flexion during imaging or procedures such as lumbar puncture.

Minimally invasive excision of lumbar epidural lipomatosis using a spinal endoscope.

In this report, we describe the case of a patient with a long-term radiculopathy due to epidural lipomatosis at the L3-4 intervertebral disc level. The fatty tissue was located on the dorsal side of the dural sac in the spinal canal and compressed the dural sac. The fatty tissue was removed endoscopically. After surgery, the symptoms disappeared, and neurological deficits normalized. We would like to state that epidural lipomatosis is a good candidate for minimally invasive endoscopic surgery because of its anatomic location.

[Morphological findings in MRI to be considered in perfoming spinal and epidural anesthesia].

The spinal cord and cauda equina move in the subarachnoid space by changing positions. The subarachnoid space is compressed from the dorsal side by epidural injection. At the end of gestation, the subarachnoid space is compressed from the ventral side by the engorged venous plexus. Idiopathic epidural lipomatosis is observed almost exclusively in the obese population. In the case of lipomatosis, the subarachnoid space is compressed by increased extradural fat around the thecal sac. We have had some severe cases of spinal canal stenosis in whom it is difficult to perform the spinal puncture. The authors showed some MR images and discussed morphological issues for spinal or epidural anesthesia.

The filum terminale externum.

OBJECT: The filum terminale externum (FTE) is the extradural component of the filum terminale internum and little attention has been dedicated to this structure in the literature. The authors theorized that the rare intrasacral ependymomas may originate from ependymal cell collections within the FTE. METHODS: To address this hypothesis, the FTE was dissected and analyzed histologically in 15 adult cadavers. None of the specimens was found to harbor ependymal or other glial cell collections. CONCLUSIONS: The authors found previously undescribed smooth-muscle cells within the FTE. Furthermore, histological analysis identified adipose, nerve, bone, and cartilage cells.

[Modified anteriolateral retroperitoneal approach for surgical treatment of patients with compression of the cauda equina and lumbar nerve roots (topographic anatomical study)]. / Modifitsirovannyi perednebokovoi retroperitoneal'nyi dostup dlia operativnogo lecheniia bol'nykh s kompressiei konskogo khvosta i spinno-mozgovykh koreshkov poiasnichnogo otdela pozvonochnika (topograficheskoe issledovanie).

Mini-invasive techniques have been increasingly used in lumbar surgery in the past decade, most commonly during operations on the intervertebral disks. However, mini-invasive interventions may be used as a modified traditional approach to treating more serious and challenging pathology, such as tumors of the lumbar vertebrae, metastatic disease, as well as lumbar fractures of different origin. In the literature, there are only several papers on the mini-invasive anterolateral retroperitoneal approach (ALMIRA) to corpectomy with repair of the lumbar spine. This paper deals with the autopsy of 15 cadavers (aged 55-83 years) and 5 blocks of the lumbar spine. The approach is described with illustrations being given. All the results are analyzed and shown in a table. Fifteen corpectomies of L2, L3, and L4 vertebrae were performed by ALMURA, using a self-retaining retractor. The duration of a procedure from skin incision to complete preparation of a spinal specimen for retractor's attachment averaged 50 min (30-70 min). The corpses were rotated in the axial plane at 45, 35, and 25 degrees for corpectomy of L2, L3, L4, respectively. The procedure was easier-to-use when convex binding of the spine was performed after the approach and before insertion of a retractor, in obese cases in particular. Damage to the peritoneum occurred in 5 cases, that to the ascending lumbar vein took place in 4 (during L4 corpectomy) and m. psoas in 2 cases, both in a cachectic cadaver. In the authors' opinion, the method is effective, but before applying it in the clinical theater, spinal surgeons should be well trained under experimental conditions.

Anatomic study of the filum terminale and its correlations with the tethered cord syndrome.

OBJECTIVE: To evaluate the intradural anatomic features of the filum terminale (FT) in fresh human cadavers, analyzing morphological parameters relevant for the diagnosis of the tethered cord syndrome. METHODS: Forty-one fresh cadavers were dissected, and the following parameters were evaluated: cadaver height, weight, and age, FT length, FT diameters at the initial point and midpoint, and topographic relationships of the initial and fusion points of the FT to the adjacent vertebrae. RESULTS: The mean FT length was 156.44 mm (range, 112.8-211.1 mm), the mean initial diameter was 1.38 mm (range, 0.4-2.5 mm), and the mean midpoint diameter was 0.76 mm (range, 0.1-1.55 mm). Four specimens (9.76%) exhibited FT thicknesses of more than 2 mm at their initial points. The FT most frequently started at the middle L1 level (19.51%) and fused with the dura mater at the upper S2 level (31.71%). Two fila (4.88%) started below the L2 level. Statistically significant correlations were observed (Pearson correlation, P < 0.05) between specimen weight and height (P = 0.019), initial point and midpoint diameters of the FT (P < 0.001), initial vertebral level and specimen height (P = 0.012), and initial and fusion vertebral levels (P = 0.004). CONCLUSION: Variation ranges were large for almost all anatomic parameters of the FT. Six cadavers (14.63%) in our study fulfilled one of the anatomic diagnostic criteria for tethered cord syndrome. Neurosurgeons must remember the normal variations in the anatomic features of this region when establishing the diagnosis of tethered cord syndrome or performing surgical procedures involving the caudal part of the dural sac.

O cone terminal da medula e a cauda equina / conus medullaris and the cauda equina: anatomy for the anesthesiologist

Segmentos lombares das colunas vertebrais de 10 cadáveres frescos foram dissecados, com o objetivo de descrever detalhes anatômicos de valor para a realizaçäo da anestesia subaracnóidea. Os detalhes anatômicos do cone terminal da medula e da cauda eqüina, vistos pelo seu aspecto anterior, foram fotografados e descritos.