Level of termination of the spinal cord and the dural sac: a magnetic resonance study

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.

Transcranial Magnetic Stimulation in the Diagnosis of Compressive Myelopathy at the Thoracolumbar Junction

PURPOSE

The disc level in the thoracolumbar junction at which measurement of the central motor conduction time in the lower limbs (CMCT-LL) is useful for a diagnosis remains unclear. Therefore, this study investigated the spinal vertebral level at which compressive myelopathy due to ossification of the ligamentum flavum in the thoracolumbar junction is detectable using CMCT-LL.

METHODS

We preoperatively measured CMCT-LL in 57 patients (42 men, 15 women; aged 35-85 years) with a single ossification of the ligamentum flavum from the T10-11 to T12-L1 disc levels and in 53 healthy controls. Motor evoked potentials after transcranial magnetic stimulation, compound muscle action potentials, and F waves were recorded from the abductor hallucis. Central motor conduction time in the lower limbs was calculated as follows: Motor evoked potential latency - (compound muscle action potential latency + F latency - 1)/2 (ms). Central motor conduction time in the lower limbs was compared between patients and controls.

RESULTS

Compressive lesions were located at the T10 to 11 level in 27 patients, the T11 to 12 level in 28, and the T12-L1 level in 2. Central motor conduction time values in the lower limbs at the T10 to 11 level (19.9 ± 4.7 ms) and T11 to 12 level (18.1 ± 3.4 ms) were significantly longer than control values (11.8 ± 1.1 ms; P < 0.01). Central motor conduction time in the lower limbs was not calculated at the T12-L1 level because motor evoked potentials were not recorded in any patient.

CONCLUSIONS

We confirmed that CMCT-LL was significantly longer in patients with ossification of the ligamentum flavum at the T10 to 11 and T11 to 12 levels because the S2 segment of the spinal cord is caudal at the T12 vertebral body level. Therefore, CMCT-LL is useful for diagnosing thoracolumbar junction disorders proximal to the T12 vertebral body level.

Assessment of the levels of termination of the conus medullaris and thecal sac in the pediatric population

PURPOSE

This study assessed the position of the termination of the conus medullaris (the point where the spinal cord tapers to an end) and thecal sac (the sheath of dura mater that surrounds the spinal cord and caudal nerve roots) in a large pediatric population, to characterise the nature of the pediatric Gaussian distribution and assess whether age affected the distribution. The study further aimed to assess the effect of gender on termination positions.

METHODS

A total of 520 MRI spine studies of children aged between 1 month and 19 years old were collected from two pediatric tertiary referral centres in the UK and Italy. Studies with pathological findings were excluded, and normal scans were found using keyword search algorithms on a database of radiologists' reports. The reported scans were individually assessed and reviewed by two experienced neuroradiologists. The termination points of the conus medullaris and thecal sac were determined for each study. Local IRB approvals were sought.

RESULTS

The results showcased a Gaussian distribution in both conus medullaris (r=0.8997) and thecal sac termination levels (r=0.9639). No statistically significant results were noted with increasing age for the termination positions of the conus medullaris or thecal sac (p = 0.154, 0.063). No statistical significance was observed with gender variation with either anatomical landmark. A weak positive correlation was observed between the termination levels of the conus medullaris and the thecal sac (r=0.2567) CONCLUSION: Termination levels across all pediatric age range followed a Gaussian distribution. Knowledge of normal termination levels has relevant clinical implications, including the assessment of patients with suspected spinal dysraphism.

Evaluation of the Level of Dural Sac Tip in Saudi Population: A Magnetic Resonance Imaging Study

Background For the success of procedures such as caudal block, craniospinal irradiation (CSI), and management of lower back pain and to minimize the risk of dural puncture the exact level of dural sac (DS) termination should be known. Objective The evaluation of DS tip location in the Saudi population and exploring possible significant factors that could be used as predictors in clinical prognosis. Methods A total of 200 patients' lumbar sagittal Weighted T2 Magnetic Resonance Imaging (MRI) study were randomly selected from a single-center hospital in-between 2020 and 2021. The DS tip location was determined by generating a perpendicular line from the longitudinal axis of its termination to the corresponding level. Then naming it after an intervertebral disk or a corresponding vertebrate that is divided into three thirds (upper, middle, and lower). Results In most cases, the level of DS termination is at the middle part of S2 (26.5%), followed by the upper part of S2 (25.1%), and the lower part of S2 (20%). In Saudi nationals, the DS tip was in the middle S2 level at 21.5%, upper S2 level at 19.1%, and lower S2 level at 17%. Factors such as age, sex, cause of referral, and nationality had no statistical significance in relation to DS tip location. Conclusion The DS termination level in the Saudi population ranges from disk between L5-S1 to the lower third of S3. Moreover, nationality, age, and cause of referral were not significant in determining the DS termination level. Therefore, it is still important to individualize patients' treatment by using MRI for each case that requires it.

Epidural anesthesia in dogs undergoing hindlimb orthopedic surgery: effects of two injection sites

This prospective clinical trial evaluated the effects of epidural anesthesia (EA) placed at the lumbosacral compared to the L5-L6 junction in dogs undergoing hindlimb orthopedic surgery. In all, 98 dogs were randomly assigned to receive injection at either L7-S1 (LS group) or L5-L6 (LL group) at the same local anesthetic regimen (1 mg/kg bupivacaine 0.5% and 0.1 mg/kg morphine 1%). Fentanyl (1 µg/kg) was the intraoperative rescue analgesia (iRA) administered if mean arterial pressure increased by 30% above pre-stimulation value. Procedural failure, iRA, hypotension, motor block resolution, and postoperative side effects were recorded. There were 7/47 (15%) epidural procedural failures in the LS group and 8/51 (16%) (P=1.00) in the LL group; iRA was administered in 21/40 (52%) LS group dogs and in 13/43 (30%) LL group dogs, respectively (P=0.047). The incidence of hypotension was 10/40 (25%) and 16/43 (37%) in the LS group and the LL group, respectively (P=0.25). Proprioceptive residual deficit at 8 hr after EA was recorded in 3/26 (12%) in group LS dogs and in 13/26 (50%) group LL dogs, respectively (P=0.01). The proprioceptive residual deficit at 24 hr in one dog (LL group) resolved within 36 hr. No episodes of postoperative urinary retention, pruritus or neurological damage were recorded. The L5-L6 EA decreased significantly iRA but delays the proprioceptive recovery time. Further studies are needed to determine whether a lower bupivacaine dose reduces the duration of the residual block retaining the same incidence of iRA.

Examination of Spinal Canal Anatomy with MRI Measurements in Lomber Disc Herniation Patients: An Anesthesiologist Viewpoint

Background and Aim:

The aim of this study is to investigate the magnetic resonance imaging (MRI) of patients with lumbar disc herniation (LDH) to identify the challenges associated with neuraxial anesthesia.

Materials and Methods:

The MRI images in the supine position of 203 patients admitted to hospital with complaints of lower back pain were studied. Medial sagittal slices of the lumbar spine were imaged from L1 to S1. LDH is classified as either bulging, extrusion, or protrusion.

Results:

For this study, 83 males and 120 females with a mean age of 43.18 ± 14.68 years were recruited. The highest herniation level was observed at L4–L5 in 145 (71.4%) patients: 76 instances of disc bulging (37.4%), 56 instances of extrusion (27.6%), and 13 instances of protrusion (6.4%). The longest distance between the skin and spinal cord was 60.06 ± 1.61 mm at L5–S1; the longest distance at width of the epidural space was 6.09 ± 1.95 mm at L3–L4. According to the disc herniation groups, no significant differences were found between the skin-to-dura distance, width of the epidural space, and depth of skin level to spinous process (P > 0.05). Moreover, the anterior dura to cord distances was significantly different from normal patients (P < 0.05). Indeed, there was a statistically weak and negative correlation between both the length and age of the lumbar spinal canal (P < 0.05, r = −0.295).

Conclusions:

Lumbar disc pathologies can cause anatomical derangements in the spinal canal, which may cause neurologic deficits by neuraxial blockade.

The Level of Conus Medullaris in 629 Healthy Japanese Individuals

The conus medullaris typically terminates at the L1 level; however, variations in its level and the factors associated with the conus medullaris level are unclear. We investigated the level of conus medullaris on magnetic resonance imaging in healthy volunteers. In total, 629 healthy adult volunteers (≥50 individuals of each sex and in each decade of age from 20 to 70) were enrolled. The level of the conus medullaris was assessed based on the T2-weighted sagittal magnetic resonance images, and factors affecting its level were investigated employing multivariate regression analysis including the participants' background and radiographical parameters. L1 was the most common conus medullaris level. Participant height was significantly shorter in the caudally placed conus medullaris (p = 0.013). With respect to the radiographical parameters, pelvic incidence (p = 0.003), and pelvic tilt (p = 0.03) were significantly smaller in participants with a caudally placed conus medullaris. Multiple regression analysis showed that the pelvic incidence (p < 0.0001) and height (p < 0.0001) were significant factors affecting the conus medullaris level. These results indicated that the length of the spinal cord varies little among individuals and that skeletal differences affect the level of the conus medullaris.

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.

Variation in the position of the conus medullaris and dural sac in adult dogs

Although it has long been stated that the level of spinal cord termination varies depending on the size of the dog, the evidence for this remains limited. The aim of this study is to investigate the position of the conus medullaris (CM) and dural sac (DS) in a population of dogs of varying size. MRIs of the thoracolumbosacral spine of 101 dogs were included. The location of CM and DS was determined on sagittal T2-weighted images and T1-weighted images, respectively, by three independent observers. The bodyweight and the back length were used as markers of size. Regression analysis showed that the termination point of the CM had a statistically significant relationship with bodyweight (R²=0.23, P<0.05). Although not statistically significant (P=0.058), a similar relationship was found between CM and back length (R²=0.21). No statistically significant relationship was found between the termination point of the DS and bodyweight (P=0.24) or back length (P=0.19). The study confirms the terminal position of the CM is dependent on size, with a more cranial position with increasing size; however, the termination point of DS remains constant irrespective of dog size.

Central neurological complications following obstetric neuraxial blockade

PURPOSE OF REVIEW

Central neuraxial blockade is increasingly the anaesthetic management of choice for parturients, including in higher risk pregnancies. Although they are usually effective and safe, there are potentially devastating neurological complications that may present either overtly or insidiously. A thorough understanding of the variety of potential neurological complications is essential to adequately consent patients in addition to diagnosing and managing complications following neuraxial anaesthesia. This review aims to describe a number of potential neurological injuries that may occur and suggested management based on available evidence.

RECENT FINDINGS

Current evidence supports neuraxial anaesthesia as a safe management strategy in low and many higher risk pregnancies, with a low overall incidence of neurological complications. Neuraxial blockade is safe in patients with platelet counts greater than 70 000/μl and the risk of infective complications secondary to epidural catheterization remains low until day five post procedure. There is also some early evidence supporting the use of transnasal local anaesthetic as a strategy for managing postdural puncture headache.

SUMMARY

Difficulty remains in establishing absolute risk of complications and optimal management strategies given the low overall number of patients affected and heterogeneity of therapy. There may be a role for centralized registration of postneuraxial complications in obstetric patients to further develop our collective understanding of these conditions.

Alternative way to find sacral hiatus for blind caudal block - Based on 3D pelvis CT anthropometry: A retrospective study

The aim of this study is to develop an alternative way to locate the sacral hiatus for blind caudal block from the anthropometrical data measured on 3D pelvic CT. The intersection of the line connecting two sacral cornua and the midline is considered the ideal point (IP) for caudal block. The mean length from the coccyx tip to the IP was measured using 3D pelvic CT images in 30 men and 30 women and was 6.5 cm and 6.0 cm, respectively. For the conventional method group, we used the conventional equilateral triangle method to find the sacral hiatus, which was named conventional method group needling point (CNP). For the experimental method group, the point 6.5 cm or 6.0 cm (mean length from the coccyx tip to the IP) away from the coccyx tip was called the experimental method group needling point (ENP). Drawing the three points of the IP, CNP, and ENP on the same patient's 3D pelvic CT, we compared the distance from the IP to the CNP with the distance from the IP to the ENP. We propose that the experimental method is comparable to the conventional method in locating the sacral hiatus, which is crucial for a successful caudal block procedure. Anthropometric measurements and virtual comparative test between two methods were done on the 3D pelvis CT. In men, the distance from the CNP to the IP was 0.8 ± 0.5 cm in the conventional method group, while the distance from the ENP to the IP was 0.5 ± 0.4 cm in the experimental method group (p < 0.05). In women, the same distances were 1.5 ± 0.8 cm and 0.7 ± 0.3 cm, respectively (p < 0.05). In conclusion, finding a point of 6.5 cm from the coccyx tip in men and 6.0 cm in women could be an alternative way to find the sacral hiatus for blind caudal block.

Reduction of vertebral height with fragility vertebral fractures can induce variety of neurological deterioration

Background

The presence of vertebral fractures affect variations in the termination level of conus medullaris (TLCM) and alter neurological findings. However, few studies have examined association between vertebral fractures, TLCM, and neurological findings. Thus, we herein studied the number and severity of vertebral fractures, TLCM, and neurological findings to clarify the mechanism of neurological deterioration in patients with vertebral fractures.

Methods

A total of 411 patients who underwent computed tomographic myelography were classified into those with (group F, n = 73) and those without vertebral fractures (group C, n = 338). We assessed correlations between TLCM and age, height, and gender in group C, differences in TLCM between groups F and C, and correlations between TLCM, and the number and severity score of fractures. Neurological evaluations were performed for the patellar tendon reflex (PTR), muscle weakness, sensory disturbance, and bladder contraction disorders.

Results

TLCM was most commonly located at the L1 vertebral body in group C and did not significantly differ with age, height, or gender. TLCM was most commonly located at L2 vertebral body in group F. TLCM was more caudally located in group F (P < 0.01). Additionally, there was a significant difference between TLCM and number of fractures, and the severity score of fractures (both P < 0.01). Twenty-three patients showed neurological deterioration by vertebral fractures. Some patients with T12 vertebral fracture showed hyperreflexia of PTR. Serious bladder contraction disorders were seen in patients with compression at close range of TLCM.

Conclusion

We confirmed that vertebral fractures altered location of the TLCM, thus altering potential neurological symptoms. Moreover, there were correlations of the TLCM with the number and severity score of vertebral fractures. Spine surgeons should be cognizant of the relationship between TLCM, level of compressive lesion, and neurological findings to avoid the wrong level in spine surgery and unexpected neurological deteriorations after surgery.

Neurologic findings caused by ossification of ligamentum flavum at the thoracolumbar junction

OBJECTIVE

To evaluate neurologic findings caused by a single ossification of ligamentum fravum (OLF) and identify the level of the lumbar segment of spinal cord.

DESIGN

Retrospective study.

METHODS

Subjects were 28 patients with a single OLF at T10-11 level (15 patients), T11-12 (11), and T12-L1 (2). The tip of the conus medullaris was assessed using computed tomographic myelography or magnetic resonance imaging. Neurologic evaluations were performed for patellar tendon reflex (PTR), sensory disturbance, and motor weakness.

RESULTS

The tip of the conus medullaris was located at the L1 vertebral body level. At the T10-11 level, all patients showed hyperreflexia of PTR. Sensory disturbance was observed for L1 dermatome and weakness of the iliopsoas was noted. At the T11-12 level, 8 of 11 patients didn't show hyperreflexia of PTR. Sensory disturbance was observed for L5 dermatome and weakness of the tibialis anterior was noted. At the T12-L1 level, all patients showed normal reflex of PTR, sensory disturbance of L5 dermatome, and weakness of the tibialis anterior.

CONCLUSION

With regard to the relationship between PTR and OLF level, all patients at the T10-11 level showed involvement of the L3 segment of spinal cord proximally. On the other hand, most patients at the T11-12 level showed involvement of the L4 segment of spinal cord distally. From all neurologic findings, we confirmed the presence of the L4 segment of spinal cord from the lower third of T11 vertebral body to the T11-12 intervertebral disc level.

Traumatic Conus Medullaris Syndrome: A Case Report and Review of the Literature

CASE

A twenty-six-year-old man was diagnosed with conus medullaris syndrome (CMS) after sustaining a traumatic L1 burst fracture. Surgical decompression and stabilization was performed within ninety-six hours of admission; postoperatively, normal bladder function rapidly returned.

CONCLUSION

CMS is difficult to diagnose because of the clinically variable presentation. There is no consensus regarding the natural history of conus medullaris injury or regarding the necessity, approach, or timing for decompression. Higher-level evidence is needed to guide treatment for acute traumatic CMS.

Relationship of the lumbar lordosis angle to the level of termination of the conus medullaris and thecal sac

The level of termination of the conus medullaris (CM) and thecal sac (TS) is subject to variations. We try to correlate in this study these variations with the lumbar lordosis angle (LLA) using MRI scans. A retrospective study was conducted using available MRI scans of the lumbar spine. The CM level of termination (CMLT) and the TS level of termination (TSLT) were identified according to a vertebral level after dividing it into 3 parts. The LLA was also identified for each individual. Linear regression models were fitted to the data available on 141 individuals. Of these 70 were males and 71 were females. The most common site of CMLT was at the upper third of L1 (32.6%) and that of the TSLT was at the middle third of S2 (29.8%). The mean LLA was 46° (20°–81°). The most proximal CMLT was at the upper third of T12, whereas the most distal one was at the upper third of L2. The most proximal TSLT was at the upper third of S1, whereas the most distal one was at S3-S4 disc space. The CMLT showed a positive correlation with the LLA. In conclusion the CMLT and TSLT may be related to variations of the LLA.

Whole-spine magnetic resonance imaging study in healthy Chinese adolescents

OBJECTIVE

To establish a preliminary magnetic resonance imaging (MRI) database of whole spine of healthy Chinese adolescents.

METHODS

MRI examination of whole spine and hindbrain was performed in 41 enrolled students aged 11-17 years (mean age 13.95; 18 males, 23 females) using a 1.5-T MR Scanner. Measurements of the ratio of anteroposterior (AP) and transverse (TS) diameters of the cord, cerebellar tonsillar level related to the basion-opsithion (BO) line, location of conus medullaris, total cord length, total vertebral length, cord/vertebral length ratio, thoracic cord area, thoracic vertebral area, thoracic cord/vertebral area ratio were obtained.

RESULTS

Mean values of cervical AP and TS were 6.63 mm and 12.21 mm, respectively. The mean level of cerebellar tonsillar related to BO line was 3.97 mm. Mean level of conus medullaris located in L1 lower 1/3. Total cord length was 399.34 mm, total vertebral length was 529.49 mm, Cord/vertebral length ratio was 0.75 and thoracic cord/vertebral area ratio was 0.17 on average. Vertebral length was correlated with age (r = 0.352, P = 0.024) whereas cord length and their ratio were not (P > 0.05). Compared with female, male had significantly larger cervical AP and TS, longer cervical cord (P < 0.01), higher position of conus medullaris (P < 0.05).

CONCLUSION

MRI is a useful tool for assessment of the whole spine. The longitudinal and cross-sectional morphology of spinal cord in healthy Chinese adolescents may benefit further study of spine cord in adolescent idiopathic scoliosis as well as in other spine diseases.

The termination level of the conus medullaris and lumbosacral transitional vertebrae

BACKGROUND

The presence of lumbosacral transitional vertebrae (LSTV) may affect the variation of the termination level of conus medullaris (TLCM). However, there have been few studies examining the association between the distribution of the TLCM and LSTV, especially in young patients. The purpose of this investigation was therefore to assess the relationship between the TLCM and LSTV in young patients.

METHODS

A total of 379 patients with lumbar herniated disks were included in this study. There were 249 males and 130 females, with a mean age of 31 years (range 15-44). The patients were classified into three groups: (1) L4/TV group (7 %): 28 patients with sacralization of the fifth lumbar vertebrae; (2) L5/TV group (11 %): 41 patients with lumbarization of the sacrum; and, (3) normal group (82 %): 310 patients without LSTV. TLCM was assessed using MRI.

RESULTS

The median TLCM of the normal, L4/TV and L5/TV groups was the middle third of L1, the upper third of L1 and the lower third of L1, respectively. The TLCM in the L4/TV group was significantly higher than that observed in the normal group (p < 0.001), while that in the L5/TV group was significantly lower than observed in the normal group (p < 0.001).

CONCLUSIONS

The presence of LSTV affected the variation of the TLCM. Therefore, the distribution of the TLCM with or without lumbosacral TV may help clinicians to identify the neurological discrepancies observed among neurologic injuries at the thoracolumbar junction.

Anatomical relationship and positions of the lumbar and sacral segments of the spinal cord according to the vertebral bodies and the spinal roots

Segments of the spinal cord generally do not correspond to the respective vertebral level and there are many anatomical variations in terms of the segment and the level of vertebra. The aim of this study is to investigate the variations and levels of lumbar and sacral spinal cord segments with reference to the axilla of the T11, T12, and L1 spinal nerve roots and adjacent vertebrae. Morphometric measurements were made on 16 formalin fixed adult cadaveric spinal cords. We observed termination of the spinal cord between the axilla of the L1 and L2 spinal nerve roots in 15 specimens (93.8%). In all cadavers the emergence of the T11, T12, and the L1 spinal nerve roots was at the level of the lower one-third of the same vertebral body. In 15 specimens (93.8%), the beginning of the lumbar spinal cord segment was found to be above the T11 spinal nerve root axilla and corresponded to the upper one-third of the T11 vertebral body. The beginning of the sacral spinal cord segment occurred above the L1 spinal nerve root axilla and corresponded to the upper one-third of the L1 vertebral body. The results of this study showed that when the conus medullaris is located at the L1-L2 level, the beginning of the lumbar spinal cord segment always corresponds to the body of T11 vertebra. This study provides detailed information about the correspondence of the spinal cord segments with reference to the axilla of the spinal nerve roots.

Inadvertent Dural Puncture during Caudal Approach by the Introducer Needle for Epidural Adhesiolysis Caused by Anatomical Variation

There have been reports of abnormalities in the lumbosacral region involving a lower-than-normal termination of the dural sac, which is caused by disease or anatomical variation. Inadvertent dural puncture or other unexpected complications can occur during caudal epidural block or adhesiolysis in patients with these variations, but only a small number of case reports have described this issue. We report a case of dural puncture by the introducer needle before attempting caudal epidural adhesiolysis, which occurred even though the needle was not advanced upward after penetrating the sacrococcygeal ligament. Dural puncture was caused by a morphological abnormality in the lumbosacral region, with no pathological condition; the dural sac terminal was located more distally than normal. However, dural puncture could have been prevented if we had checked for such an abnormality in the magnetic resonance imaging (MRI) taken before the procedure.

A methodological reappraisal of non invasive high voltage electrical stimulation of lumbosacral nerve roots

OBJECTIVE

To describe a neurophysiological method to locate the optimal stimulation site (OSS) over the vertebral column, customized to the individual subject, to achieve maximal activation of lumbosacral roots by means of non-invasive high voltage electrical stimulation (HVES).

METHODS

OSS was located in 30 volunteers by testing different stimulation points of a surface multi-electrode array placed over the dorso-lumbar junction of the vertebral column. The dorso-ventral stimulating montage was used (Troni et al., 1996). Motor responses to root stimulation (rCMAPs) were bilaterally recorded from Vastus Medialis (VM), Tibialis Anterior (TA), Soleus (SL) and Flexor Hallucis Brevis (FHB) muscles. The direct nature of rCMAPs was tested by delivering two maximal stimuli 50 ms apart.

RESULTS

Except for a few subjects with large girth, maximal rCMAPs could be obtained from all muscles with a stimulating current intensity up to 550 V (1050 mA). Maximal double HVES excluded any reflex component in the recorded rCMAPs. The procedure was well tolerated and no side effects were observed.

CONCLUSIONS

A single maximal electric shock delivered at the proper vertebral level by means of the dorso-ventral montage is able to safely achieve synchronous, bilateral maximal activation of several roots, from L3 to S1.

SIGNIFICANCE

Maximal activation of lumbosacral roots at their origin, unattainable with magnetic stimulation, is the essential requirement for direct detection of proximal nerve conduction slowing and block in lower limbs.

Spinal cerebrospinal fluid volume in healthy elderly individuals

The amount of spinal cerebrospinal fluid (CSF) could be of importance for the understanding of CSF dynamics, CSF biomarker analyses as well as for the amount and effect of anaesthesia using intrathecally administered drugs. However, knowledge of spinal CSF volumes is scarce. The main purpose of this article is to present data on spinal CSF volumes. In total, 22 healthy individuals aged between 64 and 76 years underwent MR imaging with a 3D balanced turbo field echo pulse sequence, which provided high contrast between spinal cord, CSF and the extradural surroundings. The entire spinal CSF volume, the cervical, thoracic, and lumbosacral CSF volumes and the spinal cord volume were calculated. The total spinal CSF volume was 81 ± 13 ml (range 52-103 ml). The amount of CSF in the cervical region was 19 ± 4 ml, in the thoracic region 38 ± 8 and in the lumbosacral region 25 ± 7 ml. There was no difference between genders nor was there any correlation with height. The volume of the spinal cord was 20 ± 3 ml. The results present new magnetic resonance imaging-based data on the spinal CSF volume in healthy elderly individuals.

Spinal cord termination in adult Africans: relationship with intercristal line and the transumbilical plane

The level of cord termination and level of vertebral intersection of intercristal line and transumbilical plane (TUP), frequently used landmarks, show ethnic variation. The relationship of the spinal cord termination to these lines is vital in spinal surgery and anesthesia, but data on these parameters are scarce in the African population. The purpose of this work is to determine the level of cord termination and establish its relationship with intercristal line and TUP. One hundred and twelve specimens obtained from the department of Human Anatomy at the University of Nairobi were used in this study. The conus medullaris was exposed by laminectomy and its vertebral level together with those of intercristal line and TUP recorded. The distance of conus medullaris from intercristal plane was measured in millimeters. Data obtained were coded and analyzed using Statistical Package for Social Sciences (SPSS) for windows version 16.0 Chicago, Illinois, 2002. Student's t-test was used in the statistical assessment of gender differences. A P value of less than 0.05 was considered significant. The median level of termination of the cord was the upper third of L2, 51.9% of cases terminating below this. There was no statistically significant gender difference in the level of termination of the cord. The intercristal plane passed through L4/L5 disc (70.9%) and below (29.1%). The TUP corresponded with intercristal line in 78.2% of subjects. The mean distance of the spinal cord termination from intercristal line was 99 +/- 24 mm. The spinal cord terminates at or below the upper third of L2. Care should be exercised during lumbar punctures and spinal epidural anesthesia among Africans. Intecristal line and TUP are safe landmarks to use in location of conus medullaris.

Needle-induced paresthesiae during single-shot spinal anesthesia: a comparison of sitting versus lateral decubitus position

BACKGROUND AND OBJECTIVES

Paresthesiae occasionally occur during spinal puncture or injection of local anesthetic for spinal anesthesia. No information is currently available regarding the effects of the patient's position on the incidence of needle-induced paresthesiae. The purpose of this prospective, observational study was to compare the occurrence of needle-induced paresthesiae in patients who received single-shot spinal anesthesia in the sitting position or in the lateral decubitus position.

METHODS

A total of 620 patients operated on under spinal anesthesia were included. Spinal anesthesia was performed in the sitting position in 142 patients and in the lateral decubitus position in 478 patients. All blocks were performed with a 25-gauge, 90-mm, Sprotte needle, at the L3-L4 or L4-L5 level. Patients' demographics, patients' position (lateral decubitus or sitting), number of skin punctures, incidence of paresthesiae, and success of the anesthesia were recorded.

RESULTS

The overall incidence of paresthesiae was higher in the lateral decubitus position (16.95%) compared with the sitting position (9.15%) (P = 0.0230). The number of punctures and the success rate were similar in both positions. Studying the incidence of paresthesiae for each position, when performing 1 or more punctures, there was no position-related difference noted if a single-needle puncture was sufficient to perform the block (8.0% in the lateral decubitus group versus 5.1% in the sitting group) (P = 0.3305). This difference between positions was significant when more than a single-needle puncture was required (34.1% in the lateral decubitus group versus 18.6% in the sitting group) (P = 0.0497).

CONCLUSIONS

Patient's position may influence the occurrence of needle-induced paresthesiae during spinal anesthesia. Lateral decubitus position resulted in a higher incidence of paresthesiae than the sitting position. However, there is no position-related difference noted if a single-needle puncture is sufficient to perform the block.

The effect of flexion on the level of termination of the dural sac in paediatric patients

SUMMARY

Although the anatomy of the spinal cord and its associated structures have been well defined, the effects of body position relevant to neuraxial blockade have not been elucidated. This study was designed to determine the effect of body position on the end of the dural sac in children. After induction of anaesthesia, ultrasound examination was performed to evaluate the location of the dural sac end in the lateral position with a straight back and knee, and in the lateral position with the knees, legs, and neck flexed. The level of the end of the dural sac was determined in relation to the vertebrae. Our data demonstrate that the dural sac shifts significantly cephalad in the lateral flexed position used for neuraxial blockade (p < 0.001). These results suggest that the safety margin to avoid dural puncture during hiatal or S2-3 approach for caudal block can be increased in younger children.

Determining the level of the dural sac tip: magnetic resonance imaging in an adult population

PURPOSE

To determine the variation in the location of the dural sac (DS) in a living adult population and to correlate this position with age and sex.

MATERIAL AND METHODS

T2-weighted, midline, sagittal, spin-echo magnetic resonance imaging (MRI) studies of 743 patients were assessed to identify the tip of the DS. This location was recorded in relation to the upper, middle, or lower third of the adjacent vertebral body or the adjacent intervertebral disk.

RESULTS

Frequency distribution for levels of termination of the DS on MRI demonstrated that the end of the DS was usually located at the upper one-third of S2 (25.2%). The mean level in females was also the upper one-third of S2 (26.5%) and in males the lower one-third of S2 (24.1%). The overall mean DS position was mostly at the upper one-third of S2. No significant differences in DS position were seen between male and female patients or with increasing age.

CONCLUSION

It is important to know the possible range for the termination level of the DS when performing caudal anesthesia and craniospinal irradiation in some clinical situations. The distribution of DS location in a large adult population was shown to range from the L5-S1 intervertebral disk to the upper third of S3 vertebrae.

Using MRI to Evaluate Anatomic Significance of Aortic Bifurcation, Right Renal Artery, and Conus Medullaris When Locating Lumbar Vertebral Segments

OBJECTIVE

This study evaluated the anatomic significance and sites of aortic bifurcation, right renal artery, and conus medullaris when locating lumbar vertebral segments on MRI. SUBJECTS AND METHODS. The study group was composed of 210 patients who underwent MRI of the lumbosacral spine. The position of aortic bifurcation was evaluated using MRI. Midline and sagittal MRI were also assessed to identify the proximal portion of the right renal artery and the tip of the conus medullaris. These locations were recorded in relation to the upper or lower half of the adjacent vertebral body or the adjacent intervertebral disk space.

RESULTS

The most common site of aortic bifurcation was at the L4 vertebra (83%). In most patients two separated iliac arteries were apparent at the level of the L4-L5 disk space (93%), and the right renal artery was located between the lower half of the L1 vertebra and the upper half of the L2 vertebra (92%). The position of the conus medullaris was variably located, and the most frequent site was at the L1 vertebra (56%).

CONCLUSION

The aortic bifurcation, the right renal artery, and the combination of these structures can be reliable landmarks for determining the lumbar vertebral segments on MRI or CT. However, conus medullaris cannot be considered a good landmark because of its variable locations.

Lumbar puncture: Anatomical review of a clinical skill

The safe and successful performance of a lumbar puncture demands a working and specific knowledge of anatomy. Misunderstanding of anatomy may result in failure or complications. This review attempts to aid understanding of the anatomical framework, pitfalls, and complications of lumbar puncture. It includes special reference to 3D relationships, functional and imaging anatomy, and normal variation. Lumbar puncture is carried out for diagnostic and therapeutic purposes. Epidural and spinal anesthesia, for example, are common in obstetric practice and involve the same technique as diagnostic lumbar puncture except that the needle tip is placed in the epidural space in the former. The procedure is by no means innocuous and anatomical pitfalls include inability to find the correct entry site and lack of awareness of structures in relation to the advancing needle. Headache is the most common complication and it is important to avoid traumatic and dry taps, herniation syndromes, and injury to the conus medullaris. With a thorough knowledge of the contraindications, regional anatomy and rationale of the technique, and adequate prior skills practice, a lumbar puncture can be carried out safely and successfully.