Study of the Anatomy of the Extradural Region Using Magnetic Resonance Imaging

Westbrook, J. L.; Renowden, Shelley; Carrie, L.E.S.

doi:10.1093/bja/71.4.495

Cited by 50 publications

(30 citation statements)

References 24 publications

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“…Many factors associated with neuraxial anaesthesia have been studied including the structures at the level of the termination of the spinal cord and dural sac [11], vertebral level and shape of the conus medullaris [12], shape of the epidural space [13][14][15], and distance from the skin to the epidural or subarachnoid spaces [16][17][18][19]. However, the effect of body position relevant to neuraxial blockade has not been well studied [20][21][22][23][24], especially in children.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2009

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SummaryAlthough 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. Dural puncture is a serious technical complication during single-shot caudal block, which is the most common regional technique for postoperative analgesia for paediatric subumbilical surgery. The prevalence of dural puncture associated with caudal analgesia is relatively low. It has only been shown in several case reports [1,2] or at a rate of 1.2% in previous large-scale studies [3,4]. In the study of 760 children, Busoni did not find any case of dural puncture and Dalens [5] reported only one dural puncture in his series of 750 paediatric caudals. Sometimes it is difficult to identify the sacral hiatus and the caudal space due to variations of anatomical structures or obesity. In these cases, a trans-sacral approach to caudal block, described by Busoni [6], may be used as an alternative method. Although no dural puncture was reported in several trans-sacral approach studies [6][7][8], the risk of dural puncture is a possibility. It is known that the end of the dural sac is located at the S4 level just after birth, then ascends to the S2 level as the child grows [9].The anatomy of the spinal cord and its associated structures have been well defined [10], largely based on post-mortem or imaging studies in the supine or prone positions. Many factors associated with neuraxial anaesthesia have been studied including the structures at the level of the termination of the spinal cord and dural sac [11], vertebral level and shape of the conus medullaris [12], shape of the epidural space [13][14][15], and distance from the skin to the epidural or subarachnoid spaces [16][17][18][19]. However, the effect of body position relevant to neuraxial blockade has not been well studied [20][21][22][23][24], especially in children.Ultrasonography, which is a well-established method of investigating the spinal canal, spinal cord, and meningeal coverings in infants and children, has the advantage of being real time, non invasive and safe [25][26][27]. It allows detection of congenital malformations such as myelocele, myelomeningocele, spinal lipoma, dorsal dermal sinus, tight filum terminale syndrome, diastematomyelia, hydromyelia and syri...

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Section: Discussionmentioning

confidence: 99%

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

et al. 2009

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“…The space communicates freely with the paravertebral space through the intervertebral foramina. The epidural space contains loose areolar connective tissue, semi-liquid fat, lymphatics, arteries, an extensive plexus of veins, and the spinal nerve roots as they exit the dural sac and pass through the intervertebral foramina [5–7]. …”

Section: Introductionmentioning

confidence: 99%

Complications and pitfalls of lumbar interlaminar and transforaminal epidural injections

Goodman

Posecion

Mallempati

et al. 2008

Curr Rev Musculoskelet Med

145

114

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Lumbar interlaminar and transforaminal epidural injections are used in the treatment of lumbar radicular pain and other lumbar spinal pain syndromes. Complications from these procedures arise from needle placement and the administration of medication. Potential risks include infection, hematoma, intravascular injection of medication, direct nerve trauma, subdural injection of medication, air embolism, disc entry, urinary retention, radiation exposure, and hypersensitivity reactions. The objective of this article is to review the complications of lumbar interlaminar and transforaminal epidural injections and discuss the potential pitfalls related to these procedures. We performed a comprehensive literature review through a Medline search for relevant case reports, clinical trials, and review articles. Complications from lumbar epidural injections are extremely rare. Most if not all complications can be avoided by careful technique with accurate needle placement, sterile precautions, and a thorough understanding of the relevant anatomy and contrast patterns on fluoroscopic imaging.

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“…It also seems that the shape may change depending on whether the mid-intervertebral level or vertebral level is examined [8]. Magnetic resonance imaging studies in living patients would probably reflect the clinical situation most closely and a small study of 15 patients observed similar findings to ours [9], though the author did not specify where the change from oval to triangular occurred, how often it occurred, nor how this change in shape was assessed.…”

Section: Discussionmentioning

confidence: 79%

Shape of the thecal sac: L3/4 interspace compared with L4/5*

Naji

Williams²,

Hourihan³

et al. 2008

Anaesthesia

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We retrospectively reviewed 60 normal magnetic resonance imaging scans to assess the anatomical shape of the thecal sac at the L3 ⁄ 4 and L4 ⁄ 5 vertebral interspaces. In all cases the thecal sac was oval at L3 ⁄ 4 but in 26 (43%; 95% CI 31-55%) the thecal sac changed from oval at the L3 ⁄ 4 interspace to triangular at L4 ⁄ 5 (with the apex of the triangle presenting to the posterior epidural space). We propose that this anatomical variant would make it more difficult to obtain cerebrospinal fluid at the lower level, as a slightly lateral approach could lead to identification of the epidural space but failure to puncture the thecal sac. This may offer an explanation for a 'dry tap' when a lower interspace is chosen. Damage to the conus is a potentially serious complication of inserting a needle into the thecal sac. This can occur during spinal or combined spinalepidural (CSE) anaesthesia or lumbar puncture. Following a number of case reports [1,2] it was recommended by Reynolds that these procedures should be performed at the lowest possible palpable interspace, which could be between the spinous processes of L4 and L5 or occasionally lower. It has been found that, especially during the needle-throughneedle CSE technique, the epidural space can sometimes be located but cerebrospinal fluid (CSF) not obtained because of failure to puncture the dura as the spinal needle protrudes from the Tuohy needle. The incidence of this is reported to be between 5% and 16% [3][4][5]. We have observed that this problem may occur more frequently when the lowest palpable interspace is used, with easier thecal puncture when the procedure is performed one interspace higher. We therefore undertook a retrospective review of normal lumbar magnetic resonance imaging (MRI) scans to determine if there was an anatomical reason underlying these observations. MethodsApproval was obtained from the Trust's Audit Department and the Local Research Ethics Committee considered formal review unnecessary. Magnetic resonance imaging scans of the lumbar spine with T1 and T2 weighted sagittal and axial images were retrospectively reviewed. All patients had been referred for MRI scan for the investigation of lower back pain and the scans had been reported as anatomically normal. An initial number of 100 patients was proposed but as our search criteria were very strict, looking only for normal MRI studies performed for non-neurological conditions, a total of 60 scans was found after hand searching several years of reports. A hypothetical calculation, based on our findings after 60, showed that doubling our sample size further would reduce our 95% CI by only ± 3%.On an initial review of a small number of scans it was noted that in some cases there was a change in shape of the spinal canal and thecal sac within it, on the axial images, from oval at the mid space of L3 ⁄ 4 to triangular at the mid space of L4 ⁄ 5. The review of subsequent scans was then based on this initial observation and a series of

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Study of the Anatomy of the Extradural Region Using Magnetic Resonance Imaging

Cited by 50 publications

References 24 publications

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

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

Complications and pitfalls of lumbar interlaminar and transforaminal epidural injections

Shape of the thecal sac: L3/4 interspace compared with L4/5*

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