Measurement of Shift of the Cauda Equina in the Subarachnoid Space by Changing Position

Defining the role of thoracic spinal anaesthesia in the 21st century: a narrative review

Since the performance of the first thoracic spinal anaesthetic in early 1908 many anaesthetists have gained interest in this unorthodox neuraxial anaesthetic technique. The main rationale justifying its use is to prevent complications related to general anaesthesia in high-risk patient populations. There is, however, significant debate regarding this practice around the world. The main concerns are fear of iatrogenic injury to the spinal cord, cephalad spread of local anaesthetic causing a complete spinal block, and haemodynamic instability owing to blockade of cardioaccelerator sympathetic fibres. The purpose of this narrative review is to appraise the literature critically regarding thoracic spinal anaesthesia, to synthesise the available information, and to provide a summary of evidence justifying its use in modern anaesthesia.

The Initial Subjective Sensory Change in the Dermatome During Intrathecal Injection of Plain Bupivacaine Predicts the Spread of Sensory Blockade: A Prospective Multi-Level Modeling Study

Background

Predicting the spread of anesthesia after intrathecal injection of plain local anesthetics is challenging owing to both patient and anesthesiologist-related factors.

Objectives

This study aimed to examine the initial patient-reported sensory changes during intrathecal injections and used multi-level analyses to examine the relationships between these changes and other major factors affecting the spread of anesthesia.

Methods

The participants were 120 consecutive patients with the American Society of Anesthesiologists status I and II, who were scheduled for open repair of inguinal hernias under spinal anesthesia. Lumbar puncture was performed at the midline of the L3 - L4 vertebrae and 3 mL of 0.5% isobaric bupivacaine was administered at 0.25 mL/s. The onset, dermatome, and side of the initial subjective sensory changes (ISSCs) were assessed by patient report. The extent of sensory loss to ice and pinprick stimuli, the degree of motor block in lower extremities, blood pressure, and heart rate were examined at 5-minutes intervals for 20 minutes after intrathecal injection.

Results

All patients reported ISSCs after 9 (4, 18) seconds [median (minimum, maximum)] of the intrathecal injection onset. In 66.7% of the patients, ISSCs occurred in the L1 - L5 dermatomes. Three patients experienced pain during the early intraoperative period, and described ISSCs in the sacral dermatome. Height, mean blood pressure, and ISSCs were significantly correlated with sensory loss. Faster onset, lower dermatome, and floor-side of ISSCs predicted a narrower area of sensory loss, with dermatome as the most important indicator.

Conclusions

Our findings demonstrate that ISSC, primarily based on dermatome, is a significant predictor for spinal anesthesia spread.

Are high lumbar punctures safe? A magnetic resonance imaging morphometric study of the conus medullaris

A high lumbar puncture (LP) at L2-L3 or above is often necessary to consider on technical grounds, but complications of conus medullaris (CM) damage during high LP are potentially concerning. We hypothesized that a high LP might be safer than previously thought by accounting for movements of the CM upon patient positional changes. We retrospectively reviewed standard normal supine lumbar spine magnetic resonance imaging of 58 patients and used electronic calipers on axial images at the T12-L1, L1-L2, and L2-L3 disc levels to measure the transverse diameter of the CM relative to the size of the dorsal thecal sac space (DTSS) through which a spinal needle could be inserted. On 142 axial images, the means for CM diameters were 8.2, 6.0, and 2.9 mm at the three levels, respectively. We then used known literature mean CM displacement values in the legs flexed and unflexed lateral decubitus position (LDP) to factor in CM shifts to the dependent side. We found that at all three levels, the likely positional shift of the CM would be too small and insufficient to displace the entire CM out of the DTSS. However, if needle placement could be confined to the midsagittal plane, an LP in the unflexed LDP would theoretically be entirely safe at both L1-L2 and L2-L3, and almost so at L2-L3 in the legs flexed LDP. Thus, high LPs at L1-L2 and L2-L3 are in theory likely safer than considered previously, more so in the legs unflexed than in the flexed LDP. Clin. Anat. 32:618-629, 2019. © 2019 Wiley Periodicals, Inc.

Dynamic magnetic resonance imaging parameters for objective assessment of the magnitude of tethered cord syndrome in patients with spinal dysraphism

BACKGROUND

Dynamic magnetic resonance imaging (MRI)-based criteria for diagnosing magnitude of tethered cord syndrome (TCS) in occult spinal dysraphism are proposed.

METHODS

In this prospective, case-control design study, MRI lumbosacral spine was performed in 51 subjects [pilot group (n = 10) without TCS (for defining radiological parameters), control group (n = 10) without TCS (for baseline assessment), and study group (n = 31) with spinal dysraphism (thick filum terminale [n = 12], lumbar/lumbosacral meningomyelocoele [n = 6], and lipomyelomeningocoele [n = 13])]. The parameters compared in control and study groups included oscillatory frequency (OF), difference in ratio, in supine/prone position, of distance between posterior margin of vertebral body and anterior margin of spinal cord (oscillatory distance [OD]), with canal diameter, at the level of conus as well as superior border of contiguous two vertebrae above that level; delta bending angle (ΔBA), difference, in supine/prone position, of angle between longitudinal axis of conus and that of lower spinal cord; and sagittal and axial root angles, subtended between exiting ventral nerve roots and longitudinal axis of cord. An outcome assessment at follow-up was also done.

RESULTS

In the study group (cord tethered), significantly less movement at the level of conus (OF0, p = 0.013) and one level above (OF1, p = 0.03) and significant difference in ΔBA (p = 0.0) were observed in supine and prone positions, compared to controls. Ventral nerve root stretching resulted in sagittal/axial root angle changes. Median OF (0.04) in the lipomyelomeningocoele group was significantly less than that in control group (0.23). Median OF was also lesser in patients with thick filum terminale or meningomyelocele. Difference in median sagittal and axial root angles among the study and control groups was statistically significant (p = 0.00).

CONCLUSION

New dynamic MRI-based parameters to establish the presence and magnitude of TCS have been defined. OF measured the extent of loss of translational cord displacement in supine and prone positions; ΔBA defined the relative angulation of conus with lower spinal cord, and sagittal and axial root angles represented ventral nerve root stretching. The difference in OF or ΔBA was minimum in the group with thick filum terminale and progressively increased in the groups with lipomyelomeningocele and meningomyelocele.

Successful spinal anaesthesia for caesarean section in a patient with Marfan syndrome complicated by dural ectasia

Marfan syndrome is a connective tissue disorder that may be complicated during pregnancy by aortic dissection. Caesarean section may be selected to avoid the haemodynamic challenges of vaginal birth. The common occurrence of dural ectasia in patients with Marfan syndrome is known to be associated with failed neuraxial anaesthesia. This report describes the administration of spinal anaesthesia to a woman with Marfan syndrome, and discusses why a hypobaric bupivacaine and opioid mixture, warmed to 37°C and injected intrathecally with the patient seated, produced successful surgical anaesthesia.

Spinal Cauda Equina Stimulation for Alternative Location of Spinal Cord Stimulation in Intractable Phantom Limb Pain Syndrome: A Case Report

Phantom limb pain is a phenomenon in which patients experience pain in a part of the body that no longer exists. In several treatment modalities, spinal cord stimulation (SCS) has been introduced for the management of intractable post-amputation pain. A 46-year-old male patient complained of severe ankle and foot pain, following above-the-knee amputation surgery on the right side amputation surgery three years earlier. Despite undergoing treatment with multiple modalities for pain management involving numerous oral and intravenous medications, nerve blocks, and pulsed radiofrequency (RF) treatment, the effect duration was temporary and the decreases in the patient's pain score were not acceptable. Even the use of SCS did not provide completely satisfactory pain management. However, the trial lead positioning in the cauda equina was able to stimulate the site of the severe pain, and the patient's pain score was dramatically decreased. We report a case of successful pain management with spinal cauda equina stimulation following the failure of SCS in the treatment of intractable phantom limb pain.

Apparatus for simulating dynamic interactions between the spinal cord and soft-coupled intradural implants

We have designed, built, and tested an apparatus used for investigating the biomechanical response of a novel intradural spinal cord stimulator to the simulated physiological movement of the spinal cord within the thecal sac. In this apparatus, the rostral-caudal displacements of an anthropomorphic spinal cord surrogate can be controlled with a resolution of approximately 0.1% of a target value for up to 10(7) lateral movement cycles occurring at a repetition rate of 2 Hz. Using this system, we have been able to determine that the restoring force of the stimulator's suspension system works in concert with the frictional coupling between the electrode array and the surrogate to overcome the 0.42 μN inertial force associated with the lateral motion of the array. The result is a positional stability of the array on the surrogate (in air) of better than 0.2 mm over ~500,000 movement cycles. Design modifications that might lead to improved physiological performance are discussed.

Cerebrospinal Fluid Volume and Nerve Root Vulnerability during Lumbar Puncture or Spinal Anaesthesia at Different Vertebral Levels

Cerebrospinal fluid (CSF) and nerve root volumes within the lumbosacral dural sac were estimated at various vertebral levels, in an attempt to determine any possible relevance to the incidence of nerve root trauma during lumbar puncture or spinal anaesthesia. Magnetic resonance images from seven patients were studied. Volumes were calculated by semi-automatic threshold segmentation combined with manual editing of each slice. The mean dural sac volume from S1 to T12 was 42.8±5.8 ml and the mean CSF volume 34.3±5.1 ml with the mean root volume being 10.4±2.2 cm3. The mean CSF volume per vertebral segment ranged from 4.3±0.7 ml at L5, to 5.8±2.5 ml at L1, with high inter-individual variability. The mean root volume ranged from 0.6±0.1 cm3 at L5 to 2.4±0.5 cm3 at T12.

The conus medullaris was located at L1 in four of the five patients scanned at upper lumbar levels, and at the lower border of L2 in the other. Vulnerability to nerve root damage was expressed as the Vulnerability Index (%), being defined as the ratio of root volume to dural sac volume (CSF volume + root volume). The value ranged between 7 and 14% at L5, increasing rostrally to 30 to 43% at T12. Caution is obviously required in high punctures to avoid contact with the conus medullaris, but the cauda equina is also vulnerable to contact with more caudal punctures and had a Vulnerability Index of about 25% at L4, that increased rostrally.