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The Posterior Epidural Space Is Largest at the Level of the Disc

Aldrete, J Antonio, MD, MS

Section Editor(s): Shafer, Steven L.

doi: 10.1213/01.ANE.0000227150.38865.00
Letters to the Editor: Letters & Announcements
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Department of Anesthesiology; University of Alabama at Birmingham; Aldrete Pain Care Center, Inc.; Arachnoiditis Foundation, Inc.; Birmingham, Alabama; aldrete@arachnoiditis.com

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To the Editor:

Tsui and Armstrong (1) reported a spinal cord injury without paraesthesia when the midthoracic spine was entered laterally. The axial view of the magnetic resonance image shows that the puncture was made nearly 70° from the posterior midline. At the T8 level, if the spinal cord is touched or punctured laterally it does not produce paraesthesia, as when cervical chordotomy is performed (2).

The posterior epidural space is located at the intervertebral disk level, where the space is wider (Fig. 1) and narrower at the midpoint of the vertebra. In the axial view of Tsui et al.'s magnetic resonance image, there was no posterior epidural space at that point implying that the puncture occurred where the right-sided edema of the cord is shown; precisely where the vascular pedicle enters the vertebral body anterior to the dural sac, at midvertebral point, coming from the lateral and the posterolateral aspect of the spinal cord, where the vessels run.

Figure 1.

Figure 1.

Puncture of the epidural veins and of the spinal artery is more likely when a near-lateral or paramedian translaminar entry is used. It is therefore not surprising that a right-sided extradural hematoma was also found. These minor anatomical points are relevant to avoid complications.

Other reported cases (3–6) have shown that thoracic epidural anesthesia is hazardous. If in doubt anesthesiologists may consider a high lumbar insertion of the epidural catheter; as Horlocker et al. (7) used in more than 4000 cases of upper abdominal and thoracic surgery, with “only six patients having neurological complications.”

J. Antonio Aldrete, MD, MS

Department of Anesthesiology

University of Alabama at Birmingham

Aldrete Pain Care Center, Inc.

Arachnoiditis Foundation, Inc.

Birmingham, Alabama

aldrete@arachnoiditis.com

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REFERENCES

1. Tsui BCH, Armstrong K. Can direct spinal cord injury occur without paresthesia? A report of delayed spinal cord injury after epidural placement in an awake patient. Anesth Analg 2005;101:1212–4.
2. Grant FC. Surgical methods for relief of pain. Bull N Y Acad Med 1943;19:373–9.
3. Bromage PR, Benumof JL. Paraplegia following intracord injections during attempted epidural anesthesia. Reg Anesth Pain Med 1998;23:104–7.
4. Mayal MF, Calder I. Spinal cord injury following an attempted thoracic epidural anesthesia. Anesthesia 1999;54:990–4.
5. Rou JB. Spinal cord injury in a child after single-shot epidural anesthesia. Anesth Analg 2003;96:3–6.
6. Aldrete JA, Ferrari H. Myelopathy with syringomyelia following thoracic epidural anaesthesia. Anaesth Intensive Care 2004;32:100–3.
7. Horlocker TT, Abel MD, Messick JM Jr, Schroeder DR. Small risk of complications related to lumbar epidural catheter placement in anesthetized patients. Anesth Analg 2003;96:1547–52.
© 2006 International Anesthesia Research Society