The anatomy of the thoracic spinal canal investigated with magnetic resonance imaging (MRI)

Abstract

: Background and Objectives : Anesthesiologists are reluctant to consider higher levels for spinal anesthesia, largely due to direct threats to the spinal cord. The goal of this study is to investigate, with magnetic resonance imaging (MRI), the distances between the relevant structures of the spinal canal (spinal cord, thecal tissue, etc.) to determine modal anatomical positions for neuraxial anesthesia. Method : A group of 19 patients were imaged with an MRI scanner in supine position. Medial sagittal slices of the thoracic and lumbar spine were measured for the relative distances between anatomical structures, including epidural space, dura, and spinal cord. Results : The posterior dura -spinal cord distance is significantly greater in the middle thoracic region than at upper and lower thoracic levels (e.g. T6 9.5 ± 1.8 mm, T12 3.7 ± 1.2 mm, p < 0.001, T1 4.7 ± 1.7 mm, p < 0.001). There is variation in modal distances between the structures important for neuraxial anesthesia, at different levels of the spinal canal. Conclusions :The spinal cord tends to follow the straightest line through the imposed geometry of the spine. Considering the necessary angle of entry of the needle at mid-thoracic levels, there is relatively (more than at upper thoracic and lumbar levels) substantial separation of cord and surrounding thecal tissue. Anesthesiologists perform spinal blockades up to the L2-L3 interspace, but avoid higher levels for fear of neurological damage. The information that there is substantially more space in the dorsal subarachnoid space at thoracic level, might lead to potential applications in regional anesthesia. In contrast, the cauda equina sits more dorsally in the lumbar region.

The Incidence of Paresthesia and Neurologic Complications after Lower Spinal Thoracic Puncture with Cut Needle Compared to Pencil Point Needle. Study in 300 Patients

“…of 5 per cent procaine HC1 (25 mg) at the 12 th thoracic vertebral level [2]. Recently the anatomy of the thoracic spinal canal was investigated with MRI in 19 [3] and 50 [4] patients, and it has been demonstrated the safety of the segmental spinal anesthesia at T 10 by using the combined spinal-epidural technique [5] or single puncture [6]. The T 10 level was the landmark correctly identified by the largest number (92%) of anesthesiologists.…”

Thoracic Spinal Anesthesia

“…The radiculae produce a patern resambling a crescent moon [15] spreading diffusely and filling the posterior aspect of the lumbar subarachnoid space [16,17]. Three papers on MRI present excelent information on the anatomy of the thoracic vertebral canal [18][19][20].…”

“…Because of this possibility, we have to admit that in many opportunities one may think he (she) is giving a lumbar block when they are effectively giving a thoracic block. The studies of the thoracic column with MRI [18][19][20] show that exist a space between the dura-mater and the spinal cord (medula). Van Zundert [38,39] and Imbelloni [40] have placed segmental spinal anesthesia through a combined spinal-epidural technique in a combined spinalepidural block via a thoracic approach and produced segmental spinal anesthesia using a set of combined spinal epidural block and a thoracic approach without any complication.…”

Jonnesco: um século de história da anestesia raquídea

“…The rootlets form a pattern similar to a crescent shape 12 spreading diffusely and occupying the posterior region of the lumbar space 13,14 . The MNR has provided detailed information on the anatomy of the thoracic vertebral canal [15][16][17] . Van Zundert 18,19 and Imbelloni 20 described the performance of the combined spinal-epidural block through thoracic puncture, without complications.…”