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Clinical High Resolution CISS Imaging of the Spinal Nerves in Health and Disease 2011

General Spine

Ari, M, Blitz, MD
Leonardo, M, Macedo, MD, Non ASSR Member
James, X, Chen, BA, Non ASSR Member
Nafi, Aygun, MD, Non ASSR Member
Izlem, Izbudak, MD, Non ASSR Member
Anna, E, Nidecker, MD, Non ASSR Member

Paper/Mentor

Purpose

Magnetic resonance imaging with constructive interference in the steady state (CISS) allows for high spatial resolution imaging with a heavily T2 weighted appearance in a clinically acceptable time period. Despite having long been used as a component of standard imaging protocols in other contexts and notwithstanding the first description of its use for spinal imaging nearly a decade ago [1], CISS imaging of the spine has yet to gain wide acceptance. The authors review the relevant anatomy as revealed on high resolution imaging and describe our initial experience over the last two years with this technique as a tool for clarification in cases in which standard MRI imaging has not satisfactorily answered the clinical question.

Methods & Materials

CISS was performed as an adjunct to conventional spinal MR imaging when the initial studies failed to sufficiently clarify the diagnosis. Each of the examinations was directly supervised or personally performed by the attending neuroradiologist, and tailored to the individual clinical question. For this presentation we have selected cases of normal and pathological spinal anatomy that best exemplify the strengths of CISS imaging. CISS imaging in the spine presents a different set of challenges than elsewhere and our approach has evolved significantly over time. We will discuss parameter selection for high resolution imaging acquisition within a clinically acceptable time period. 3D isotropic acquisition of images allows for reconstruction in any arbitrary plane and results in a wealth of information. In addition to static images this presentation will employ embedded scrollable datasets to allow for real time discussion of the relationship of structures passing through multiple two dimensional images and discussion of strategies for review.

Results

Previous publications have principally focused on the utility of CISS imaging for evaluation of vascular malformations, tumors, syringohydromyelia [1] and arachnoid adhesions [2] but have largely neglected the wealth of anatomic detail that CISS provides with respect to the spinal nerves. The ability of CISS imaging to reveal anatomic detail at the level of the rootlets (Figure 1,2) or proximal rami (Figure 2,3), for example, enables localization of pathology that may not be evident on conventional MRI. Additionally, we describe cases in which high resolution evaluation demonstrates deformity of the foraminal components of the spinal nerves in the absence of visualization of compression on standard imaging. Significant anatomic variation in the course of nerve roots has been previously described [3]. The absence of a precise description of the number and course of nerve roots on conventional MR imaging may contribute to confusion in correlating clinical findings to pathology on imaging. CISS imaging, on the other hand, allows for a precise demonstration of the number and course of the nerve roots and reveals atypical anatomic features and their spatial relation to regions of pathology. It is widely recognized that MRI findings of disc herniation do not correlate well with clinical presentation or prognosis, [4] and many patients present with significant pain without obvious etiology on imaging. Imaging assessment has focused primarily on the presence or absence of gross disease within the spinal canal and neural foramen. In selected high resolution case material we suggest that symptoms may result from pathology in regions that are difficult to confidently assess, or at a scale that is likewise challenging to visualize, without high resolution imaging (Figure 4).

Conclusion

High resolution CISS imaging allows for discrimination of fine details of spinal nerve anatomy, typically not well visualized on standard MR imaging. The authors review the anatomy of the spinal nerves on high resolution imaging, tracing the appearance of the rootlets, foraminal roots, dorsal root ganglia and proximal extraforaminal branching pattern in the cervical, thoracic and lumbar regions. As is widely acknowledged the clinical presentation of back pain often seemingly has no clear correlate on spinal MRI as currently practiced. The authors present several cases where high resolution imaging suggested a possible locus of spinal nerve compression not visualized on standard imaging and suggest that high resolution imaging may have a role to play in clarification of such challenging cases in the future.

References/Financial Disclosures

1. Ramli N, Cooper A, Jaspan T. High resolution CISS imaging of the spine. Br J Radiol 2001;74:862-73. 2. Gottschalk A, Schmitz B, Mauer UM, et al. Dynamic visualization of arachnoid adhesions in a patient with idiopathic syringomyelia using high-resolution cine magnetic resonance imaging at 3T. J Magn Reson Imaging;32:218-22. 3. Neidre A, MacNab I. Anomalies of the lumbosacral nerve roots. Review of 16 cases and classification. Spine (Phila Pa 1976) 1983;8:294-9. 4. Maus T. Imaging the back pain patient. Phys Med Rehabil Clin N Am;21:725-66.

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