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Application of Brachial Plexus Neurography in a Private Practice Environment – a Five Year Experience. 2007

General Spine

Phil R Chapman, MD
Jay Johnson, MD, Non ASSR Member
Dave Munoz, MD, Non ASSR Member
James W Taylor, MD, Non ASSR Member

Scientific Paper

Purpose

In the late 1990's, high resolution brachial plexus neurography emerged as a new technique for evaluating the brachial plexus. Early work was concentrated in a few academic centers. Our private practice institution began dedicated brachial plexus studies in 2001. Over the next five years we performed approximately 500 brachial plexus examinations. We performed a comprehensive review of all of these studies in an effort to document the implementation and utilization of brachial plexus neurography in a single private practice institution.

Methods & Materials

All brachial plexus examinations (and their reports) performed between January 1, 2001 and April 28, 2006 were reviewed. All studies were performed with the same basic technique, using torso phased array coils and a GE 1.5 Tesla magnet (see attached description for technique). The initial interpretations were made by a subspecialized group of 9 neuroradiologists. This included 6 fellowship trained neuroradiologists and 3 other radiologists that devoted greater than 30% of their professional time interpreting neuroradiologic examinations. Experience in years post-training ranged form 6-20.

Patient age, gender, symptoms, chronicity of symptoms, and pertinent medical and surgical history were reviewed. Records were also reviewed to determine if patients had a specific incidence of trauma or injury, and if the injury was work-related.

The original reports were categorized as normal or abnormal as they pertained to the brachial plexus itself (extrinsic abnormalities such as shoulder pathology were omitted). “Abnormal” studies were further classified according to the nature of the abnormality, including elevated T2 signal (diffuse, focal, multifocal or regional), fascicular distortion, intrinsic or extrinsic mass, infiltrating processes (ex. radiation), anatomic distortion or kinking, or frank anatomic compression.

In addition 10 studies were performed on normal, asymptomatic patients.

Results

A total of 499 studies were reviewed, along with their original final reports, and categorized according to the criteria described. The age of the patients at the time of exam ranged from 11 to 85 years (mean of 44.2). 62% of patients were female (309/499), and 58% were male (290/499).

55% of all studies (275/499) were reported as abnormal in the original report. The number of exams reported as abnormal varied by year, with 86% in 2001, 71% in 2002, 21% in 2003, 29% in 2004, 24% in 2005, and 24% in 2006. The percentage of abnormal studies with “diffusely increased T2 signal” as the major abnormality ranged from 73% in 2001 down to 9% in 2005.

The number of examinations performed ranged from a peak of 199 in 2002, down to 21 exams during the first 4 months of 2006.

37% of all studies (181/499) were related to labor and industry claims. 1.8% of studies (9/499) were determined to be nondiagnostic at the time of initial interpretation, generally due to patient motion or metallic artifact (humerus or shoulder surgery).

Conclusion

Our findings indicate that brachial plexography is feasible in a busy private practice setting. Our data also indicate a significant shift in the way brachial plexus studies were interpreted and utilized during the study time. In the first two years (2001and 2002), there was a strong trend toward greater sensitivity (higher percentage of positive exams) and corresponding greater utilization of the brachial plexus examinations. In the latter three years (2003-2006) there was a shift in the trend toward greater specificity, with a smaller percentage of positive examinations, and ultimately, less referrals and total utilization. This shift, in essence, reflected a “learning curve” for the neuroradiologists, and pivoted around the subjective interpretations of T2 signal. T2 signal interpretations are difficult due to wide normal variability in T2 signal of plexus, lack of appropriate T2 quantification method, a lack of adequate reference, magic angle effects, respiratory /motion artifacts and fat-saturation artifacts. T2 signal in and of itself should be interpreted with caution.

References

1. Todd M, Shah GV, Mukherji SK. MR Imaging of Brachial Plexus. Top Magn Reson Imaging. 2004;15:113-125.
2. Bowen BC, Pattany PM, Saraf-Lavi S, Maravilla, KR. The brachial plexus: normal anatomy, pathology and MR imaging. Neuroimag Clinics of North America. 2004;14:59-85.
3. Van Es, HW. MRI of the brachial plexus. Eur Radiol. 2001; 11:325-336.
4. Wittenberg KH, Adkins MC. MR Imaging of Nontraumatic Brachial Plexopathies: Frequency and Spectrum of Findings. Radiographics. 2000;20:1023-1032.
5. Maravilla KR, Aagaard BD, Kliot, M. MR Imaging of Peripheral Nerves. MRI Clinics of North America. 1998;6:179-194.

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