Sciatic neuromuscular variants on MR neurography: frequency study and interobserver performance.

OBJECTIVE To evaluate the frequency of sciatic neuromuscular variants on MR neurography and determine the interobserver variability. METHODS A retrospective evaluation of 137 consecutive lumbosacral plexus magnetic resonance neurography examinations was performed. All examinations were performed using nerve selective 3D imaging and independently reviewed by two readers for the presence of sciatic neuromuscular variants and piriformis muscle asymmetry. Inter- and intraobserver performance were evaluated. RESULTS There were a total of 44/268 (16.4%) extremities with sciatic neuromuscular variants. The interobserver performance in the identification of sciatic nerve variants was excellent (kappa values from 0.8-0.9). There was a total of 45/134 (33.6%) patients with piriformis muscle asymmetry. Of these, 7/134 (5.2%) had piriformis muscle atrophy and 38/134 (28.4%) had piriformis muscle hypertrophy. The interobserver performance in the identification of piriformis muscle atrophy and hypertrophy was moderate to good (kappa values from 0.39-0.61). The intraobserver performance revealed kappa values of 0.735 and 0.821 on right and left, respectively. CONCLUSION Sciatic neuromuscular variants and piriformis muscle asymmetry are frequent on lumbosacral plexus MRN with moderate to excellent interobserver performance. Advances in knowledge: Sciatic neuromuscular variants and piriformis asymmetry on MR neurography are frequent and the prevalence is similar to cumulative prevalence from available scientific series. Interobserver performance for identification of sciatic neuromuscular variants is excellent, and moderate-good for piriformis muscle asymmetry.

[1]  I. Jahan,et al.  Piriformis syndrome: a case series of 31 Bangladeshi people with literature review , 2017, European Journal of Orthopaedic Surgery & Traumatology.

[2]  J. Bencardino,et al.  Focus on advanced magnetic resonance techniques in clinical practice: magnetic resonance neurography. , 2015, Radiologic clinics of North America.

[3]  A. Chhabra,et al.  SHINKEI—a novel 3D isotropic MR neurography technique: technical advantages over 3DIRTSE-based imaging , 2015, European Radiology.

[4]  N. Smoll.  Variations of the piriformis and sciatic nerve with clinical consequence: A review , 2010, Clinical anatomy.

[5]  S. Naderi,et al.  Variations in the high division of the sciatic nerve and relationship between the sciatic nerve and the piriformis. , 2009, Turkish neurosurgery.

[6]  Laura W. Bancroft,et al.  Magnetic resonance imaging of the sacral plexus and piriformis muscles , 2008, Skeletal Radiology.

[7]  V. Pinskerova,et al.  Topographic variations of the relationship of the sciatic nerve and the piriformis muscle and its relevance to palsy after total hip arthroplasty , 2006, Surgical and Radiologic Anatomy.

[8]  J. Katz,et al.  Piriformis Syndrome: Anatomic Considerations, a New Injection Technique, and a Review of the Literature , 2003, Anesthesiology.

[9]  Christopher Michaelsen,et al.  Piriformis syndrome: diagnosis, treatment, and outcome--a 10-year study. , 2002, Archives of physical medicine and rehabilitation.

[10]  T. Kasai,et al.  [Perforation of dorsal branches of the sacral nerve plexus through the piriformis muscle and its relation to changes of segmental arrangements of the vertebral column and others]. , 1994, Kaibogaku zasshi. Journal of anatomy.

[11]  S. Chiba.  [Multiple positional relationships of nerves arising from the sacral plexus to the piriformis muscle in humans]. , 1992, Kaibogaku zasshi. Journal of anatomy.

[12]  P'an Ming-Tzu.  The relation of the sciatic nerve to the piriformis muscle in the Chinese , 1941 .

[13]  B. Anson,et al.  The relation of the sciatic nerve and of its subdivisions to the piriformis muscle , 1937 .

[14]  M. Trotter.  The relation of the sciatic nerve to the piriformis muscle in American whites and negroes , 1932 .

[15]  A. Keith,et al.  Sixth Annual Report of the Committee of Collective Investigation of the Anatomical Society of Great Britain and Ireland, 1895-96. , 1896, Journal of anatomy and physiology.

[16]  V. Krstić,et al.  [The level of the sciatic nerve division and its relations to the piriform muscle]. , 2005, Vojnosanitetski pregled.

[17]  A. Sosna,et al.  [Anatomic variability of the relation of pelvitrochanteric muscles and sciatic nerve.]. , 1998, Acta chirurgiae orthopaedicae et traumatologiae Cechoslovaca.

[18]  M. Pećina.  Contribution to the etiological explanation of the piriformis syndrome. , 1979, Acta anatomica.

[19]  C. S. Lee,et al.  [The relation of the sciatic nerve to the piriformis muscle]. , 1974, Taiwan yi xue hui za zhi. Journal of the Formosan Medical Association.

[20]  C. Niżankowski,et al.  [Variations in the anatomy of the sciatic nerve in man]. , 1972, Folia Morphologica.

[21]  M. Pan.  RELATION OF THE SCIATIC NERVE TO THE PIRIFORMIS MUSCLE IN THE CHINESE , 1962 .

[22]  Anne M.R. Agur,et al.  Grant's Atlas of Anatomy , 1943 .