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Positive straight leg raising test secondary to conjoined lumbosacral nerve roots 

Figure  Axial and sagittal T2-weighted MRIs of lumbosacral spine

(A.a–D.a) Serial sagittal T2-weighted images of lumbar spine frommidline to periphery showing single nerve root splitting into left L4 and L5 nerve roots (arrows). (E.a)Right paramedian sagittal section showing normal location of nerve roots (arrows). (A.b–E.b) Axial T2-weighted images at L4-5 disk level showing “parallel sign” (arrowhead).

A 53-year-old man presented with low backache and left lower limb pain of 3 months’ duration, without radicular pain or lower limb weakness. Straight leg raising test was positive but the remainder of the neurologic examination was normal. His lumbosacral spine MRI revealed left L4 and L5 conjoined nerve roots (figure, A.a–D.a). The imaging was positive for sagittal“shoulder sign”(figure, A.a) and axial image“parallel sign”(figure, A.b), both favoring conjoined nerve roots.1 The absence of other neurologic signs with no imaging evidence of nerve root compression on the left suggests that the positive straight leg raising test was attributable to conjoined lumbosacral nerve roots.2

Kamble J. Harsha, MD, DM, Jain G. Panattil, MS, Mch

From the Departments of Neuroimageology and Interventional Neuroradiology (K.J.H.) and Neurosurgery (J.G.P.), Indo-American Hospital: Brain & Spine Centre, Chemmankary, Vaikom, India.

Author contributions: Dr. Harsha: MRI evaluation, drafting and revising the manuscript. Dr. Panattil: examination of the patient, reviewing the manuscript.

Study funding: No targeted funding reported.

Disclosure: The authors report no disclosures relevant to the manuscript. Go to Neurology.org for full disclosures.

Correspondence to Dr. Harsha: kjharsha@gmail.com

 1. Song SJ, Lee JW, Choi JY, et al. Imaging features suggestive of conjoined nerve root on routine  axial MRI. Skeletal Radiol 2008; 37:133–138.

 2. Lotan R, Al-Rashdi A, Yee A, Finkelstein J. Clinical features of conjoined lumbosacral nerve roots versus lumbar intervertebral disc herniations. Eur Spine J 2010;19:1094–1098.