Compared with the Conventional MR Imaging, Do the Constructive Interference Steady State Sequence and Diffusion Weighted Imaging Aid in the Diagnosis of Lumbar Disc Hernias?

Agreement between transverse T2-weighted and three-dimensional constructive interference in steady state sequences in the evaluation of spinal cord disease in dogs

The constructive interference in steady state (CISS) sequence has been widely used in human neuroimaging. It has been shown to be advantageous in the evaluation of intra-axial and extra-axial cystic abnormalities, arteriovenous and dysraphic malformations and disturbances of cerebrospinal fluid circulation. To assess the utility of this technique in small animals, interpretations based on this sequence were compared with those based on T2-weighted (T2W) sequences in 145 dogs that underwent MRI of the spine for suspected spinal cord disease. Two sets of images (T2W and CISS) were reviewed separately by three observers in random order and intraobserver and interobserver agreements between both sequences were evaluated for several categorical variables. The overall agreement between T2W and CISS sequences was good. The highest agreement was observed for lesion diagnosis (0.739<k<0.928), treatment recommendation (0.715<k<0.833) and degree of spinal cord compression (0.772<k<0.952). The agreement for intramedullary intensity change (0.192<k<0.332) was lower compared with the other variables. Lesions that were predominantly characterised by focal hyperintense parenchymal changes on T2W were in some instances undetected on the CISS sequence while lesions consistent with spinal arachnoid diverticula on CISS sequences were occasionally missed on T2W. CISS enabled demonstration that lesions were directly affecting associated spinal nerves in some cases where T2W sequence was equivocal. Although CISS does not replace standard spin echo sequences, the results support inclusion of this sequence in small animal spinal MRI studies when subarachnoid diverticula or spinal nerve compression is suspected.

Intradural lumbar disc herniation detected by 3D CISS MRI

A 73-year-old man who presented with right lumbosciatic pain underwent a neurosurgical operation for a voluminous L2–L3 disc herniation, seen on conventional MRI images. No disc herniation was identified in the epidural space during the surgery. Just after the operation, the patient started to present pain in the left L3 territory and was not able to walk any more. A second MRI including three-dimensional (3D) high-resolution constructive interference in steady state (CISS) sequence showed that the voluminous L2–L3 disc split the posterior longitudinal ligament and the anterior dura mater, extended intradurally and compressed the cauda equina to the right. The patient underwent a second surgery, which permitted to cure the symptoms. 3D high-resolution CISS should be considered to accurately depict intradural disc herniation in order to optimally guide the surgical approach.