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The degree of stenosis predictive of a clinically significant pressure gradient (30-35%) in the venous sinuses is considerably lower than the arterial stenosis at which pathologic hemodynamic alterations occur. While highly predictive of a venous pressure gradient when a stenosis is identified, non-invasive imaging does not appear to be a suitable diagnostic evaluation for the purpose of ruling out clinically significant cerebral VSS.

laboratory iNveStigatioNC erviCal open-door laminoplasty (ODL) decompresses the spinal canal while maintaining nearphysiological cervical range of motion (ROM). In contrast to a standard laminectomy, which leads to postlaminectomy kyphosis in 15%-43% of cases, ODL is purported to reduce this adverse outcome. 2,3,5,16,28 Despite these advantages, reports have shown that ODL may lead to persistent neck and shoulder pain, progressive loss of ROM, and progressive cervical kyphosis. [6][7][8]11,29 There are various approaches used to perform cervical laminoplasty, many of which involve spinous process resection and disruption of intervening interspinales musculature and supraspinous ligaments (intraspinous and supraspinous ligaments [ISLs]). 5,9,20 Alternative methods have been reported that retain the dorsal ligamentous complex, and small cohorts have shown it may protect from loss of sagittal balance, while not statistically reducing cervical ROM. obJective Cervical open-door laminoplasty (ODL) is designed to decompress the spinal cord, maintain motion, and prevent postlaminectomy kyphosis. Many traditional laminoplasty techniques involve disruption of the posterior ligamentous structures, most notably the C7-T1 supraspinous ligament and interspinales muscle complex (intraspinous and supraspinous ligaments [ISLs]). methodS Eight human cervical cadaveric specimens (C2-T1) were used to investigate the subaxial kinematics following ODL with varying degrees of posterior element disruption. Ligamentous integrity was preserved and specimens were tested utilizing force control in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) in the native state, and following 1) C3-7 ODL, 2) ODL with terminal ISL resection, 3) ODL with C3-7 spinous process resection, and 4) C3-7 laminectomy. Range of motion (ROM) was measured across C2-T1, "global," and at the segmental level. reSultS Compared with ODL, sectioning the terminal ISLs resulted in global ROM increases by 7.9% in FE, 2.4% in LB, and 5.6% in AR (p > 0.05), whereas laminectomy increased global ROM by 36.0% in FE (p = 0.002) and a 26.3% increase in AR ROM (p = 0.01). When considering segmental ROM, resection of the terminal ISLs increased ROM in FE by 36.5% at C2-3 (p = 0.019) and 25.4% at C7-T1 (p > 0.05). Segmental increases following C3-7 spinous process resection averaged less than 3% per level, compared with up to 40% increases in ROM per level after laminectomy. coNcluSioNS Laminectomy resulted in the greatest increase in global cervical ROM. Resection of the ISLs at C2-3 and C7-T1 increased segmental ROM at these specific levels to a similar extent that laminectomy increased ROM at each cervical level. This segmental ROM may contribute to pain or postprocedural deformity and highlights the importance of the ISLs at the terminal ends of the ODL.