The Restless Spinal Cord in Degenerative Cervical Myelopathy

Abstract

BACKGROUND AND PURPOSE:The spinal cord is subject to a periodic, cardiac-related movement, which is increased at the level of a cervical stenosis. Increased oscillations may exert mechanical stress on spinal cord tissue causing intramedullary damage. Motion analysis thus holds promise as a biomarker related to disease progression in degenerative cervical myelopathy. Our aim was characterization of the cervical spinal cord motion in patients with degenerative cervical myelopathy. MATERIALS AND METHODS: Phase-contrast MR imaging data were analyzed in 55 patients (37 men; mean age, 56.2 [SD,12.0] years; 36 multisegmental stenoses) and 18 controls (9 men, P ¼ .368; mean age, 62.2 [SD, 6.5] years; P ¼ .024). Parameters of interest included the displacement and motion pattern. Motion data were pooled on the segmental level for comparison between groups. RESULTS: In patients, mean craniocaudal oscillations were increased manifold at any level of a cervical stenosis (eg, C5 displacement: controls [n ¼ 18], 0.54 [SD, 0.16] mm; patients [n ¼ 29], monosegmental stenosis [n ¼ 10], 1.86 [SD, 0.92] mm; P , .001) and even in segments remote from the level of the stenosis (eg, C2 displacement: controls [n ¼ 18], 0.36 [SD, 0.09] mm; patients [n ¼ 52]; stenosis: C3, n ¼ 21; C4, n ¼ 11; C5, n ¼ 18; C6, n ¼ 2; 0.85 [SD, 0.46] mm; P , .001). Motion at C2 differed with the distance to the next stenotic segment and the number of stenotic segments. The motion pattern in most patients showed continuous spinal cord motion throughout the cardiac cycle.CONCLUSIONS: Patients with degenerative cervical myelopathy show altered spinal cord motion with increased and ongoing oscillations at and also beyond the focal level of stenosis. Phase-contrast MR imaging has promise as a biomarker to reveal mechanical stress to the cord and may be applicable to predict disease progression and the impact of surgical interventions.

Spinal Cord Motion in Degenerative Cervical Myelopathy: The Level of the Stenotic Segment and Gender Cause Altered Pathodynamics

“…The current data replicates the dynamic alterations already observed at C5/C6 also at other stenotic cervical segments [10,12,13]. This is of interest, as the segment C5/C6 is located at the maximum of the cervical lordosis and healthy controls show a physiological increase of spinal cord motion at this segment [11,12]; Figure 3.…”

“…As the mean duration of the heartbeat was not different between men and women, a lower peak but with similar total displacement indicated a flattened peak and a prolonged sinusoidal spinal cord motion curve over one heartbeat among women. This finding is complementary to the recently described spinal cord motion curve pattern among DCM patients by Hupp et al In contrast to controls with a short, singular spinal cord oscillation within the heart cycle, DCM patients showed an ongoing spinal cord motion during the entire heart cycle [13]. Among women, this effect seems to be intensified.…”

“…Consistent with earlier findings [10,12], automated measurements of the severity of the stenosis (aMCC, aSCOR) did not predict the extent of spinal cord motion, emphasizing a focal disarrangement of spinal cord dynamics and anatomy. The generally suspected origin of spinal cord motion has been extensively discussed previously [10][11][12][13]. In summary, known influences on intraspinal dynamics can be divided in global (e.g., heartbeat [24][25][26]), breathing [27], and pulsatile CSF-flow [28]) and focal effects, such as loss of compensatory buffer zone for the expansion of pulsatile local arteries [28]).…”

“…Recent findings based on phase-contrast MRI (PC-MRI) have demonstrated significantly increased craniocaudal spinal cord motion among patients with degenerative cervical myelopathy (DCM) at the most commonly affected segment C5/C6 [8][9][10][11][12]. The increase of motion was demonstrated to be a focal phenomenon specifically at the stenotic segment C5/C6 [10,12], and also at the stenotic segment C4/C5 in a small group of four patients [13]. The spinal cord motion at more cranial segments remained unaffected [10,12].…”

“…As there are many uncertainties regarding the spontaneous course, and consecutively, the treatment decision of mildly affected or multimorbid DCM patients, these new quantitative, non-invasively, and reliably assessable PC-MRI parameters [10][11][12][13] may be of future interest in the clinical decision-making process. Still, at the current state of basic research, there are many unanswered questions concerning the dynamic behavior of the cervical spinal cord and its influencing factors.…”