Degenerative spinal stenosis may influence Normal Pressure Hydrocephalus (NPH)-related imaging characteristics

The etiology of NPH is unknown, but might be related to altered craniospinal compliance caused by spinal canal narrowing, as has been suggested by in-vitro simulation studies. However, clinical evidence is lacking. We explored associations between cervical (CS) and lumbar (LS) spinal stenoses, and NPH-imaging characteristics.

Spinal MRI of NPH-patients scheduled for shunt-surgery was retrospectively evaluated by measuring the minimal dural sac cross-sectional area (DSCSA), and anterior-posterior diameter (AP) in CS and LS. Cranial-CT was evaluated regarding Evans-Index, callosal angle (CA), and Radscale-Score. CS and LS were each sub-grouped by median split into small/large DSCSA and small/large AP, and CT-parameters compared using Mann-Whitney-U-Tests, tested one-sided (p < .05, Bonferroni-Holm-corrected for multiple comparisons p _Holm). Partial correlations were explored between stenoses- and cranial-imaging parameters.

Out of 426 NPH-patients screened, 114 patients had spinal-MRI. Of those with cervical-MRI (n = 100), 90% had CS, of those with lumbar-MRI (n = 86), 71% had LS. Among these, 60 patients had cervical and lumbar MRI, of which 63% showed combined CS and LS. CA was larger in CS patients with small as compared to large AP (p = .045, r = .235, 95%CI [.002, .444]), and in LS patients with small as compared to large DSCSA (p = .022, r = .330, 95%CI [.060, .555]), which did however not remain significant after correction for multiple comparisons (p _Holm> .05). Lumbar AP tended to be negatively correlated to the Radscale-Score (p = .041, r = -0.31, 95%CI [-.561,-.014], p _Holm> .05).

Spinal stenosis might be associated with NPH-related imaging characteristics. Prospective studies should investigate the potential pathophysiological impact of degenerative spine-disease on NPH.