Magnetic resonance imaging evaluation of cervical paraspinal muscles in dropped head syndrome.

Purpose: The pathomechanism of dropped head syndrome (DHS) is unclear. In this study, we aimed to examine the features of the paraspinal cervical muscles in patients with DHS by analyzing the volume of these muscles using magnetic resonance imaging (MRI).

Methods: Thirty-six patients with DHS and 25 patients with cervical spondylotic myelopathy (controls) were enrolled. The volume analyzer measured the cross-sectional area (CSA) of the paraspinal muscles on the axial image of a T2-weighted MRI at each level, from C2/3 to C6/7. The histogram used pixel intensities to measure the fat infiltration in the extensor muscles. The data were compared between the groups.

Results: The CSA of the semispinalis capitis and the splenius capitis and cervicis from the extensor muscles in DHS was larger than that of the control group at almost all levels. The CSAs of other extensor muscles were equivalent to those of the controls. The CSA of the sternocleidomastoideus in DHS was smaller than in the control group at C4/5/6/7. The CSA of any extensor muscle in the chronic group of the DHS was smaller than that of the acute group at the lower levels. The percentage of fat infiltration was not significantly different between the groups.

Conclusion: MRI analyses of the present study revealed that neither the extensor muscles in DHS were atrophic nor the flexor muscles were hypertrophic. Further, fatty infiltration of the extensor muscles may not induce muscle weakness of the extensors in patients with DHS.