This case report describes abnormalities in bilateral rectus capitis poster
ior minor muscles in one individual with persistent head and neck pain. The
se findings are muscle atrophy, fatty infiltration on magnetic resonance im
aging, and electromyographic abnormalities compatible with denervated muscl
e. The objective of the study contained herein was to determine if fatty in
filtration on magnetic resonance imaging of the rectus capitis posterior mi
nor muscle is the result of disuse or denervation. Electromyography and mag
netic resonance imaging data were collected from normal and atrophied muscl
es. Electromyography and magnetic resonance imaging abnormalities compatibl
e with denervation atrophy were detected. Although we cannot rule out aging
or other unknown causes, we suspect that denervation is caused by nerve da
mage from trauma to the C-1 dorsal ramus as a consequence of entrapment wit
hin the rectus capitis posterior major muscle.