Bilateral anomaly of rectus capitis posterior muscles in the suboccipital triangle and its clinical implication.

Rectus capitis posterior muscles are located in the suboccipital triangle and function in extension and lateral rotation of the head and neck. There are two of these muscles on each side: the rectus capitis posterior major and the rectus capitis posterior minor. In the present case we observed bilateral double rectus capitis posterior major muscle and bilateral absence of rectus capitis posterior minor muscle. The additional rectus capitis posterior major may put more strain to the spine of the axis and mean time the bilateral absence of rectus capitis posterior minor muscles will result in muscular in coordination in the suboccipital region while balancing the head. The present variation should be considered in the aetiology of cervicogenic headache.