Sleep-Related Rhythmic Movement Disorder (RMD) may cause insomnia or excessive daytime sleepiness due to disturbed sleep, as well as head and limb injuries (such as forehead bruises or other abrasions) resulting from the movements.⁸⁷

References 

⁸⁷ Thorpy M, “Classification of Sleep Disorders,” in Kryger M, Roth T, Dement W (ed.), Principles and Practice of Sleep Medicine (5th Edition), St. Louis: Elsevier Saunders, 2011, pages 680 - 693.