Cranial nerve 12 is the hypoglossal nerve. It supplies the tongue muscles. It starts in medulla and passes through jaw and reaches the tongue. It can be damaged at 3 levels: nuclear, supranuclear or infranuclear level. Damage to any level leads to fasciculation of tongue (looks scalloped) and will atrophy eventually. On protruding the tongue, the tongue deviates towards the abnormal side due to action of genioglossus muscle. It is examined by asking the patient to stock the tongue out and inspecting deviation and atrophy signs. Hypoglossal nerve can be damaged by tumors, infections, or trauma.