Most basilar/basal skull fractures are caused by high-velocity blunt trauma such as motor vehicle collisions, motorcycle crashes, and pedestrian injuries. 

Structures involved: petrous temporaL bone (MC), the external auditory canal, and tympanic membrane.

Signs of basal skull fracture

• Hemotympanum (blood pooling behind tympanic membrane making it appear purple - earliest finding)
• Cerebrospinal fluid (CSF) otorrhea or rhinorrhea (“Halo” sign is the double ring pattern described when bloody fluid from the ear or nose containing CSF is dripped onto paper or linen)
• Battle sign (retroauricular or mastoid ecchymosis
• Raccoon/Panda eyes (periorbital ecchymosis).