Differential Diagnosis for the 32-year-old man in a motor vehicle collision

• Single most likely diagnosis:
  • Temporal bone: The presence of hemotympanum (blood behind the tympanic membrane) is a strong indicator of temporal bone injury. The temporal bone houses the structures of the ear and is susceptible to fracture in the setting of head trauma, especially in high-impact collisions where the head may strike the steering wheel or windshield, leading to basilar skull fractures which can involve the temporal bone.
• Other Likely diagnoses:
  • Cribriform plate: While less directly indicated by the symptoms, the cribriform plate, part of the ethmoid bone, can be injured in severe head trauma. However, its injury is more commonly associated with cerebrospinal fluid (CSF) leaks and less directly with the symptoms presented.
  • Occipital bone: The occipital bone forms the back and base of the skull. Injuries here could occur from a significant impact, especially if the individual's head strikes a surface. However, the specific symptom of hemotympanum does not directly suggest an occipital bone fracture.
  • Orbital plate: The orbital plate, part of the frontal bone, could be injured in facial trauma. While possible, the symptoms provided do not directly suggest an injury to this area.
• Do Not Miss diagnoses:
  • Basilar skull fracture: This is a critical diagnosis not to miss, as it can have significant complications, including CSF leaks, meningitis, and damage to cranial nerves. The presence of hemotympanum and the mechanism of injury make this a potential concern.
  • Intracranial hemorrhage: Given the high-impact nature of the collision and the patient's tachycardia and tachypnea, it's crucial to consider the possibility of an intracranial hemorrhage, which could be life-threatening if not promptly addressed.
• Rare diagnoses:
  • Carotid artery dissection: While rare, the mechanism of injury could potentially lead to a carotid artery dissection, especially if there was significant neck trauma or hyperextension. This would be a rare but potentially devastating injury.
  • Petrous apex fracture: A specific type of temporal bone fracture involving the petrous apex, which could lead to complications such as cranial nerve palsies or CSF leaks. This is less common but should be considered in the differential for temporal bone injuries.