Answer:
The common signs and symptoms of a serious head injury include:
1. Rapid, thready pulse: This refers to a weak and fast heartbeat. It can be a sign of shock or inadequate blood flow to the body's tissues. However, it is not specifically associated with a head injury.
2. Widening pulse pressure: Pulse pressure is the difference between the systolic and diastolic blood pressure readings. A widening pulse pressure can indicate increased intracranial pressure, which may occur in some severe head injuries.
3. Cerebrospinal fluid leakage from the ears: Cerebrospinal fluid (CSF) is a clear fluid that surrounds and protects the brain and spinal cord. Leakage of CSF from the ears can indicate a fracture of the skull base, which can occur in severe head injuries.
4. Decerebrate posturing: Decerebrate posturing is an abnormal body posture characterized by rigid extension of the limbs. It is a sign of severe brain injury, specifically affecting the brainstem.
Therefore, the correct answer is "a rapid, thready pulse." While it can be associated with other medical conditions, it is not a specific sign of a serious head injury.