A 45-year-old female with a recent history of subarachnoid hemorrhage suddenly becomes unresponsive. Her ICP reading spikes to 35 mmHg. Which of the following is the most appropriate immediate action?

A. Subdural hematoma is incorrect because subdural hematomas usually develop more gradually, particularly in younger patients. They often result from venous bleeding, and symptoms can appear over hours to days, rather than the rapid deterioration seen in this case.

B. Epidural hematoma is correct because this scenario describes the classic “lucid interval”followed by rapid neurological deterioration. Epidural hematomas are typically caused by arterial bleeding, often from the middle meningeal artery after a temporal skull fracture. The sudden dilation of one pupil (ipsilateral to the hematoma) indicates uncal herniation, and symptoms such as vomiting, drowsiness, and increasing ICP are consistent with this neurological emergency. Immediate neurosurgical intervention is usually required.

C. Intracerebral hemorrhage is incorrect because it involves bleeding within the brain tissueitself, often without the brief lucid period. It is more common in patients with hypertension, vascular malformations, or coagulopathy. The rapid, post-trauma lucid interval makes epidural hematoma more likely in this young trauma patient.

D. Subarachnoid hemorrhage is incorrect because it usually presents with a sudden, severe “thunderclap” headache, often described as the worst headache of the patient’s life, sometimes with nuchal rigidity and photophobia. It is less commonly associated with trauma in young adults.

A. The P2 wave is higher than P1 is incorrect because P2 reflects intracranial compliance, or the brain’s ability to accommodate changes in volume. When P2 becomes equal to or higher than P1, it indicates reduced compliance and rising intracranial pressure. This pattern is associated with conditions such as cerebral edema, intracranial bleeding, or mass lesions and represents an abnormal finding rather than a normal waveform.

B. P1 wave is higher than P2 is correct because this represents a normal intracranial pressure waveform. P1, also known as the percussion wave, is generated by arterial pulsations transmitted from the choroid plexus during systole. When P1 is the highest peak, it indicates normal transmission of arterial pressure and normal intracranial compliance. The expected normal ICP waveform follows the pattern P1 greater than P2 greater than P3.

C. P3 wave is higher than P1 is incorrect because P3, the dicrotic wave, corresponds to closure of the aortic valve during diastole and is normally the smallest component of the ICP waveform. An elevated P3 is not expected and suggests abnormal cerebrovascular dynamics or increased intracranial pressure.

D. P3 is higher than P2 is incorrect because under normal conditions P3 remains lower than P2. If P3 exceeds P2, the waveform is considered abnormal and may indicate disrupted cerebral blood flow or altered pressure transmission within the cranial vault.