Differential Diagnosis
The patient's presentation of a severe, progressively worsening headache, along with signs of increased intracranial pressure and focal neurological deficits, suggests a catastrophic intracranial event. The following differential diagnoses are considered:
Single most likely diagnosis
- Subarachnoid hemorrhage (E): The sudden onset of a severe headache, elevated blood pressure, and signs of increased intracranial pressure (e.g., obtundation, pupillary dysfunction) are highly suggestive of a subarachnoid hemorrhage, likely due to a ruptured aneurysm. The absence of neck rigidity does not rule out this diagnosis, as it may not always be present.
Other Likely diagnoses
- Intraparenchymal hemorrhage (B): Although less likely than subarachnoid hemorrhage given the pupillary findings, an intraparenchymal hemorrhage could still present with sudden headache, elevated blood pressure, and focal neurological deficits.
- Pituitary apoplexy (D): This condition, involving hemorrhage or infarction of the pituitary gland, can present with sudden headache, visual disturbances, and altered mental status. However, the presence of right hemiparesis and the specific pupillary findings make it less likely.
Do Not Miss diagnoses
- Meningoencephalitis (C): Although the patient's temperature is only slightly elevated, meningoencephalitis can present with severe headache, altered mental status, and focal neurological signs. It is crucial to consider and rule out this diagnosis due to its potential for severe consequences if untreated.
- Cluster headache (A): While cluster headaches are extremely painful and can occur with autonomic features like pupillary changes, they typically do not cause the degree of altered mental status or focal neurological deficits seen in this patient. However, given the severity of the headache, it's essential to consider this diagnosis to avoid missing a potentially treatable condition.
Rare diagnoses
- Other rare conditions, such as a cerebral venous sinus thrombosis or a colloid cyst of the third ventricle, could potentially present with similar symptoms. However, these are less likely given the patient's presentation and would be considered after more common diagnoses have been ruled out.