Tension Headache or Sinusitis-related Headache: The patient's symptoms and the CT findings of paranasal sinusitis with prominent mucosal thickening in the frontal, right ethmoid, and maxillary sinuses suggest that the headache could be related to the sinusitis. The fact that the headache subsided with Toradol (a nonsteroidal anti-inflammatory drug) yesterday also supports this diagnosis, as NSAIDs can be effective in treating tension headaches and headaches associated with sinusitis.

Hypertension-related Headache: Although the patient's blood pressure is not extremely high, it is elevated, and hypertension can cause headaches. The fact that the blood pressure was 156/92 yesterday and 158/87 today suggests that hypertension could be a contributing factor to the headache.
Migraine: Although there's no specific information provided about the characteristics of the headache (e.g., unilateral, throbbing, associated with nausea or photophobia), migraines are a common cause of headaches in adults and could be considered, especially if the patient has a history of migraines.

Subarachnoid Hemorrhage or Other Intracranial Hemorrhage: Although the CT head without contrast did not show any acute intracranial abnormality, it's crucial to consider the possibility of a hemorrhage, especially if the patient's symptoms worsen or if there are any "red flag" symptoms (e.g., sudden onset, worst headache of life, fever, stiff neck). A lumbar puncture might be necessary if clinical suspicion remains high.
Temporal Arteritis: This condition, also known as giant cell arteritis, is a serious cause of headache in older adults and can lead to blindness if not promptly treated. The presence of jaw claudication, visual disturbances, or polymyalgia rheumatica symptoms would increase the suspicion for this diagnosis.
Meningitis: Although less likely given the lack of fever, stiff neck, or other systemic symptoms, meningitis is a potentially life-threatening condition that requires prompt diagnosis and treatment.

Brain Tumor: While the CT did not show any acute intracranial abnormality, it's possible that a brain tumor could cause headaches. However, this would be less likely without other symptoms such as seizures, focal neurological deficits, or a history of cancer.
Pituitary Apoplexy: This is a rare condition where a pituitary tumor suddenly hemorrhages or infarcts, leading to severe headache, visual disturbances, and acute hormonal deficiencies. It's an emergency that requires immediate medical attention.