Progression of Stroke or Recurrent Stroke: The worsening symptoms, including the new onset of excessive salivation, could indicate an expansion of the initial stroke area or a new stroke event. This is a common cause of worsening symptoms in post-stroke patients.

Stroke Complications (e.g., Pneumonia, Urinary Tract Infection): Infections are common in post-stroke patients due to decreased mobility, dysphagia, and other factors. These complications can lead to worsening of neurological symptoms indirectly.
Seizures: Post-stroke seizures can occur and may present with a variety of symptoms, including changes in salivation, although this is less common.
Medication Side Effects: Certain medications used in the management of stroke or its complications can have side effects that worsen symptoms or cause new ones, such as excessive salivation.

Pulmonary Embolism: Although less likely, pulmonary embolism is a potentially life-threatening condition that can occur in immobile post-stroke patients. It might not directly cause salivation changes but is critical to rule out due to its high mortality rate.
Meningitis or Encephalitis: Infections of the central nervous system can present with worsening neurological symptoms and are medical emergencies.
Hydrocephalus: Obstructive or non-obstructive hydrocephalus can occur post-stroke and lead to worsening symptoms, including changes in mental status and focal neurological deficits.

Cerebral Vasculitis: An inflammation of the blood vessels in the brain, which is rare but can cause stroke-like symptoms or worsening of existing stroke symptoms.
Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS): A rare mitochondrial disorder that can cause stroke-like episodes, among other symptoms.
Post-Stroke Dystonia or Other Movement Disorders: Rarely, post-stroke patients can develop movement disorders, which might include dystonic reactions that could potentially cause excessive salivation, although this is uncommon.