Which of these is NOT a toxic-metabolic cause of altered mental status?

Liver failure is indeed a toxic-metabolic cause of altered mental status, primarily because it can lead to hepatic encephalopathy. This condition results from the buildup of toxins in the blood due to the liver's inability to filter them out, directly affecting cognitive function and consciousness.

In contrast, a brain tumor represents a structural cause of altered mental status rather than a toxic-metabolic one. Brain tumors can disrupt normal brain function through mass effect or by causing increased intracranial pressure, which may lead to changes in mental status.

Degenerative brain diseases, such as Alzheimer's or Parkinson's disease, primarily lead to alterations in mental processing due to the degeneration of neural pathways rather than the effects of toxins or metabolic factors.

A hemorrhagic stroke typically results from bleeding in the brain, leading to pressure on surrounding tissues and potential damage, which is also categorized as a structural cause rather than a toxic-metabolic one. Therefore, both the brain tumor, degenerative brain disease, and hemorrhagic stroke do not primarily involve toxic or metabolic pathways for their impact on mental status.