Valproic Acid-Induced Tremors: Valproic acid is known to cause tremors as a side effect, especially at high doses or in susceptible individuals. The patient's recent onset of dementia and initiation of valproic acid could be contributing to the development of tremors.

Olanzapine-Induced Tremors: Olanzapine, an atypical antipsychotic, can also cause tremors, especially in elderly patients. The combination of olanzapine and valproic acid may be exacerbating the tremors.
Parkinson's Disease: Although the patient is on donepezil and memantine, which are used to treat Alzheimer's disease, Parkinson's disease can also present with dementia and tremors. The severe uncontrolled tremors could be a symptom of Parkinson's disease.
Essential Tremor: Essential tremor is a common movement disorder that can cause bilateral tremors, especially in older adults. The patient's age and the severity of the tremors make this a possible diagnosis.

Hyperthyroidism: Hyperthyroidism can cause tremors, and it is essential to rule out this condition, as it can be life-threatening if left untreated. Although less likely, it is crucial to consider and test for hyperthyroidism.
Lithium Toxicity: Although the patient is on valproic acid and olanzapine, lithium is another medication that can cause tremors. If the patient is taking lithium, toxicity should be considered, especially given the severity of the tremors.
Wilson's Disease: Wilson's disease is a rare genetic disorder that can cause tremors, among other symptoms. Although unlikely, it is essential to consider and rule out this condition, as it can be fatal if left untreated.

Cerebellar Degeneration: Cerebellar degeneration can cause tremors, among other symptoms. This is a rare condition, but it should be considered if other diagnoses are ruled out.
Multiple System Atrophy: Multiple system atrophy is a rare neurodegenerative disorder that can cause tremors, among other symptoms. This diagnosis is unlikely but should be considered if other diagnoses are ruled out.