Dementia in Parkinson's Disease

Dementia in Parkinson's disease encompasses a spectrum relating to motor, psychiatric, and cognitive symptoms that are classified as either Dementia with Lewy Bodies (DLB) (initial cognitive symptoms) or Parkinson's Disease Dementia (PDD) (initial motor signs preceding cognitive symptoms by at least a year). Anticholinergic and antipsychotic drugs have a high risk of adverse cognitive and/or motor effects, so their use should be minimized or avoided. Neuroleptic sensitivity is a severe psychomotor adverse reaction that is particularly associated with potent dopamine-blocking agents such as haloperidol. It occurs in up to 50% of individuals with PDD or DLB. Mild psychotic symptoms should first be addressed by reducing anticholinergic and/or dopaminergic agents, if possible. Patients with psychotic symptoms that threaten the safety of the patient or caregiver may benefit from treatment with quetiapine or, in refractory cases, clozapine. Cholinesterase inhibitors as a drug class have been shown to have beneficial effects on cognition in DLB and PDD, and may help to alleviate some psychiatric symptoms, such as apathy, anxiety, hallucinations, and delusions. Memantine may help to moderate cognitive symptoms in DLB and PDD, although current data suggest a more variable response, particularly in PDD. Parkinsonian motor signs that are accompanied by clinically significant cognitive impairment should be treated with carbidopa/levodopa only, as dopamine agonists and other antiparkinsonian medications generally carry a higher risk of provoking or exacerbating psychotic symptoms. Excessive daytime sleepiness and REM sleep behavior disorder are common associated features of PDD and DLB. Minimizing sedating medications during the day and promoting nocturnal sleep may help the daytime sleepiness; melatonin, clonazepam, gabapentin, and possibly memantine may be useful in treating REM sleep behavior disorder. Orthostatic hypotension can be managed with various nonpharmacologic interventions, and if needed, fludrocortisone and pyridostigmine. Midodrine should be used cautiously, if at all.