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.