Cognitive and behavioral problems are significant challenges in the treatment of Parkinson's disease.

Parkinson's disease (PD) is a movement disorder characterized by tremor, rigidity, bradykinesia and postural instability.   Focus on these easily identified motor signs often overshadows the many nonmotor symptoms that coexist in this disorder. Under recognition of nonmotor symptoms by clinicians may reflect the tendency to focus primarily on the more apparent motor features of PD and/or lack of awareness of the nonmotor symptoms. Depression and cognitive problems are considerable concerns given the direct impact they have on QOL. In fact these problems contribute significantly to impair QOL and their effect together is synergistic- affecting lives more significantly than motor function.

Dementia can occur in about 20-30% of patients with Parkinson disease (Aarsland, 2005).  Parkinson's dementia is one of the classic sub-cortical dementias and differs from Alzheimer's disease and other cortical dementias associated with problems such as memory loss, language difficulties or apraxia. The cognitive problems in PD represent a continuum ranging from mild cognitive deficits to dementia.

Depression, like other cognitive behavioral symptoms, is both under-recognized and undertreated.
 

Depression is among the most common neuropsychiatric symptoms in PD with a prevalence of up to 76% of patients with PD ( Veazey, 2005). The diagnosis of depression in PD is critical due to its impact on physical symptoms, cognitive status, perception of quality of life, and caregiver distress.  Depression can be difficult to diagnose.  Loss of spontaneous facial expression, bradyphrenia, apathy, and social withdrawal due to apathy or physical disability can be mistaken for depression.  The Beck Depression Inventory is sensitive to the depression evident in PD and thus, may be a reasonable tool to screen patients for depression.

Depression can occur as a general feature but also as an end of dose phenomenon emerging just prior to the patient's next dose of levodopa.  It is important to ask patients if their depression fluctuates throughout the day to assess the possible relationship to dopaminergic therapies.  Depression can also coexist with anxiety.

Psychotherapy and behavioral techniques such as cognitive behavioral therapy and guided relaxation, attention to sleep hygiene, social engagement and exercise are first line therapies for mild depression.  Medical therapies include SSRIs especially when anxiety is a problem and nonselective agents.  All serotonergic agents should be used with caution in combination with MAO inhibitors, which are often employed for the treatment of motor symptoms in PD, due to the risk of developing serotonin syndrome.  Serotonin syndrome is characterized by fever, altered mental status, myoclonus, tremor, hyper-reflexia, and diaphoresis and may be fatal.

Apathy is present in approximately 30% of patients with PD (Kirsch-Darrow, 2006). Apathy can occur with depression and without depression.  The diagnosis of apathy without depression should be considered if no improvement is noted with standard therapy.

Clinical pearl: Apathy is poorly treated with medicines but can respond to a behavioral approach.  When apathy is severe, it can significantly limit daily ADLS. An occupational therapist or recreational therapist can help you establish a schedule, prioritize activities and set a strategy to accomplish important tasks.