Apathy as a Key Symptom in Behavior Disorders: Difference Between Alzheimer’s Disease and Subcortical Vascular Dementia

There is currently no consensus on the nosological position of apathy in clinical practice. The clinical significance of negative symptoms such as apathy is increasingly recognized in neurological and psychiatric disorders, particularly those associated with frontal-subcortical dysfunction (Starkstein et al., 2008; Moretti et al., 2012). Apathy is defined as lack of motiva‐ tion as manifested by diminished goal-directed behavior, reduced goal-directed cognition, and decreased emotional engagement, a reduced interest and participation in normal pur‐ poseful behavior, problems in initiation or sustaining an activity, lack of concern or indiffer‐ ence, and a flattening of affect. The prevalence of apathy in neurodegenerative disorders, such as Parkinson’s disease vary between 16.5% and 51%, depending upon the instrument for assessment and on the samples examined. Apathy is quite common also in sVAD; differ‐ ent studies try to define its role in AD, but, even the most recent and well-conducted did not distinguish between early and advanced stages of AD, or even between AD and AD with parkinsonism (Starkstein et al., 2008; Stuss et al., 2000; Dujardin et al., 2009). It has been hy‐ pothesized that dysfunction of the nigro-striatal pathway may play an important role in the pathophysiology of apathy in neuro-degenerative disorders. In fact, apathy seems to be in‐ dependent of disease duration, disability and severity of parkinsonism, and levodopa dose in PD, indicating that the brain changes underlying apathy differ from those associated with motor symptoms. Much more interesting is that not all the PD patients become apathetic, indicating that apathy should not entirely be considered a dopamine-dependent syndrome