Chronic apathy following a major depressive episode: What is it?

Distinguishing between neurological and psychiatric disorders can be challenging, particularly when apathy serves as the primary symptom, as it is a common manifestation in both neurodegenerative diseases and mood disorders. We present a cohort of 11 patients (7 females and 4 males) aged over 50 years (mean age 61.36 ± 5.870 SD). These individuals exhibited a prolonged and isolated apathy lasting over a year, without concurrent dysthymia, but with a history of a preceding major depressive episode. This article aims to comprehensively profile these patients and to explore whether this condition represents an unconventional clinical presentation of a well-established disorder or introduces a hitherto unrecognized clinical entity. Key characteristics of this group included the following: sustained use of one or more typically effective antidepressant medications during the depressive episode prior to the onset of apathy, with no improvement of apathy during follow-up; a partial response to a single dose of zolpidem; the presence of a dysexecutive syndrome, with minimal or absent neurological signs except for mild extrapyramidal signs in a subset of patients; and the identification of mesial frontal abnormalities in neuroimaging studies (involving atrophy and/or hypoperfusion and/or hypometabolism) in eight patients. Only two patients received a neurological diagnosis during follow-up, characterized by a DAT Scan suggestive of Parkinson's disease. The underlying cause of this syndrome remains uncertain, possibly multifactorial, and yet to be determined. To advance understanding and treatment of this condition, it is imperative for neurologists and psychiatrists to be aware of and recognize this syndrome.