Depressive Pseudodementia with Reversible AD-like Brain Hypometabolism: A Case Report and a Review of the Literature

Abstract

Recent European guidelines recommend using brain FDG-PET to differentiate between Alzheimer’s disease (AD) and depressive pseudodementia (DP), with specific hypometabolism patterns across the former group, and typically normal or frontal hypometabolism in the latter. We report the case of a 74 years-old man with DP (MMSE 16/30), whose FDG-PET visual rating and semiquantitative analysis closely mimicked the typical AD pattern, showing severe hypometabolism in bilateral precuneus, parietal and temporal lobes, and sparing frontal areas, suggesting the diagnosis of moderate AD. Shortly after starting antidepressant polytherapy, he underwent formal NPS testing, which revealed moderate impairment of episodic memory and mild impairment on executive and visuospatial tests, judged consistent with neurodegenerative dementia and concomitant depression. Over the following two years, he improved dramatically: repeated NPS assessment did not show significant deficits, and FDG-PET showed restoration of cerebral metabolism. The confirmation of PET findings via semiquantitative analysis, and their reversion to normality with antidepressant treatment, proved the non-neurodegenerative origin of the initial AD-like FDG-PET abnormalities. We review similar cases and provide a comprehensive analysis of their implications, concluding that reversible FDG-PET widespread hypometabolism might represent a biomarker of pseudodementia. Therefore, we suggest caution when interpreting FDG-PET scans of depressed patients with cognitive impairment.

Pseudodementia in Patients with Unipolar and Bipolar Disorders: A Case Series and Literature Review

“…Nevertheless, those in whom hypometabolism was discovered experienced functional, behavioral, and/or cognitive impairment during follow-up, providing evidence in favor of FDG-PET’s predictive utility for early identification of cognitive decline [ 59 ]. However, hypometabolism has been previously reported in a patient with depressive pseudodementia who showed a restoration of cerebral metabolism after antidepressant treatment [ 60 ]. This suggests that hypometabolism at FDG-PET cannot be regarded as distinctive of neurodegeneration since it can also be found in patients with depressive pseudodementia.…”

Depression and Pseudodementia: Decoding the Intricate Bonds in an Italian Outpatient Setting

“…The possible correlation between cognitive impairment and the severity of the depressive episode was also investigated. This study is valuable even because, to our knowledge, the information on this topic in our country is limited to case reports, reviews, or Delphi studies [ 55 , 72 , 73 , 74 ].…”