Apparent Brain Atrophy in Anorexia Nervosa: Diagnostic Insights from Cross-Sectional Brain CT Imaging

 

Apparent Brain Atrophy in Anorexia Nervosa

Introduction

Apparent brain atrophy, or pseudoatrophy, is a significant yet underrecognized phenomenon in adolescent neuroimaging, particularly among patients with severe weight loss, such as those with anorexia nervosa (AN). Characterized by an apparent reduction in brain volume without actual neuronal loss, pseudoatrophy mimics irreversible cortical atrophy, leading to potential diagnostic dilemmas. This column examines a representative brain CT scan from a 14-year-old girl with suspected AN-induced pseudoatrophy and discusses key differentiating features, clinical implications, and the potential for reversibility.

Case Overview and Imaging Findings

A 14-year-old female patient underwent a cross-sectional brain CT revealing:

• Prominent cerebral sulci bilaterally

• Dilated cerebrospinal fluid (CSF) spaces

• Apparent brain volume reduction is inconsistent with her age

• No evidence of traumatic or degenerative lesions

These features suggest pseudoatrophy likely induced by prolonged malnutrition secondary to anorexia nervosa. Notably, the Evans index was mildly increased, indicating ventricular dilation—a hallmark of generalized cerebral atrophy. Yet, the diagnosis of irreversible cortical atrophy remains uncertain without follow-up imaging after nutritional rehabilitation.

Pathophysiology of Pseudoatrophy in Anorexia Nervosa

Pseudoatrophy arises primarily from volume shifts, mainly due to reduced water content and tissue dehydration, rather than true neurodegeneration. In AN, starvation-induced catabolism affects glial volume and extracellular fluid balance, leading to transient cerebral volume loss. Unlike irreversible atrophy, which reflects axonal degeneration and neuronal death (e.g., in Alzheimer's or traumatic brain injury), pseudoatrophy may resolve with rehydration and nutritional repletion.

Key Differentiating Factors:

Feature	Pseudoatrophy	Irreversible Atrophy
Onset	Rapid (weeks–months)	Gradual (months–years)
Etiology	Nutritional, hormonal	Neurodegeneration, trauma
Imaging	Enlarged sulci/ventricles	Similar findings
Reversibility	Yes (with weight gain)	No
Clinical relevance	May not correlate with cognition	Usually correlates with dysfunction

Evans Index as a Quantitative Marker

The Evans index, defined as the ratio of the maximal width of the frontal horns to the maximum internal diameter of the skull, is an objective metric. In this case, the index measured >0.25, suggesting moderate ventricular enlargement. Post-treatment scans in similar cases showed normalization of this index, confirming the reversible nature of atrophy.

Clinical Implications

Recognizing pseudoatrophy is crucial for clinicians and radiologists:

1. Avoids misdiagnosis of irreversible conditions like dementia

2. Encourages early nutritional rehabilitation

3. Helps track treatment response via serial imaging

4. Prevents unnecessary pharmacologic interventions

Conclusion

Apparent cerebral atrophy in young patients with anorexia nervosa represents a potentially reversible phenomenon tied to malnutrition and dehydration. Differentiation from true cortical atrophy requires thorough history-taking and longitudinal imaging. Early intervention can lead to complete structural and functional recovery.

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References

1. Swayze VW, Anderson J, Arndt S, et al. Brain tissue volume segmentation in patients with anorexia nervosa before and after weight gain. Am J Psychiatry. 2003;160(1):132-134. https://doi.org/10.1176/appi.ajp.160.1.132

2. Katzman DK, Lambe EK, Mikulis DJ, et al. Cerebral gray matter and white matter reductions in adolescents with anorexia nervosa: A longitudinal magnetic resonance imaging study. Biol Psychiatry. 1997;42(8):633-639. https://doi.org/10.1016/S0006-3223(96)00476-X

3. Frank GK, Shott ME, Hagman JO, Mittal VA. Alterations in brain structures related to taste reward circuitry in ill and recovered anorexia nervosa. Am J Psychiatry. 2013;170(10):1152-1160. https://doi.org/10.1176/appi.ajp.2013.12101294

4. Sone D, Sato N, Ota M, Kanai C, Yokoyama K. Reversible brain atrophy and cognitive impairment in Cushing syndrome. Neuropsychiatr Dis Treat. 2014;10:1743–1746. https://doi.org/10.2147/NDT.S70611

5. Seitz J, Buhren K, von Polier GG, et al. Morphological changes in the brain of acutely ill and weight-recovered patients with anorexia nervosa: A meta-analysis and qualitative review. Z Kinder Jugendpsychiatr Psychother. 2014;42(1):7-17. https://doi.org/10.1024/1422-4917/a000270

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Quiz

1. What is the primary mechanism behind pseudoatrophy observed in anorexia nervosa?

A. Neuronal apoptosis
B. Axonal degeneration
C. Tissue dehydration and glial volume reduction
D. Cortical demyelination

Explanation: Pseudoatrophy reflects an apparent decrease in brain volume, primarily due to reversible fluid loss and reduction in glial cell volume, not true neuronal loss.

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2. Which of the following statements about the Evans index is TRUE?

A. A value below 0.20 is diagnostic for atrophy
B. It measures the ratio between the lateral ventricle and the brainstem diameter
C. It is used to assess the severity of hydrocephalus and atrophy
D. It is not useful in adolescent patients

Explanation: The Evans index is commonly used to measure ventricular enlargement and assess both hydrocephalus and cerebral atrophy. A value >0.3 may indicate significant atrophy or hydrocephalus.