Frontal lobe syndromes: a neuropsychiatric review of clinical phenotypes, neurocircuitry, and differential diagnosis

Introduction / Objectives

Frontal lobe syndrome (FLS) encompasses a diverse array of cognitive, behavioural, and emotional impairments resulting from structural or functional disruption of the prefrontal cortex and its subcortical connections. Historically viewed through a vague topographical lens, contemporary neuropsychiatry has shifted toward a circuit-based paradigm, defining FLS through the disruption of specific frontal-subcortical networks [1, 2]. The primary objective of this narrative review was to synthesise the functional neuroanatomy, clinical phenotypes, and differential diagnosis of prefrontal syndromes, with the aim of enhancing diagnostic accuracy in psychiatric clinical practice.

Methods

A narrative review was conducted using PubMed with Medical Subject Headings (MeSH) terms including Frontal Lobe, Prefrontal Cortex, Executive Function, Frontotemporal Dementia, Neuropsychiatric Disorders, and Differential Diagnosis. Articles published from inception to December 2025 were selected based on clinical and scientific relevance, covering neuroanatomical, phenomenological, diagnostic, and therapeutic dimensions of FLS.

Results

The circuit-based paradigm has major implications for neuropsychiatric practice, as symptoms traditionally attributed to cortical pathology may arise from lesions in the basal ganglia, thalamus, or connecting white matter tracts, regardless of cortical integrity [3]. Disruption within these networks produces three primary clinical sub-syndromes: a dysexecutive syndrome (dorsolateral prefrontal circuit), characterised by cognitive rigidity, impaired working memory, and poor task organisation; a disinhibited syndrome (orbitofrontal circuit), featuring impulsivity, emotional lability, and loss of social decorum – often mimicking acquired psychopathy; and an apathetic/amotivational syndrome (anterior cingulate circuit), marked by abulia and, in severe bilateral cases, akinetic mutism [3, 4]. White matter integrity, particularly of the uncinate fasciculus and cingulum bundle, is essential for functional output; its degeneration produces disconnection syndromes clinically indistinguishable from cortical FLS [5]. Etiologically, FLS arises from traumatic brain injury, cerebrovascular disease, and neurodegenerative conditions, most notably behavioural variant frontotemporal dementia (bvFTD). Standard screening tools such as the Mini-Mental State Examination are frequently insensitive to early FLS, necessitating targeted neuropsychological batteries and advanced neuroimaging, particularly FDG-PET [5]. Differentiating FLS from primary psychiatric disorders, including major depression, bipolar disorder, antisocial personality disorder, and adult ADHD, represents the central clinical challenge, as symptom overlap is substantial and misclassification carries serious therapeutic and forensic consequences [3, 4]. Key distinguishing features include the trajectory of symptom onset, the qualitative distinction between apathy and depressive affect, and the absence of a premorbid personality deviation.

Discussion / Conclusion

FLS sits at the complex intersection of neurology and psychiatry. Transitioning from a lobar to a circuit-based model enables a more sophisticated interpretation of neurobehavioural symptoms. Prioritising detailed clinical history, mandatory informant corroboration, and targeted executive function assessment is paramount to accurately differentiating FLS from primary psychiatric conditions is essential. This distinction is critical to avoid iatrogenic harm from inappropriate psychotropic medications, significantly reduce caregiver burden, and facilitate the timely introduction of multidisciplinary, non-pharmacological management strategies and emerging disease-modifying therapies [5]. As molecular biomarkers and disease-modifying therapies continue to emerge, early circuit-level diagnosis will become the standard of care.

References

1. Krudop, W. A., & Pijnenburg, Y. A. (2015). Historical evolution of the frontal lobe syndrome. Psychopathology, 48(4), 222–229.
2. DeRight J. (2019). History of “Frontal” Syndromes and Executive Dysfunction. Frontiers of neurology and neuroscience, 44, 100–107.
3. Pirau, L., & Lui, F. (2023). Frontal Lobe Syndrome. In StatPearls. StatPearls Publishing.
4. Falchi, Diego. 2022. “Frontal Lobe Syndrome: A Mini Review”. Journal of Clinical Trials and Experimental Investigations 1 (3). Turkey:71-74.
5. Henri-Bhargava, A., Stuss, D. T., & Freedman, M. (2018). Clinical Assessment of Prefrontal Lobe Functions. Continuum (Minneapolis, Minn.), 24(3, BEHAVIORAL NEUROLOGY AND PSYCHIATRY), 704–726.