The study followed a longitudinal A–B single-case structure, including a stable baseline (A) phase before the intervention (B). This allowed for qualitative observation of change patterns while controlling for regression to the mean and external factors (Kazdin, 2021). This idiographic single-case approach follows the renewed emphasis on the methodological value of individualized designs in cognitive neurorehabilitation (Bordón Guerra et al., 2025).

The patient was an adult who had sustained a mild acquired brain injury (ABI) approximately 1 year prior to beginning treatment. The study follows an exploratory, idiographic, qualitatively oriented single-case design. The psychotherapeutic process extended over 1 year, encompassing approximately 40 sessions. Clinical information was organized into three phases: (Cuijpers et al., 2019) baseline assessment, including neuropsychological tests and diffusion tensor imaging (DTI) tractography; (Cammisuli and Castelnuovo, 2023) intervention planning, guided by interhemispheric asymmetries and functional viability; and (Wampold and Imel, 2015) post-treatment reassessment, integrating psychometric data and qualitative clinical review. The therapeutic work was conducted in an outpatient neurorehabilitation setting under continuous clinical supervision. The overall clinical timeline of the case is summarized in Table 1.

Genetic factors and relevant family medical history were not considered variables of interest in this case, given the clinical focus on neurofunctional and psychotherapeutic processes.

Emotional functioning was assessed using the Hospital Anxiety and Depression Scale (HADS). The neuropsychological battery included the Montreal Cognitive Assessment (MoCA), WAIS-III Digit Span (forward and backward), Trail Making Test (TMT-A and TMT-B), and the Rey–Osterrieth Complex Figure (copy), applying Spanish normative data where appropriate (Peña-Casanova et al., 2009).

The patient initially showed adequate general cognitive performance but reported fatigue, attentional instability, and difficulties in emotional regulation and social interactions. Psychologically, there was a tendency toward hypervigilance, affective overcontrol, and episodic dissociation under stress.

Structural MRI and diffusion tensor imaging were performed on a Philips Achieva 1.5T scanner. Tractography reconstruction used Elements Fibertracking (Brainlab, v2.0), providing fractional anisotropy and fiber volume values for associative and commissural tracts (superior/inferior fronto-occipital fasciculi, superior/inferior longitudinal fasciculi, uncinate, cingulum, and corpus callosum).

Acquisition parameters were as follows: 128 × 128 matrix, 2 mm slice thickness, b = 1000 s/mm². The tractography was interpreted by a neuroradiologist experienced in DTI. Interhemispheric asymmetry was used as a descriptive index of relative connectivity, defined as:

where R and L represent right and left tract volumes, respectively. Asymmetries with | IAI| ≥ 0.20 were considered clinically relevant, based on structural lateralization research, the 0.20 cutoff was selected as a conservative threshold representing asymmetries exceeding typical interindividual variability (Forkel et al., 2022; Karolis et al., 2020). The evaluation of contralateral hemisphere integrity and interhemispheric balance has been highlighted as a critical factor in understanding clinical manifestations and recovery potential across various neurological conditions (Gul et al., 2024). Recent advances in personalized connectomics also highlight the importance of considering individual variability in white matter anatomy (Nozais et al., 2023).

At baseline, tractography showed globally preserved white-matter organization but with rightward asymmetries in the uncinate and superior longitudinal fasciculi (IAI ≈ +0.22 and +0.27; see Figure 1). This pattern suggested reduced efficiency of left-lateralized verbal–affective integration and greater reliance on right-hemisphere experiential and regulatory networks.

Given the rightward asymmetry in the uncinate and superior longitudinal fasciculi, interventions emphasized right-hemisphere experiential processes. Techniques derived from Acceptance and Commitment Therapy (ACT) and mindfulness approaches (Farb et al., 2013; Hayes et al., 2012) enhanced interoceptive awareness and emotional regulation, minimizing verbal–analytic load on left-hemisphere systems.

After 1 year of psychotherapy, re-evaluation indicated improvements across multiple domains: attention, working memory, cognitive flexibility, and emotional regulation. Anxiety decreased to non-clinical levels, accompanied by an adaptive increase in affective awareness. Table 1 summarizes the neuropsychological and emotional results before and after treatment.

Clinically, the patient transitioned from reactive and fragmented coping to a more regulated, self-reflective functioning. Impulsivity and physiological hyperreactivity diminished, while tolerance for affect and the capacity for self-observation increased.

No post-treatment DTI was performed, as the primary aim was to evaluate functional reorganization inferred from behavioral and psychometric changes, rather than structural modification (Goya-Maldonado et al., 2025; Menon, 2023; Perez et al., 2025).

Table 2 summarizes the pre- and post-treatment measures. Performance improved in attention, cognitive flexibility, and processing speed. The patient showed faster completion times on the Trail Making Test (A: 62 → 45 s; B: 190 → 128 s), greater balance between immediate and working memory in the WAIS-III Digit Span (forward/backward = 9/4 → 8/6), and an increase in MoCA score (25 → 28). Copy performance on the Rey–Osterrieth Complex Figure rose from the 50th to the 60th percentile, indicating better planning and visuospatial control.

Emotionally, anxiety scores on the HADS decreased from 11 to 6, shifting from a clinical to a non-clinical range, while depressive symptoms slightly increased (6 → 8), reflecting adaptive affective awareness rather than psychopathology. This change was statistically reliable according to the Reliable Change Index (RCI = −2.1; Jacobson and Truax, 1991) and is generally considered clinically meaningful in applied neuropsychological and psychotherapeutic contexts, particularly within single-case designs. Empathy measures (TECA – Understanding/Perspective-taking) rose from 36/34 to 42/40, suggesting improved mentalization and cognitive empathy. The patient’s subjective well-being rating increased from 3 to 4 (on a 1–5 scale), indicating enhanced emotional stability and clarity.

The observed improvements met established criteria for Minimal Clinically Important Differences (MCID) in several domains⁵⁵⁵. Specifically, the reduction in TMT-B completion time (32% improvement) significantly exceeds the 20%–25% threshold typically considered representative of genuine functional gain in brain injury populations, rather than mere practice effects⁶⁶⁶⁶⁶. Furthermore, the decrease in the HADS-A score (11 to 6) represents a critical clinical transition, as the patient moved from the “clinical case” range to the “non-clinical” range, falling below the standard cut-off of 8 points⁷⁷⁷⁷. The Reliable Change Index ($RCI = −2.1$) further confirms that these emotional changes are statistically robust and not attributable to measurement error.

Clinically, the patient evolved from reactive, fragmented coping to a more regulated and reflective style of self-management. Impulsivity and physiological hyperreactivity decreased, while tolerance of affect and sustained emotional ambivalence improved. The patient reported greater capacity to recognize and verbalize emotions without dissociation or avoidance.

Qualitatively, therapy facilitated the integration of bodily, emotional, and cognitive signals through attentional and experiential work. The observed functional improvements were consistent with compensatory engagement of right-hemisphere networks–particularly those implicated in experiential regulation and self-awareness (Bubb et al., 2018; Forkel et al., 2022).

No post-treatment DTI was obtained, as the study aimed to evaluate functional reorganization inferred from behavioral and psychometric change, rather than structural modification (Goya-Maldonado et al., 2025; Menon, 2023; Perez et al., 2025). The pattern of clinical recovery–reduced anxiety, enhanced cognitive flexibility, and increased affective awareness–suggests that therapeutic change may occur through optimization of pre-existing neurofunctional resources rather than through measurable anatomical plasticity.

Together, these findings support the hypothesis that psychotherapeutic effectiveness can emerge when the technical demands of treatment are functionally compatible with the patient’s available neurocognitive capacities.

From the patient’s perspective, therapy facilitated a gradual reduction in anxiety and an increased capacity to tolerate and recognize emotional experiences without avoidance or dissociation. The patient reported greater emotional clarity, improved interpersonal functioning, and a renewed sense of coherence in daily life following the injury.

Despite its clinical and conceptual value, this case report has inherent limitations. First, as an exploratory, single-case study, generalizability is intrinsically low, and causal inferences must be interpreted cautiously. While the longitudinal A–B design helps control for regression to the mean, time and non-specific factors cannot be entirely ruled out (Kazdin, 2021). Critically, although practice effects are a potential confound in longitudinal assessments, the 1-year interval between evaluations and the 32% magnitude of change in high-complexity tasks–such as the TMT-B–suggest that these gains reflect a meaningful optimization of neural resources rather than test-retest familiarity. Second, the absence of post-treatment DTI data is a methodological constraint. Although post-treatment DTI data would have strengthened the neurobiological interpretation, the primary aim of this case report was not to assess structural change, but to illustrate how baseline neurofunctional information can guide clinically meaningful psychotherapeutic decision-making. While we infer functional reorganization from psychometric and behavioral change, structural validation requires future studies featuring longitudinal imaging and functional connectivity analyses (Goya-Maldonado et al., 2025; Menon, 2023).

Furthermore, the asymmetry threshold of | IAI| ≥ 0.20 is a descriptive index that requires validation in larger clinical cohorts to establish its precise prognostic relevance. Despite these methodological constraints, context-sensitive case analyses like this are increasingly recognized as essential to neuropsychological recovery research (Allum et al., 2025). Future investigations should include randomized controlled trials to formally validate the functional compatibility construct and comparative studies to assess whether tailored interventions yield superior outcomes than standard protocols, thereby advancing the field of precision psychotherapy (McCracken, 2023; Norcross and Lambert, 2019).