This review aims to analyze the neurobiological, pathophysiological, and ethological foundations of emotional pain in non-human mammals, with particular emphasis on the transition from adaptive responses to pathological states such as animal dysthymia and Takotsubo syndrome. In the review, four conditions that can activate emotional systems will be discussed, such as pain derived from surgery or injury, stressful conditions that do not cause pain (e.g., unknown noises or smells), separation stress where an animal is isolated from the group (e.g., dam-calf separation), and death of a familiar animal or conspecific. The review will examine the role of subcortical brain regions, highlighting the amygdala-particularly the basolateral complex and central nucleus-as key integrators of negative affect and stress responses. In addition, it will address the contribution of cortical regions, such as the anterior cingulate cortex, and their interaction with the endogenous opioid system in the processing of affective suffering. The review will also incorporate evidence of thanatological behaviors and mourning-like responses, suggesting a degree of death awareness and social sensitivity to loss across multiple species. While the function of these neural circuits is fundamentally adaptive, chronic activation may induce neuroplastic changes and neurotransmitter dysregulation, leading to maladaptive outcomes. These include persistent anxiety, depression-like states, thanatological behaviors, and stress-related cardiac conditions such as Takotsubo syndrome, all of which may compromise animal welfare. Finally, further comparative research is needed to deepen our understanding of emotional pain in non-human animals.

Peroneal spastic flatfoot (PSFF) involves peroneal spasm and subtalar restriction, yet optimal conservative care is undefined. This pilot retrospective study explored the preliminary outcomes of botulinum toxin type A (BoNT-A) injection combined with rehabilitation in 19 PSFF patients (10 with structural abnormalities [SA], 9 without [NSA]). Pain (VAS), spasticity (MAS), and function (AOFAS-AH) were assessed at baseline, 1, 3, and 6 months. Significant improvements were observed across all metrics (P < 0.05). The median VAS decreased from 4 to 0, median AOFAS-AH improved from 67 to 100, and median MAS reduced from grade 4 to grade 0 at 6 months relative to baseline. In subgroup comparisons, NSA patients achieved superior outcomes, with significantly higher AOFAS-AH and lower MAS at 3 and 6 months (P < 0.05) and 100% satisfaction versus 40% in SA patients (P < 0.05). One patient experienced transient calf swelling. These exploratory findings suggest BoNT-A combined with rehabilitation may warrant further investigation as a potential conservative option for PSFF, particularly among patients without structural abnormalities. Due to the small sample size and lack of control group, these results should be interpreted as exploratory rather than confirmatory. LEVEL OF EVIDENCE: Level IV, retrospective case series.

Muscle herniation is an uncommon musculoskeletal condition that may present with non-specific lower limb symptoms and, in rare cases, result in peripheral nerve compression. We report the case of a 32-year-old woman who presented with a two-year history of progressive exertional bilateral lateral calf pain and dysesthesia initially suspected to represent neurogenic claudication. Lumbar spine magnetic resonance imaging (MRI) demonstrated no evidence of spinal canal stenosis, intervertebral disc herniation or nerve root compression. Subsequent MRI of both calves performed on a 1.5-T MRI system revealed bilateral focal fascial defects (measuring approximately 5-8 mm) within the lateral compartments with herniation of the peroneus longus muscles and associated compression of the superficial peroneal nerves at their fascial exit points. No vascular compression or alternative cause of nerve entrapment was identified. The patient underwent bilateral fasciotomy with superficial peroneal nerve decompression, resulting in complete resolution of symptoms. This case highlights an uncommon cause of bilateral exertional leg pain mimicking spinal claudication and emphasizes the importance of considering peripheral nerve entrapment secondary to muscle herniation when spinal investigations are inconclusive. MRI plays a key role in identifying fascial defects, muscle herniation and associated nerve compression, thereby facilitating appropriate surgical management.

Vascular landmarks are routinely used in ultrasound-guided regional anesthesia to aid in identifying small or difficult-to-visualize nerves. In the context of ultrasound-guided ankle blocks, well-described adjacent blood vessels assist localization of all relevant nerves except the superficial peroneal nerve, for which no consistent vascular landmark is currently described in the literature. However, in our clinical practice, we have repeatedly identified a small artery in proximity to the superficial peroneal nerve in the mid-third of the leg, aiding its identification, which we believe represents the superficial peroneal nerve accessory artery (SPNAA). In this article, we provide a brief technical report on how to locate the SPNAA adjacent to the superficial peroneal nerve.

To investigate the associations of waist circumference (WC) and calf circumference (CC) with functional performance in women with symptomatic radiographic knee osteoarthritis (OA), and to explore whether lower-leg muscle quality influences the relationship between CC and functional outcomes. This exploratory cross-sectional study included 28 women with symptomatic radiographic knee OA (Kellgren-Lawrence grades II-IV). WC and CC were measured using standardized anthropometric procedures andCC was analyzed as both raw and after correction for subcutaneous fat-thickness. Functional performance was evaluated using the 6-minute walk test (6MWT) and the 30-second chair stand test (30sCST). Lower-leg muscle quality was estimated using ultrasound echo intensity. Associations between anthropometric measures and functional outcomes were examined using Spearman correlation coefficients. Associations identified in correlation analyses were further explored using regression models to examine the potential influence of lower-leg muscle quality on the associations involving CC and to examine influence of pain intensity and radiographic severity on the associations of WC with functional performance. Greater WC was associated with poorer performance in both the 6MWT (ρ = -0.706, p = 0.001) and the 30sCST (ρ = -0.648, p = 0.001). Associations between CC and functional performance were weaker and less consistent. In the most affected limb, CC was not associated with 6MWT distance and showed a borderline association with 30sCST performance (ρ = -0.360, p = 0.060). In the contralateral limb, greater CC was inversely associated with 30sCST performance before (ρ = -0.482, p = 0.009) and after correction for subcutaneous fat thickness (ρ = -0.452, p = 0.016). These associations were no longer statistically significant after adjustment for lower-leg muscle quality. In the primary regression models, WC remained as the only significant predictor and explained 53% of the variance in 6MWT distance and 37% of the variance in 30sCST performance. Forced adjustment for pain intensity and radiographic severity produced only minimal changes in the WC coefficients. In women with symptomatic radiographic knee OA, greater WC was consistently associated with poorer functional performance, supporting its potential value as a simple anthropometric marker of functional vulnerability. CC did not behave as an indicator of better functional capacity; when associations were observed, they were inverse and appeared to be influenced by muscle quality, suggesting that CC alone may not adequately reflect functional muscle mass in this population. Larger longitudinal studies are needed to confirm these findings and clarify their clinical utility.