## 2 Results  
A total of 2049 records resulted from searching the databases and registers. After the duplicates were removed, 1519 remained for title and abstract review, including 142 records identified by manual screening of references. Following the full-text review of 111 documents, 22 articles were included [13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34]. The full [PERSON] report is displayed in Supplementary File S1. A full list of citations that were excluded is available upon request.  
We did not include in our review 89 records requiring adjudication regarding eligibility, and the reasons for exclusion were listed and are also available upon request. Of these, we have tried to contact the authors of five studies for more information regarding the location of chronic lesions and/or BoNT intervention [35; 36; 37; 38; 39], and one study using a model of hypertrophic scarring that did not report whether BoNT was administered into the wound or an established hypertrophic scar [40]. Only one author replied to confirm that the \"rosacea-like inflammation\" model was established below the head and neck [36], and hence all six studies were excluded (Supplementary File S2, Table S1). The selection process is illustrated in the PRISMA Flow Diagram (Figure 1) [41].  
Figure 1: PRISMA 2020 flow diagram for new systematic reviews which included searches of databases, registers, and other sources [41]. * Articles Recovered for further assessment [18] ** Articles requiring adjudication regarding eligibility; *** Protocol for missing information (contact 1 st attempt 28 February 2024; 2 nd attempt 11 March 2024; 3 rd attempt 26 March 2024) [35; 36; 37; 38; 39; 40].  
The Supplementary File S3, Table S2 provides full methodological detail regarding the included records. Table 1 shows the summary of the characteristics of the 22 included studies. These were published between 2009 and 2023. Sample sizes ranged from 12 to 525, with nine studies not providing a clear study sample [15; 18; 21; 23; 24; 26; 29; 31; 32]. Only inferior animals were used for the experiments and there were variations in terms of species, weight, and age. Among the 22 studies, male animals represented the majority, only three studies used female animals [19; 27; 30], and one study did not specify this variable [25]. Studies also reported different timing and routes of BoNT administration, as well as variations in models for induction of diseases in animals. Overall, nine studies focused on disease models of trigeminal neuralgia [14; 17; 20; 23; 26; 28; 29; 31; 32], four studies explored scenarios of temporomandibular joint (TMJ) arthritis such as TMJ osteoarthritis (\(n=1\)) [13], and TMJ rheumatoid arthritis (\(n=3\)) [15; 16; 22], three records described experiments on depression [18; 21; 24], including one in major depressive disorder (MDD) [24], two articles reported on hypertrophic scar settings [25; 30], while migraine [19], atopic dermatitis [27], anxiety [34], and chronic dry skin itch conditions were each discussed in one article [33]. The most commonly reported animal species were Sprague Dawley rats (\(n=8\)) and Wistar rats (\(n=5\)). The specific instant in time for the measurement of the biomarker used in each study ranged from 30 min to 60 days following the administration of BoNT. Biological sampling locations included rostral dorsal skin, serum (retro orbital plexus), ear scar tissues, (periarticular) TMJ tissues, trigeminal ganglia (TG), TG sensory neurons, TG mandibular V3 division and boundary area, trigeminal (sub)nucleus caudalis (TNC), jugular plasma and medulla oblongata containing TNC, brainstem Vc region (caudal subnucleus of the spinal trigeminal nucleus), substantia nigra pars compacta, ventrolateral periaqueductal gray, hippocampus, hypothalamus, prefrontal cortex, amygdala, dura mater, cranial dura plasma protein complexes, dorsal root ganglia, medullary dorsal horn, and cerebrospinal fluid sampling.