Scalp Expansion Research Articles

36-year Follow-up on Scalp Reconstruction Using Free Latissimus Dorsi Muscle Flap, Skin Grafting, and Scalp Expansion.

Immediate coverage of a large area of exposed skull is the first step in reconstructing a major scalp loss. In the 1970s, the free omental flap was used for scalp reconstruction, replacing removal of the external table and skin grafting only. Introduction of flaps and expanders has revolutionized reconstruction of major scalp losses. A free muscle flap is used to cover the exposed skull. Skin graft covers the muscle flap, and next, the expanded scalp is used to restore the scalp to its original shape. In certain cases, a hair transplant could help create a more natural hairline. In this case, in 1987, a free latissimus dorsi muscle flap and skin grafting were used in a 27-year-old man with major scalp loss. The left latissimus dorsi muscle was harvested with its vascular pedicle intact. Left superficial temporal vessels were used as recipients. After complete healing of the free flap, scalp and forehead skin were expanded and used to restore the scalp to its preinjury shape. Coverage of the exposed parietal skull with free latissimus dorsi muscle flap and skin graft was successful. Then, scalp tissue surrounding the defect and forehead skin were expanded and used to restore the scalp to its original shape. This 36-year follow-up in a patient who had major scalp reconstruction using free latissimus dorsi muscle and skin grafting followed by scalp and forehead expansion shows that this method provides an excellent and reliable long-term coverage for such an injury.

Skin Expander for Scalp Reconstruction: Reappraisal of a Reconstructive Procedure for Aplasia Cutis Congenita.

Aplasia cutis congenita (ACC) is a heterogeneous group of congenital disorders characterized by the absence of epidermis, dermis, appendages, subcutaneous tissue, and bone. The aim of the study is to describe a clinical report of ACC of the scalp treated with skin expanders. In October 2019, a 16-year-old female patient underwent scalp expansion with 2 rectangular devices (150 and 250cm3; Radovan Mentor-Johnson&Johnson). The inflation started 30 days after surgery and continued once every 7 to 10 days to gain 10% of overexpansion. After 3 months, the patient underwent the second surgical step with the expanded scalp transposed to close the defect. Clinical examination 6 months after surgery revealed an acceptable cosmetic result with a hidden surgical scar and hair growth in the previous area of frontoparietal alopecia. Skin expander for the reconstruction of extensive ACC defects of the scalp is a valid procedure.

Novel strategies in scalp expansion: improvements and applications of tissue expanders.

Novel strategies in scalp expansion: improvements and applications of tissue expanders.

"Decoding a Decade: The Daring Dance of Over inflation in Tissue Expanders – Unveiling Our Unique Journey."

Background: Reconstruction of large scalp defect like post burn alopecia, post traumatic alopecia and congenital naevi require not only well-vascularized skin but also hair bearing scalp for better aesthetic outcome. Tissue expansion has always been the valuable reconstructive option in scalp reconstruction and is superior to any other option as it provides hair-bearing scalp. We have changed the traditional way of tissue expansion by using over expansion to two to three times of its recommended expansion to prevent multiple expansions. Methodology: This prospective case series was conducted from January 2013 - December 2022. Patients requiring scalp expansion for reconstruction of post burn alopecia , congenital melanotic naevi and post traumatic alopecia were included in this study. Flap advancement for covering the percentage area of the scalp defect was assessed as the outcome. Results: 13 patients were included, 6 (46%) patients required 2 expanders and 7(54%) patients required single tissue expander. Average flap advancement was 9 cm. Average tissue expansion was 650 ml, over expanded twice to thrice the recommended volume. No patient had any expander complication, wound breakdown or flap necrosis. Hair density was adequate on visual analogue scale. Conclusion: two to three times over expansion in tissue expander is valuable and safe tool for covering large area of alopecia without the need of expansion multiple times. Keywords: Tissue expansion, scalp alopecia, post burn scalp defects, congenital melanotic nevus scalp

Activating autophagy promotes skin regeneration induced by mechanical stretch during tissue expansion.

Tissue expansion, a technique in which skin regeneration is induced by mechanical stretch stimuli, is commonly used for tissue repair and reconstruction. In this study, we aimed to monitor the autophagy levels of expanded skin after the application of expansion stimuli and explore the effect of autophagy modulation on skin regeneration. A rat scalp expansion model was established to provide a stable expanded skin response to mechanical stretch. Autophagy levels at different time points (6, 12, 24, 48 and 72h after the last expansion) were detected via western blotting. The effect of autophagy regulation on skin regeneration during tissue expansion was evaluated via skin expansion efficiency assessment, western blotting, immunofluorescence staining, TUNEL staining and laser Doppler blood flow imaging. The autophagic flux reached its highest level 48h after tissue expansion. Activating autophagy by rapamycin increased the area of expanded skin as well as the thicknesses of epidermis and dermis. Furthermore, activating autophagy accelerated skin regeneration during tissue expansion by enhancing the proliferation of cells and the number of epidermal basal and hair follicle stem cells, reducing apoptosis, improving angiogenesis, and promoting collagen synthesis and growth factor secretion. Conversely, the regenerative effects were reversed when autophagy was blocked. Autophagy modulation may be a promising therapeutic strategy for improving the efficiency of tissue expansion and preventing the incidence of the complication of skin necrosis.

Macrophage contribution to the survival of transferred expanded skin flap through angiogenesis.

Despite the application of tissue expansion in the reconstruction of significant tissue defects, complications with expanded random-pattern skin flaps remain a major challenge. Insufficient angiogenesis is one of the keys factors in flap ischemia and dysfunction. Macrophages play a key role in promoting tissue angiogenesis, but their effects on expanded flap angiogenesis and the survival of the transferred skin flap are still unknown. A rat scalp expansion model was established to evaluate the dynamic changes of macrophages in expanded skin. Clodronate liposomes (Clo-lipo) were injected into the expanded scalps to deplete the macrophages, and the expanded scalp flaps with macrophage depletion were orthotopically transferred. The remaining expanded rat scalp flaps were treated with either a macrophage-colony stimulating factor (M-CSF) alone or M-CSF in combination with Clo-lipo and transferred. The number of macrophages, blood perfusion, microvascular densities (MVDs), flap survival, histological changes, and gene expression related to macrophage polarization and angiogenesis were determined with immunofluorescence (IF) staining, full-field laser perfusion imager, hematoxylin and eosin (HE) staining, and quantitative real-time polymerase chain reaction. The number of pan-macrophages significantly increased in the expanded scalp on days 14 and 21 after expander placement. The depletion rate after treatment with Clo-lipo was 29.06%, and the number of macrophages was significantly reduced in the group that underwent Clo-lipo treatment on day 14 before flap transfer (P<0.05). Macrophage depletion resulted in decreased blood perfusion, reduced MVDs, lower expression of factors, and poor survival rate. The recruitment of macrophages with a M-CSF led to higher blood perfusion, increased MVDs, greater expression of angiogenic factors, and better flap survival after flap transfer. Alternatively activated macrophages in the expanded flap could significantly promote angiogenesis, improve blood perfusion, and ultimately increase the flap survival rate. Modulating alternatively activated macrophages may provide a key therapeutic strategy to promote expanded skin flap survival. Our study has provided a basis for clinically improving random-pattern skin flap survival.

The Efficacy of Anterior Capsulotomy and Basal Capsulectomy Adherent to Expanded Scalp Flap During Alopecia Reconstruction in Pediatric Burned Patients.

Scalp expansion is an optimal treatment for alopecia resulting from burn injuries, especially in the pediatric population through providing highly vascularized adjacent local tissues with optimal hair density, color matching, texture, and hair-bearing characteristics. The aim of this study was to evaluate the efficacy of anterior capsulotomy and basal capsulectomy adherent to expanded scalp flap during alopecia reconstruction with scalp expansion in pediatric burned patients. The study was conducted on 127 patients with an age range of 5 to 19 years who presented with postburn alopecia accompanied by hairline loss. The patients were divided into 2 groups: group I consisted of 58 patients who were operated on using conventional technique, and group II consisted of 69 patients who were operated using modified technique including basal capsulectomy on the skull side and anterior capsulotomy on the expanded scalp flap. The Hairdex, a validated questionnaire of Hair-Specific Health-Related Quality of Life measures, showed that percentage of satisfaction concerning outcomes was 91.50%, psychological well-being was 95%, and self-confidence was 84.30% in group II, compared with 63%, 55.70%, and 66.20%, respectively, in group I. This significant values had a great positive effect on patient satisfaction, changing child's behavior and self-confidence. Although physiological background of tissue expansion is the same, proper flap design with anterior capsulotomy on flap undersurface and basal capsulectomy on the skull side improve results of the traditional method significantly and minimize the complication rate. These surgical modifications provide maximum benefits from expanded tissue, with restoration of the hairline and a uniform hair direction. Level III, case-control study.

Scalp reconstruction by tissue expansion: tips and tricks.

Numerous details regarding preoperative planning of scalp expansion are of the utmost importance for maximizing the results of this procedure. The purpose of this paper is to describe the tips and tricks useful for obtaining the best results in scalp expansion. Basic concepts and operative technique are discussed and detailed. In scalp reconstruction, the use of tissue expansion allows to obtain successful results, Anyhow, it is mandatory to follow some basic rules, dictated by anatomical, technical, and psychological considerations.

Reconstruction of Facial Multiunit Defects Using Expanded Scalp Flap with Laser Depilation in a Group of Predominantly Pediatric Patients.

Background: The cervical or thoracic region is currently the main donor site for repair of facial multiunit defects (FMUDs); however, its extensive clinical utilization encompasses the need for flap prefabrication and microsurgical techniques. Objective: To illuminate the feasibility of treating FMUD with expanded scalp flaps and laser depilation. Methods: From 2016 to 2020, 17 patients with facial giant congenital melanocytic nevi (GCMN) underwent scalp expansion for FMUD reconstruction. A three-stage surgical treatment plan was attempted and laser depilation was scheduled during the expansion period and postrepair surgeries. Results: All the flaps survived successfully and were able to cover the entire facial defect. The average three-stage treatment time was 4.5 ± 1.3 months. The defect sites included the forehead, nose, cheek, temporal, and eye areas. The maximum defect area was 9 × 30 cm. The average number of laser treatments was 4.6 ± 2.9 times. The average treatment period was 26.8 months. Sixteen patients (94.1%) reported satisfactory outcome. Conclusion: Expanded scalp flap combined with laser depilation is feasible for FMUD repair and warrants further investigation. Clinical Trail Registration Information: Translational Medicine Ethics Review Committee, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine (SH9H-2021-T144-3).

Extended Scalp Expansion for Larger Defects During Staged Cranioplasty.

Secondary cranioplasty is often required following trauma, infection, radiation, or oncologic care, but is complicated by soft-tissue deficits with limited regional options. Scalp tissue expanders can provide hair-bearing, vascularized tissue for tension- free closure yielding optimal aesthetic results. However, the upper limit of safe scalp expansion has not been explored. This study sought to evaluate the efficacy of extended scalp tissue expansion for challenging cranioplasties in a consecutive series. Patients who underwent scalp tissue expansion before cranioplasty were retrospectively identified from a single institution between the years 2017 and 2020. Patient demographics, tissue expansion characteristics, and complications during expansion and after cranioplasty were collected. Six patients were identified who underwent staged scalp expansion for cranioplasty; 5 were male (83.3%) with a mean age of 43.8 ± 12.5 years. Indications for cranioplasty included 2 epilepsy- related procedures, 1 oligodendroglioma, 2 infectious processes, and 1 traumatic incident. A single expander was used in 5 cases, whereas 2 were used in the remaining case. The average expander fill volume was 434.3 ± 115 ccs with a mean expansion time of 3.3 ± 1.4 months. Expander infection occurred in 1 case and expander exposure in another, but adequate scalp expansion was still achieved in both. Successful closure over cranioplasty was obtained in 5 cases (83.3%); 1 patient ultimately required free flap reconstruction for soft-tissue coverage. In cases of extended scalp defects, scalp tissue expansion remains the preferred method for recruiting large quantities of like tissue before implant cranioplasty.

Post-operative Helmet Therapy in Patients with Unilateral Coronal Craniosynostosis

Statement of the problemOut of all the synostotic corrective surgeries, fronto-orbital advancement and cranial vault remodeling for patients with unilateral coronal synostosis is 1 of the hardest to maintain ideal correction without relapse.1,2 Over the course of 20 years operating on these patients, the senior author (MMU) has made multiple adjustments to compensate for this relapse, including overcorrection on the affected side, superior orbital rim grafting, additional points of fixation, periosteal release, and scalp expansion with galeal scoring to minimize tension of the closure. As a result of these interventions, researchers have seen a positive increase of on-table results. However, the researchers have continued to note relapse postoperatively. As such, MMU has started to implement postoperative helmet therapy (PHT) to help maintain the surgical correction, improve brachycephaly, and increase overall symmetry. Methods and materialsAn IRB-approved retrospective review of all patients who underwent FOA and CRV followed by PHT for isolated unilateral nonsyndromic coronal synostosis at an institution between April 2017 and April 2020 was performed. Patients with insufficient data, significant deformational plagiocephaly, and multi-suture craniosynostosis and those not treated at Cranial Technologies (Pasadena, CA) for PHT were excluded for consistency of measurements and outcomes. Data collected included age at surgery, age at helmet initiation, follow-up duration, and PHT duration. Anthropometric measurements were performed using a proprietary machine learning application (Landmarks3D, Cranial Technologies, Tempe, AZ). Anthropometric data were collected, including cranial index and cranial vault asymmetry index (CVAI) at initiation (int) of helmet therapy and at termination (final) of helmet therapy. ResultsEleven patients (4 male, 7 female) meeting criteria were treated in the studied time period. Six patients had right UCS and 5 patients had left UCS. The median age at surgery was 8.5 months (range 7 to 11). The median time from surgery to initiating helmet therapy after fittings and swelling reduction was 1.56 months (range 0.65 to 3.35). The median duration of PHT was 5.4 months (range 4.1 to 9.8). The mean CI int was 92.67 (SD 2.54). The mean CI final was 87.41 (SD 4.16). The mean CVAI int was 4.80 (SD 1.29). The mean CVAI final was 3.13 (SD 1.40). Outcomes dataIn patients with unilateral coronal synostosis, postoperative helmet therapy can minimize the amount of relapse often observed in this condition. ConclusionPostoperative helmet therapy for patients with unilateral coronal synostosis is a reasonable low-risk complement to fronto-orbital advancement and cranial vault remolding. Clinically, PHT appears to help minimize relapse and improve overall head symmetry. Further investigation and increased patient enrollment are required to determine the true benefits of PHT in this patient population.

Transcriptome Profiling Reveals Important Transcription Factors and Biological Processes in Skin Regeneration Mediated by Mechanical Stretch.

Background: Mechanical stretch is utilized to promote skin regeneration during tissue expansion for reconstructive surgery. Although mechanical stretch induces characteristic morphological changes in the skin, the biological processes and molecular mechanisms involved in mechanically induced skin regeneration are not well elucidated. Methods: A male rat scalp expansion model was established and the important biological processes related to mechanical stretch-induced skin regeneration were identified using Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and gene set enrichment analysis (GSEA). Analysis was also conducted by constructing a protein–protein interaction (PPI) network, identifying key modules and hub genes, determining transcription factor (TF)-mRNA regulatory relationships, and confirming the expression pattern of the TFs and hub genes. Results: We identified nine robust hub genes (CXCL1, NEB, ACTN3, MYOZ1, ACTA1, TNNT3, PYGM, AMPD1, and CKM) that may serve as key molecules in skin growth. These genes were determined to be involved in several important biological processes, including keratinocyte differentiation, cytoskeleton reorganization, chemokine signaling pathway, glycogen metabolism, and voltage-gated ion channel activity. The potentially significant pathways, including the glucagon signaling pathway, the Wnt signaling pathway, and cytokine–cytokine receptor interaction, were distinguished. In addition, we identified six TFs (LEF1, TCF7, HMGA1, TFAP2C, FOSL1, and ELF5) and constructed regulatory TF–mRNA interaction networks. Conclusion: This study generated a comprehensive overview of the gene networks underlying mechanically induced skin regeneration. The functions of these key genes and the pathways in which they participate may reveal new aspects of skin regeneration under mechanical strain. Furthermore, the identified TF regulators can be used as potential candidates for clinical therapeutics for skin pretreatment before reconstructive surgery.

Postoperative helmet therapy following fronto-orbital advancement and cranial vault remodeling in patients with unilateral coronal synostosis.

Out of all the synostotic corrective surgeries, fronto-orbital advancement and cranial vault remodeling for patients with unilateral coronal synostosis is one of the hardest to maintain symmetric and proportional correction without some amount of relapse. Over the course of 20 years operating on these patients, the senior author has made multiple adjustments to compensate for relapse asymmetry, including overcorrection on the affected side, increased points of fixation, periosteal release, and scalp expansion with galeal scoring to minimize tension of the closure. As a result of these interventions, we have seen improved immediate results following surgery. However, we have continued to note clinically significant relapse postoperatively. As such, we have started to implement postoperative helmet therapy (PHT) to help maintain the surgical correction, improve secondary brachycephaly, and increase overall symmetry. PHT is a reasonable low-risk complement to fronto-orbital advancement and cranial vault remolding. Clinically, PHT appears to help minimize relapse and improve overall head symmetry. Further investigation and increased patient enrollment are required to determine the true benefits of PHT in this patient population.

Follicular Unit Transplantation Versus Scalp Expansion in Management of Secondary Cicatricial Alopecia

Background: The bad impact of cicatricial alopecia amongpopulation leads to increase the desire of correcting that typeof hair loss. There are many methods of hair restoration, butthe efficacy of each, its indications and the possible hazardshasn't yet been clearly identified.Objective: To evaluate the use of two different techniquesfor hair restoration in patients with secondary cicatricialalopecia. Either using follicular unit extraction (FUE) or scalp expanders (SE) to correct the deformity depending upon manyfactors (Inclusion & Exclusion criteria). Indications, operativetime, Aesthetic outcome and complications are to be discussed.Patients and Methods: This study included 30 patientswho were grouped into two populations. The first one (Group A) those who underwent FUE included 13 cases while thesecond group was SE (Group B) included 17. All of themwere suffering from secondary cicatricial alopecia and theywere grouped according to the surface area of the alopecia.Results: The mean value of the surface area of alopeciawas significantly larger in the SE group than FUE group witha p-value <0.001. Post-operative recovery was nearly similarapart from being faster gain in group B and better hair density.Conclusion: In management of secondary cicatricialalopecia, many factors affect surgical planning. Both FUEand SE are very useful tools in managing those patients whenproperly selected and tailored to the patient

Early histological and ultrastructural changes in expanded murine scalp

ABSTRACT Tissue expansion has been widely used for plastic, reconstructive, and esthetic surgeries. A mouse scalp expansion model can effectively mimic the characteristics of human skin expansion. However, a detailed study of the histological features and ultrastructural characteristics of expanded scalp is lacking, especially early ultrastructural changes. Here, a mouse scalp expansion model was established and the expanded scalp samples were obtained on day 2 (group I) and 4 (group II) post final injection. Histological analysis revealed epidermal thickening, dermal thinning, subcutaneous fat thinning, and capsule formation in the expanded samples. Ultrastructural evaluation showed the presence of keratinocytes with numerous tonofibrils and damaged mitochondria, and several ruptured collagen fibers and increased number of active fibroblasts and myofibroblasts were observed in the dermis and capsules. Adipocyte dedifferentiation was detected in the expanded samples of both groups, but formation of autophagosomes was only detected in the dermal fibroblasts of group I. Thus, early changes in expanded tissue should be carefully monitored, as it may help avoid dermal thinning and promote expanded tissue regeneration.

Autologus Hair Transplantation Vs Skin Expansion in Management of Cicatricial Alopecia; A Comparative Study

Background: The bad impact of cicatricial alopecia among population lead to increase the desire of correction of that type of hair loss. Although, there are many methods of hair restoration but the efficacy of each, indications and possible hazards has not yet been clearly identified. Objective: To compare between hair transplantation using follicular unit extraction and skin expansion surgeries in the field of hair restoration in secondary cicatricial alopecia regarding aesthetic outcome, operative duration, optimum patient selection and complications of both techniques. Subjects and methods: Twenty four patients suffering from alopecia were involved in this study 15 males (62.5%) and 9 females (37.5%). Patient’s age ranged from 7 to 26 years old. Patients were divided into two groups according to the procedure done. Group (A) 12 patients done hair transplantation surgeries. Group (B) 12 patients done scalp expansion surgeries. Results: There was a non-significant difference between both groups regarding the mean age or the mean operation duration (P > 0.05). The mean values of the surface area of alopecia, in tissue expander group (B) was significantly larger than that of hair transplantation in group (A) (P < 0.001). However the time since exposure to the causative injury was significantly longer in group (A) than that of group (B) (P < 0.01). Hair transplantation tends to have less recovery time highly indicated in adults with smaller non-dependent areas of alopecia, while expanders with long recovery period solve bigger problems of alopecia in younger patients. Conclusion: Multiple factors interfere with the surgical plan age, gender, occupation, size and site of alopecia and time since injury. Both hair transplantation and skin expansion are very useful in the field of cicatricial alopecia treatment. While hair transplantation has less hazards during anesthesia, less post-operative scars and less recovery time, skin expansion is a good solution for bigger problems like big area of alopecia or younger patients.

Tissue expansion in operated cases of transposition flap of scalp for correction of donor site alopecia and patient’s satisfaction

Background: Scalp defects managed by local transposition flaps with donor site alopecia are aesthetically not acceptable to patients. Scalp expansion with tissue expanders is needed for proper correction of this deformity.Methods: Authors retrospectively reviewed all cases of post traumatic and post burn scalp defects that were managed initially by local transposition flap and later by scalp expansion by tissue expanders at our institute over a period of 5 years and conducted an outcome survey. Authors’ institutional protocol in such patients and results of the review are presented.Results: Twenty-eight patients were included in the study. Eight patients had post traumatic and 20 cases had post electric burn scalp defect. The mean age of patients was 28.92±8.26 years. Thirty-eight tissue expanders of various sizes (200-600 ml) were used in 28 patients. The mean follow-up time was 9.07±1.92 months. Major complication rate in present study was 2.63%. Results of outcome survey revealed more than 90% patients were satisfied after third surgery.Conclusions: Scalp transposition flap donor site alopecia can be easily corrected by tissue expansion. The complications are not severe and can be managed easily. It should be offered to all such types of patients, as it leads to proper social rehabilitation and satisfaction among these groups of patients.

Application of soft tissue expander in plastic reconstruction of head

Objective To explore the timing of surgical operation and surgical incision for the treatment of head of electrical injury and scarred alopecia with soft tissue expander. Methods Twenty-three patients with high tension electrical injury and scarred alopecia were collected, the soft tissue expander was used to repair the wound and scar area.Selected the expander to embed the incision: patients with scarred alopecia were selected to be near the hair area in the scar; high tension electrical injury in patients with incision location selection based on the time of injury and wound repair requirements vary; within 5 days after injury, surgery incision can be selected from the wound about 2-3cm; more than 5 days after injury, the patients chose to stay away from the wound incision, incision about 4-5cm. Results Of 23 patients, postoperative scalp expansion flap good blood supply, a period to solve the high tension electrical injury caused by skull necrosis and scarred alopecia problems.The patients according to the wound debridement and repair requirements using different surgical incision for dilator implantation, wound and flap infection, dilated flap poor blood supply, necrosis, dilator exposed and other issues did not occur after surgery. Conclusion Flexible use of expander embedded surgical incision can be more effectively adapted to the wound repair requirements, timely reduction of implantation expander surgery when the difficulty of stripping, shorten the operation time, the maximum possible protection of healthy scalp tissue, and eventually get a satisfactory clinical cosmetic repair effect. Key words: Tissue expansion device; Electric injuries; Alopecia; Reconstructive surgical procedures

Heart-Brain Interactions in the MR Environment: Characterization of the Ballistocardiogram in EEG Signals Collected During Simultaneous fMRI.

The ballistocardiographic (BCG) artifact is linked to cardiac activity and occurs in electroencephalographic (EEG) recordings acquired inside the magnetic resonance (MR) environment. Its variability in terms of amplitude, waveform shape and spatial distribution over subject's scalp makes its attenuation a challenging task. In this study, we aimed to provide a detailed characterization of the BCG properties, including its temporal dependency on cardiac events and its spatio-temporal dynamics. To this end, we used high-density EEG data acquired during simultaneous functional MR imaging in six healthy volunteers. First, we investigated the relationship between cardiac activity and BCG occurrences in the EEG recordings. We observed large variability in the delay between ECG and subsequent BCG events (ECG-BCG delay) across subjects and non-negligible epoch-by-epoch variations at the single subject level. The inspection of spatial-temporal variations revealed a prominent non-stationarity of the BCG signal. We identified five main BCG waves, which were common across subjects. Principal component analysis revealed two spatially distinct patterns to explain most of the variance (85% in total). These components are possibly related to head rotation and pulse-driven scalp expansion, respectively. Our results may inspire the development of novel, more effective methods for the removal of the BCG, capable of isolating and attenuating artifact occurrences while preserving true neuronal activity.

Scalp expansion: Surgical considerations and possible future directions.

Introduction:Repairing large scalp defects has always been a difficult task for plastic surgeons. This is because the requirements of such procedures are two-fold: sufficient soft-tissue coverage is required, and to obtain a satisfactory aesthetic outcome, a sufficient number of covering hairs should be ideally provided.Materials and Methods:Based on the author's experience in this repair technique over a 20-year period, this article presents some technical details of scalp expansion, surgical refinements and possible directions for further technical advancement.Results:Data and details on relevant scalp anatomy, expander choice, expander placement, subgaleal undermining, galeotomies and acute scalp expansion are provided.Conclusions:The author hopes that the above-mentioned details may be of some utility in the complex field of scalp expansion.