Seeding the Electrothermal Instability through a Three-Dimensional, Nonlinear Perturbation

Electrothermal instability plays an important role in applications of current-driven metal, creating striations (which seed the magneto-Rayleigh-Taylor instability) and filaments (which provide a more rapid path to plasma formation). However, the initial formation of both structures is not well understood. Simulations show for the first time how a commonly occurring isolated defect transforms into the larger striation and filament, through a feedback loop connecting current and electrical conductivity. Simulations have been experimentally validated using defect-driven self-emission patterns.

Three-dimensional feedback processes in current-driven metal

Using three-dimensional (3D) magnetohydrodynamic simulations, we study how a pit on a metal surface evolves when driven by intense electrical current density j. Redistribution of j around the pit initiates a feedback loop: j both reacts to and alters the electrical conductivity σ, through Joule heating and hydrodynamic expansion, so that j and σ are constantly in flux. Thus, the pit transforms into larger striation and filament structures predicted by the electrothermal instability theory. Both structures are important in applications of current-driven metal: The striation constitutes a density perturbation that can seed the magneto-Rayleigh-Taylor instability, while the filament provides a more rapid path to plasma formation, through 3D j redistribution. Simulations predict distinctive self-emission patterns, thus allowing for experimental observation and comparison.

Visual Impact of Large and Giant Congenital Naevi: Comparison of Surgical Scars with Naevi Before Surgery

Surgical attempts to remove large/giant congenital melanocytic naevi (LGCMN) are supported mainly by the theoretical improvement in patients’ self-image; however such surgery can result in unaesthetic scarring. We hypothesize that difference in appearance itself has an impact, and hence surgery cannot negate this impact. The aim of this cross-sectional study was to explore how LGCMN and scarring are perceived by non-affected people. We surveyed the visual impact on 1,015 health and non-health professionals working in a university hospital. Participants were assigned to 1 of 3 surveys, which, based on photographs of children: (i) assessed the visual impact of LGCMN; (ii) the visual impact of scarring; (iii) compared the impact of LGCMN and scarring. Feelings and perceptions evoked by images of children, either with LGCMN or with scarring, were remarkably similar. However, when the images of the same child (with LGCMN or scarring) were shown together, respondents showed significantly increased preference for scarring.

Novel response to neoadjuvant anti-PD1 therapy for a patient with retrocaval melanotic schwannoma

Melanotic schwannoma is a rare nerve sheath tumor composed of melanin-producing Schwann cells with the potential for metastasis. These tumors can be associated with familial tumor syndromes and can cause significant symptoms related to nerve compression and mass effect. Due to the rarity of these lesions, they can be initially misidentified as melanocytomas, pigmented dermatofibrosarcoma protuberans, neurofibromas or malignant melanomas. Surgical excision is the mainstay of treatment with limited benefit from adjuvant systemic chemotherapy or radiation. Modern treatments with immune checkpoint blockade have demonstrated significant improvements in progression-free and overall survival for a variety of cancer histologies; however, anti-PD1 therapy has yet to be evaluated in patients with melanotic schwannoma. This report demonstrates a significant improvement in symptomatology and tumor stability with neoadjuvant anti-PD1 therapy for a retrocaval melanotic schwannoma initially masquerading as malignant melanoma. This report demonstrates the potential benefit of a novel therapeutic option for patients with melanotic schwannoma.

Experimental observation of the stratified electrothermal instability on aluminum with thickness greater than a skin depth

A direct observation of the stratified electrothermal instability on the surface of thick metal is reported. Aluminum rods coated with 70μm Parylene-N were driven to 1 MA in 100ns, with the metal thicker than the skin depth. The dielectric coating suppressed plasma formation, enabling persistent observation of discrete azimuthally correlated stratified thermal perturbations perpendicular to the current whose wave numbers, k, grew exponentially with rate γ(k)=0.06ns^{-1}-(0.4ns^{-1}μm^{2}rad^{-2})k^{2} in ∼1g/cm^{3}, ∼7000K aluminum.

Chronic Glaucoma in Dogs: Relationships Between Histologic Lesions and the Gonioscopic Diagnosis of Pectinate Ligament Dysplasia

Pectinate ligament dysplasia (PLD) is a common cause of canine glaucoma and the definitive clinical diagnosis is based on gonioscopy. Although the histologic lesions of PLD have been described, it has not been determined whether these changes are specific for PLD or if similar histologic changes can develop as a consequence of secondary glaucoma. The filtration angles of 61 enucleated canine globes with chronic glaucoma were evaluated with light microscopy by 3 examiners who were masked to the clinical history, signalment, and gonioscopic results. A histologic diagnosis of PLD versus non-PLD was determined by each examiner based on previously reported morphologic criteria and compared with the clinical gonioscopic diagnosis. Of the 61 enucleated glaucomatous eyes, 40 were clinically diagnosed with PLD. For all 3 examiners, a histologic diagnosis of PLD corresponded poorly with the clinical diagnosis of PLD (range of kappa score: 0.149-0.269; range of AUC: 0.592-0.621). There was no difference between examiners in their ability to correctly diagnose PLD histologically (P = .978). A fair degree of agreement was noted among examiners in obtaining their suspected histologic diagnosis of PLD (kappa score 0.256). No individual or sets of histologic ICA features were consistent with clinical PLD. The results indicate the histologic ICA changes proposed to be characteristic of PLD are also noted in canine globes affected with chronic secondary glaucoma. Therefore, using routine histologic evaluation, a histologic diagnosis of PLD is not possible in the face of chronic canine glaucoma.

Nevospheres from neurocutaneous melanocytosis cells show reduced viability when treated with specific inhibitors of NRAS signaling pathway

BACKGROUND

Neurocutaneous melanocytosis (NCM) is characterized by clonal nevomelanocytic proliferations in the CNS and skin. Given the scarcity of effective therapeutic targets, testing new drugs requires a reliable and reproducible in vitro cellular model of the disease.

METHODS

We generated nevomelanocytic spheroids in vitro from lesions of the spinal cord, brain, and skin from 4 NCM patients. Nevomelanocytic cells were grown as monolayers or spheroids and their growth characteristics were evaluated. Cultured cell identity was confirmed by demonstration of the same NRAS mutation found in the original lesions and by immunophenotyping. Nevomelanocytic spheroids were treated with inhibitors of specific mediators of the NRAS signaling pathway (vemurafenib, MEK162, GDC0941, and GSK2126458). Drug sensitivity and cell viability were assessed.

RESULTS

Cultured cells were growth-factor dependent, grew as spheroids on Geltrex matrix, and maintained their clonogenicity in vitro over passages. Skin-derived cells formed more colonies than CNS-derived cells. Inhibitors of specific mediators of the NRAS signaling pathway reduced viability of NRAS mutated cells. The highest effect was obtained with GSK2126458, showing a viability reduction below 50%.

CONCLUSIONS

NRAS mutated cells derived from clinical NCM samples are capable of continuous growth as spheroid colonies in vitro and retain their genetic identity. Drugs targeting the NRAS signaling pathway reduce in vitro viability of NCM cells. NCM lesional spheroids represent a new and reliable experimental model of NCM for use in drug testing and mechanistic studies.

BRAF mutations are also associated with neurocutaneous melanocytosis and large/giant congenital melanocytic nevi

NRAS and BRAF mutations occur in congenital melanocytic nevi (CMN), but results are contradictory. Sixty-six prospectively collected CMN patients were analyzed for NRAS Q61 mutations using Sanger sequencing. Negative cases were evaluated for BRAF V600E mutation. NRAS Q61 mutations affected 51 patients (77.3%), and BRAF V600E was found in 5 (7.6%). NRAS Q61 mutation affected 29 (80.6%) of 36 giant, 16 (80.0%) of 20 large, and 5 (62.5%) of 8 medium-size CMN; BRAF mutation affected 1 (5%) of 20 large and 4 (11.4%) of 36 giant CMN. Compared to NRAS, BRAF-mutated nevi show scattered/extensive dermal and subcutaneous nodules (100% BRAF+ vs 34.8% NRAS+) (P=0.002). Neurocutaneous melanocytosis (NCM) affected 16 (24.2%) of 66 patients, with NRAS Q61 mutation in 12 (75.0%), and BRAF V600E in 2 (12.5%), P=0.009. Two patients were negative for both mutations (12.5%). In conclusion, although NRAS Q61 mutations predominate, BRAF V600E mutation also affects patients with large/giant CMN (L/GCMN), and with NCM, a novel finding. BRAF V600E is also associated with increased dermal/subcutaneous nodules. These findings open the possibility of BRAF-targeted therapy in some L/GCMN and NCM cases.

Skin of patients with large/giant congenital melanocytic nevi shows increased mast cells

Nevocytes (NC) and mastocytes (MC) have different progenitors but share stem cell factor as regulator/activator of NC and for differentiation/proliferation of MC. Both cell types express stem cell factor receptor CD117. We hypothesize that large/giant congenital melanocytic nevi (L/GCMN) may associate with MC hyperplasia. Forty-nine L/GCMN were examined, 12 samples from uninvolved skin of L/GCMN patients and 6 control skin samples studied with Giemsa and immunohistochemistry for CD117 and MC-tryptase. Picrosirius red (PR) was used to assess fibrosis. Digital images were used to count MC/mm(2) using ImageJ software. Western blot (WB) for MC-tryptase in 12 GCMN and 12 non-nevus samples was performed. Analysis of variance (Tukey) and Pearson statistical tests were applied. Increased MCs were observed in nevus tissue (75.1 ± 35.3 MCs/mm(2)) and in uninvolved skin (53.74 ± 27.7 MC/ mm(2)). P  =  0.109 from patients with L/GCMN, compared with controls from individuals without L/GCMN (28.74 ± 8.4 MC/mm(2)); P  =  0.001 supported by results of WB analysis for tryptase. A positive trend toward correlation of MC numbers with fibrosis, assessed by PR staining fell short of statistical significance (r  =  0.245; P  =  0.086); no difference in fibrosis was found between nevus and non-nevus skin from patients with L/GCMN (P  =  0.136). We found a higher density of MC, both in normal-appearing skin and nevus areas of L/GCMN patients, compared with control skin samples from individuals without nevi. Given the abnormal wound healing and allergic reactions described in L/GCMN patients, these findings suggest a potential role for MC in the biology of L/GCMN, making them a potential target for therapeutic intervention.

Threshold for thermal ionization of an aluminum surface by pulsed megagauss magnetic field

The first measurement of the threshold for thermal ionization of the surface of thick metal by pulsed magnetic field (B) is reported. Thick aluminum-with depth greater than the magnetic skin layer-was pulsed with partial differential B/ partial differential t from 30-80 MG/micros. Novel loads avoided nonthermal plasma (from electron avalanche, or energetic particles or photons from arcs). Thermal plasma forms from 6061-alloy aluminum when the surface magnetic field reaches 2.2 MG, in qualitative agreement with numerical simulation results by Garanin et al. [J. Appl. Mech. Tech. Phys. 46, 153 (2005)].

Radiation magnetohydrodynamic simulation of plasma formed on a surface by a megagauss field

Radiation magnetohydrodynamic modeling is used to study the plasma formed on the surface of a cylindrical metallic load, driven by megagauss magnetic field at the 1MA Zebra generator (University of Nevada, Reno). An ionized aluminum plasma is used to represent the "core-corona" behavior in which a heterogeneous Z-pinch consists of a hot low-density corona surrounding a dense low-temperature core. The radiation dynamics model included simultaneously a self-consistent treatment of both the opaque and transparent plasma regions in a corona. For the parameters of this experiment, the boundary of the opaque plasma region emits the major radiation power with Planckian black-body spectrum in the extreme ultraviolet corresponding to an equilibrium temperature of 16 eV. The radiation heat transport significantly exceeds the electron and ion kinetic heat transport in the outer layers of the opaque plasma. Electromagnetic field energy is partly radiated (13%) and partly deposited into inner corona and core regions (87%). Surface temperature estimates are sensitive to the radiation effects, but the surface motion in response to pressure and magnetic forces is not. The general results of the present investigation are applicable to the liner compression experiments at multi-MA long-pulse current accelerators such as Atlas and Shiva Star. Also the radiation magnetohydrodynamic model discussed in the paper may be useful for understanding key effects of wire array implosion dynamics.

Treatment of large and giant nevi

Excision of large and giant melanocytic nevi presents a distinct challenge to the pediatric plastic surgeon. The exact risk of malignant degeneration remains unknown. These unsightly lesions can be psychologically damaging to both parent and child. The pediatric plastic surgeon must have an armamentarium of techniques for reconstructing the various body areas and must always balance aesthetic and functional outcomes against an unknown but low risk of malignancy.

The importance of conchal resection in correcting the prominent ear

The authors believe that conchal hypertrophy plays a more significant role in ear prominence than has been indicated in the literature. Instead of focusing on the antihelical fold, this otoplasty technique emphasizes chondrocutaneous resection. With even limited resection and resuturing of the cut concha, the antihelix yields to posterior suture placement with a soft, smooth, rounded shape unmarred by any sharp, irregular surfaces.

The Expanded Transposition Flap: Shifting Paradigms Based on Experience Gained from Two Decades of Pediatric Tissue Expansion

The authors present their experience with the design of expanded skin flaps gained over the past two decades in a large series of 995 expanded flap reconstructions performed in 626 operations in 430 patients. The indications for tissue expansion were giant congenital pigmented nevi (72.7 percent), scar contractures (11.2 percent), and a remainder for a variety of congenital and acquired deformities. Surgical strategies were reviewed retrospectively to determine the location in the body where the tissue expansion was performed, the number of procedures required to accomplish the reconstructive goal, and the design of the expanded flap that was used to reconstruct the involved area. Specific points that were noticed included contour deformities (such as webbing, dog-ears, or decreased limb circumference) following flap reconstruction, anatomic distortions (such as distortion of the eyebrow or the distance from the brow to hairline) following reconstruction, final position of the scars in relation to anatomic landmarks, borders of aesthetic units, and relaxed skin tension lines, and the potential for later scar contracture. Careful examination of reconstruction by region of involvement demonstrated significant advantages in the use of expanded transposition flaps over pure advancement. These advantages and the modifications in the design of expanded flaps for each body region are discussed in a series of representative cases. They emphasize the ability of transposition flaps to dissipate tension away from the flap apex and distribute it more proximally, thus redirecting the tension lines so there is less likelihood of anatomic distortion in the reconstructed area. Also, flaps designed in this manner allow improved contour by avoiding webbing, tenting across concavities, and bunching of skin laterally. The authors conclude that restricting the expanded flap design to advancement alone to minimize potential scarring severely limits the reconstructive capabilities of the added tissue and distracts from the surgeon's ability to accomplish the initial reconstructive goal. The cost of additional incisions is worthwhile to achieve better final contour of the reconstructed part, lesser risk of anatomic distortion, better position of the scars, and lowered risk of scar contracture.

Large and Giant Congenital Pigmented Nevi of the Upper Extremity: An Algorithm to Surgical Management

The timing and choice of treatment of congenital giant pigmented nevi continues to evolve under the influence of changing opinions regarding the risk of malignant degeneration and the impact of excision and reconstruction on the affected child. Many studies exist to support a notable enough risk of malignancy to warrant excision, yet other series and pigmented lesion clinics suggest that the risk of malignancy does not warrant the potential scarring and deformity that has followed the surgery necessary to remove these giant lesions. To satisfy both sides in this controversy, we have been challenged to modify our surgical techniques in a manner that minimizes the risk of malignant degeneration and at the same time provides optimal functional and aesthetic outcomes for these complex reconstructions. Thirty consecutive patients with large and giant nevi of the upper extremity were treated over a 23-year period (1979-2002) by the senior author. These patients represent a subset of 259 children (12%) with large or giant congenital pigmented nevi treated and followed during this period of time. In proximal upper extremity lesions, expanded transposition flaps from the upper back and shoulder have effectively eliminated contour defects or circumferential constriction in the upper arm and axilla. An expanded free transverse rectus abdominis musculocutaneous flap has offered a possible avenue for larger lesions (shoulder and upper extremity to below the elbow), and pedicle flaps from the flank (both expanded and nonexpanded) have offered ways of improving the long-term contour in the forearm. Expanded and nonexpanded full-thickness skin grafts were chosen for reconstruction of the hand and the fingers. The authors describe in detail the surgical strategies and the techniques for reconstruction of each region of the upper extremity and then bring these ideas together in an algorithm for assessment and treatment of these challenging lesions.

Distraction Osteogenesis of the Mandible With an Internal Bioresorbable Device

Lengthening of the mandible by distraction osteogenesis has been shown to be an effective treatment of hypoplastic mandibles. Use of an internal technique with a bioresorbable distraction device is presented. Mandibular lengthening was performed in seven patients aged 3.2 to 7 years. Six of the patients were diagnosed with craniofacial microsomia, anthe buccal aspect of the mandible, and distraction was started on the second postoperative day at the rate of d one was diagnosed with Nager syndrome. An internal bioresorbable device was placed along 1 mm/d and continued for 17 to 20 days. The distractor screw was maintained for retention for an additional 6 weeks and was then removed. All the patients showed clinical improvement. The postdistraction craniofacial computed tomography scans demonstrated elongation of the mandible with increase in the bony mass. The complications included device failure in one patient. The advantage of this method compared with the internal metal device is that it does not necessitate an additional procedure for device removal.

Juvenile xanthogranuloma invading the muscles in the head and neck: clinicopathological case report

Juvenile xanthogranuloma (JXG) is a member of the non-Langerhans cell group of histiocytic proliferative disorders. It typically presents as a solitary, benign, rapidly growing cutaneous tumor that may regress spontaneously. Most cutaneous lesions of JXG occur in the head and neck region of infants and young children. JXG has been documented in many visceral locations including the lung, bone, testis, gastrointestinal tract, kidney, heart, eye, and oral cavity. Intramuscular location is extremely rare. The few intramuscular lesions that have been described involve the trunk, with the musculature of the back involved most frequently. The authors present a patient with juvenile xanthogranuloma on her chin deeply invading the underlying facial muscles. Histopathological analysis confirmed the intramuscular extension. To the authors' knowledge, this is the first detailed clinicopathological report of juvenile xanthogranuloma infiltrating the muscles in the head and neck.

Surgical management of the cutaneous manifestations of linear nevus sebaceus syndrome

Linear nevus sebaceus syndrome is characterized by the association of nevus sebaceus covering extensive areas on the head and scalp with abnormalities of the central nervous system, ophthalmologic and skeletal changes, and malignancies. The incidence is approximately one per 10,000 live births, and there is no sexual predilection reported. The original description of this syndrome was followed by extensive literature describing the dermatologic, neurologic, and ophthalmologic manifestations of this disease. The objective of this report is to describe the surgical approach for the excision and reconstruction of giant sebaceous nevi of the face and scalp in children with linear nevus sebaceus syndrome on the basis of a consecutive series of five patients treated over 10 years in the same institution. To the authors' knowledge, this report represents the largest surgical series and suggests a reliable approach to the treatment of the cutaneous manifestations of this syndrome.

Ear reconstruction after auricular chondritis secondary to ear piercing

The recent fad of high ear piercing in the pinna has led to an increased incidence of auricular chondritis, which leads to dissolution of the cartilage and residual ear deformity. The typical postpiercing chondritis deformity presents as a structural collapse of the superior helical rim, scaphal cartilage, and the adjacent antihelix. The skin envelope is usually preserved, but it may be scarred from the infectious process and from previous drainage incisions. In the present article, the authors present a systematic approach to reconstruction of these acquired ear deformities. Careful assessment of the residual tissue is requisite to planning and appropriate reconstruction. The greater the cartilage loss, the more structural support is required to expand the skin envelope to its normal size and shape. The choice of cartilage donor site is made on the basis of the size of the defect and may include ipsilateral or contralateral conchal cartilage, bilateral conchal cartilage, or costal cartilage. Redraping of the carefully dissected skin and fixation of the flaps to the newly reconstructed cartilaginous framework usually provide sufficient soft-tissue coverage. A temporal-parietal fascial flap is preserved for the rare cases of extensive full-thickness skin loss or badly damaged and scarred auricular skin.

Congenital dermatofibrosarcoma protuberans: variability in presentation

BACKGROUND

Dermatofibrosarcoma protuberans (DFSP) is an uncommon low-grade fibrohistiocytic tumor that usually occurs on the trunk or proximal extremities and typically appears during the second to fifth decade of life. It most commonly begins as a red-blue plaque that grows slowly and ultimately becomes nodular. The tumor is associated with a high recurrence rate but low metastatic potential. It rarely presents in childhood and is even more rarely present at birth. The clinical diagnosis of DFSP in infancy or childhood may be difficult because, in its early stages, the tumor often resembles a vascular birthmark.

OBSERVATIONS

We studied 6 patients with congenital DFSP who were initially thought to have other diagnoses, highlighting the potential clinical variability in presentation. Half of the cases in this series occurred in areas of the body outside of the typically reported distribution pattern of acquired DFSP and in locations that, therefore, may not arouse suspicion of congenital DFSP.

CONCLUSIONS

Given the aggressive local potential and high recurrence rate of DFSP, early diagnosis is preferable to facilitate appropriate excision. We recommend that any infant or child presenting with a cutaneous plaque or nodule, even congenital, that does not have characteristic or diagnostic clinical features undergo tissue biopsy for histologic evaluation.

Combined otoplasty technique: chondrocutaneous conchal resection as the cornerstone to correction of the prominent ear

The failure to correctly analyze the complex deformity that comprises the prominent ear is the most common cause of the undesired surgical result. Recognizing conchal hypertrophy as one of the leading causes of the prominent ear deformity has led to a versatile and reproducible otoplasty technique that is easily modified to the common side-to-side variation in deformity. From January of 1993 to August of 2000, chondrocutaneous conchal resection has been used as the cornerstone to a combined sequence of maneuvers in otoplasty. The operation was performed on 47 patients (40 bilateral cases and 7 unilateral), and the total number of ears operated on was 87. There were three complications requiring revision surgery, and follow-up periods ranged from 6 months to 7 years, with all patients achieving a satisfactory result. Detailed methods of chondrocutaneous conchal resection along with the sequence of the authors' combined otoplasty techniques are presented.

Full-thickness surgical excision for the treatment of inflammatory linear verrucous epidermal nevus

Inflammatory linear verrucous epidermal nevus (ILVEN) is a benign cutaneous hamartoma characterized by intensely erythematous, pruritic, inflammatory papules that occur as linear bands along the lines of Blaschko. Because of its chronic and unremitting symptomatology, patients with ILVEN seek medical treatment for relief of discomfort as well as concerns regarding cosmetic appearance. Reported therapeutic approaches include topical agents, dermabrasion, cryotherapy, laser therapy, and partial-thickness excision. Unfortunately, no one therapy has been successful consistently. Medical management is often unsatisfactory, because improvement tends to be temporary. Surgical modalities have met with better success in relief of symptoms but at the risk of marked scarring and a high rate of recurrence. Furthermore, the occurrence of extensive ILVEN or localization to certain anatomic regions has been considered previously a relative contraindication to excision. The authors report 4 patients with extensive ILVEN treated successfully with full-thickness surgical excision. Our report underscores the effectiveness of this surgical modality for the definitive treatment of ILVEN.

The role of tissue expansion in the management of large congenital pigmented nevi of the forehead in the pediatric patient

The authors present a cohort of 21 consecutive patients who had congenital pigmented nevi covering 15 to 65 percent of the forehead and adjacent scalp and who were treated at their institution within the last 12 years. All patients were treated with an expansion of the adjacent texture- and color-matched skin as the primary modality of treatment. The median age at presentation was approximately 1 year; mean postoperative follow-up was 4 years. Nevi were classified according to the predominant anatomic areas they occupied (temporal, hemiforehead, and midforehead/central); some of the lesions involved more than one aesthetic subunit. The authors propose the following guidelines: (1) Midforehead nevi are best treated using an expansion of bilateral normal forehead segments and advancement of the flaps medially, with scars placed along the brow and at or posterior to the hairline. (2) Hemiforehead nevi often require serial expansion of the uninvolved half of the forehead to minimize the need for a back-cut to release the advancing flap. (3) Nevi of the supraorbital and temporal forehead are preferentially treated with a transposition of a portion of the expanded normal skin medial to the nevus. (4) When the temporal scalp is minimally involved with nevus, the parietal scalp can be expanded and advanced to create the new hairline. When the temporoparietal scalp is also involved with nevus, a transposition flap (actually a combined advancement and transposition flap because the base of the pedicle moves forward as well) provides the optimal hair direction for the temporal hairline and allows significantly greater movement of the expanded flap, thereby minimizing the need for serial expansion. (5) Once the brow is significantly elevated on either the ipsilateral or contralateral side from the reconstruction, it can only be returned to the preoperative position with the interposition of additional, non-hair-bearing forehead skin. Expansion of the deficient area alone will not reliably lower the brow once a skin deficiency exists. (6) In general, one should always use the largest expander possible beneath the uninvolved forehead skin, occasionally even carrying the expander under the lesion. Expanders are often overexpanded.

Enhanced forward scattering in the case of two crossed laser beams interacting with a plasma

The nonlinear enhancement of large-angle forward scattering of two identical laser beams propagating in a preformed plasma has been observed experimentally. The spectral analysis of the forward-scattered light shows two components, one which is unshifted with respect to the initial laser light frequency, and the other which is redshifted by a few angstroms. The redshifted component is found to be strongly enhanced in the case of crossed beam interaction in comparison with that of one beam illumination. Two-dimensional numerical simulations show that this enhancement is due to large-angle forward stimulated Brillouin scattering in which each beam serves as seed for the forward scattering of the other.

Congenital primitive neuroectodermal tumor of the hand: a case report

A congenital peripheral primitive neuroectodermal tumor of the hand demonstrating aggressive behavior by rapid growth and ulceration, as well as early diffuse metastasis is presented. Management consisted of below-elbow amputation and chemotherapy. Despite the tumor's initial response, intracranial metastases occurred 7 months later. The patient died shortly thereafter, 15 months after presentation.

Nevus cells and special nevomelanocytic lesions in children

Nevomelanocytic lesions in children represent a wide spectrum of proliferative neurocristopathies, ranging from the common small and benign congenital nevi to the garment-type congenital lesions. Included in this spectrum are some rare entities like neurocutaneous melanocytosis, malignant melanoma simulants, and special variants of congenital pigmented nevi. Here, we analyze some tissue culture characteristics of nevomelanocytic cells from giant and small congenital nevi, neurocutaneous melanocytosis, and a rare variant of nevus named "bulky nevocytoma." Correlations with their histological, immunohistochemical, and ultrastructural features are addressed.

Release of acquired syndactylies in Kindler syndrome

Kindler syndrome is a rare, blistering skin disease characterized by acral bullae, poikiloderma, and diffuse cutaneous atrophy. Kindler syndrome has been established as a separate entity from epidermolysis bullosa; however, controversy still remains as to whether Kindler syndrome can be differentiated from Weary's hereditary acrokeratotic poikiloderma. Fusion of the digits secondary to blistering and scarring, "pseudosyndactyly," has been reported in several patients with Kindler syndrome; however, surgical correction of the syndactylies in these patients has not been described. In this report, a patient with Kindler syndrome underwent surgical treatment of acquired syndactylies. Treatment included a tailored approach to preparation of the patient for surgery, surgical separation of fused tissues, selection of donor site for skin-graft harvest, postoperative dressings, splinting, and therapy. Results in our patient 2 years after correction demonstrate that syndactyly release in Kindler syndrome can be accomplished effectively, with improvement in both function and appearance.

Resection of lymphatic malformation of the scrotum

It is important for clinicians to consider lymphatic malformations in the differential diagnosis of chronic skin lesions, no matter where they appear anatomically. We report a case of deep surgical excision of an extensive lymphatic malformation of the scrotum using regional flaps from uninvolved scrotal tissue. Removal of the lesion not only allowed the patient more comfort but also may have ultimately cured his symptomatology.

Expanded full-thickness skin grafts in children: case selection, planning, and management

Since our initial presentation of our experience with tissue expansion as a means of harvesting large full-thickness skin grafts in children in 1987, we have continued to "expand" both the size of full-thickness skin grafts harvested and the range of reconstructive problems to which we have applied the technique. Sixteen expanded full-thickness grafts have been used for immediate reconstruction following giant nevus excision and in postburn reconstruction. Patients ranged in age from 6 months to 15 years, with follow-up ranging from 6 months to 6 1/2 years. Grafts ranging in size from approximately 60 cm2 (excluding the dimensions of one submental graft) to greater than 700 cm2 were harvested from expanded donor sites on unilateral or bilateral groin/lower abdomen, clavicular, and a single submental expansion. Five expanded full-thickness grafts were used in facial reconstruction for single aesthetic unit coverage, multiple unit, and one single-sheet full facial graft. One expanded full-thickness graft was used on the breast. Three grafts were used in dorsal hand and finger coverage, and seven were used on the lower extremity, including an entire plantar surface and toes. Graft loss was confined to a 6.25-cm2 area on one cheek in the full facial expanded full-thickness grafts and a 9-cm2 area on the non-weight-bearing area of the full plantar graft. Donor-site complications were negligible. The anatomic confines of the donor sites and size of the patient may require expander replacement (in situ serial expansion) in order to obtain a large enough graft and accomplish primary donor-site closure. Expander and injection port placement in children for ease of injection and planned expander change must be anticipated. Our protocol from preoperative teaching through graft take is reviewed. Experience has demonstrated that expanded full-thickness grafts maintain all the characteristics of non-expanded full-thickness skin grafts and are an excellent reconstructive option in children.

Tissue expansion in a patient with extensive nevus comedonicus

Nevus comedonicus is a rare developmental abnormality of the pilosebaceous apparatus that presents as an aggregation of dilated follicular orifices filled with pigmented keratinous material. Occurrence of extensive or giant lesions is even more rare. Indications for treatment include recurrent infections and cosmetic reasons. Therapeutic approaches include topical keratolytic agents, manual extraction of comedones, dermabrasion, and excision of smaller lesions. Increasing clinical experience with tissue expansion has suggested that it might be used effectively in the definitive treatment of an extensive nevus comedonicus previously considered too large to excise without the use of a skin graft, despite the potential risk of infection within the lesion during the course of expansion. We report the first patient with giant nevus comedonicus to be treated using tissue expansion. This patient demonstrates that prompt treatment of cellulitis and abscesses within the lesion will keep this process isolated from the adjacent expanders and will not compromise a planned excision and reconstruction.

Bulky naevocytoma of the perineum: a singular variant of congenital giant pigmented naevus

We describe two instances of a previously unrecognized variant of congenital giant pigmented naevus (GPN), presenting as a bulky naevocytic tumour in the perineal region. In both cases the lesion was present at birth and attained massive dimensions. In addition to the characteristic histological patterns found in GPN, which included extensive areas with a neural appearance, these tumours presented an uncommon tendency to form pseudo-follicular structures lined by naevus cells. No features suggestive of malignant transformation were found. Because GPN may associate with an underlying malignancy, accurate diagnosis of this lesion is important in clinical practice.

Anaesthetic management of Miller's syndrome

Miller's syndrome is a rare congenital disorder with facial features similar to that of Treacher-Collins syndrome. This report details the anaesthetic management of an infant during multiple surgical procedures, beginning with pylormyotomy at one month of age. Airway management was difficult because of severe micrognathia and was accomplished using an awake intubation with a conventional straight blade modified for continuous administration of oxygen ("oxyscope"). Due to recurrent upper airway obstruction and the anticipated need for multiple surgical procedures in the first years of life, a tracheostomy was placed. Because of the multiple airway, orthopaedic, and nutritional difficulties, it is important that a prospective, multidisciplinary approach be used in these patients' care. Consideration should be given to early tracheostomy for airway maintenance.

The role of tissue expansion in reconstruction of the ear

The following guidelines are suggested for the use of tissue expansion in ear reconstruction based on both personal experience and my evaluation of the reported results of expansion in the hands of other surgeons experienced in ear reconstruction: 1) Cases should be carefully selected to avoid those with excess scarring from previous surgery or trauma as well as avoid the other common contraindications to the use of tissue expansion. 2) In most congenital cases the expander should be placed through a remote incision within the postauricular hairline, and excision of the cartilage vestige delayed until expansion is completed and the framework is ready for placement. 3) A remote valve expander of a crescent shape with a volume of 60-100cc is ideal; low profile expanders may even be safer. 4) The pocket for the expander should be dissected immediately above the fascia and against the cartilage remnant. 5) Rapid expansion should be avoided; ideally injections should be carried out one time each week and with relatively small quantities (5-10cc per injection). 6) At the time of expander removal and placement of the cartilage framework the capsule should be meticulously excised to allow tight skin-cartilage coaptation. This is further enhanced by effective suction drainage following wound closure.

The role of tissue expansion in pediatric plastic surgery

The ability to increase available local tissue by controlled soft tissue expansion (TE) has led to a rapid increase in the use of TE in clinical practice. This article reviews some general guidelines when using TE in children and addresses some of the concerns previously expressed regarding the effects of TE on growth in infants and children.

Maintenance of airway patency following treatment of choanal atresia

Airway patency following repair for choanal atresia is effectively maintained utilizing Argyle polyethylene chest tubes as stents. Retrograde placement of the tubes from the mouth into the nasal passage is accomplished so that once secured, the largest diameter of the tubes is wedged against the posterior portion of the nasal ostium. This approach limits anterior migration of the tubes, preserving the columella and nasal rims while ensuring maintenance of airway patency following treatment of choanal atresia.

Treatment of mandibular fractures in children

Thirty-seven mandibular fractures were treated in 25 patients between January 1984 and January 1988. The patients' ages ranged from 4 months to 16 years (6.9 +/- 4.6 years [mean +/- standard deviation]). Nineteen of the patients were male and 6 were female, indicating a significant gender predilection (p less than 0.05). A treatment approach based on the patients' dental maturity and fracture location has evolved that stresses rapid restoration of osseous continuity and preoperative occlusion while striving to minimize risk to unerupted dentition.