Dermoid and epidermoid cysts are the most common scalp lesions in the pediatric population, comprising over 20 % of all scalp lesions [2]. Both are subcutaneous thin-walled sacs lined with stratified squamous epithelium, formed by entrapment of ectodermal elements during embryologic development partitioning ectodermal inclusion cysts in areas of suture closure, neural tube closure and division of cerebral hemispheres [3, 4]. They are thus commonly located along the midline, such as glabella, anterior fontanelle, nasion, and vertex, whereas epidermoid cysts are located more off-midline (Fig. 10.1). Both are more commonly located in the anterior scalp (e.g., in the periorbital area, over the anterior fontanelle, or frontotemporal region) than the posterior parietal and occipital regions [4]. Dermoid cysts and tracts, containing a wider variety of dermal components than epidermoid counterparts, mostly present to clinical attention in infancy and early childhood while epidermoid cysts more frequently do not become symptomatic until adolescence or adulthood; there is no clear gender predilection [4]. Intracranial extension has been reported in approximately 36 % of cases, with intradural extension in 16 % [5].

Dermoid and epidermoid cysts present as well-circumscribed non-tender slowly growing masses of with intact overlying skin. Growth occurs due to epithelial desquamation and keratin accumulation. Focal alopecia has also been described. Embryologically, dermoid cysts contain both dermal and epidermal elements whereas epidermoid cysts only contain epidermal elements. Although they are commonly isolated to the skin and subcutaneous tissue, they may have intracranial extension with a dermal sinus, and may present with meningitis.

Radiographically, dermoid cysts are nonenhancing soft-tissue masses that may result in scalloping of the adjacent bone on CT, while MRI may evaluate the presence of intracranial extension. Epidermoid cysts are typically lytic on CT, and T2 bright and diffusion restricting on MRI; they can have a heterogeneous appearance depending on the heterogeneity of their contents [1]. In many cases the signal characteristics on imaging alone can distinguish between these two processes (with dermoid cysts often similar to fat on CT/MRI and with epidermoid cysts with characteristics more similar to simple fluid), this distinction frequently does not alter the decision of how to manage these lesions [6].

While dermoid cysts are most commonly painless and otherwise asymptomatic, surgical removal is usually recommended given their potential to enlarge and penetrate the skull (Fig. 10.2). In cases of dermal sinus tract, the feared complication of meningitis makes exploration a necessity. Preoperative MRI scans are frequently unnecessary but may be recommended for surgical planning to rule out, for example, sagittal sinus involvement. Most lesions can be removed in a surgical procedure lasting less than an hour. Recurrence has been reported both intracranially and extracranially [7].

Cephaloceles are defects of the cranial vault and leptomeninges (Fig. 10.3). Based on the type of tissue herniating through the defect, cephaloceles are classified as either meningoceles, if they solely contain meninges and cerebrospinal fluid or as encephaloceles, if brain tissue is also herniated. Atretic encephaloceles, comprising approximately 37.5–50 % of encephaloceles contain a small nodule of fibro-fatty neural rests that are attached to the dura through a connective tissue stalk [6, 8, 9]. Reported incidence of encephaloceles varies widely in the literature, from 1 in every 40,000 live births to 7 % depending on the geographical and demographic characteristics of the studied population [10–13].

Cephaloceles occur either due to incomplete closure of the calvarium, such as defective induction of bone formation or due to bone erosion caused by an intracranial mass or cyst. The latter is the mechanism for acquired encephaloceles. The meningeal sac most commonly protrudes with or without brain tissue in the occipital or parietal regions (75 %), with only 15 % of cases presenting with protrusions in the fronto-ethmoidal area and 10 % in the skull base region, specifically the naso-pharynx [13]. Moreover, frontoethmoidal encephaloceles are more common in patients of southeastern Asian descent .

Occipital cephaloceles are more common in girls [10]. While most are sporadic, some cases are syndromic, for example as seen in Meckel syndrome, and with Chiari III and Dandy-Walker malformations as well as with severe callosal abnormalities [10, 11]. For syndromic etiologies, MKS1, TMEM67, TMEM216, RPGRIP1L, and CEP290 aberrancies have been associated with cephalocele formation [10].

MR and ultrasound are capable of evaluating the extent of brain and CSF extrusion; ultrasound has the advantage of allowing rapid prenatal or postnatal visualization of the sac and its likely contributory compartments, while MRI provides the precise intracranial anatomic definition necessary for the thorough work-up required for these patients. Evaluating occipital encephaloceles for cerebellar and venous sinus involvement is essential prior to surgery [14]. CT may be used to assist with defining bony boundaries preoperatively .

The surgical management of cephaloceles involves resection of the sac with ligature of the base and closure of the defect, for example with pericranial grafts, and is associated with good cosmetic outcomes [15]. Careful dissection of the herniated sac is of utmost importance, as the dura is thin and very adherent to the bone in pediatric patients. For skull base and fronto-ethmoidal encephaloceles, endonasal endoscopic repair is a viable option [16, 17]. Fronto-ethmoidal encephaloceles frequently require complex combined craniofacial approaches. Common complications of the surgical procedure are CSF leaks, meningitis and wound compromise .

Aplasia cutis congenita (ACC ) is a rare congenital syndrome characterized by the focal absence of cutaneous tissue, frequently affecting all layers of the skin and adjacent tissue (Fig. 10.4) [18]. Furthermore, in 15–30 % of patients, defects of the skull bone and/or dura can also occur, exposing the brain and sagittal sinus and thereby increasing the risk of infection, thrombosis and hemorrhage [19]. Dural and skull defects can also lead to associated encephaloceles, further complicating the differential diagnosis. The most common location is the vertex, accounting for over 70 % of cases [19]. The lesion is usually solitary, although multiple lesions have also been reported [20]. Its incidence is 1 in 10,000, with a slight female predominance (7:5) [19, 21]. Although the exact etiology is unknown, autosomal dominant inheritance has been demonstrated in 25 % of cases [4]. Associations with other syndromes have also been described such as the Adams-Oliver syndrome with absence of lower extremities below calf region, absence of all upper extremity digits, cutis marmorata telangiectatica, cortical fissure, and/or bilateral clubfoot [22].

Untreated ACC can lead to meningitis, hemorrhage with exsanguination, sagittal sinus thrombosis, and seizures. Mortality rates in these cases are as high as 20–50 %, and are higher in patients with complex lesions affecting the bone and dura [18, 23]. Management is guided by the extent of the lesion, location and the affected structures. Treatment of small lesions may consist of careful wound dressing, regular wound inspection and prophylactic antibiotics, followed by delayed scar excision as needed. Newer dressing modalities, such as Omiderm, Xeroform, Acticoat, and Elasto-Gel, have decreased the need for cumbersome frequent dressing changes. These dressing techniques also decrease inflammation and infection therefore promoting wound healing. The purpose of wound dressing is to maintain a moist healing environment and prevent eschar formation [18]. Bacteriostatic dressings further decrease the risk of infection and should be considered as the treatment of choice. Conservative measures have been proven beneficial even in large defects though very frequently result in local alopecia. Several reports suggest conservative management to be the preferred method of choice in the neonatal period in order to avoid surgical complications [18, 20]. Frequently, lesions involving the vertex and therefore underlying the posterior fontanel close spontaneously at 6–8 weeks, together with the normal closure of the fontanel [18]. However, for lesions exposing the dura or brain, prompt early surgical management is imperative. Surgical reconstruction techniques have varied from full-thickness skin grafts to local scalp flaps, pericranial flaps, autologous bone grafts, tissue expansion, and free flaps. Local flaps can provide immediate coverage of exposed neural structures and therefore reduce the risk of infection. Cranioplasty using the split-rib technique or using autologous pericranium has been proven beneficial in lesions involving the skull. In certain cases, staged tissue expansion and skull reconstruction might be necessary. In such cases, tissue expanders are used to construct a well-vascularized space for the cranioplasty. Graft failure and necrosis are potential complications of the reconstruction surgery along with sagittal sinus thrombosis, mostly due to abnormal vascular supply and vascular anastomoses of the region .

In the newborn, a variety of birth trauma-related lesions may be manifest in the scalp depending on the compartment injured and occur in 1–2 % of spontaneous vaginal deliveries and 3–4 % in forceps assisted deliveries A full description of the various manifestations of bleeding in and around the skull layers is available in Chap. 3, but a figure is included here summarizing the various traumatic lesions as they are important to keep in mind within the first few years of life when formulating a differential diagnosis in a child with a skull mass (Fig. 10.5) [24].

Sinus pericranii is a rare slow-flow vascular anomaly involving extracranial and intracranial veins. It is a collection of congenital scalp veins that communicate with intracranial venous sinuses through numerous dilated diploic veins. Typically congenital, cases of posttraumatic sinus pericranii have also been reported [25]. It typically presents as a soft, bulging but compressible mass of 1.5 cm or smaller diameter over or paramedian to the sagittal midline, mostly over the central or posterior third of the superior sagittal sinus. Parietal (34 %), occipital (23 %), and temporal (4 %) locations are also possible [26]. The lesion enlarges with the Valsalva maneuver, crying, neck flexion, or other maneuvers increasing intracranial pressure and reduces with elevation or direct pressure. It is mostly asymptomatic and pulsations or bruits are not observed [27]. Contrast-enhanced CT or MR imaging demonstrates significant extracranial venous flow and frequently can pinpoint the connecting venous channel; an evaluation of previse venous anatomy are essential to rule out additional vascular abnormalities which may include aneurysmal malformations of the internal veins, cavernous hemangiomas, and venous angiomas. CT typically also demonstrates scalloping of the inner or outer table of the cranial vault owing to erosion.

Surgical management is generally not required unless the lesion causes discomfort, as the natural history of these involves involution following puberty, while thrombosis is also possible [28]. If resection is desired for cosmetic concerns, careful resection of the vascular lesions with or without preoperative embolization is curative, and large bony defects can be repaired. Preoperative vascular imaging is essential to rule out communication with the superior sagittal sinus. It has been suggested that the role of the vascular anomaly in normal venous drainage of the brain should be carefully evaluated prior to resection [26]. Therefore, a rare complication is thrombosis of the sagittal sinus and should be avoided .

Scalp hemangiomas are relatively common benign endothelial proliferations that rapidly increase in size in the first years of life and gradually involute in late childhood or after puberty .

They are seen in some 1–2 % of infants (3:1 female:male ratio and with 60 % in the head and neck), and are associated with prematurity and a variety of syndromes [13, 29]. Depending on the depth of vascular proliferation, the hemangioma appears either as a bright red maculopapular lesion if superficial, or blue if deep. These may involve the skull or intracranial compartment primarily or by erosion, while primary calvarial hemangiomas are most commonly seen externally given the relatively thin scalp of children [30]. Multiple in 15 % of cases, hemangiomas are usually asymptomatic, classically compress with dependency or external pressure given their low intrinsic pressure, and rarely bleed or ulcerate [31]. Rare cases of infection and painful thrombosis have been reported [32]. Depending on location, hemangiomas can also lead to facial paralysis and hearing loss via compression of the associated peripheral nerves or external ear structures. When located within the calvarial bone, hemangiomas can lead to headaches, scalp pain, and palpable masses.

Hemangiomas of the scalp are generally benign with involution and/or complete regression by 10 years and rarely require treatment. Prognosis is excellent even without therapy [32]. However, giant hemangiomas, rarely reported in the literature, are more prone to complications such as high-output heart failure, or thrombocytopenia with associated hemorrhagic complications as part of the Kasabach Merritt syndrome, and should therefore be closely monitored [33]. Intralesional or systemic steroids, embolization, interferon alfa-2a, or cryosurgery as well as surgical resection are part of the therapeutic armamentarium for these lesions. Location and depth of the hemangioma as well as the potential for complications are indications for aggressive surgical management. Esthetically incapacitating lesions, lesions that have recurrent hemorrhage or ulcerations along with giant hemangiomas require prompt surgical intervention. Most lesion regress by late childhood and are more adequately managed with conservative measures [32].

The port-wine stain is the most common syndromic face and scalp hemangioma and is associated with Sturge-Weber syndrome. This “port-wine” stain is a pink or red macule located on the forehead, face and nuchal area of newborns, and is associated with a 5 % rate of underlying intracranial malformations. Similarly, diffuse hemangiomas demand further workup for the PHACES syndrome (posterior fossa malformations, hemangiomas, arterial anomalies, coarctation of the aorta, eye anomalies, sternal cleftin, or supraumbilical raphe). Peri-orbital hemangiomas require imagistic workup in order to assess intracranial extension. MR imaging is sufficient to assess intracranial extension and to rule out potential intracranial malformations. Typical MRI findings include homogenous T2 brightness with associated small flow voids [13].

Arterio-venous malformations are rare congenital or posttraumatic aberrant vascular lesions that are have been encountered in the scalp as pulsatile masses with palpable thrills in infants with high-output cardiac physiology [34]. These children also have dilated scalp, facial and neck veins owing to the venous hypertension related to their malformation. These lesions typically are progressive and are diagnosed on MRI in the setting of a tangle of flow voids. Angiography is an important diagnostic tool in AVMs , and should be considered prior to treatment especially given the potential existence of associated aneurysms or of communication with large dural sinuses which are relevant surgically [35]. Treatment generally consists of embolization or surgical resection of the nidus or and may require a combination of these techniques. Preoperative embolization should be considered if excessive blood loss is possible and may pose a risk, especially in infants and young children. Potential postoperative complications are scalp necrosis and venous thrombosis due to communications of the vascular malformation with the normal scalp circulation.

In contrast, venous malformations are congenital dysmorphic venous lesions that occur in the head and neck area in up to 40 % of cases, and are not associated with high pressure or high flow. They are grossly bluish and nonpulsatile; on MRI they are typically T2-bright with septations and heterogenous enhancement, do not demonstrate flow voids, and commonly have associated small venous calcifications (phleboliths) [13]. Venous malformations are typically treated with sclerotherapy .