Are You Confident of the Diagnosis?
Nasal gliomas are masses that consist of heterotopic glial tissue. They are thought by some to be encephaloceles that have lost the intracranial connection and by others to be formes fruste of nasal dermal sinus tracts. Although there is no patent cerebrospinal fluid (CSF) connection to the subarachnoid space, in up to 20% of gliomas there is a fibrous stalk that connects to the intracranial space. Only rarely will there be a bony defect that allows leakage of CSF. On histology, a glioma is composed of disorganized dysplastic neuroglial and fibrovascular tissue, which is different from the often well differentiated neural elements present in encephaloceles. Note also that gliomas distinctively lack ependymal tissue, a characteristic seen in encephaloceles.
Dermoids are masses that consist of ectodermal tissue. This includes skin, hair follicles, and sebaceous and eccrine glands. Epidermoid cysts do not contain any elements of the deeper dermal appendages, and as such contain only skin. A dermal sinus is a defect of the skin that leads inward overlying the midline of the nose. When the sinus connects the skin to the contents of the cyst, it is called a fistula. Nasal dermoids represent only 1-3% of all dermoids found throughout the body, but they remain the most common congenital midline nasal mass by far. Other common locations include the lateral eyebrow.
What you should be alert for in the history
History reveals a midline mass noticed at birth or at an early age, possibly with fluctuation in size. A history of meningitis, CSF leak or other associated midline defects is uncommon. Cranial base lesions located intranasally may have history of airway obstruction. Those lesions not in the midline will be found at another suture line.
An external dermoid is firm, noncompressible, possibly lobulated, nonpulsatile, and will not transilluminate. A nasal dermoid will not change size with Valsalva. Nasal dermoids that extend across the cranium are associated with a bony defect and inherent risk of CSF leak and meningitis. Local infections with cellulitis or abcess formation are not uncommon, along with recurrent expression of caseating material from a central pore.
Characteristic findings on physical examination
Extranasal gliomas are smooth, round, noncompressible masses. Most often they are seen at the glabella, but can found lateral to the nose, at the naso maxillary suture line (Figure 1). Intranasal gliomas present as polypoid masses within the nostril, occasionally visible due to protrusion from the nostril base, and often causing obstructive symptoms on the affected side. The intranasal lesions usually arise from the lateral nasal wall in the region of the middle turbinate or occasionally from the septum. Infrequently, nasal gliomas will extend into the orbit, frontal sinus, oral cavity, or posteriorly into the nasopharynx. Due to the lack of cerebrospinal fluid communication with intracranial contents, gliomas do not change size with Valsalva maneuver, and they do not transilluminate.
Dermoid cysts will present in many forms, including a dermal sinus alone, a dermoid cyst without fistulous connection, an external nasal mass, an intranasal mass, or an extracranial-intracranial mass. The presence of a cutaneous dermal sinus or fistula appears as a small deformity, or pore, along the nasal midline between the radix and the tip, often visible from the side profile, and heralded by the presence of several small hairs exiting the pore. This appearance is pathognomonic for a nasal dermoid. Intranasal dermoid cysts may present with obstruction. Intrancranial extension occurs 4-45% of the time, and can be heralded by recurrent meningitis from skin flora organisms. Nasal dermoids do not enlarge with Valsalva and do not transilluminate.
Expected results of diagnostic studies
Preoperative imaging must be considered for all congenital midline masses to evaluate the possibility of intracranial involvement and thus aid in narrowing the differential diagnosis. The study of choice in the current era is a computed tomography (CT) scan of the head, conducted under pediatric protocols to minimize radiation exposure. Findings that can be common to all congenital midline masses with intracranial extension include widening of the nasal septum, erosion of adjacent bones with formation of a cyst-like cavity, increased interorbital distance, or defect of the cribriform plate (Figure 2, arrows indicate a midline dermoid starting from a subcutaneous cyst and extending along the nasal septum through the cribriform plate).
The limitation of the CT scan is in the ability to identify small lesions with narrow stalks. Although imaging should be conducted preoperatively in every case, the CT scan is particularly helpful when an intracranial abnormality is identified. Magnetic resonance imaging (MRI) can add more accurate imaging of the soft tissues and possible connections to the central nervous system and is a nice adjunct to the CT. Nasal endoscopy can also be employed, giving information on the location, origin, and extent of intranasal portions of the mass. Ultrasound can be used to ascertain the contents of a midline mass, but the type of anatomic information needed for pre-operative planning requires the detail found in a CT scan or MRI.
For nasal dermoids, both CT and MRI can be used to yield complementary information. Fine cut CT scans delineate the fine bony anatomy and of nose and anterior skull base. Intracranial dermoids will include a bifid crista galli and enlarged foramen cecum; in fact when these structures appear normal, intracranial extension can be ruled out. MRI with contrast is used to further define the detail of the soft tissues, and can aid in distinguishing the nonenhancing dermoid from enhancing lesions such as hemangiomas and teratomas.
The midline nasal mass has an extensive differential diagnosis including congenital and acquired lesions. Congenital masses include encephalocele, glioma, dermoid cyst, sinus pericranium, and simple inclusion cyst. Acquired masses include polyp, frontal sinus mucocele, sebaceous cyst, lipoma, fibroma, neurofibroma, adenoma, chondroma, ganglioneuroma, carcinoma, and Pott’s puffy tumor (A Pott’s puffy tumor stems from acute sinusitis and is characterized by osteomyelitis of the frontal bone with breakthrough of the anterior table resulting in a swelling on the forehead, hence the name. The infection can also spread inwards, leading to an intracranial abcess).
Despite the long differential, most possibilities are eliminated on the basis of history and physical alone. The main entities to consider are the encephalocele, dermoid cyst, glioma, and polyp. Defining characteristics are listed in Table I, but there remains overlap. Encephaloceles, meningoencephaloceles, meningioceles contain either brain matter, meninges, or both. They are associated with a cranial defect, are pulsatile, bluish in color, and increase in size with occlusion of the jugular veins.
|Patient age||Infancy||Usually childhood||Any||Primarily adulthood|
|Past history||meningitis||local infection||no||sinus disease|
|Location||Intranasal External||Intranasal External||Intranasal External||Intranasal|
|Furstenberg Test (jugular vein compression)||positive||negative||negative||negative|
CSF, cerebrospinal fluid.
Dermoid cysts are ectodermal in origin and may contain skin, hair follicles, sweat glands, or sebaceous glands. A dermoid may have a central punctum with hair protruding through the opening, or a history of drainage or intermittent infection. Nasal gliomas arise from the glial cells and are thought to be encephaloceles that have lost their connection with the meninges. Mucosal polyps will be seen only intranasally and are more common in adults.
Who is at Risk for Developing this Disease?
Congenital midline nasal masses are rare, occurring in 1:20,000 to 1:40,000 live births. Of these rare lesions, the encephalocele, glioma, and dermoid are the most common. Neural tube defects in general have been found to have slight female predominance, with environmental factors such as maternal alcohol consumption and nutritional status playing a role.
Approximately 10% of all congenital hernias of the cranium are intranasal encephaloceles. Nasal encephaloceles are more common in Southwest Asia than in the United States or Western Europe. Nasal gliomas as a whole are exceedingly rare, with a slight predominance in males (3 males:2 females). They are found externally in 60% of cases, intranasally in 30% and combined in 10% of cases.
Dermoid cysts are the most common of the congenital midline nasal masses. Most occur sporadically with a slight male predominance. Familial association have been reported but without implication of a specific gene. Nasal dermoids may be seen in the presence of other deformities including ear and branchial arch anomalies, cleft lip and palate, hypertelorism, and hemifacial microsomia in up to 41% of cases. One commonly sited association is that of hemifacial microsomia and the presence of epibulbar dermoid cysts, a constellation of symptoms known as Goldenhar’s Syndrome.
What is the Cause of the Disease?
The key underlying event in the development of meningoceles, encephaloceles and gliomas is faulty closure of the anterior neuropore. Normal embryology involves closure of the ectoderm and fusion of associated mesodermal bony elements. In normal sequence the ectodermal portion will form and fuse prior to the mesenchymal elements at the base of the skull, including the sphenoid, ethmoid, frontal, and nasal bones.
The space between the developing frontal and nasal bones is known as the fonticulus frontalis. This area is supposed to fuse with the foramen cecum near the developing cribriform plate to separate the intracranial structures from the intracranial structures of the nose. When fusion of the bony elements is incomplete, but the ectodermal neuropore closes normally, intracranial contents may herniate through the fonticulus frontalis resulting in intranasal or extranasal encephalocele/meningocele.
In another scenario, the bony elements fuse in an essentially normal fashion, but there is faulty closure in the ectodermal neuropore, leading to formation of extracranial rests of glial tissue known as gliomas. Gliomas may be attached to the intracranial structures by a fibrous stalk. Incomplete closure of the cranial bones along with a defect in the dura can lead to a cerebrospinal fluid leak in any of these entities, though very rare in the nasal glioma.
There are several theories to explain the development of nasal dermoids. Superficial dermoid and epidermoid cysts can be explained by inclusions of ectodermal elements in facial clefts, aberrant development of skin appendages, and simple inclusion cysts, perhaps introduced by minor skin trauma. Midline dermoids may be related to failure of the neural tube (particularly the anterior neuropore) to close, and abnormal separation and obliteration of the prenasal space. Failure of bony closure of the fonticulus frontalis or of the foramen cecum in the region of the cribriform plate may allow dermal elements to invaginate through the patent frontonasal suture or between the developing nasal bone and cartilage. Failure of separation of the dura as it retracts away from the skin can result in neuroepithelium remaining in contact with the epithelium of the skin with a dermal fistula serving as the connection.
Systemic Implications and Complications
Associated systemic disorders
No specific syndrome is associated with the presence of a glioma, but these lesions can be seen with children born with a craniofacial cleft deformity. Craniofacial clefts, defects of bone and/or soft tissue of the face or cranium, occur in defined anatomic locations and are numbered 1 through 14 by a system described by Paul Tessier. Tessier’s clefts can be seen sporadically or as part of a spectrum in another syndrome.
Frontonasal dysplasia, acrofrontofacionasal dysostosis, frontofacionasal dysplasia and oculoauriculofrontonasal syndrome comprise a spectrum of syndromes known by the eponym Morning Glory syndrome, with midline facial defects, callosal agenesis, basal encephaloceles, and eye anomalies. The anomalies observed are related to failure of appropriate development of the frontonasal process, midface structures, eye primordia, and midline cranial structures. Some case reports show association with genetic mutation in the TGIF gene but a majority are multifactorial in nature.
Dermoid cysts may be seen in the presence of other deformities, including ear and branchial arch anomalies, cleft lip and palate, hypertelorism, and hemifacial microsomia in up to 41% of cases. One commonly cited association is that of hemifacial microsomia and the presence of epibulbar dermoid cysts, a constellation of symptoms known as Goldenhar’s syndrome. Hemifacial microsomia is seen as part of a spectrum of disorders best described by the OMENS classification, which grades each deformity in terms of severity. The spectrum includes Orbital, Mandibular, Ear, Nerve (facial nerve/cranial nerve), and Soft tissue defects, including macrostomia.
Medical Options (Topical, Systemic)
Other than careful observation, there are no medical treatments to treat nasal gliomas or nasal dermoids. In the dreaded complication of meningitis, hospital admission is warranted with aggressive antibiotic therapy. Development of an abscess would require urgent neurosurgical intervention for consideration of drainage and debridement. In the case of dermoid cysts, local infection including cellulitis of the surrounding tissues may be addressed with outpatient antibiotics. No medical therapy will be effective at eliminating the mass.
For all congenital anterior neuropore lesions, the treatment of choice is complete surgical excision. A multidisciplinary approach combining plastic surgery or otolaryngology with neurosurgery is ideal. Early excision is advocated to minimize the effect of time and growth on the surrounding tissues. Growth can lead to further distortion of nasal bones or septum, and additional time can lead to more opportunities for meningitis to develop. Aspiration, incision and drainage, curettage, and subtotal excision are associated with high recurrence rates and thus these lesser procedures are not recommended.
Preoperative imaging should include CT and/or MRI of the head to delineate the anatomy of the lesion. Operative approach will depend on the location, size and extent of the mass. Although cosmesis is always a consideration, the approach must provide adequate access to any intracranial extension of the lesion in question.
For extranasal gliomas, the mass can be approached via lateral rhinotomy, open rhinoplasty, transglabellar subcranial, bicoronal or midline nasal incisions. When a fibrous stalk is identified, extending deep to the nasal bones, heading toward the base of the skull, nasal osteotomies are performed. The stalk is then followed further. If there is communication intracranially, either identified preoperatively or suspected intraoperatively, a bicoronal incision is conducted with craniotomy to allow access to the remainder of the fistula tract. Due to improvements in surgical instrumentation, many nasal gliomas can now be resected with the use of nasal endoscopy.
Goals of the extracranial access incision include providing excellent access to the midline, access to the base of the skull, exposure for reconstruction of the nasal dorsum and an acceptable scar. The traditional open rhinoplasty approach is the most widely used, due to excellent exposure and cosmetic result. For lesions in the glabellar region, the open rhinoplasty is not adequate, and the lateral rhinotomy or midline vertical incision are valuable tools. Glabellar lesions with a sinus opening require an elliptical excision of the pore.
Masses with intracranial extension require bicoronal incision with either frontal craniotomy or anterior small window craniotomy to allow excision of intracranial portion. The tract itself is evaluated intraoperatively and craniotomy avoided if the tract is seen to disappear. Some surgeons advocate the use of frozen section of the tract base and if it is devoid of dermal structures, no further resection is persued (Figure 3, Figure 4, Figure 5, Figure 6).
Optimal Therapeutic Approach for this Disease
The treatment of choice for meningocele, encephaloceles, nasal gliomas, and nasal dermoids is complete excision. Early intervention, generally when the child is at least 10 weeks of age and 10 pounds in weight, is preferable to minimize distortion of the surrounding anatomy. Normal anatomy can be distorted by growth of the lesion as well as recurrent inflammation. Preoperative imaging should include CT or MRI of the head to delineate the anatomy of the lesion. Surgery is conducted as a combined approach of plastic or otorhinolaryngology surgery and neurosurgery. The entire lesion must be excised, including any existing fistula tract in order to prevent recurrence.
Many surgical approaches have been tried, specifically in the case of midline nasal masses. The most important factor is correct identification of intracranial extension, determining if craniotomy will become necessary in addition to extracranial resection. Preoperative imaging is helpful in this respect, but other methods have been used to confirm this information in the operating room.
One method involved injecting the fistula tract with methylene blue and following the tract to the base. If the tract disappears prior to the skull, no intracranial exploration is warranted. Other surgeons describe the use of frozen sections of the tract base. If fibrous tissue alone is identified, the resection is complete. If cyst is identified, intracranial extension is explored.
In patients with distortion of facial features, the first priority is correction of the skull deformity and repair of any dural defects. Reconstruction defects in the forehead, nose, or brow often require multiple procedures as the child ages. The ability to restore normal appearance will vary based on the degree of the defect. Nasal masses can be approached via traditional rhinoplasty incisions aiding in post-resection reconstruction, not uncommonly requiring additional use or ear or rib cartilage to restore adequate support.
Surgical resection of the extracranial portion alone is not advised if there is significant intracranial extension. This leads to increased risk of persistent communication with the cerebrospinal fluid and resultant meningitis Surgical resection offers definitive treatment. Recurrence of the mass would signify incomplete excision.
Surgery requires an inpatient stay for monitoring of neurological status. A significant amount of edema can be expected following bicoronal incision and craniotomy, occasionally requiring additional length of hospital stay to allow edema to decrease to a point where the patient can open his/her eyes. Postoperative follow-up is required evaluate proper healing of the incision. Development of fever or other clinical deterioration postoperatively should raise high clinical suspicion for meningitis, necessitating readmission, possible lumbar puncture, and administration of intravenous antibiotics.
Reconstruction of facial defects must be staged. The patient and his/her family can expect a long relationship with the plastic and reconstructive surgeon in the setting of a severe facial defect (Figure 7, Figure 8).
Unusual Clinical Scenarios to Consider in Patient Management
Midline nasal masses can be problematic in that an outwardly benign appearing lesion can serve as the tip of the iceberg to the real clinical problem. The visible cyst is therefore occasionally treated as an inclusion cyst anywhere else on the body, without consideration of potential deeper, possibly intracranial extension. This can lead to complications varying from a mere nuisance of inadequate resection and subsequent recurrence, to life threatening infection in the form of meningitis or encephalitis.
Referral to a plastic surgeon or neurosurgeon is appropriate in this case to allow for proper evaluation and coordination of operative intervention with Neurosurgery as well as reconstruction of associated facial defects and proper follow-up.
What is the Evidence?
Elluru, RG, Wootten, CT, Flint, PW, Haughey, BH, Lund, VJ, Niparko, JK, Richardson, MA, Robbins, KT, Thomas, JR. “Chapter 188-Congenital malformations of the nose”. Cummings otolaryngology: head & neck surgery. 2010. (Congenital malformations of the nose and paranasal sinuses are rare manifestations of disordered development located at the origin of the aerodigestive tract. Clinical presentations range from subtle cosmetic deformities to life-threatening acute upper airway obstruction and feeding difficulties in neonates. This chapter focuses on the most common congenital lesions in the nose and paranasal sinuses. These lesions are considered within the framework of possible developmental errors in specific anatomic zones: (1) errors at the anterior neuropore, (2) errors of the central midface, and (3) errors of the nasobuccal membrane. Mesodermal and germline malformations not unique to the nose and paranasal sinuses also are discussed.)
Gougoutas, AJ, Singh, DJ, Low, DW, Bartlett, SP. “Hemifacial microsomia: clinical features and pictographic representation of the OMENS classification system”. Plast Reconstr Surg. vol. 120(7). 2007. pp. 112-120e. (The clinical manifestations of hemifacial microsomia comprise a spectrum that is both broad and complex. The fundamental features include unilateral hypoplasia of the craniofacial skeleton and its overlying soft tissue. Numerous schemes have been developed to classify this spectrum. One of the most recent classification systems, the OMENS system, scores five clinical manifestations of hemifacial microsomia according to dysmorphic severity on a scale from 0 to 3: orbital asymmetry, mandibular hypoplasia, ear deformity, nerve dysfunction, and soft tissue deficiency. The OMENS system represents the most comprehensive, versatile, objective, and easily adaptable attempt at clinical classification of hemifacial microsomia to date. The authors propose a concise clinical evaluation form using a modified version of the system to promote the use of the OMENS system, to aid in the evaluation of hemifacial microsomia patients, and to assist in data sharing among academic institutions.)
Hughes, GB, Sharpino, G, Hunt, W, Tucker, HM. “Management of the congenital midline nasal mass: a review”. Head and Heck Surg. vol. 2. 1980. pp. 222-33. (The nasal encephalocele, the glioma, and the dermoid are the most common of the congenital midline nasal masses. Due to similar embryologic development, each of these lesions may be associated with bony cranial defects and intracranial abnormalities, as well as CSF leakage and the potential for fatal meningitis if not handled properly. Properative manipulation should be avoided. Radiologic studies are instructive only if they are positive. If intracranial attachments are identified radiologically or suspected clinically, neurosurgical consultation should be obtained, and intracranial exploration and resection should be carried out as the initial procedure. Extra-cranial resection of the remaining mass may be performed immediately after intracranial resection, may be postponed, or may become unnecessary.)
Losee, JE, Kirschner, RE, Whitaker, LA, Bartlett, SP. “Congenital nasal anomalies: a classification scheme”. Plast Reconstr Surg.. vol. 113. 2004. pp. 676-89. (The purpose of this work was to develop a simple yet comprehensive classification scheme dedicated to congenital nasal anomalies. To date, no such classification system has been proposed and widely used. A 22-year retrospective review was performed. Two hundred sixty-one patients with congenital nasal anomalies were identified. From this extensive database, a systematic morphogenic classification system was devised. Congenital nasal deformities were classified into four categories. Type I, hypoplasia and atrophy, represents paucity, atrophy, or underdevelopments of skin, subcutaneous tissue, muscle, cartilage, and/or bone. Type II, hyperplasia and duplications, representing anomalies of excess tissue, ranging from duplications of parts to complete multiples, are categorized here. In the type III category, clefts, the comprehensive and widely utilized Tessier classification of craniofacial clefts is applied. Type IV deformities consist of neoplasms and vascular anomalies. Both benign and malignant neoplasms are found in this category.Despite the complicated development of the nose, congenital anomalies are rare, with an incidence of one in every 20,000 to 40,000 live births. Despite the apparently similar presentations, these anomalies vary in their nature and position. Nasal anomalies are rarely seen, which may account for misdiagnosis and treatment plans that result in a less than satisfactory outcome. Several attempts at classifying craniofacial deformities have been reported. To date, no classification system committed to congenital nasal deformities has been proposed and widely used. It was the purpose of this work to develop a simple yet comprehensive classification scheme dedicated to congenital nasal anomalies, based upon the clinical experience of a large craniofacial center and an extensive review of the literature.)
Pollock, RA. “Surgical approached to the nasal dermoid”. Ann Plast Surg. vol. 10. 1983. pp. 498-501. (The dermoid cyst usually presents as a mass of the nasal dorsum with or without evidence of a fistulous tract, lined by normal skin, including hair. Approximately 50% of the time the dermoid cyst is deeply located and septal distortion, bone erosion, or intracranial connection may on occasion be discovered. The variations in presentation of these cysts have provoked a variety of recommendations regarding surgical excision. Historical approaches are briefly reviewed. The author favors one of three surgical approaches utilizing incisions that offer good exposure and cosmetically favorable scars. These are outlined in detail. Careful preoperative planning is encouraged, as is the intraoperative use of a lacrimal probe, blunt dissection, and the operating microscope.)
Richieri-Costa, A, Guion-Almeida, ML. “The syndrome of frontonasal dysplasia, callosal agenesis, basal encephalocele, and eye anomalies-phenotypic and aetiological considerations”. Int J Med Sci. vol. 1. 2004. pp. 34-42. (We report 10 sporadic cases of Brazilian patients with facial midline defects, callosal agenesis, basal encephalocele, and ocular anomalies. This very rare cluster of anomalies has been well reported before. However, only until recently it is recognized as a syndrome belonging to frontonasal dysplasia spectrum. The 10 cases confirm a distinct clinical entity and help to define the phenotype more precisely than previously. Up to now etiology remains unknown, although we conjecture that it is due to a mutation in TGIF gene.)
Wardinsky, TD, Pagon, RA, Kropp, RJ, Hayden, PW, Clarren, SK. “Nasal dermoid sinus cysts: association with intracranial extension and multiple malformations”. Cleft Palat Craniofac J. vol. 28. 1991 Jan. pp. 87-95. (Nasal dermoid and sinus cysts (NDSC) are uncommon congenital anomalies that may have intracranial extension and can be associated with other anomalies. We identified 22 patients in a retrospective review of cases diagnosed with NDSC at the authors’ institution over the past 10 years. Nine (41 percent) had associated anomalies and ten (45 percent) had intracranial extension of the sinus. In half of the patients with intracranial extension, the sinus transversed either the cribriform plate or foramen cecum and attached to the dura; in the other half, the sinus extended to cysts within the falx or other brain structures. Of the patients with multiple anomalies, six (67 percent) had intracranial extension. Presurgical complications occurred in a total of eight patients (36 percent): two had meningitis, two had osteomyelitis, four had periorbital-nasal cellulitis, three had nasal abscess, and four had nose anomalies requiring rhinoplasty.)
Winterton, RI, Wilks, DJ, Chumas, PD, Russell, JL, Liddington, MI. “Surgical correction of midline nasal dermoid sinus cysts”. J Craniofac Surg. vol. 21. 2010 Mar. pp. 295-300. (Nasal dermoid sinus cysts (NDSCs) are rare congenital anomalies affecting approximately 1 in 30,000 live births. Nasal dermoid sinus cysts are unsightly, prone to infection, and, importantly, may communicate with the central nervous system. Treatment is complete surgical excision. This study retrospectively evaluated management of a large single-center cohort of intracranial NDSCs.Nineteen patients with NDSC were identified from all patients presenting to the Leeds craniofacial service between June 2000 and August 2008. Patient demographics, clinical presentation, preoperative investigations, and surgical procedures undertaken were analyzed.Mean age at presentation and surgery were 6.3 and 7.6 years, respectively. Fifty-three percent were males. CT and MRI were performed in 15 and 17 patients, respectively. One patient (5.3%) required local excision only. Eighteen (96.7%) underwent a bicoronal approach, and 13 (68.4%) of these required a craniotomy. The dura was opened in 7 (36.8%) patients. Neither CT nor MRI predicted the presence or absence of intracranial extension in all patients. Positive and negative predictive values for intracranial extension were 85.7% and 50% for CT and were 100% and 50.0% for MRI. Mean follow-up of 4.1 years shows no deep recurrences and 5 (26.3%) were superficial nasal recurrences only.A multidisciplinary approach can achieve good results with infrequent intracranial recurrence. We used a bicoronal approach to facilitate craniotomy when required intraoperatively because imaging is unable to diagnose intracranial extension with sufficient accuracy.)
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