primary intraosseous or ectopic meningioma of the skull is a rare tumor accounting for about 1% of meningiomas .
it is postulated to arise from arachnoid cell rests captured at inappropriate sites during embryonic development or implantation of these cells by some mechanical insult like trauma or dural tear .
their origin can also be attributed to cellular dedifferentiation within the diploic space or cranial nerve sheath cells during their course through dipoles .
these arise in paranasal sinuses , neck , and orbit and very rarely in diploe of cranial bones .
these tumors are observed mostly within the first two decades of life and histologically are usually of psammomatous variety .
here the authors present a case of a 16-year - old female who had progressive proptosis with intact vision and was managed successfully surgically .
this patient presented to our out - door department with complaints of progressive proptosis of the right eye for the last 2 years with associated occasional mild to moderate headache .
there was neither associated history of diminution of vision on the affected side nor diplopia in any of the gaze . on examination
, there was axial proptosis on right side without any restriction of the extraocular movements .
visual acuity as per snellen 's chart was 6/6 in bilateral eyes with normal visual fields and fundus examination .
computerized axial tomography ( ct ) scan with thin cuts of the orbit suggested a hyperdense lesion of about 4 cm  5 cm size at the orbital roof causing splaying of the outer and inner tables with extension into the superior and supero - lateral aspects of right orbit displacing the globe antero - medially and enlargement of the right orbit [ figure 1 ] .
it also encroached upon the ethmoidal , sphenoid and frontal sinuses but without any bony destruction .
preoperative ct brain coronal bone cuts ( b ) preoperative contrast computed tomography brain sagittal magnetic resonance imaging ( mri ) showed t1-weighted iso - hypointense and t2-weighted heterogeneous mass lesion in the right orbital roof with intense postgadolinium enhancement [ figure 3 ] .
mri brain post gadolinium sagittal ( b ) routine presurgical work - up was done , and the patient was electively taken up for microsurgical excision under general anesthesia .
tumor was found to be completely extra - axial destroying the orbital roof and extending into the basifrontal region and into the sphenoid sinus .
orbital roof was reconstructed using split calvarial bone graft to avoid any postoperative pulsatile proptosis .
lumbar drain was placed to prevent any cerebrospinal fluid ( csf ) leak from the basifrontal dura and consequent csf rhinorrhoea .
mostly meningioma are considered as primary intradural lesion , however those originating from location other than meninges are called extra calvarial or ectopic meningioma .
they can originate from subcutaneous tissue of skin , paranasal sinus , orbit , neck , salivary gland , calvaria and along per neural sheath of cranial nerves .
extradural meningioma arising in the skull is usually referred as intraosseous , calvarial or intradiploic .
intraosseous meningioma denotes a subset of extradural meningioma arising in bone and accounts for about two - third of extradural meningioma .
after reviewing 31 cases of intraosseous meningioma , observed that orbital and frontoparietal regions are the most common locations .
intradiploic meningioma is very rare in children and reported in isolated case reports . in 2011 , khalatbari et al .
could find only seven cases of intradiploic meningioma of the orbital roof published in the western literature and added their one own case in a 14-year - old female .
crawford et al . reported the diagnostic criteria mass has histopathology consistent with a meningioma , located in epidural and intraosseous compartment ; however brain , arachnoid and dura matter is not involved .
one postulate is that intradiploic meningioma originates from entrapment of arachnoid cells within the bone .
multiple theories exist on how the cells become located in the skull ; although none are universally accepted , and different origins are possible .
head trauma , abnormal cranial moldings and embryogenesis , and arachnoid cells accompanying blood vessels and cranial nerves as they traverse the skull , can all result in the entrapment of arachnoid cells or meningocytes in the bone .
it is presumed that intradiploic meningioma arise from these entrapped cell rests in the calvarium .
classified primary extradural meningioma in three groups , first being purely extracalvarial , next purely calvarial , and finally the third group represents calvarial meningioma with extracalvarial extension .
clinically these case present with exophthalmos , on the involved side , tends to occur predominantly in early second decade of life .
however , vision is usually unaffected and in addition they can have a subcutaneous mass .
radiographically , x - ray can delineate location and its chronic pressure effect on surrounding bone .
it shows generally osteoplastic or hyperostosis reaction in the form of granular or speckled calcification which involves roof or wall of the orbit .
radiologically intradiploic meningiomas are typically either osteoplastic or osteolytic , however , mixed versions also have been reported although the majority are osteoblastic , extremely rarely are osteolytic or very extremely have a mixed pattern .
these can present with opacity of the orbital roof on x - ray skull study .
the osteolytic subtype of intradiploic meningiomas are more likely to be malignant than the osteoblastic subtype .
intradiploic meningiomas should be considered in the differential diagnosis of patients presenting with osteoblastic or osteolytic skull lesions .
the osteolytic lesions typically cause thinning , expansion , and interruption of the inner or outer tables of the skull and these lesions also enhance homogeneously after contrast administration .
however , ct imaging can reveal osteoplastic , intradiploic placement of meningioma , mri can show better delineation of extension of meningioma and soft tissue involvement .
however , clinically intradiploic orbital roof meningioma presents with proptosis , but intraorbital meningioma presents with proptosis and decline in visual acuity to almost complete vision loss . however ,
ct scan and mri will clearly delineate even intraorbital meningioma . rarely rapidly progressing chondrosarcoma , can sometimes occur in orbital wall , is known for aggressive behavior with a high recurrence rate and causes distant metastasis .
hence , preferably orbital chondrosarcoma should be excised along with an eye ball and the orbital contents to prevent recurrence in future . in the present case ,
the lesion appeared as an osteolytic variety , with an interruption of the outer table as well as an intact inner table with extensions as described earlier .
surgery is usually the standard mode of treatment , and all reported pediatric cases had surgical excision , and no recurrence is reported in pediatric cases .
however , meticulous reconstruction of the orbital roof is essential and can be done using calvarial bone graft or titanium plate . in the present case , we achieved complete microsurgical excision of the lesion with reconstruction with split calvarial bone graft with excellent neurological and cosmetic results without any postoperative complications .
histopathology of previously reported five cases were the psammomatous meningioma with one cases each of transitional , transitional with psammomatous body , and meningothelial meningioma .
khalatbari et al . also reported a case occurred in 14 years who presented with exophthalmos and double vision .
ct scan and mri showed an intradiploic orbital roof tumor causing expansion of diploic space and associated pneumosinus dilatans .
she also underwent complete surgical resection , and histopathological study of the specimen revealed the transitional meningioma .
authors have previously reported a transitional meningioma in a 40-year - old male , who underwent surgical excision with reconstruction of the orbital roof ; he had no recurrence or exophthalmos in the follow - up period .
intradiploic meningiomas are extremely rare lesions and usually do not cause dural infiltration , so extradural complete surgical excision is preferred , and intradural exploration is usually not required .
however , intradural exploration is advised only if there is extensive dural infiltration or dural breach is observed .
 primary intraosseous or ectopic meningioma of the skull is a rare tumor accounting for about 1% of meningioma . 
 intradiploic meningioma is an extremely rare type of extraneuraxial meningiomas . 
 intradiploic meningioma of the orbit is extremely rare , and < 8 such cases are reported till date in western literature occurring in the pediatric age group . here 
 the authors present a case of 16-year - old female , who presented with progressive proptosis , with normal vision and was managed successfully surgically . 
 clinical features , pathophysiology , and surgical management of this rare entity are discussed in the context of pertinent literature . 
Introduction
Case Report
Discussion
Conclusion