osteoblastomas are rare , osteoid - forming tumors first described by lichtenstein and jaffe in 1956 . twenty - six cases of osteoblastoma involving the temporal bone have been reported so far . localized pain and swelling with occasional 7 and 8 cranial nerve compression are the main presenting clinical features . raised intracranial pressure ( icp ) caused by mass effect has been reported in one case , and in another case , 6 nerve palsy caused by compression of the cavernous sinus has been described . the gold standard for the treatment of this type of lesions consists in the complete surgical resection , which unfortunately is not possible in every occasion . we report on the management of a small right temporal bone osteoblastoma causing compression of the right transverse - sigmoid sinus junction , which became clinically evident with isolated intracranial hypertension syndrome ( ihs ) . a 7-year - old boy with a history of autism presented to a peripheral hospital complaining of headache and neck pain followed by visual disturbance . the ophthalmic examination documented a bilateral loss of visual acuity ( 2/10 ) , fixed bilateral mydriasis and a grade iv bilateral papilledema . the noncontrast - enhanced computed tomography ( ct ) scan of the head was unremarkable . the patient was transferred to the pediatric ward of our hospital with a provisional diagnosis of pseudotumor cerebri . the patient underwent a magnetic resonance imaging ( mri ) scan of the brain with gadolinium which showed signs in keeping with longstanding raised icp , including bilateral kinking of the optic nerves within the orbit , enlargement of subarachnoid spaces , flattening of the posterior sclera , and the empty sella sign [ figure 1b ] . the same investigation documented a single , 16 mm , oval , t1 and t2 isointense , contrast - enhancing lesion arising in the right mastoid region , and narrowing the transverse - sigmoid sinus junction [ figure 2b ] . ( a ) coronal slice from the follow - up angio - magnetic resonance imaging showing the reconstitution of the physiological caliber of the right transverse - sigmoid sinus . comparison between preoperative ( b ) and follow - up ( c ) axial magnetic resonance imaging images demonstrating the resolution of two important radiological signs of intracranial hypertension : the posterior flattening of the ocular globes and the papillary protrusion ( a ) angiographic sequence showing the mild right sinus dominance and the clear effect of the compression on the transverse - sigmoid junction . ( b ) angio - magnetic resonance imaging coronal slice showing the hyperintense solid lesion responsible for the hampering of the venous blood flow a cerebral angiography digital subtraction angiography documented the compression of the right transverse - sigmoid junction distal to the vein of labb , within a picture of mild right side dominance of the venous sinuses circulation in the posterior fossa [ figure 2a ] . a diagnosis of raised icp related to impaired cerebrospinal fluid ( csf ) absorption was supposed , considering the intracranial venous hypertension due to the lesion compressing the sinus . intraoperatively , an osteolytic lesion was found on the asterion with a moderately bleeding core underneath , extending in the right mastoid . the lesion did not involve the dura and was indenting and stretching the right transverse sinus . we also considered the possibility to measure intraoperatively the hydrostatic pressure in the transverse sinus proximally to the lesion , but the potential risks related to a maneuver involving a puncture of the sinus outweighed the benefits . the histological examination was in keeping with a diagnosis of osteoblastoma [ figure 3 ] . it shows the typical structure of the osteoblastoma consisting in anastomosing bone trabeculae embedded in a loose fibro - vascular stroma ( h and e , 200 ) on the postoperative time , a right mastoiditis occurred , which was successfully treated . the postoperative course was characterized by a prompt resolution of a headache and a progressive improvement of the visual acuity over the following weeks . indeed , a 4-week follow - up ophthalmic exam documented a visual acuity of 7/10 in the right eye and 4/10 in the left , associated with a complete resolution of the papilledema and some degree of residual left optic atrophy . a follow - up mri after 4 months showed the normalization of the diameter of the right transverse - sigmoid junction [ figure 1a ] , and a significant regression of the signs of increased icp [ figure 1c ] . the morphological features of the venous sinuses in the general population are extremely variable : a symmetrical venous drainage in both transverse sinuses is reported in no more than 65% of cases and a prevalence of the right dominance account for 40%60% . venous flow impairment through the transverse - sigmoid sinus has been often observed as a potential ihs - triggering mechanism , in particular , if associated with contralateral sinus hypoplasia . several different conditions can account for venous sinus obstruction , including thrombosis and tumor compression . a recent retrospective study on a pediatric series 145 mr - venograms of patients diagnosed with idiopathic intracranial hypertension , was reviewed to assess the potential role of venous outflow impairment . furthermore , obstruction of a dominant sinus was significantly associated with an increased opening pressure after lumbar puncture ( median value 34 cm h2o and highest value 65 cm h2o ) . the presence of dominant - sided venous outflow obstruction was associated with pathological collateral venous circulation in 68% of patients . nevertheless , maiuri et al . recently observed that a nondominant sinus compression may lead to raised icp , whereas obstruction of a dominant sinus may remain without clinical consequences . such findings , contrasting with the intuitive common sense , highlight the complexity of the venous sinuses as an anatomic - functional system , where an active role is also played by the development of an adequate collateral circulation . the temporal bone is the site where the transverse and sigmoid sinuses are located and so the development of an even small mass in this position may cause a compression of these vascular structures . the histopathological diagnosis in our case was in keeping with osteoblastoma , an osteoid - forming tumor that usually develops in the long bones or in the posterior vertebral arches . the rising from the temporal bone is extremely unusual , with only 26 cases described in the literature . the clinical presentation of temporal bone osteoblastomas is quite heterogeneous : the most common presenting symptoms are swelling and localized pain not relieved by salicylates ; hearing loss , tinnitus and facial palsy occurred in 30% of cases . only two other cases were reported with symptoms and signs similar to those found in our patient , but the mechanism responsible for that clinical condition was different . the first case presented with ihs due to the prevalent mass effect of a huge osteoblastoma ( 10 cm  6 cm  6 cm ) located in the left temporal bone ; the second case presented with headache and diplopia due to an osteoblastoma invading the apex of the cavernous sinus and causing 6 cranial nerve 's palsy . in our case , we postulate that a decrease in csf reabsorption due to venous sinus obstruction was the underlying cause of the ihs . it should be noted that our patient suffered from learning disabilities , and this may have led to a diagnostic delay and the evidence of left optic atrophy suggests a longstanding raise in icp . noncontrast - enhanced ct scan does not help the diagnosis as in our case , whereas the mri was essential to show the lesion and to document the characteristic signs of raised icp . a cerebral angiography was performed to assess the extent of sinus obstruction , as in our case the mri - angiogram proved to be of low accuracy to such purpose . the management of symptomatic patients with compression of a cerebral venous sinus entails restoring the normal venous drainage . radiotherapy , which has been used in the past , has shown to be ineffective or even detrimental because it can promote malignant degeneration . chemotherapy , on the other hand , does not have a role in the treatment of the primary singular benign bone tumor . we report the novel finding of ihs caused by a small temporal osteoblastoma obstructing the transverse - sigmoid junction in a pediatric patient . complete resection of the lesion restored the venous drainage , leading to prompt clinical improvement . in the management of patients with a venous sinus compression , restoration of venous drainage
osteoblastomas are rare , benign bone tumors mainly arising from the long bones and the posterior vertebral arches 
 . skull localizations account for approximately 15% of cases . 
 a total amount of thirty cases involving the temporal bone are reported in the literature . 
 clinical presentation of temporal osteoblastomas often includes local pain and swelling , while 7th and 8th cranial nerve impairment is rare . 
 we report the novel finding of increase intracranial pressure syndrome secondary to dominant transverse - sigmoid sinus junction compression caused by a small temporal bone osteoblastoma . 
 excision of the tumor with the restoration of venous flow in the sigmoid sinus was followed by a prompt clinical improvement . in the management of patients with a venous sinus compression , restoration of venous drainage 
 should be a priority .