epidermoid cysts are rare , slow - growing , congenital , space - occupying lesions accounting for 0.2 - 1.8% of all primary brain tumors .
epidermoid cysts involving the brainstem are extremely rare , with only 18 reported cases in the literature and only five purely intrinsic epidermoid cysts within this group .
typically , epidermoids appear hypointense on t1-weighted magnetic resonance ( mr ) images , and hyperintense on t2-weighted sequences .
dense  or  white epidermoids  have high protein content and show reversed signal intensity on mr images , with high signal intensity on t1-weighted images and low signal intensity on t2-weighted images . here , we report an interesting case of intrinsic brainstem  dense  or  white epidermoid cyst  in a 15-year - old girl . the clinical presentation , radiological imaging , and surgical management are discussed , along with a review of pertinent literature .
a 15-year - old girl presented with a one - year history of progressive quadriparesis , diplopia , dysphagia , dysarthria , and unsteadiness of gait with frequent falls to either side .
her neurological examination revealed upper motor neuron type of quadriparesis with multiple cranial nerve involvement ( v , vi , ix , x , and xii ) .
brain mr imaging ( mri ) demonstrated an atypical intra - axial pontomedullary lesion , which had a high t1 signal , a low t2 signal , and subtle contrast enhancement [ figure 1 ] .
for further confirmation , a diffusion - weighted imaging ( dwi ) sequence was obtained [ figure 2 ] , which revealed a bright signal within the tumor suggestive of an epidermoid cyst rather than a cavernous malformation or brain tumor .
on splitting the vermis , the floor of the fourth ventricle was exposed and found to be distended from the underlying cyst .
a myelotomy was performed through the thinned - out floor , revealing a pearly white , viscous substance that was resected gross totally with the aid of micro - neurosurgery .
postoperatively , the patient experienced mild , transient sixth cranial nerve palsy that resolved completely within several weeks .
postoperative computed tomography ( ct ) scan confirmed the intraoperative impression of gross - total removal [ figure 3 ] , and histological testing confirmed the presence of an epidermoid cyst .
sagittal t1-weighted brain magnetic resonance imaging showing an apparently intra - axial space - occupying lesion of the pontomedullary region ( a ) with subtle contrast enhancement ( b ) , the lesion is hyperintense in axial t1-weighted images ( c ) and hypointense in t2-weighted images ( d ) magnetic resonance diffusion - weighted image revealing a bright signal within the tumor postoperative computed tomography scans sagittal ( a ) and axial ( b ) demonstrate gross - total removal of the brainstem tumor
epidermoid cysts are rare , slow - growing , congenital , space - occupying lesions accounting for 0.2 - 1.8% of all primary brain tumors .
these primarily arise in the basal subarachnoid spaces and commonly involve the cerebellopontine angle and juxtasellar areas .
those located in the brainstem occur very rarely , and purely intrinsic lesions as described in the present case have been reported previously in five cases only .
patients harboring these cysts typically become symptomatic between the ages of 20 and 40 years . due to the insidious manner in which these grow , brainstem epidermoid cysts in children are extremely rare and
the pathogenesis of true intra - axial brainstem epidermoid is unclear and usually not considered in the preoperative differential diagnosis of brainstem tumors .
although considered as histologically benign , epidermoid cysts can cause significant neurological defects by compressing vital structures .
patients presenting with intrinsic epidermoid cysts commonly exhibit symptoms related to the compression of associated brainstem structures . in the present case ,
the presentation suggested lesion enlargement that resulted in pyramidal tract involvement , multiple cranial nerve palsy , and balance problem .
the best diagnostic clue is a cerebrospinal fluid ( csf)-like mass that insinuates within cisterns , encasing adjacent neurovascular structures .
typically , epidermoids appear hypointense on t1-weighted mri scans , but might also have an intermediate intensity between the brain and csf on t1 , whereas they are usually hyperintense on t2-weighted sequences . however , signal intensity can be variable depending on the relative amount of lipid , cholesterol , keratin , and proteins and seldom show contrast enhancement .
white epidermoids  have high protein content and may appear hyperattenuated on ct scans . compared with the classic epidermoid cyst , these  dense  or white epidermoids show reversed signal intensity on mr images , with high signal intensity on t1-weighted images and low signal intensity on t2-weighted images .
the rarity of brainstem epidermoid cysts can make their diagnosis difficult ; thus , the use of modern mri techniques , such as dwi and fluid attenuated inversion recovery ( flair ) imaging , might be helpful in establishing the diagnosis in such cases .
they do not suppress completely on flair images and restrict ( show high signal intensity ) on dwis . in our case ,
the radiological presentation was unusual , fitting rightly to the rare type of  white epidermoids  .
although there appears to be a consensus about surgical resection being the best therapeutic option for the treatment of epidermoid cysts , these tumors pose a surgical challenge and attempts for aggressive removal of the cyst wall are fraught with increased risks of morbidity and mortality .
on the other hand , cases treated more conservatively show good or excellent results with minimal complications .
nevertheless , ziyal et al . pointed out that surgical resection should be as radical as possible .
neurosurgical judgment at the time of surgery is warranted to ensure maximum resection while minimizing postoperative neurologic deficits .
the use of modern diffusion - weighted mri techniques might be helpful in establishing the diagnosis in such cases .
neurosurgical judgment at the time of surgery is warranted to ensure maximum resection while minimizing postoperative neurologic deficits .
 epidermoid cysts involving the brainstem are extremely rare , with only 18 reported cases in the literature and only five purely intrinsic epidermoid cysts within this group .  
 white epidermoids  , a rare entity , 
 have high protein content and show reversed signal intensity on magnetic resonance images . 
 in contrast to the classical variety , these cysts show high signal intensity on t1-weighted images and low signal intensity on t2-weighted images . here , we report an interesting case of intrinsic brainstem  white epidermoid cyst  in a 15-year - old girl and discuss its clinical characteristics , radiological features , and surgical treatment . the girl presented with a one - year history of progressive quadriparesis , and features of multiple cranial nerve involvement . because the cyst was purely intrinsic and 
 had altered signal intensity , the diagnosis was initially unclear until definitive neuroimaging was performed using diffusion - weighted magnetic resonance imaging ( dw - mri ) sequences . 
Introduction
Case Report
Discussion
Conclusion