usually fungal infections caused by opportunistic and pathogenic fungi were an important cause of morbidity and mortality among in patients having severe basic internal diseases , and also the sufferers did not have any characteristic significant symptoms . and the epidemiology , transport , and pathogenic mechanisms had not been well known .
historically the development of mycosis had been depended primarily on the immune defense competence of the patients .
in addition , the clinical pictures of immunocompromised mycotic infections had been different with one another and investigative studies had been diversely accumulated hitherto . however , pathogenic fungal infections in an immunocompetent had been rare and neglected into clinical studies .
especially cryptococcal brainstem abscess mimicking brain tumors had been also much more rare maybe due to blood brain barrier competence and indolent characteristics of such infections in an immunocompetent .
this 47-year - old man presented with a history of progressively worsening headache and nausea for 1 month and several days of vomituritions before admission .
a computed tomography ( ct ) scan revealed enhancing mass lesion with central necrosis and peripheral edema in the left pons compressing the fourth ventricle ( fig .
1 ) , and subsequent simple , diffusion , and perfusion mri demonstrated a rim - enhancing about 1.81.72.0 cm sized , highly perfusing mass lesion with heterogeneous low or iso - signal intensity ( fig .
2 ) , and also positron emission tomogram ( pet ) scans of the whole body comprising brainstem demonstrated a hot uptake of fluorodeoxy - glucose ( fdg ) on the brainstem lesion without having any evidences of systemic metastasis ( fig .
gross total mass resection was achieved with lateral suboccipital approach with the help of neuronavigation system and somatosensory evoked potential monitoring ( fig .
this 47-year - old man presented with a history of progressively worsening headache and nausea for 1 month and several days of vomituritions before admission .
a computed tomography ( ct ) scan revealed enhancing mass lesion with central necrosis and peripheral edema in the left pons compressing the fourth ventricle ( fig .
1 ) , and subsequent simple , diffusion , and perfusion mri demonstrated a rim - enhancing about 1.81.72.0 cm sized , highly perfusing mass lesion with heterogeneous low or iso - signal intensity ( fig .
2 ) , and also positron emission tomogram ( pet ) scans of the whole body comprising brainstem demonstrated a hot uptake of fluorodeoxy - glucose ( fdg ) on the brainstem lesion without having any evidences of systemic metastasis ( fig .
gross total mass resection was achieved with lateral suboccipital approach with the help of neuronavigation system and somatosensory evoked potential monitoring ( fig .
cryptococcus neoformans is a medically important encapsulated pathogenic yeast often responsible for potentially life - threatening meningoencephalitis in humans .
cryptococcosis occurs world wide , and its incidence has increased with the onslaught of the human immunodeficiency virus / acquired immunodeficiency syndrome pandemic . in nature , cryptococcus ( c. ) neoformans exists in two biochemically distinguishable varieties , c. var .
gatti , and also is subdivided into 5 serotyes : a , d , ad , serotypes corresponding to c. var .
differences among the specific serotypes are based on the antigenic differences resulting from structural variations of the major capsular polysaccharide glucuronoxylomannan .
the specific serotypes of clinical cryptococcal isolates can be correlated with differences in epidemiology , pathogenesis , clinical presentations and patient management9 ) . c. neoformans is an opportunistic fungus that typically affects patients who are hiv - positive and other patients with compromised immune systems .
disseminated disease may occur in up to 62% of hiv - seronegative patients with cryptococcosis2 ) .
these fungi are present in the air , on medical objects and instrumentations , in the respiratory tract and on the hands of hospital staff , and so transplantations have been the most frequent risk factors7 ) .
cryptococcus neoformans infections usually presents as a meningitis with t - lymphocyte defects but not as a cerebral mass lesion3 ) . however , cryptococcal mass lesion ( cryptococcoma ) rarely occurred even in apparently immunocompetent child in one series4 ) . in a diagnostic study we performed
perfusion - weighted mr imaging , hakyemez et al.7 ) previously reported 105 patients with lesion [ high - grade glioma ( n=23 ) , low - grade glioma ( n=11 ) , meningioma ( n=23 ) , metastasis ( n=25 ) , hemangioblastoma ( n=6 ) , pyogenic abscess ( n= 4 ) , schwannoma ( n=5 ) , and lymphoma ( n=5 ) ] .
the regional cerebral blood volume ( rcbv ) ratio of the lesions were obtained by dividing the values obtained from the normal white matter .
the rcbv ratio was 5.76 in high - grade glioma , 8.02 in meningioma , 5.27 in metastasis , 11.36 in hemangioblastoma , 0.76 in abscesses , 1.10 in lymphoma , and 3.23 in schwannomas . in conclusion ,
rcbv ratios on perfusion mri scan can be used to discriminate various intracranial space occupying lesions by comparing vascularities . with this rcbv tool
we can discriminate between ring enhancing abscess and high - grade glioma with hemorrhagic necrosis and single metastasis1 )
historically lesions of the pons and brachium pontis have long been considered as a difficult diagnostic and surgical challenge .
a presumptive diagnosis can often be made based upon characteristic ct and mr imaging appearances therefore , patients have been treated purely on the basis of radiologic findings in the absence of a diagnostic tissue specimen .
patients are frequently administered inappropriate empirical therapy because their diagnoses were based upon clinical and radiographic impressions not on histological grounds . and
surgical approaches to the pons have generally been one of the following : 1 ) the suboccipital approach via the fourth ventricle ; 2 ) an approach through a retromastoid suboccipital craniectomy via the cerebellar pontine angle ; 3 ) the subtemporal transtentorial technique ; or 4 ) a ct - guided stereotactic suboccipital transcerebellar biopsy .
the open conventional surgical methods carry inherent risks in compromised patients and are associated with a low diagnostic yield .
stereotaxic biopsy has been shown effective and consistent in obtaining diagnostic tissue samples through a transcortical frontal trajectory or by a suboccipital transcerebellar approach6 ) .
there have been only three previously reported cases of pontine biopsies obtained by the suboccipital transcerebellar method5,6 ) .
abernathey et al.1 ) present 26 cases of pontine mass lesions biopsied through a suboccipital transcerebellar approach traversing the middle cerebellar peduncle .
interestingly in this series we safely performed direct gross total mass resection simply with lateral suboccipital approach with the help of neuronavigation and ssep monitoring system .
generally immunocompromised brain abscess medication plan is amphotericin b 0.7 mg / kg intravenous+flucytosine 100 mg / kg per os ( po ) daily for 2 weeks , then fluconazole 400 mg po daily for 8 weeks , then fluconazole 200 mg po daily till stable , however , we prescribed amphotericin or fluconazole 5 mg / kg po for 2 - 3 mo8 ) .
this is a previously unreported rare case of brainstem cryptococcal abscess mimicking brain tumors in an immunocompetent host without having any apparent typical cryptococcal meningeal symptoms and signs with resultant good neurosurgical recovery .
 usually fungal infections caused by opportunistic and pathogenic fungi had been an important cause of morbidity and mortality among immunocompromised patients . 
 however clinical data and investigations for immunocompetent pathogenic fungal infections had been rare and neglected into clinical studies . 
 especially cryptococcal brainstem abscess cases mimicking brain tumors were also much more rare . 
 so we report this unusual case . 
 this 47-year - old man presented with a history of progressively worsening headache and nausea for 1 month and several days of vomituritions before admission . 
 neurological and laboratory examinations performed demonstrated no abnormal findings . 
 previously he was healthy and did not have any significant medical illnesses . 
 a ct and mri scan revealed enhancing 1.81.72.0 cm mass lesion in the left pons having central necrosis and peripheral edema compressing the fourth ventricle . and also positron emission tomogram scan demonstrated a hot uptake of fluoro - deoxy - glucose on the brainstem lesion without any evidences of systemic metastasis . 
 gross total mass resection was achieved with lateral suboccipital approach with neuronavigation system . 
 postoperatively he recovered without any neurological deficits . 
 pathologic report confirmed cryptococcus neoformans and he was successively treated with antifungal medications . 
 this is a previously unreported rare case of brainstem cryptococcal abscess mimicking brain tumors in immunocompetent host without having any apparent typical meningeal symptoms and signs with resultant good neurosurgical recovery . 