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the patient was a 23-year - old woman , a known case of arnold - chiari malformation with peripheral neuropathy and muscular atrophy , who presented with headache , drowsiness , decreased vision , and severe gait dysfunction lasting for several years .
brain magnetic resonance imaging ( mri ) confirmed a hypointense - signal mass in the left hemisphere of the cerebellum causing mass effects on the fourth ventricle , which shifted it , accompanied with dilation of third and lateral ventricles .
hypertensive cerebrospinal fluid ( csf ) form of hydrocephaly was seen in the supratentorial region , but the fourth ventricle was normal .
the possibility of aqueduct stenosis or obstruction was mentioned ( 
 fig . 1 
 ) .
cervical spine mri revealed a normal spinal column with herniation of the cerebellar tonsil ( 
 fig . 2 
 ) . 

brain magnetic resonance imaging . a hypointense signal mass in the left hemisphere of the cerebellum causing mass effects on the fourth ventricle , which shifted it , accompanied with dilation of third and lateral ventricles . 

tonsillar herniation to the cervical spine is seen . with the impression of tonsillar herniation and cerebellar tumor in the sense of arnold - chiari syndrome , external ventricular drainage with external reservoir
a cream - white tight mass was seen , which could not be extracted by suction and thus was totally resected .
simultaneously , regarding the arnold - chiari malformation and tonsillar herniation , the patient underwent suboccipital decompression and microscopic laminectomy of c2 vertebrae with excision of foramen magnum and duraplasty .
gross examination revealed multiple pieces of irregular cream tissue totally measuring 2.5  2.0  0.7 cm .
microscopic assessment confirmed a granulomatous inflammation composed of aggregation of epithelioid histiocytes associated with giant cells and lymphocyte cuffing foci of caseating necrosis compatible with tuberculoma .
postoperative spiral chest computed tomography ( ct ) scan showed a normal pulmonary parenchyma without evidence for pulmonary tuberculosis , thus , the patient had a primary extrapulmonary cerebellar tuberculoma ( 
 fig .
the patient has been followed to now ; the neurological symptoms were alleviated 6 months subsequent to the surgery . 

chiari malformations are rare congenital anomalies with an estimated prevalence of 0.1 to 0.5%5 ; however , the true frequency is unknown . in most cases , due to the small posterior fossa
the main pathogenesis of this malformation remains the subject of debate and involves patients presenting with a wide spectrum of clinical symptoms.1 
  arnold - chiari syndrome is usually detected prenatally or at birth , as it is nearly always associated with lumbosacral or thoracic myelomeningocele.1 weakness , stridor , apneic spells , aspiration , and dysphagia are the common manifestations in infancy,6 followed by progressive hydrocephalus in childhood.1 it may be associated with other syndromes like syringomyelia and scoliosis.7 
 8 our case presented with headache , drowsiness , decreased vision , and severe gait dysfunction lasting for several years .
arnold - chiari syndrome should be considered in any fetus or newborn with clinical evidence of a spinal myelomeningocele .
neuroimaging plays the main role in confirming the diagnosis , and mri is the best imaging modality for evaluation.9 mri of the brain along with the entire spinal cord ( cervical ) is appropriate to demonstrate downward displacement of the inferior cerebellar vermis and medulla through the foramen magnum into the upper cervical canal . despite these typical findings , brain mri in our case showed an unusual mass in the left cerebellar hemisphere causing mass effect .
the patient underwent the most common procedure for arnold - chiari malformations , which is posterior decompression via suboccipital craniotomy with duraplasty.10 
 11 simultaneously , regarding the cerebellar mass with the primary impression of cerebellar tumor , posterior fossa craniotomy and resection of the mass were performed .
postoperative histopathologic evaluation showed that the mass was in fact a granulomatous tuberculoma . because no pulmonary involvement was found in either clinical manifestation or pulmonary ct scan , it was diagnosed as a primary extrapulmonary cerebellar tuberculoma mimicking a cerebellar tumor .
although tuberculosis is considered primarily a pulmonary disease , it can affect any organ system .
however , central nerves system ( cns ) involvement is so rare , it is associated with potentially devastating complications ; it affects both immunocompetent and immunologically incompetent populations .
, only a few numbers of cases with cerebellar tuberculoma have been reported , and most of them are secondary to the pulmonary involvement12 and occurred in immunocompromised patients.13 
 14 primary cerebellar tuberculoma is rare in an immunologically incompetent patient like our case . to our knowledge
, this is the first reported case of primary cerebellar tuberculoma mimicking a posterior fossa tumor in a patient with arnold - chiari malformation . depending upon the involved part of the cns , various spectrums of clinical manifestations
intracranial tuberculoma may present as either a solitary or multiple lesions in the brain parenchyma .
a ring - enhanced area on ct scan or mri is a characteristic appearance , but when there are no accompanied clinical manifestation or laboratory findings for tuberculosis , it would be so difficult to differentiate it from other cns tumors .
despite being rare , cns involvement of tuberculosis always should be kept in mind in any patient with neurological complaints from regions with a high endemic rate of tuberculosis , either in those being immunocompetent or immunologically incompetent .
chiari malformations are a congenital heterogeneous group of disorders characterized by anatomic anomalies of the cerebellum , brain stem , and craniocervical junction associated with downward displacement of the cerebellum , alone or with lower medulla , into the cervical spine canal . 
 the patient was a 23-year - old woman , a known case of arnold - chiari malformation with peripheral neuropathy and muscular atrophy , who presented with headache , drowsiness , decreased vision , and severe gait dysfunction lasting for several years . 
 brain magnetic resonance imaging confirmed a hypointense signal mass in the left hemisphere of the cerebellum causing mass effects on the fourth ventricle , which shifted it , accompanied with dilation of third and lateral ventricles .