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primary leptomeningeal oligodendrogliomatosis ( plo ) is a rare condition which shows near - normal mri in the early presentation and slowly progresses to mild hydrocephalus with few cysts and leptomeningeal enhancement .
eventually , entire neuraxis is involved with multiple leptomeningeal cysts , progressive hydrocephalus , and pial surface edema .
it is postulated that it arises from leptomeningeal heterotopias or already existing small undetected parenchymal primary .
secondary leptomeningeal gliomatosis is a known entity that results from invasion of the subarachnoid space or ventricular system by a primary intraparenchymal glioma .
so , it is prudent to identify this rare condition in the early stage to initiate the treatment at the earliest .
the case reported here is a child who was born by normal vaginal delivery in a tertiary care hospital with uneventful birth history .
the child was asymptomatic till 2 years of age when he presented to the hospital with one episode of simple partial seizure , for which an mri was done in march 2013 [ figure 1 ] .
the mr findings were mildly dilated ventricles with periventricular t2 hyperintensity representing interstitial edema and prominent tiny cysts along the cerebellar folia .
follow - up mri after 1 month [ figure 2 ] showed progressive communicating moderate hydrocephalus with periventricular csf seepage and diffuse leptomeningeal enhancement along the tentorium , prepontine , quadrigeminal and ambient cisterns , with increase in the number of cerebellar cystic lesions .
tuberculous meningitis with communicating hydrocephalus was considered as the primary diagnosis because of the endemicity .
csf analysis was nondiagnostic for the nature of leptomeningeal disease and showed glucose 50 mg / dl , protein 58 mg / dl , 97 rbcs / mm , 12 nucleated cells / mm ( 36% lymphocytes , 58% monocytes , and 6% macrophages ) with negative gram stain , acid fast bacilli stain , and cryptococcal antigen .
cytologic studies did not reveal a neoplastic process . during the course of illness , the child 's mother noticed regression of certain previously attained milestones , such as inability to walk and loss of head control .
since the clinical status continued deteriorating , ventriculoperitoneal ( vp ) shunting was performed to relieve the hydrocephalus .
a follow - up contrast mri brain and spine in june 2013 [ figure 3 ] showed resolution of hydrocephalus and appearance of multiple new t2-hyperintense small cystic lesions predominantly in the infratentorial region , and also involving the lateral ventricles , cerebral sulci , and the entire spinal canal .
leptomeningeal biopsy [ figure 4 ] showed tumor cells with sharply defined cell borders , clear cytoplasm , and rounded nuclei , consistent with an oligodendroglioma ( who grade ii ) .
the pathologic specimens were negative for 1p or 19q chromosomal deletions , pointing to the diagnosis of plo .
( a ) mri findings ( march 2013 ) a : t2 flair axial image shows moderate hydrocephalus ( straight arrow ) with cavum septum pellucidum with periventricular hyperintensity ( curved arrow ) ( b ) mri findings ( march 2013 ) : t2 flair axial image shows prominent cerebellar foliae ( straight arrow ) ( c ) t2 sagittal image shows few hyperintense cystic lesions in the cerebellum ( straight arrow ) .
the cyst appears to be intraparenchymal without perilesional edema ( d ) t2 sagittal image shows few hyperintense cystic lesions in the upper cervical cord in extra medullary location ( straight arrow ) ( a ) mri findings ( april 2013 ) : t2 sagittal image shows periventricular white matter hyperintensity ( straight arrow ) ( b ) t1-weighted post contrast images show diffuse leptomeningeal enhancement ( staright arrow ) ( c ) t1-weighted post contrast images show diffuse leptomeningeal enhancement ( staright arrow ) ( d ) mri spine screening appears relatively normal and is given for comparison with the follow up mri mri findings ( june 2013 ) ( a - d ) : t2 axial and sagittal images show diffuse t2 hyperintense small cystic lesions more in the basilar region and cerebellar foliae and also involving the lateral ventricles , cerebral sulci and spinal cord extending upto the conus medullaris .
( e ) t2 axial image of the spinal cord shows the leptomeningeal cysts at the surface of the spinal cord .
( g ) mr spectroscopy at te 135 shows increased lactate and decreased naa peaks .
no significant elevated choline peak leptomeningeal biopsy shows tumor cells with sharply defined cell borders , clear cytoplasm , and rounded nuclei consistent with an oligodendroglioma
in 1954 , moore first described a diffuse form of a primary leptomeningeal astrocytoma ( pla ) .
primary diffuse leptomeningeal gliomatosis ( pdlg ) can be pathologically differentiated into two common types : pla and plo .
histopathological type of pdlg has no significant prognostic importance and no treatment has proved successful .
secondary leptomeningeal gliomatosis is a known entity that results from invasion of the subarachnoid space or ventricular system by a primary intraparenchymal glioma .
it is postulated that primary leptomeningeal gliomatosis arises from leptomeningeal heterotopias or from local or metastatic spread from undetected small intraaxial primary tumor .
the age distribution covers a wide range from 2 years to 78 years , the peak incidence being in children less than 10 years of age .
the diagnostic criteria of pla were first given by cooper and kernohan as : no apparent attachment of extramedullary meningeal tumor to the neural tissue , no evidence of primary neoplasia within the neuraxis , and the existence of distinct leptomeningeal encapsulation around the tumor .
plas may have two well - established anatomic and clinical forms : nodular form , first described by bailey and dietrich as  a solitary or focal leptomeningeal gliomatosis , defined by limited tumor masses in cranial or spinal leptomeninges ,  and a diffuse form , first reported by korein as  an extension , outside the nervous parenchyma , of glial tumor cells over a wide area of the cns .
 the classical appearance of extra - axial multiple tiny cystic lesions is mentioned in the literature in the subsequent reported cases . in this case , gradual radiological progression was observed .
initial findings were mild communicating hydrocephalus , periventricular interstitial edema , few tiny leptomeningeal cystic lesions , and mild leptomeningeal enhancement , suggestive of an infective etiology . later , frank multiple small leptomeningeal cysts with a diffuse leptomeningeal distribution in the brain as well as spinal column were noted .
neurocysticercosis was considered as the principal diagnosis , though intracystic eccentric nodule was not observed .
subsequent progression of the disease showed leptomeningeal enhancement with communicating hydrocephalus , for which the differential diagnoses of tuberculous meningitis , leptomeningeal tumor spread , and cysticercal meningitis were considered .
cysts in neurocysticercosis show intracystic eccentric nodule appearing as pea in a pod and perilesional edema in inflammatory stage which is not seen in our case .
csf examination typically shows increased proteins , decreased glucose concentration , and lymphocytosis in tuberculous meningitis , which were not observed . even though csf culture for mycobacterium was negative , empirical anti - tubercular and anti - inflammatory drugs
were started to assess the response . as there was no improvement with treatment , patient
histopathology showed tumor cells with sharply defined cell borders , clear cytoplasm , and rounded nuclei , consistent with an oligodendroglioma ( who grade ii ) .
bourne et al . reported stable disease after chemotherapy with cisplatin , vincristine , cyclophosphamide , and etoposide , while franceschi et al .
however , 6 - 7 years of good - quality life have been reported following palliative therapy . to the authors ' knowledge ,
only six cases of these rare tumors have been treated with adjuvant chemo - radiotherapy .
to conclude , plo has a sequential progression from few tiny leptomeningeal cysts to florid disease .
so , if the clinical picture shows mild hydrocephalus with tiny cysts and mild leptomeningeal enhancement without scolex or ring enhancment or significant perilesional edema , then plo can be considered .
awareness , early detection and treatment of the disease are imperative to reduce the morbidity .
primary leptomeningeal oligodendrogliomatosis ( plo ) is a rare low - grade intracranial and spinal canal subarachnoid neoplasm without an obvious primary neoplasm in the brain or spinal cord parenchyma . 
 we present here the serial progression of radiological findings of this rare disease in a 2-year - old male child whose clinical status deteriorated over a period of 4 months with the main complaint of partial seizures . during this period , 
 the mr findings progressed from mild hydrocephalus with minimal leptomeningeal enhancement to leptomeningeal multiple cystic lesions in the entire neuraxis including the spine .