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Year : 2000  |  Volume : 48  |  Issue : 4  |  Page : 365--9

Co-existence of dual intracranial pathology clinical relevance of proton MRS.

RP Tripathi, A Gupta, S Gupta, SS Kumaran, S Khushu, A Dev, Balwant 
 NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences, Lucknow Road, Timarpur, New Delhi, 110054, India., India

Correspondence Address:
R P Tripathi
NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences, Lucknow Road, Timarpur, New Delhi, 110054, India.


The co-existence of neuro-cysticercosis (NCC) and intracranial neoplasm in an individual is a rare entity. Atypical presentation of cerebral cysticercosis may mimic glioma, metastasis, cerebral abscess or vice versa. The dual existence of these two lesions have led to several postulates which may have clinical impact in due course of time i.e. NCC as an oncogenetic factor for glioma or similarity of antigen found in glioma and NCC etc. An adequate management of such cases poses a challenge to both imageologists as well as clinicians. Thus, a proper diagnostic evaluation is essential for successful management of such cases. MR spectroscopy (MRS), although still a clinical research tool, may be extremely useful for exclusion or confirmation of neoplastic lesions in such a clinical scenario. The findings of MRS in collaboration with imaging parameters may increase the diagnostic yield of a MR investigation. The authors encountered five cases of dual intracranial pathologies i.e. neurocysticercosis and glioma. MR spectroscopy was useful to arrive at a definitive diagnosis in such a situation.

How to cite this article:
Tripathi R P, Gupta A, Gupta S, Kumaran S S, Khushu S, Dev A, Balwant. Co-existence of dual intracranial pathology clinical relevance of proton MRS. Neurol India 2000;48:365-9

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Tripathi R P, Gupta A, Gupta S, Kumaran S S, Khushu S, Dev A, Balwant. Co-existence of dual intracranial pathology clinical relevance of proton MRS. Neurol India [serial online] 2000 [cited 2023 Feb 5 ];48:365-9
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  ::   IntroductionTop

The co-existence of a parasitic and neoplastic intracranial lesion is a rare entity. The incidence of neurocysticercosis (NCC) among intracranial space occupying lesions is reported to be 1.2% to 2.5%.[1],[2],[3],[4] Cerebral cysticercosis may be associated with glioma[5] or cerebral abscess.[4] Single large abscess or racemose cysticerci may be difficult to differentiate from neoplastic conditions. At times a cerebral abscess may be difficult to distinguish from glioma. Similarly, a large cysticercosis also mimics a glioma, making a definite diagnosis difficult on imaging parameters alone. We encountered five cases of such a coexistence. All cases were followed up after a course of conservative line of treatment and surgery. MR spectroscopy (MRS) was utilised in all cases to differentiate neoplastic from parasitic disease or inflammatory focal lesion. Two cases are reported for illustration.

  ::   Material and methodsTop

A total of 46 patients with a clinical diagnosis of brain tumour were studied in our centre over a span of one year. The age of the patients ranged from 6 yrs. to 72 yrs. There were 16 female and 30 male patients. A total of 5 cases revealed coexistence of dual intracranial pathology. 39 patients had previous contrast CT studies available for comparison. Multiplanar magnetic resonance imaging studies were performed with T1 and T2 weighted pulse sequences i.e. spin echo (SE),turbo gradient spin echo (TGSE), T1 WI (TR=650 ms, TE=14 ms) T2 WI (TR=7400 ms, TE=115 ms). Post contrast T1 weighted multiplanar studies were performed in all cases. MRS study was undertaken 3-4 days after plain and contrast MR study to avoid the paramagnetic effects of the contrast media. Both MR imaging and proton spectroscopy were performed with 1.5 Tesla (Magnetom Vision) MR system using a circularly polarised head coil.

Single Voxel MR spectroscopic (SV MRS) study was undertaken with a volume of 8 cm3 (2x2x2), and a solid area was selected from the intracranial space occupying lesions (ICSOL) to minimise partial volume effects from the necrotic regions. Prior to spectroscopic measurements the magnetic field in the areas of interest was adequately shimmed followed by selective fully optimised water suppression pulse, so that the water signal from the target volume was minimum and other peaks could also be visualised. All the 'proton' H1 MRS measurements were done with single voxel spectroscopy utilising spin echo pulse sequence with the following parameters : TR (pulse repetition time) 1500 milliseconds, TE (echo time) 135 milliseconds, TA (acquisition time) 1.43 minutes, AC (acquisition) 64. Test-retest reliability was established by repeating the H1 MRS procedures in control patients, earlier in our institute. The spectra were analysed by an experienced analyser, who was blind to the clinical diagnosis.

Case 1 : A 30 year old female presented with features of left focal seizures with secondary generalisation and weakness of left hand of one month's duration. Examination revealed normal fundus and power of grade 4/5 in the left hand. Initial MR examination revealed evidence of dual intracranial pathology with varying imaging characteristics. The right parietal region showed evidence of a small cystic lesion towards the parafalcine region with a hypointense rim, eccentric mural nodules and marked perifocal oedema on T2 WI. Posteriorly, there was another large focal lesion with well-defined borders displaying cystic degeneration within it, on T1 and T2 weighted images. No other abnormal signal intensity was discernible. It was difficult to arrive at a common definitive diagnosis based on imaging parameters alone. In view of the presence of two focal lesions with different image characteristics, the individual was subjected to MRS using chemical shift imaging (CSI) technique, the results of which proved equivocal. However, a probable diagnosis of neurocysticercosis was made in view of the typical neurocysticercosis findings in the smaller lesion. The large cystic lesion, undergoing cystic degeneration was also attributed to a giant cysticercus cyst or abscess. Accordingly, the patient was treated with albendazole. There was a significant improvement in the patient's symptomatology. A review MR study with dynamic contrast imaging and SVS MRS was undertaken after 8 months which showed disappearance of the smaller cystic lesion in the right parietal lobe anteriorly on T2 WI, but persistence of the large focal lesion, posteriorly. The persistent posterior focal lesion displayed mild contrast enhancement. On post contrast T1 WI there was small enhancing nodule in place of the original NCC lesion, suggestive of resolving neuro-cysticercosis [Figure. 1a],[Figure. 1b] and [Figure. 1c]. Single voxel proton MR spectroscopy showed evidence of raised choline (C) content and comparative diminution of N-acetyle-l-aspartate (NAA) (A) and normal creatine (B) level. In addition to above a characteristic lactate peak (D) was also seen at 1.41 ppm [Figure. 2], suggestive of anaerobic glycolysis within the tumour mass. Its reversal with TE (270 ms) could not be studied due to uncooperative patient. The metabolic ratios and integral values from the persistent posterior focal lesion are as per table I and II.

The MR spectroscopic findings were suggestive of a mitotic lesion i.e. astrocytoma. The patient subsequently underwent right posterior frontal trephine craniotomy with tumour decompression. On histopathology the diagnosis of astrocytoma was confirmed. The postoperative phase was uneventful. The left hemiparesis gradually improving with physiotherapy.

Case 2 : A 9 year old female child, with a history of seizures since the last two months, was referred for MRI study. The seizures were generalised, tonic clonic in nature. MRI study revealed a well-defined heterogeneous intensity mass lesion on both T1 and T2 WI, involving the mid brain, pons, extending posteriorly to the left and right cerebellar regions. The fourth ventricle was pushed backwards with minimal indentation. In addition, the right frontal lobe showed a well-defined cystic lesion, with eccentric mural nodules, which was isointense to cerebral white matter on T1 and T2 WI. T2 WI revealed a welldefined cystic mass with no perifocal oedema. Post contrast study showed a well defined heterogeneous intensity pattern mass lesion in the posterior fossa as mentioned above. The cystic lesion revealed marked capsular enhancement with eccentric mural nodules [Figure. 3a] and [Figure. 3b]. Thus, in this case the smaller lesions showed diagnostic imaging morphology of NCC while the larger posterior fossa lesion was suggestive of a neoplastic lesion. No other abnormal signal intensity was seen. SVS MR spectroscopic findings of the posterior fossa lesion were characteristic of a mitotic lesion, although in this particular case image

  ::   DiscussionTop

The co-existence of dual (i.e. parasitic and neoplastic) intracranial pathology has been reported in literature.[4],[5] However, the application of MRS in such clinical situations has not been reported earlier in MRI literature. Parasites have been implicated in the pathogenesis of human malignancy. Anecdotal reports have suggested an association between neurocysticercosis and brain neoplasms. The study conducted by Del Brutto et al suggested that neurocysticercosis is a risk factor for cerebral glioma.[6] The study was conducted in 43 consecutive patients with proven cerebral glioma and 172 controls matched for age, sex and socio-economic status. The study revealed that 16.8 % of 43 patients with cerebral glioma had cysticercosis, while 5 out of 172 (2.9%) controls had neurocysticercosis (p<0.006). The odds ratio for the association was 7.63 (95% CI-2.03-31.09). Glioblastoma multiforme was more frequent among cases of neurocysticercosis than among those without neurocysticercosis (87.5% ? s 48.6%), although the difference was not statistically significant (p=0.24). In our series of 5 cases of dual pathology, 3 cases were of glioblastoma multiforme and the remaining two were of astrocytoma. It is postulated that intense astrocytic gliosis that surrounds calcified cysticerci, together with suppression of cellular immunity by cysticerci, may contribute to development of malignant glial cells in patients with neurocysticercosis (NCC). Multifocal metastases in the brain have been confused with NCC. Cystic oligodendroglioma have also shown false positive immunological reactions for cysticercosis. Agapejev et al suggested the following possible mechanisms : (1) NCC may have acted as an oncogenetic factor for glioma (2) similarity of antigen for glioma and NCC in terms of mol. wt. and nature of glycoprotein etc.[7] Most of the times the differentiation is quite easy as depicted in case 2. However it may be difficult to discern the nature of one or both the lesions on imaging parameters alone, as seen in case 1. In cases where the imaging parameters are quite convincing for NCC, it is worthwhile treating the patient with a course of anticysticercus drug and following it up. It may obviate unnecessary surgical procedures in selected cases.[8] If the lesion(s) does not subside the case should be subjected to MRS either by SVS or CSI technique to determine the metabolic pattern, which may enable further differentiation of lesions, as malignant lesions show characteristic spectral pattern if the tumour is not very heterogeneous in nature. Proton MRS readily distinguishes normal brain tissue from astrocytomas.[9],[10],[11] In astrocytomas, the typical proton MRS reveals a significant reduction in NAA , a moderate reduction in creatine and elevation of choline.[10],[12] Generally tumour cells show a marked increase in choline content and reduction of NAA associated with a lactate peak. Chang et al showed that a few tumours including malignant gliomas and metastases may show lipid signal combined with lactate signal.[13] In cysticercosis, resonances of lactate, succinate, alanine, acetate and/or unassigned resonances have been reported.[13] In the first case in this report, the cysticercus lesion almost subsided following albendazole therapy and the residual large lesion following therapy mimicked a large cysticercus cyst, abscess or a glioma. Dynamic contrast enhanced MRI showed the vascularity of the lesion and further facilitated the accurate localisation of a solid area within a heterogeneous cystic area to carry out adequate single voxel MRS study. Based on SVS MRS finding we conclusively demonstrated the residual lesion as glioma. This was further confirmed by histopathology post operatively. Thus pre operative MRS study confirmed the nature of the lesion and added to the diagnostic confidence of radiologist. It is strongly felt that MRS must be a part of the diagnostic work up of all inconclusive cases in such a clinical scenario.


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