Role of Magnetic Resonance Imaging in Intracranial Infections at a Tertiary Level Medical College

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1 ISSN ORIGINAL ARTICLE Role of Magneti Resonane Imaging in Intraranial Infetions at a Tertiary Level Medial College 1 1* Shweta Gupta, Jeevan A. Vernekar, Sahin S. Amate, Jagdish A. Caodar, Anish J. Vernekar 1 2 Department of Radio-diagnosis, Department of Preventive Soial Mediine, Goa Medial College, Bambolim (Goa) India Abstrat: Bakground: Intraranial infetions range from indolent to life threatening and from self limited to relentlessly progressive. Early detetion and aurate haraterization with MRI an allow appropriate therapy to be initiated and ompliation to be managed appropriately. Aim and Objetives: This prospetive diagnosti study was onduted to evaluate role of MRI in diagnosis of intraranial infetion and to study its speifiity in various intraranial infetions. Material and Methods: A prospetive study of 100 patients with linial presentation of intraranial infetions was onduted in the Department of Radiodiagnosis at the tertiary are hospital in Goa (Goa Medial College), over a period of one year and six months by using 1.5 Tesla superondutive unit. Results and Conlusions: MRI is undoubtedly an indispensible tool to evaluate patients presenting with intraranial infetions. Careful evaluation of magneti resonane behaviour of infetious lesions helps in identifying not only the preise loation and extent of the lesion, but also in proposing a speifi etiology in many suh patients. Keywords: MRI(Magneti Resonane Imaging), Intraranial Infetion Introdution: Many patients are routinely referred with linial presentation suggestive of intraranial infetion to tertiary are hospital. Performing MRI in these patients is highly benefiial in diagnosing or ruling out presene of intra ranial infetion and it often helps in suggesting nature of infetion. Foerster et al [1] also onluded that the radiologist play entral role in the diagnosis and management of patients with intraranial infetions. MRI is muh more sensitive than CT san for defining the extent of infetion, and identifying infetion related ompliations suh as subdural effusion. A thorough understanding of the imaging patterns assoiated with ommon intraranial infetions allows radiologist to help narrow the differential diagnosis and failitate early implementation of appropriate therapies. This artile desribes the MRI findings of 100 patients referred to tertiary hospital in Goa Medial College with linial presentations suggestive of intraranial infetion. Material and Methods: A prospetive diagnosti ase series study of 100 patients with linial presentation of intraranial infetions was onduted in the Department of Radio diagnosis at the tertiary are hospital in Goa (Goa Medial College), over a period of one year and six months. During Otober 2009 till April 2011 a total 100 patients who reported to the Neurosurgery, Mediine or Neurology Departments with signs and symptoms of intraranial infetions were inluded in the study. Exlusion Criteria were patients with paemakers, ferromagneti prostheti valve, aneurysm lips and Claustrophobia. Findings of laboratory investigations e.g. CSF analysis, IgG antibody titres (eg. toxoplasmosis) were reorded Journal of Krishna Institute of Medial Sienes University 35

2 in the proforma of the study. Ethial Clearane for the study was obtained before ommenement of the study from Institutional Ethis Committee, Goa Medial College, Bambolim Goa. Diagnosis was onfirmed on CSF analysis and/or response to appropriate therapy. Images were aquired on a 1.5 Tesla superondutive unit (Magnetom Avento, Siemens), using a dediated head oil. In some patients intravenous Gadolinium (MRI ontrast agent) was injeted wherever indiated. No speifi patient preparation was required for the normal level study; however patients were advised to remain fasting for at least 4 hrs for ontrast imaging study. It was ensured that renal funtion test were within normal limits before injeting ontrast agent and no ontraindiations to Magneti Resonane Imaging existed among the patients. Standard MRI sequenes were used and MR imaging protool was as per aepted norms. These inluded ross setional axial images in T1 weighted imaging (T1WI) and T2 weighted imaging (T2WI). Images were also obtained in oronal and sagittal plane using T1WI and T2WI. Wherever neessary speial sequenes were obtained. This inlude Fluid attenuated inversion reovery (FLAIR), Diffusion weighted Imaging (DWI) and Apparent diffusion oeffiient (ADC). Additional MR sequenes like Gradient eho sequenes and MR spetrosopy were performed as and when indiated. Paramagneti MR ontrast medium, intravenous Gadolinium enhaned T1 weighted images were obtained whenever onsidered neessary. Finally, the results of Magneti Resonane Imaging were orrelated with the histopathologial, CSF & other laboratory investigation findings. Results: Maximum of 56 (56%) patients with intraranial infetion were < 30years of age with peak inidene at year. 31 (31%) of patients were between the years. Only 13 (13%) patients were above the age of 50 years (Table 1). Seizure (64%) was the most ommon presentation in patients with intraranial infetion, followed by fever (39%) and altered sensorium (25%) (Table 2). Tuberulosis was the most ommon intraranial infetion found in the urrent study, followed by parasiti, pyogeni (baterial) and viral. Fungal infetion was the least ommon. Amongst parasiti neuroystierosis was the most ommon. Most ommon imaging manifestation of pyogeni (baterial) infetion is meningitis; followed by brain absess and sub/epidural empyema (Table 3 and 5). Out of total 100 patients with intraranial infetions 23 (23%) patients were HIV positive. Tuberulosis (30.4%) was the most ommon intraranial infetion found in HIV positive individuals, followed by toxoplasmosis (26%). Least ommon intraranial infetion assoiated with HIV is Progressive Multifoal Leukoenephalopathy (0.04%) (Table 4). Journal of Krishna Institute of Medial Sienes University 36

3 Table 1: Age and Sex Distribution in Intraranial Infetions Age Group Male Female Total Number Perent Number Perent Number Perent Total Table 2: Symptomatology in 100 Patients Suspeted To Have Intraranial Infetions Symptoms/Signs Number Perent Seizures Fever Altered Sensorium Headahe Vomiting 5 5 Nek stiffness 3 3 Visual disturbane 2 2 Cranial Nerve Palsies 2 2 Dementia 2 2 Hemiplegia 1 1 Behavioural abnormality 1 1 Total Journal of Krishna Institute of Medial Sienes University 37

4 Table 3: Distribution of Intraranial Infetions Type of Intraranial Infetion Number Perent Tuberulosis Neuroystierosis Pyogeni Meningitis 6 6 Toxoplasmosis 6 6 Herpes Simplex Enephalitis 5 5 Pyogeni Absess 4 4 Fungal 4 4 Pyogeni subdural/epidural effusion 2 2 Japanese Enephalitis 2 2 Aute Disseminated Enephalomyelitis 2 2 Human Immune Defiieny Enephalopathy 2 2 Progressive Multifoal Leukoenephalopathy (PMLE) 1 1 Sub-Aute Slerosing Panenephalitis 1 1 Creutzfeldt Jaob Disease 1 1 Total Table 4: Intraranial Infetions among HIV infeted patients Type of Intraranial Infetion Number Perent Tuberulosis Toxoplasmosis Baterial Fungal HIV Enephalopathy PMLE Total Journal of Krishna Institute of Medial Sienes University 38

5 Table 5: Types of Lesions Sr. No Type of Lesions Number (Perent) MRI Diagnosti Ability (%) 1 Tuberular 44 (44) 70 % 2 Parasiti 26 (26) 90 % 3 Pyogeni 12 (12) 83 % 4 Viral 12 (12) 66 % 5 Fungal 4 (4) 50 % 6 Misellaneous 2 (2) - Total Tuberulosis: In 31 patients (70%) onfident diagnosis of intraranial tuberulosis was made based on harateristi MRI findings. The remaining 13 patients (30%) required ombination of linial, CSF hanges and imaging findings to onlude the diagnosis. 2. Parasiti: Presumptive diagnosis of intra ranial parasiti infetion was made in 23 patients (90%) based on typial MRI findings whih were later onfirmed with supportive laboratory findings. 3. Pyogeni: Diagnosis of intraranial pyogeni infetion was made in 10 patients (83%) based on MRI findings only. Remaining 2 patients (17%) required linio-laboratory orrelation before initiating therapy. 4. Viral: Out of total 12 patients with viral intraranial infetion 8 patients (66%) were diagnosed based on MRI findings alone. The remaining 4 patients (34%) required imaging and linio-laboratory orrelation to reah to diagnosis of viral etiology. 5. Fungal: Diagnosis of fungal intra-ranial infetion was made in 2 patients (50%) based on MRI findings alone; whereas the remaining 2 patients (50%) required orrelation with linial, mirobiologial and imaging findings to onlude the diagnosis. Findings in Pyogeni Intraranial Infetions: Meningitis / Cerebritis Six ases of pyogeni CNS infetions who presented with headahe, vomiting and nek stiffness were studied. 4 patients were females and 2 were males. Maximum inidene was in the age group of years. Isolated foal erebritis was seen in 3 (50%) patients, isolated meningitis was seen in 2 (33.3%) patients and both meningitis and erebritis was seen in 1 (16.6%) patient. The lesion appeared isointense in 4 (66%) patients and hypointense in remaining 2 (34%) patients on T1WI. On T2WI the lesion appeared isointense in 3 (50%) patients and hyperintense in 3 (50%) patients. These hanges represent ishemia and / or edema. All these lesions showed restrited diffusion on DWI. Gd- DTPA enhaned sans were performed in all 6 patients and found that 2 (33.3%) patients showed isolated meningeal enhanement, 3 (50%) patient showed gyriform enhanement and 1 (16.6%) patients showed both gyriform and meningeal enhanement. Subdural / Epidural effusions / Empyemas Two patients presented with high fever and altered sensoriums were studied in this group. The site of empyema was the interhemispheri fissure in 1 ase, and erebral onvexity in the other ase. In Journal of Krishna Institute of Medial Sienes University 39

6 both the ases, the olletions were isointense to hyperintense on T1WI and hyperintense on T2WI. In the present study, rim enhanement of the olletion with assoiated meningeal enhanement was noted in both ases on post ontrast images (Fig.1). hypointense on T2WI in all 4 patients. Surrounding perilesional hyperintensity was seen on T2WI in all the ases suggestive of perilesional edema. Mass effet on surrounding strutures was seen in 3 patients. On ontrast injetion, rim Fig. 1:Sagittal Post Contrast T1WI Fat Sat: Shows A Multi-Loulated Extra Axial Colletion Over Right Cerebral Convexity Showing Peripheral Rim Enhanement with Assoiated Meningeal Enhanement along the Right Tentorium Cerebelli. Pyogeni Absess Patients in this group presented with high fever, seizures, and one of the patients with right sided hemiplegia. The inidene was found to be higher in the first and seond deade of life; mostly due ontiguous spread of infetion from otitis media whih is ommon in younger age groups. The absesses were single in 1 patient and multiple in 3 patients. In 2 (50%) patients, the absesses were supratentorial and in the remaining 2 (50%) patients, the absesses were infratentorial. In all 4 patients, the absess avity was hypointense on T1WI and hyperintense on T2WI and FLAIR. The apsule was hyperintense on T1WI and enhanement was seen in all ases with smaller daughter absesses seen in 2 patients (fig. 2). In our study, none of the patients showed intraventriular extension / rupture. The role of DWI in distinguishing a pyogeni absess from a neroti tumor was studied. It was found that in all 4 ases, the absesses were hyperintense on DWI and showed low ADC Values, in omparison to neroti tumors whih are hypointense on DWI and hyperintense on ADC. MR Spetrosopy was performed in 3 ases. Lipid latate peaks at 0.3 ppm were obtained along with amino aids at 0.9 ppm in all 3 patients. Journal of Krishna Institute of Medial Sienes University 40

7 Fig. 2: Axial Post Contrast T1WI Fat Sat: Shows a Large Rim Enhaning Lesion in the Left Parietal Lobe, With a Smaller Daughter Absesses Anterior to it. The Absess is Causing Mass Effet on the Lateral Ventrile and Midline Shift to the Right. Findings in Intraranial Tuberulosis Forty four patients of intraranial tuberulosis were studied. The maximum inidene of intraranial tuberulosis was in the age group of years. 35(79.5%) ases presented with seizures, 26(59%) with fever, 8(18%) with headahe, 8(18%) with ranial nerve palsies, 7(15.9%) with altered sensorium, 4(9%) with vomiting, 2(4.5%) with nek stiffness and 1(2.2%) with visual disturbane. 34 ases (77.2%) had isolated parenhymal enhaning lesions, 3 patients (6.8%) showed isolated leptomeningeal enhanement (tuberulous meningitis) and 5 patients (11.3%) had both parenhymal and leptomeningeal enhanement. Contrast enhaned sans were obtained in all ases of suspeted tuberulosis and signifiant enhanement of the meninges and basal isterns was seen in 8 (18.8%) ases, out of whih 5 (11.3%) ases had assoiated enhaning granulomata and 3 (6.8%) had isolated enhanement of meninges. Assoiated ependymal enhanement was seen in 2 patients (4.5%). In the present study, ompliations of tuberulous meningitis like ommuniating hydroephalus was seen in 6 (13.6%) patients. 41 ases of parenhymal tuberulosis were studied. Single ring enhaning lesion was seen in 19 ases (46%) and multiple in 22 (54%) ases. The lesions were supratentorial in 32 ases (78%), infratentorial in 2 ases (4.8 %) whereas in 7 ases (17%) both ompartments were involved. We haraterized the parenhymal lesions based on their findings and found that in 22 ases, the tuberulomas were aseating i.e. hypointense on T1 and T2WI with surrounding perilesional edema with ring enhanement on ontrast sans and in 15 ases, they were aseating with entral liquefation i.e. hypointense on T1WI and hyperintense on T2WI with ring enhanement. In 4 ases, the tuberulomas were non aseating i.e. hypointense on T1WI, hyperintense on T2WI and show homogenous/nodular enhanement on post ontrast sans. Parenhymal lesions had a ring enhaning pattern in 31 ases (fig. 3.1) and nodular homogenous pattern in 3 ases. Conglomerate lesions were seen in 6 ases (14.6 %). Seven ases of intraranial tuberulosis in HIV patients were studied. All 7 (100%) patients presented with fever, while 3 (60%) presented Journal of Krishna Institute of Medial Sienes University 41

8 with headahe, 4 (80%) presented with altered mental sensorium and 2 (40%) presented with seizures. 2 (40%) patients had isolated meningeal enhanement, 3 (71%) patients had tuberulomas in both thalami (fig. 3.2), 2 (28.5%) patients had meningeal and ring enhanement, whereas 1(14.2%) patient had tuberulomas with assoiated ependymal enhanement. MR Spetrosopy was performed in 10 ases of tuberulomas. They demonstrate prominent lipid latate peaks, but no amino aid peaks were seen. Findings in Viral Intraranial Infetions: Herpes Simplex Enephalitis (HSE) 5 ases of HSE who presented with fever, behavioural abnormality and altered sensorium, were studied. The inidene was highest in the age group of years. The harateristi sites were medial temporal lobe in 4 (80%) out of 5 ases, insular ortex in 3 patients, ingulate gyrus in 3 patients and thalami in 1 patient (Fig. 4a). The typial imaging features of HSV that we found in the present study were, inreased signal seen in the temporal and inferior frontal lobes on T2- weighted with a variable degree of mass effet. The lesions were more onspiuous on FLAIR sequene (Fig. 4b). Fig. 3.1: Axial Post Contrast T1WI Fat Sat: Shows Ring Enhanement of the Caseating Granuloma With Central Liquefation. Fig. 3.2: Axial Post Contrast T1WI Fat Sat: Shows Irregular, Nodular Enhanement of Conglomerate Tuberulomas in a Seropositive Patient Fig. 4: Axial T2WI (a) and Flair (b): Shows Hyperintense Signal in the Hippoampal Region Bilaterally in a Patient of HSV. Journal of Krishna Institute of Medial Sienes University 42

9 HIV enephalopathy In the present study, we studied 2 patients of HIV enephalopathy. 1 patient was a 25 year old male and 1 was a 60 year old female. Both patients presented with progressive dementia and unexplained weight loss. Both patients showed bilaterally symmetrial white matter hyperintensities on T2-weighted images. We ompared T2WI with FLAIR sequenes in detetion of white matter lesions in ortial and subortial loation, in AIDS patients. Due to its improved lesion detetion rate and higher overall lesion onspiuity we onluded that FLAIR sequenes are superior to T2WI in detetion of white matter lesions. Aute Disseminated Enephalomyelitis (ADEM) ` Two ases of ADEM were studied. One was a 25 year old male and the other was a 3 month old female infant. The infant had history of vaination prior to development of symptoms while the adult male had an episode of flu like viral illness prior to the development of symptoms whih made ADEM a likely diagnosis. The lesions were multiple in both ases. The typial sites of involvement were periventriular white matter in both ases. Hyperintense signal was seen in the periventriular white matter on T2WI and FLAIR sequenes (fig. 5), whih did not show restrition on DWI. No signifiant ontrast enhanement was seen in both. MRI of the spine revealed no abnormal signal in the spinal ord. Fig. 5.: Axial T2WI and Flair: Shows White Matter Hyperintensities in Bilateral Centrum Semiovale, in a Patient with ADEM Japanese Enephalitis 2 ases of Japanese enephalitis were studied. Both patients were males between years. Both the patients presented with fever and altered sensorium. The harateristi sites involved were bilateral thalami in both patients and bilateral basal ganglia in 1 patient. The lesions were seen as isointense on T1WI and hyperintense on T2WI (Fig. 6a) and FLAIR (Fig. 6b). Journal of Krishna Institute of Medial Sienes University 43

10 Fig. 6: Axial T2WI (a) and Flair (b): Shows Hyperintense Signal in Cingulate Gyrus and both Thalami, in a Patient with Japanese Enephalitis Subaute Slerosing Panenephalitis (SSPE) One ase of SSPE was studied in 18 year old female who presented with behavioral abnormalities. MRI revealed inreased signal intensity in the periventriular white matter and in both entrum semiovale on T2WI and FLAIR. DWI revealed no restrition of these hyperintensities and no ontrast enhanement was seen. EEG findings (Burst Suppression Pattern) in this patient were found to be onsistent with the diagnosis of SSPE. Parasiti Infetions: Neuroystierosis There were 20 ases of neuroystierosis in the present study. 15 of these were males and 5 were females. The highest inidene was observed in the age group of years. All 20 patients presented with seizures, while 5 presented with headahe, 2 with fever and 1 with visual disturbane. The lesions were single in 10 ases and multiple in 10 ases. The ystieral lesions in our study, were parenhymal in 19 patients (95%), intraventriular in 1 patient (5%) and both intraventriular and parenhymal, in 3 patients (15%). There were 3 intraventriular ystieral lesions (15%). The lesion was an isolated intraventriular lesion in the third ventrile in 1 ase and in 2 (66.6%) ases; the lesions were assoiated with parenhymal lesions. The intraventriular lesions rd were loated in the 3 ventrile in 1 (33.3%) ases, frontal horn of the right lateral ventrile in 1 (33.3%) and fourth ventrile in 1 patient. Assoiated hydroephalus and periventriular hyperintensity was noted in 1 lesion. Out of the parenhymal lesions, 16 were supratentorial (80%) and 3 were supra and infratentorial (15%). Purely infratentorial lesions were not seen in our study. The lesions were in the vesiular stage in 9 (45%) ases, olloid vesiular in 12 (60%) ases, granular nodular in 6 (30%) patients and alified in 1 (5%) patient. Multiple stages were found to oexist in 8 patients. T2W images showed small hyperintense rounded lesions with perilesional edema (fig.7.1b). Central high signal intensity nodule within the lesion, suggestive of solex (fig. 7.1a), was seen in 13 ases, whih was best seen on FLAIR sequenes in our study. Intense ring enhanement (fig. 7.1b), with surrounding perilesional edema is noted in 15 patients suggestive of ative lesions. MRI was found to be superior to CT san for the detetion and haraterization of ystieri lesions. In the present study, 5 patients underwent follow up MRI after 3 months of treatment whih revealed a derease in the number of lesions as well as perilesional edema. Journal of Krishna Institute of Medial Sienes University 44

11 Fig. 7(a): Sagittal T1WI: Shows Hypointense Neuroystierosis Lesions in the Parietal and Oipital Lobes Showing Hyperintense Central Foi within suggestive of Solies. Toxoplasmosis In the present study, we enountered 6 patients with toxoplasmosis. All these patients were HIV positive. Inidene was maximum in the age group of years. 5 patients presented with altered sensorium, 2 with seizures and 1 with fever. The harateristi sites of Toxoplasma lesions in our study were thalami in 2 (33.3%) patients, basal ganglia in 2 (33.3%) patients; ortiomedullary juntion in 2 (33.3%) patients and 1 (16%) patient had involvement of the infratentorial ompart- Fig. 7(b): Coronal Post Contrast Fat Sat: Ring Enhaning Lesion Seen in Left Temporal Lobe with a Central Solex within. ment. Perilesional edema was seen in all 6 patients and mass effet was seen in 2 patients. The lesions were hyperintense on T2WI and FLAIR (Fig. 8.1). On T1WI, lesions were isointense in 5 patients and hypointense in 1 patient. On ontrast injetion, ring enhanement were observed (Fig. 8.2) in all 6 ases with typial target pattern of enhanement being present in 3 patients. MR Spetrosopy performed showed lipid latate peak in 5 patients. MR Spetrosopy ould not be performed in 1 patient due to proximity of the lesion to skull vault. Fig. 8.1: Axial Flair : Shows Multiple, Isointense, Toxoplasma Lesions in the Right Basal Ganglia, Right Frontal Lobe and Left Thalamus, with Extensive Surrounding Perilesional Edema, in a Seropositive Patient. Fig. 8.2: Coronal T1WI Fat Sat: In the Same Patient Shows Ring Enhaning Lesion in the Right Thalamus. Journal of Krishna Institute of Medial Sienes University 45

12 Fungal Infetions 4 ases of intraranial fungal infetions were studied. Three patients were HIV positive. Majority of ases were in the years age group. All 4 patients presented with fever, 2 with altered sensorium, and 1 with headahe and vomiting. In one of the HIV positive ase, there was hyperintense signal intensity in the left temporo parietal region with few hypointense areas within on T2WI and FLAIR sequenes and hyperintense areas were seen within an isointense lesion on T1WI and showed intense enhanement of meninges over the left erebral onvexity and the basal isterns suggestive of meningoenephalitis. CD4 ount was 11. In the seond patient, enhaning soft tissue with extension into the right temporal lobe was noted, suggestive of fungal sinusitis with intraranial extension (Fig. 9.1). In the third HIV positive patient, there were few non enhaning CSF intensity lesions in the basal ganglia orresponding to dilated Virhow Robin spaes with CSF showing lymphoytosis and Cryptoous on India ink staining (fig. 9.2). Fig. 9.1: Axial Post Contrast Fat Sat: Shows Intraranial Extension of the Sinusoidal Soft Tissue into the Right Temporal Lobe, in a Patient with Fungal Sinusitis. Disussion : MRI is the most preferred imaging modality of hoie to evaluate infetious diseases of the brain due to its multiplanar imaging and anatomial details provided by various MR sequenes. Besides it is radiation free, and has high sensitivity and speifiity to suggest speifi etiology in many infetive lesions. Most ommonly identified pathology was intraranial tuberulosis whih was seen in 44% of the patients in both parenhymal and meningeal forms. Charaterization of the parenhymal lesions as aseating, non- aseating, Fig. 9.2: Sagittal Post Contrast T1wi Fat Sat: Shows Peripherally Enhaning Cryptooal Lesions in the Left Oipital Lobe, in a Seropositive Patient. and aseating with entral liquefation is possible on MRI, based on their imaging features on T1WI, T2WI and post ontrast imaging. Our findings were omparable to Morgado C et al [2] who onluded that the MRI findings of tuberulomas depend on whether the tuberuloma is aseating, and if so, whether the enter is liquid or solid. Neuroystierosis was the most ommon parasiti infetion of the brain (20%), enountered in this study. The most ommon presentation being seizure / epilepsy whih were seen in all 20 patients orresponds with Sotelo et al [3]. MRI is far Journal of Krishna Institute of Medial Sienes University 46

13 superior to CT san to evaluate the various stages of neuroystierosis lesions. Multiple stages of disease were found to o-exist in 40% patients; and 15% of the patients had intraventriular ysts. FLAIR sequenes demonstrated an intraysti solex in 65% of the patients, thus helping to differentiate these lesions from a tuberuloma, whih was omparable to a study onduted by Luato et al [4]. We onluded that ative neuroystierosis lesions and their response to treatment were better deteted with MRI than with CT (85%) whih orrelated with Martinez et al and Suss et al [5]. Among viral lesions herpes simplex enephalitis had the highest inidene (50%) in our study. It was observed that diffusion weighted imaging was highly sensitive in delineating the involved sites mores onspiuously vis-a-vis onventional sequenes in viral enephalitis. The imaging findings orrelated with Randy Jenkins and James Provenzale [6] and Sawlani et al [7]. With the typial loation of the lesions on MRI, ombined with linial features and laboratory investigations it was possible to narrow down the differential diagnosis of viral infetions in most patients. Most patients with intraranial fungal infetions were HIV positive (75%), Common MRI findings in these patients were fungal absess (50%), meningoenephalitis (25%) and intraranial extension of fungal sinusitis (25%). All patients in our study with intraranial toxoplasmosis were HIV positive whih orrelated with Wright et al [8] who reported that erebral toxoplasmosis was the most ommon opportunisti intraranial infetion in AIDS patients. In all 6 patients, the lesions were multiple whih orrelated with Miguel et al [9]. The harateristi site of these lesions was found to be the basal ganglia, these findings orrelated with Miguel et al [9, 10].MRI features when orrelated with the CD4 ounts assisted in pin pointing the diagnosis and administration of appropriate therapy to the patient. MR spetrosopy was of great help in diagnosing as well as differentiating the lesion from neoplasti etiology. Lipid latate peak were seen in both pyogeni absess [11] as well as tuberulomas. Presene of amino aid at 0.9 ppm helped to differentiate pyogeni absesses from tuberulomas. This orrelates with Gupta et al [12] who used in vivo proton MR Spetrosopy imaging to differentiate tuberulous from pyogeni absesses. Presene of lipid latate peak in toxoplasmosis helped to distinguish toxoplasma lesions from lymphoma whih showed marked elevation of holine and lipids with signifiant redution of N-aetylaspartate (NAA) as demonstrated by Chang et al [13] in their study. In the present study role of Magnetization Transfer Imaging (MTT) and MR perfusion in intraranial infetions were not evaluated. There were few limitations of MRI. Abnormalities of bone were diffiult to reognize. Califiation ould not be readily identified on MRI. Motion degrades images to the point that they were not interpretable, thus requiring patient o-operation, sedation or general anesthesia. Conlusion: MRI was undoubtedly an indispensable tool to evaluate patients presenting with intraranial infetions. Most of the ases were pathognomoni in imaging appearane; while some required linio-laboratory orrelation. Careful evaluation of MR behaviour of infetious lesions helped in identifying not only the preise loation and extent of the lesion, but also in proposing a speifi etiology in many suh patients. Journal of Krishna Institute of Medial Sienes University 47

14 1. Foerster BR, Thurnher MM, Malani PN, Petrou M, Carets Zumelzu F, Sundgren PC. Intraranial infetions: linial and imaging harateristis. Ata Radiol 2007; 48: Morgado C, Ruivo N. Imaging Meningo-Enephali tuberulosis. Eur J Radiol2005; 55(2): Sotelo J, Guerrero V, Rubio F Neuroystierosis: A new lassifiation based on ative and inative forms a study of 753 ases. Arh Intern Med 1985; 145(3): Luato LT, Guedes MS, Sato JR, Baheshi LA, Mahado LRand Leite CC. The role of onventional mr imaging sequenes in the evaluation of neuroystierosis: Impat on haraterization of the solex and lesion burden. Amerian J Neuroradio 2007; 28: Suss RA, Maravilla KR, Thompson J. MR imaging of intraranial ystierosis: Comparison with CT and anatomopathologial features. AJNR 1986; 7(2): Jinkins R, Provenzale J. Brain and spine imaging findings in AIDS patients. Radiol Clin of North Ameria 1995; 33 (4): Sawlani V. Diffusion-weighted imaging and apparent diffusion oeffiient evaluation of herpes simplex Referenes enephalitis and Japanese enephalitis. J Neurol Si 2009; 287(1-2): Wright D, Shneider A, Berger JR. Central nervous system opportunisti infetions. Neuroimaging Clin N Am1997; 7(3): Miguel J, Champalimaud JL, Borges A, et al. [Cerebral toxoplasmosis in AIDS Patients, CT and MRI images and differential diagnosti problems]. [Portugese]. Ata Med Port 1996; 9(1): Porter SB, Sande MA. Toxoplasmosis of the entral nervous system in the aquired immuno defiieny syndrome. N Engl J Med 1992; 327(23): Pal D, Bhattaharyya A, Hussain M, Prasad KN, Pandey CM, Gupta RK. In vivo Proton MR Spetrosopy Evaluation of Pyogeni Brain Absesses: A Report of 194 ases. Amerian J Neuroradiology 2010; 31: Gupta RK, Vatsal DK, Husain N, et al. Differentiation of tuberulous from pyogeni brain absesses with in vivo proton MR Spetrosopy and magnetization transfer MR imaging. Am J Neuroradiol 2001; 22(8): ChangL, Miller BL, MBride D, et al. Brain lesions in patients with AIDS: H-1 MR spetrosopy. Radiology 1995; 197(2): * Author for Correspondene: Dr. Jeevan A. Vernekar, Department of Radiology, Goa Medial College, Bambolim Goa, , India Cell: jeevanvernekar11@gmail.om Journal of Krishna Institute of Medial Sienes University 48