MR imaging spectrum of bilateral symmetric hippocampal lesions

Transcription

1 MR imaging spectrum of bilateral symmetric hippocampal lesions Poster No.: C-2510 Congress: ECR 2010 Type: Educational Exhibit Topic: Neuro Authors: P. S. Naphade, M. D. Agrawal, S. S. Sankhe, K. M. Siva, B. K. Jain; Mumbai/IN Keywords: Bilateral hippocampal lesions, Hippocampal atrophy, Extrapontine myelinolysis DOI: /ecr2010/C-2510 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 35

2 Learning objectives To describe the MR imaging features in bilateral symmetric hippocampal lesions. In this educational exhibit we will review the immense contribution of Magnetic Resonance Imaging in evaluating patients with bilateral symmetric hippocampal lesions. The aim is to get familiar with the common causes of symmetric hippocampal lesions and provide an algorithm which will enable a faster and easier differentiation and efficient patient management. Background Hippocampus is a complex and vital structure found in each cerebral hemisphere which is a part of limbic system. One should be thorough with the anatomy of hippocampus for recognition and accurate interpretation of MRI findings. The hippocampus is a curved structure on the medial aspect of temporal lobe consisting of complex U shaped layers of dentate gyrus and cornu ammonis, which are interlocked together. The cornu ammonis blends into subiculum, which forms transition to neocortex of parahippocampal gyrus.the hippocampus forms 4 to 4.5 cm long curved elevation in the floor of temporal horn of lateral ventricle. The hippocampus is subdivided into three segments- the bulbous anterior head with three to four superior digitations, the body continues posteriorly around midbrain, and the slender posterior tail. Fornices arise from hippocampal tails and continue cephalad to undersurface of corpus callosum.amygdala is a grey matter structure located superomedial to tip of temporal horn of lateral ventricle, which separates it from hippocampal head. Page 2 of 35

3 Fig.: Fig.: T2 Coronal oblique Page 3 of 35

4 Fig.: Fig.: T2 Coronal oblique showing hippocampal body Page 4 of 35

5 Fig.: Fig.: T2 Coronal oblique showing hippocampal tail Page 5 of 35

6 Fig.: Fig.: T1 Sagittal Image demonstrating the hippocampus For optimal imaging of hippocampus, sequences with superior grey white matter differentiation should be used. Coronal oblique plane (perpendicular to long axis of hippocampus) is best for evaluation of hippocampus. MR Sequences T2 coronal oblique 3mm Page 6 of 35

7 T2 TIRM coronal oblique 3mm T1 TIRM coronal oblique 3mm Fig.: Fig.: Planning of coronal oblique sequence perpendicular to hippocampus on T1 Sagittal Image Page 7 of 35

8 Fig.: Fig.: Planning of coronal oblique sequence on T2 axial image for maintaining symmetry Hippocampi are isointense to grey matter on all pulse sequences; however they may be slightly hyperintense on FLAIR images due to incomplete suppression of CSF. Page 8 of 35

9 As bilateral hippocampal involvement can result in significant functional impairment (recent memory loss), one should be conversant with MR imaging features for ordered differential diagnosis. We present MR imaging features of pathologies affecting bilateral hippocampus symmetrically. Imaging findings OR Procedure details What to look forhippocampal size - increased, decreased or normal Hippocampal intensity - increased, decreased or normal How to proceedbilateral symmetric Hippocampus atrophy Increased T2 signal intensity - Mesial temporal sclerosis T2 isointense to grey matter - Dementia - Alzheimers disease - Frontotemporal dementia Bilateral symmetric Hippocampus enlargement Increased T2 signal intensity - HSV encephalitis - Extrapontine myelinolysis - Limbic encephalitis Increased T2 signal intensity with normal or mildly increased hippocampal volume - Ischemia /Infarction Page 9 of 35

10 - Global hypoxic injury as in Cardiac arrest - Acute perinatal hypoxia Mesial Temporal Sclerosis - This is most common cause of temporal lobe epilepsy. It commonly presents with complex partial seizures with or without secondary generalisation.hippocampus, parahippocampal gyri and amygdala constitute the mesial temporal lobe. Pathologically it is characterized by neuronal loss and gliosis in hippocampus. Diagnosis is based upon findings of Hippocampal and temporal lobe atrophy Increased T2/FLAIR signal hyperintensity Loss of internal architecture Loss of undulations of superior margin Dilatation of temporal horn of lateral ventricle Atrophy of fornix and mammillary bodies Hippocampus atrophy is judged visually, by actually calculating the volume of hippocampus and associated dilatation of temporal horn of lateral ventricle. Page 10 of 35

11 Fig.: Fig.: T2 Coronal oblique image shows bilateral hippocampal sclerosis Page 11 of 35

12 Fig.: Fig.: FLAIR Coronal oblique image shows bilateral hippocampal hyperintense signal and atrophy Page 12 of 35

13 Fig.: Fig.: FLAIR Axial image shows bilateral hippocampal hyperintense signal and atrophy Hippocampal T2 hyperintensity is a common presentation in mesial temporal sclerosis; the specificity for diagnosing mesial temporal sclerosis on the basis of this finding increases if it is associated with ipsilateral hippocampal and temporal lobe atrophy. Finally, hippocampal atrophy in mesial temporal sclerosis correlates with the duration of seizures. Page 13 of 35

14 Fig.: Fig.: T2 Coronal oblique image in a case of anterior temporal lobectomy for mesial temporal sclerosis Most patients respond to antiepileptic therapy. However those cases which are refractory to antiepileptic require anterior temporal lobectomy.surgery leads to cure in many cases emphasizing the preoperative role in the diagnosis of mesial temporal sclerosis. Dementia- Bilateral symmetric hippocampal atrophy without T2 hyperintense signal is classically seen with Alzheimers disease and is associated with predominant parietotemporal atrophy or moderate to gross generalized cerebral atrophy.however Page 14 of 35

15 cases with frontotemporal dementia can also present with similar findings and in these cases, the atrophy is predominantly in frontotemporal lobes. Fig.: Fig.: T2 Coronal oblique image shows bilateral hippocampal atrophy without hyperintense signal and generalized cerebral atrophy in Alzheimers disease Page 15 of 35

16 Fig.: Fig.: T1 Sagittal image shows significant hippocampal atrophy and generalized cerebral atrophy in Alzheimers disease Page 16 of 35

17 Fig.: Fig.: FLAIR Axial image shows significant hippocampal atrophy in Alzheimers disease Page 17 of 35

18 Fig.: Fig.: FLAIR Coronal oblique image shows significant hippocampal atrophy and frontotemporal atrophy in frontotemporal dementia Page 18 of 35

19 Evaluation of patients with dementia with MRI helps to exclude treatable causes of dementia and detect Alzheimers disease early in its course for efficient management. Further the severity of dementia correlates with severity of hippocampal and cortical atrophy in cases with Alzheimers disease and vascular dementia while there is no significant correlation in cases of frontotemporal dementia. Herpes encephalitis - It is most common sporadic encephalitis.it is usually caused by HSV-1.Regional involvement is due to retrograde spread from reactivation of latent infection in trigeminal ganglion. Classically it presents with headache, fever, altered sensorium and seizures. MRI classically shows T2/FLAIR hyperintense signal in hippocampi, temporal lobes and basifrontal lobes. Insular cortex and cingulate gyrus can also be involved.bilateral involvement is extremely common though one lobe involvement usually precedes the other.haemorhagic foci may be seen in involved areas.diffusion restriction can be seen on Diffusion Weighted images(dwi) due to cytotoxic edema and is more sensitive in detection of HSV encephalitis than conventional MRI sequences. Although in most cases there is no post contrast enhancement, patchy enhancement may be seen. Page 19 of 35

20 Fig.: Fig.: FLAIR Axial image shows significant enlargement and hyperintense signal in bilalateral hippocampi and insular cortex Page 20 of 35

21 Fig.: Fig.: T2 Coronal oblique image in a case of Herpes encephalitis. Page 21 of 35

22 Fig.: Fig.: Diffusion weighted image shows restricted diffusion in temporal lobes and insular cortex in a case of Herpes encephalitis Page 22 of 35

23 Fig.: Fig.: Diffusion weighted image shows restricted diffusion in posterior temporal lobes and insular cortex in a case of Herpes encephalitis Prompt therapy with Acyclovir leads to imroved survival. Therefore the MRI is of paramount importance in establishing the early diagnosis of herpes encephalitis. Extrapontine Myelinolysis- Osmotic demyelination syndrome(odm) is caused by rapid shift of serum osmolality.sudden change in osmolality causes endothelial damage and break of Blood brain barrier and accumulation of hypertonic fluid in Extracellular Page 23 of 35

24 spaces. Classically it occurs in alcoholics with rapid correction of hyponatremia.osmotic derangement associated with hyperglycemia and ketoacidosis can also cause ODM. Clinically it presents with altered mental status and seizures. Fig.: Fig.: T2 Coronal oblique image shows bilateral hippocampal mild enlargement and hyperintense signal Page 24 of 35

25 Fig.: Fig.: FLAIR Axial image shows minimal enlargement and hyperintense signal in bilalateral hippocampi in a case of osmotic demyelination Page 25 of 35

26 Fig.: Fig.: Diffusion weighted image shows restricted diffusion in bilateral hippocampi due to osmotic demyelination Page 26 of 35

27 Fig.: Fig.: T2 Axial image shows bilateral basal ganglia enlargement and hyperintensity in a case of extrapontine demyelination Page 27 of 35

28 Central Pons is involved in almost half of cases while extrapontine involvement occurs in the rest. Basal ganglia are most common structure to be involved in EPM (Extra pontine myelinolysis).hippocampus can also be involved in EPM. Regardless of the site of involvenment, bilateral symmetric T2/FLAIR hyperintensities are seen. It does not show postcontrast enhancement. Ischemia/Infarction- Bilateral hippocampal T2 hyperintense signal without alteration in its volume can be seen hypoxic injuries such as cardiac arrest, status epilepticus, and acute hypoxic injury during prenatal period such as abruption placenta. Clinical profile provides the clue. Page 28 of 35

29 Fig.: Fig.: FLAIR Axial image shows hyperintense signal in bilalateral hippocampi without alteration in its size in a case of cardiac arrest Page 29 of 35

30 Fig.: Fig.: Diffusion weighted image shows restricted diffusion in bilateral hippocampi due to ischemia in a case of cardiac arrest Page 30 of 35

31 Fig.: Fig.: FLAIR Coronal oblique image shows mild hippocampal enlargement and hyperintense signal in a case of status epilepticus Page 31 of 35

32 Fig.: Fig.: Diffusion weighted image shows restricted diffusion in bilateral hippocampi due to ischemia in a case of status epilepticus Page 32 of 35

33 Fig.: Fig.: Diffusion weighted Sagittal image shows restricted diffusion in bilateral hippocampi due to ischemia in a case of status epilepticus Conclusion Page 33 of 35

34 MRI is accurate in the identification of the hippocampal anatomy and delineation of its internal signal and volume. The grey white matter differentiation is extremely good. These features allow narrowing the differential diagnosis in symmetric hippocampal lesions. Clinical profile of patient provides additional clues towards the diagnosis. Key MR imaging features when interpreted in correct clinical context allow accurate diagnosis of hippocampal lesions.. Personal Information P.S. Naphade, M.D. Agrawal, S.S. Sankhe, Jain; Department of Radiology, Seth G.S.Medical Hospital,Parel,Mumbai ,Maharashtra,India. K.M. Siva, college and B.K. KEM References 1.L A van de Pol, A Hensel, W M van der Flier, P-J Visser, Y A L Pijnenburg, F Barkhof, H Josef Gertz, P Scheltens; Hippocampal atrophy on MRI in frontotemporal lobar degeneration and Alzheimer's disease, J Neurol Neurosurg Psychiatry 2006;77: doi: /jnnp Masayuki Fujiokaa, Kenji Nishio, Seiji Miyamoto, Ken-Ichiro Hiramatsu, Toshisuke Sakaki, Kazuo Okuchi, Toshiaki Taoka, Susumu Fujioka; Hippocampal Damage in the Human Brain after Cardiac Arrest; Cerebrovasc Dis 2000;10:2-7 (DOI: / ) 3. G; Di Sclafani V; Tanabe J; Cardenas V; Weiner M W; Jagust W J; Reed B R; Norman D; Schuff N; Kusdra L; Greenfield T; Chui H, Hippocampal and cortical atrophy predict dementia in subcortical ischemic vascular disease; Neurology 2000;55(11): Page 34 of 35

35 4.Donald H. Lee, Fu-Qiang Gao, John M. Rogers, Irene Gulka, Ian R. A. Mackenzie,Andrew G. Parrent, Cynthia S. Kubu, David G. Munoz, Richard S. McLachlan,Warren T. Blume, and John P. Girvin; MR in Temporal Lobe Epilepsy: Analysis with Pathologic Confirmation; AJNR Am J Neuroradiol 19:19-27, January 1998 Page 35 of 35