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Remember the Limbic System?: Aftermr the First Generalized Anatomy Seizure Oc- and Pathology Curred

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Remember the Limbic System?: Aftermr the First Generalized Anatomy Seizure Oc- and Pathology Curred 508 THUERL AJNR: 24, March 2003 508 THUERL AJNR: 24, March 2003 FIG 1. Initial MR images obtained 1 day afterF theIG 1. first Initial generalized MR images seizure obtained oc- 1 day Remember the Limbic System?: afterMR the first generalized Anatomy seizure oc- and Pathology curred. A, Axialcurred.fluid-attenuated inversion recov- ery imageA, Axial (9000/110fluid-attenuated [TR/TE]; inversion inversion recov- time,ery 2261 image ms) shows (9000/110 a slightly [TR/TE]; elevated inversion signaltime, intensity 2261 of ms) both shows hippocampal a slightly forma- elevated Review of Structures Involved in Emotiontionssignal (black intensity arrows)andamygdala( of both hippocampalwhite forma-and Memory Formation arrowstions). (black arrows)andamygdala(white B,arrows Coronal). conventional T2-weighted turbo spin-echoB, Coronal image conventional (4462/120/3 T2-weighted [TR/ Jane Ball,BS; David Sawyer,BS; Adam Blanchard,MD; KrystleTE/NEX]) Barhaghi,MDturbo shows spin-echo no signal image intensity (4462/120/3 abnor- [TR/; Enrique Palacios,MD; Jeremy Nguyen,MD. mality.TE/NEX]) shows no signal intensity abnor- Tulane University School of Medicinemality. Department of Radiology Introduction Structural Review Limbic Encephalitis Klüver-Bucy Syndrome Rather than a single, defined structure within the brain, the Klüver-Bucy Syndrome (KBS) is a clinical diagnosis limbic system is a collection of interrelated structures characterized by visual agnosia, hyperorality, involved in learning, memory, emotional responses, hypersexuality, placidity, abnormal dietary changes, homeostasis and primitive drives. Different reference hypermetamorphosis, dementia, and amnesia. Limbic sources include and exclude structures within the limbic encephalitis is the most common cause of KBS, and KBS system. Some structures share formations or groupings has been associated with other neurological disorders and have additional functions beyond their roles in the including traumatic brain injury, anoxia-ischemic limbic system. Generally, the hippocampal formation, encephalopathy, Pick’s disease, Alzheimer’s disease, amygdala, hypothalamus and limbic cortex form the limbic bilateral temporal lobectomy, tuberculous meningitis, and system. The limbic cortex includes the fornix, cinngulate neurocysticerosis. MR findings in KBS include bilateral gyrus, prefrontal cortex, septal area, and parahipocampal temporal lobe atrophy, bilateral hippocampi atrophy, gyrus. Closely related structures include the basal ganglia, atrophy of other limbic structures, cystic or necrotic foci in thalamus, and mamillary bodies. This poster reviews the the limbic areas and edema within and surrounding the functions, anatomy and neuroimaging appearances of temporal lobes.15-17 limbic system components in disease states. FIG 2.FIG Follow-up2. Follow-up MR images MR images obtained obtained 4 4 daysdays after theafter first the seizure first seizure occurred. occurred. A, Fluid-attenuatedA, Fluid-attenuated inversion inversion recovery recovery im- im- age showsage shows high signal high signal intensity intensity in both in me- both me- Functional Review FLAIR images of autopsy-proven paraneoplastic limbicdial temporaldial temporal lobes lobes and hyperintensities and hyperintensities of of 10 the rightthe frontobasalright frontobasal cortex cortex (arrowhead (arrowhead). ). encephalitis. Images from Thuerl et al. B, Fluid-attenuatedB, Fluid-attenuated inversion inversion recovery recovery imageimage shows shows high signalhigh signal intensity intensity in both in both In this section, the limbic-related related functions of the medialmedial temporal temporal lobes lobes and hyperintensities and hyperintensities structures are reviewed. Other functions such as their A. Axial FLAIR image with findings that include increasedof theof right the right insular insular cortex cortex (arrowhead (arrowhead). No). No massmass effect effect was seen. was seen. influence on the autonomic nervous system and hormonal signal intensity in the medial temporal lobes bilaterally asC , Diffusion-weightedC, Diffusion-weighted echo-planar echo-planar image image well as in the right frontobasal cortex (arrowhead). (5400/103/1;(5400/103/1; b value b value of 1000 of 1000 s/mm s/mm2) shows2) shows secretions not explicitly related to the limbic system are the correspondingthe corresponding alterations alterations of the of limbic the limbic beyond the scope of this poster. (arrows(arrows) and) the and right the frontobasal right frontobasal cortex cortex (ar- (ar- B. Axial FLAIR image with findings that include increasedrowhead rowhead). ). • Hippocampal formation: short-term and immediate D, T1-weightedD, T1-weighted image image (548/12/2) (548/12/2) shows shows signal intensity in the medial temporal lobes bilaterally aslow signallow signal intensity intensity of the of right the medial right medial tem- tem- 1 poralporal lobe ( lobearrow (arrow). ). explicit memory consolidation into long-term storage A B well as in the right insular cortex (arrowhead). E, Contrast-enhancedE, Contrast-enhanced T1-weighted T1-weighted im- im- • Amygdala: emotional interpretation of external stimuli age (525/17/2)age (525/17/2) shows shows no contrast no contrast enhance- enhance- and internal states, including fear and aversion ment.ment. responses1 Images of a 3 year-old female with Klver-Bucy syndrome from • Limbic Cortex Ozawa et al.15 • Fornix: encoding and recall of new Hippocampal Sclerosis information, as one part within the Papez A. Coronal T1 image demonstrating diffuse brain atrophy circuit2 (DBA), including in the Hippocampal sclerosis, also known as mesial temporal bilateral temporal lobes and hippocampi (arrows). • Cingulate gyrus: selection of appropriate sclerosis, is a condition characterized by neuronal cell loss responses to stimuli and projections to other and gliosis in the hippocampus, particularly in the cornu B. Coronal T2 image demonstrating DBA, especially in the structures within the limbic system 1 ammonis regions.11 It is commonly found in asymptomatic bilateral hippocampi. • Prefrontal cortex: integrates information from persons at autopsy, but is clinically most associated with many areas of the brain including limbic temporal lobe epilepsy. Patients with longstanding epilepsy structures and may influence complex can also demonstrate abnormalities of the structures 5 Conclusions behaviors based on that information MR Pathology connected to the hippocampus along the Papez circuit, • Septal area: roles in behavior, attention, and such as the fornix and mammillary bodies.12 This suggests Limbic System pathology often presents with a clinical memory MR is the preferred method in evaluation of disease that hippocampal sclerosis is in fact a disease involving the picture that correlates with the imaging findings on MR. • Parahippocampal gyrus: processes contextual processes that affect soft tissue structures of the brain. MR entire limbic system. Knowledge of the clinical presentation may aid in associations roles in episodic memory and allows for greater soft tissue contrast between structures distinguishing similar imaging findings and vice versa. 6 visuospatial processing than CT allows. Pathologies affecting the limbic system Hippocampal sclerosis is best demonstrated on MR • Entorhinal cortex: sensory input modulation may mimic one another at first inspection. Some methods imaging using a dedicated temporal lobe epilepsy protocol. and integration with the hippocampus memory to clarify a diagnosis include optimized imaging such as 13 Characteristic findings include atrophy of the affected References 1 circuits different sequences, history and physical exam hippocampus and hyperintensity on T2-weighted images.14 • Hypothalamus: response coordination to internal and 1. Felton DL, O’Banion MK, Maida MS. Autonomic-Hypothalamic-Limbic Systems. Netter’s Atlas of correlations, or laboratory testing such as serum Gadolinium is not useful in evaluating hippocampal Neuroscience. 3rd ed. Philadelphia, PA: Elsevier; 2016:421-461. external stimuli, especially in regards to homeostasis and antibodies, CSF antibodies, CSF cell analysis, and biopsy. sclerosis. 2. Thomas AG, Koumellis P, Dineen RA. The Fornix in Health and Disease: An Imaging Review. 1 RadioGraphics. 2011; 31:1107-1121. doi: 10.1148/rg.314105729. primal drives such as hunger; role in sleep and alertness 3. Mark LP, Daniels DL, Naidich TP, Borne JA. Limbic System Anatomy: An Overview. Am J Neuroradiol. 1993; 14:349-352. 4. Concha L, Gross DW, Beaulieu C. Diffusion Tensor Tractography of the Limbic System. Am J Neuroradiol. 2005; 26:2267-2274. 5. Miller EK, Wallis JD. The Prefrontal Cortex and Executive Brain Functions. In: Squire L, Berg D, Structural Review Limbic Encephalitis Bloom FE, du Lac S, Ghosh A, Spitzer NC, eds. Fundamental Neuroscience. 4th ed. Oxford, UK: Elsevier; 2013:1069-1089. 6. Aminoff EM, Kveraga K, Bar M. The Role of the Parahippocampal Cortex in Cognition. Trends Cogn Sci. 2013; 17(8):379-390. MR images that demonstrate the previously described Limbic Encephalitis (LE) presents with seizures, confusion, 7. Samarasekera SR, Vincent A, Welch JL, Jackson M, Nichols P, Griffiths TD. Course and Outcome of Acute Limbic Encephalitis with Negative Voltage-gated Potassium Channel Antibodies. structures: memory loss, anterograde amnesia, and/or irritability J Neurol Neurosurg Psychiatry. 2007; 78:391-394. manifesting over days to weeks to months. LE is often 8. Gultekin SH, Rosenfeld MR, Voltz R, Eichen J, Posner JB, Dalmau J. Paraneoplastic Limbic
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