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Magnetic Resonance Spectroscopy of the hippocampus

Magnetic Resonance Spectroscopy of the hippocampus. Marton A 1 , Bús L 2 , Juhos V 3 , Rudas G 2 , Barsi P 2 1 University of Pécs, 2 SU MR Research Centre 3 St. Stephen Hospital Dept. of Neurology Budapest, Hungary. Why hippocampus?. Common focuse region ,

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Magnetic Resonance Spectroscopy of the hippocampus

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  1. MagneticResonanceSpectroscopy of thehippocampus Marton A 1, Bús L2, Juhos V3, Rudas G2, Barsi P2 1 University of Pécs, 2 SU MR Research Centre 3 St. Stephen Hospital Dept. of Neurology Budapest, Hungary

  2. Why hippocampus? • Common focuse region, mostly when complex partial seizures are seen. • Only certain structural lesions are MRI-visible. • Correct lateralisation is crucial to obtain favorable postoperative outcome

  3. WhyMRspectroscopy? • Noninvasivemeasurement of molecularcontentin vivo. • Early detectionof metabolic alterations, even in the silent intervall and prior to structural changes. • Reveals exact spatial extent and the severity of the disease may predict outcome. • When EEG and MRI findings are not concordant further invasive methods are needed for preoperative evaluation of intractable epilepsy.

  4. Clinical relevance

  5. Taking up the challenge • Small and elongated shape • Heterogeneous histology, different subregions • Water signal from adjacent cerebrospinal fluid • Field distortions due to skull base www.morphonix.com Hippocampal sclerosis on the right side.

  6. Patients and method • 18 TLE patients. 13 unilateral hippocampal sclerosis proved by MRI, 5 without visible abnormality • 3T magnet (Philips Achieva X-series), SENSE 8-channel phased array head coil • Single voxel technique, PRESS localisation, CHESS water suppression, short echo time (TE) 35 ms, long TE 288 ms, repetition time 2000 ms, 128 of averages • Comparison between two sides was done by calculating asymmetry coefficient: • Results were compared with MRI and EEG findings.

  7. 30 (AP) x 8 (RL) x 6 (FH) mm Voxel positioning

  8. Results TE 35 ms right side TE 35 ms leftside TE 288 ms right side TE 288 ms leftside MRI showshippocampal sclerosis onthe right side.

  9. Means of NAA/Choand NAA/Cr werelower, Cho/Cr washigheripsilaterally. The degreeof metabolic asymmetry wasconsistentlyhigherinunilateralcases. Correctlateralizationratewas 50-84% dependingontheappliedparameters. Results

  10. Discussion • Where lateralisation by MRS was mistaken, EEG and MRI findings were also contradictory or dual pathology (tumor, malrotation) was associated with TLE • Presumably there are underlying metabolic changes contralaterally as well which explains the uncertainty of the asymmetry coefficient. • Even if the hippocampus is considered as normal it is still possible that a lesion has evolved in an early stage causing mild asymmetry.

  11. A small and elongatedvoxel is preferabletocover most of thehippocampus, whileexcludingsurroundingstructures. Ratiosindicatetheaffectedsideinunilateralcases. Short TE is more precise for quantification at higher fields. Additional metabolites and neurotransmitters provides more detailed information on pathophysiological processes. Conclusions

  12. Further aims • Involving a healthy control group is needed for validation issues. Enlarge patient group to determine cut off value. • Automation and visualisation tools would be useful in clinical practice. • Absolute quantification. Correction of partial volume effects could improve sensitivity.

  13. Contact: martonandrea53@gmail.com Grazie per l’attenzione! Thank You for your attention! Köszönöm a figyelmet!

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