Despite its high prevalence, essential tremor (ET) it is among the least-studied and most poorly- understood neurological diseases. On the most basic biological level, little is known about its underlying pathologic-anatomy and pathophysiology. Recent postmortem studies report a 30 - 40% loss of Purkinje cells (PCs) in ET, suggesting that on a mechanistic level, this common neurological disease could be neurodegenerative. But postmortem results have been mixed. At the moment, the central debate in the ET field revolves around the question, "is PC loss a feature of ET"? Unfortunately, the approach to this question has thus far been limited to postmortem studies and a fresh approach is needed. PCs, in the cerebellar cortex, are the major storehouse of brain gamma-aminobutyric acid (GABA), releasing their GABA into the synaptic cleft at the level of the cerebellar dentate nucleus. Thus, cerebellar dentate GABA level is a convenient in vivo marker of PC number. Furthermore, N-acetylaspartate (NAA), an amino acid found in the cytosol of neurons, is a convenient in vivo marker of neuronal integrity in the cerebellar cortex. The long-term goal of the proposed research is to elucidate the basic nature of the underlying pathophysiology of ET. The objective of this research project, which is the next step toward attainment of this long-term goal, is to perform in-vivo magnetic resonance spectroscopy (MRS) to quantify levels of GABA in the cerebellar dentate and NAA in the cerebellar cortex in 50 ET cases vs. 50 controls, both cross-sectionally and longitudinally. The central hypothesis for the proposed research is that there is a progressive destruction of PCs in ET. We plan to accomplish the overall objective of this application by pursuing the following three aims.
Aim 1 : In this cross-sectional neuroimaging aim, we will use MRS at baseline (Years 1 - 2) to assess in vivo cerebellar dentate GABA levels and cerebellar cortex NAA levels (NAA/total creatine, tCR) in ET cases and controls.
Aim 2 : In this longitudinal neuroimaging aim, we will perform a second MRS study (Years 4 - 5) to assess in vivo cerebellar cortex NAA/tCR levels and, in an exploratory manner, dentate GABA levels, to determine whether there is a longitudinal decline in these levels in 50 ET cases in excess of any longitudinal decline in these levels in 50 controls.
Aim 3 : We will cross validate the in vivo MRS findings with postmortem histological and biochemical findings in the brains of 10 - 15 of 50 ET cases whom we expect to die during the 5 year study. We expect that the proposed research will elucidate the underlying disease pathophysiology and provide useful diagnostic biomarkers as well as markers of disease progression for future neuroprotective trials.
Recent postmortem studies report a 30 - 40% loss of Purkinje cells in essential tremor (ET), suggesting that on a mechanistic level, this extraordinarily common neurological disease could very well be neurodegenerative. At the moment, the central debate in the ET field revolves around the question, is Purkinje cell loss a feature of ET?;the goal of the proposed research, which uses in-vivo magnetic resonance spectroscopy to measure gamma-aminobutyric acid and N-acetylaspartate levels in the cerebellum, is to address this question. We expect that the proposed research will elucidate the underlying disease pathophysiology and provide useful diagnostic biomarkers as well as markers of disease progression for future neuroprotective trials.
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|Louis, Elan D; Hernandez, Nora; Dyke, Jonathan P et al. (2016) Effect of Primidone on Dentate Nucleus Î³-Aminobutyric Acid Concentration in Patients With Essential Tremor. Clin Neuropharmacol 39:24-8|
|Louis, Elan D (2016) Essential tremor in 'The tremulous hand of Worcester': additional comments. Brain 139:e15|
|Louis, Elan D; Rabinowitz, Daniel; Choe, Matthew et al. (2016) Mapping Purkinje Cell Placement Along the Purkinje Cell Layer: an Analysis of Postmortem Tissue from Essential Tremor Patients vs. Controls. Cerebellum 15:726-731|
|Choe, Matthew; CortÃ©s, Etty; Vonsattel, Jean-Paul G et al. (2016) Purkinje cell loss in essential tremor: Random sampling quantification and nearest neighbor analysis. Mov Disord 31:393-401|
|Louis, Elan D; Collins, Kathleen; Rohl, Brittany et al. (2016) Self-reported physical activity in essential tremor: Relationship with tremor, balance, and cognitive function. J Neurol Sci 366:240-5|
|Louis, Elan D (2016) More Time with Tremor: The Experience of Essential Tremor Versus Parkinson's Disease Patients. Mov Disord Clin Pract 3:36-42|
|Shalaby, Sherif Y; Louis, Elan D (2016) Increased Odds of Melanoma: Parkinson's Disease, Essential Tremor, Dystonia versus Controls. Neuroepidemiology 46:128-36|
|Kuo, Sheng-Han; Lin, Chi-Ying; Wang, Jie et al. (2016) Deep brain stimulation and climbing fiber synaptic pathology in essential tremor. Ann Neurol 80:461-5|
|Robakis, Daphne; Louis, Elan D (2016) Head tremor in essential tremor: "Yes-yes", "no-no", or "round and round"? Parkinsonism Relat Disord 22:98-101|
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