Magnetic resonance spectroscopy in Parkinson’s disease

Introduction Parkinson’s disease (PD) is a progressive neurodegenerative disorder that usually appears after the age of 50 and occurs in all ethnic groups [1]. The major pathological marker of PD is the degeneration of nigrostriatal dopaminergic neurons, which leads to a reduction in dopamine (DA) content within the striatum [2]. While loss of the nigrostriatal dopaminergic neurons represents a hallmark of PD, the pathology in PD extends beyond these neurons. Recent evidence indicates that caudal brainstem structures are involved in PD pathology even before the nigrostriatal pathology [3]. Several processes have been proposed to underlie neurodegeneration in PD, including mitochondrial dysfunction [4] and iron-related oxidative stress [5]. Although there have been many advances in understanding the pathophysiology of PD, the diagnosis of PD still largely relies on the clinical judgment of a neurologist. Misdiagnoses could compromise therapeutic decisions. Hence, the development of biomarkers to confirm diagnosis and to monitor progression and response to therapeutic interventions is of critical importance to clinical practice. Neuroimaging techniques have much to offer for an objective and potentially more accurate in vivo means to assess the brain structure, physiology, chemistry, and function in PD. Non-invasive magnetic resonance spectroscopy (MRS) techniques can be utilized for the evaluation of brain physiology, chemistry, and function in neurodegenerative disorders since they provide unique information on chemical composition of the brain tissue. Using MRS at 7T it is possible to measure the signals from up to 17 metabolites [6] that are reflective of different pathophysiological processes of PD. Thus, this method has the potential to improve the understanding of the etiology, progression, and the response to therapy in PD. In this chapter we will review MRS studies that were used to investigate neurochemical alterations in PD.