Functional Optical Hemodynamic Imaging of the Olfactory Cortex in Patients with Parkinson’s Disease

Functional Optical Hemodynamic Imaging of the Olfactory Cortex in Patients with Parkinson’s Disease

Masayuki Karaki, Eiji Kobayashi, Ryuichi Kobayashi, Kosuke Akiyama, Tetsuo Toge, Nozomu Mori
Copyright: © 2011 |Pages: 5
DOI: 10.4018/978-1-60960-559-9.ch022
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Abstract

Olfactory dysfunction is a frequent non-motor symptom in Parkinson’s disease (PD). This symptom is considered to be an early manifestation of the disease. The aim of this study was to establish the cortical basis of olfactory function in patients with PD. This study was conducted on ten healthy, normosmic subjects and seven patients with PD (one with subjective olfactory dysfunction and nine without subjective olfactory dysfunction). We employed a 22-channel near-infrared spectroscopy (NIRS) device with eight light-incident fibers and seven light-detector fibers, each with an inter-optode distance of 2.5 centimeters on the frontal head. Isovaleric acid was used as the odor stimulant. We measured the change in total hemoglobin concentrations (totalHb) from pre-baseline values and compared the results obtained for healthy normosmic subjects and patients with PD. In all healthy normosmic subjects and three patients with PD, isovaleric acid caused remarkable changes in (totalHb), especially in the lower areas of the frontal cortex. However, in four patients with PD, isovaleric acid caused no changes. This result indicates that subjective symptoms are different from objective test results in patients with PD. These activated areas may be related to the orbitofrontal cortex corresponding to the olfactory cortices. This study suggests that normosmic subjects with PD already have damage to their olfactory function.
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Materials And Methods

Multi-Channel Near-Infrared Spectroscopy

The 22-channel near-infrared spectroscopy device (Hitachi Medico Co., Japan) that we employed has seven light-incident fibers and eight light-detector fibers, each with an inter-optode distance of 2.5 centimeters. The light sources were two 0.5 mW continuous laser diodes with wavelengths of 780 and 830 nm. Figure 1 shows the 22 measurement positions in which the 15 fibers were placed in a 5 centimeter by 10 centimeter field over the frontal cortex. These channels could measure changes in concentrations of oxyHb, deoxyHb and totalHb from the pre-baseline values.

Figure 1.

Comparisons between the maximum changes in [totalHb] of normosmic subjects and patients with PD

978-1-60960-559-9.ch022.f01

Subjects

This study was conducted on ten normosmic subjects (four males and six females: mean age, 28.9 years; range, 22-39 years) and seven PD patients (five males and two females: mean age, 66.8 years; range, 58-77 years). Among the PD patients, one had subjective olfactory dysfunction. All subjects understood the aim of this study and gave informed consent for participation, and the study’s protocol was approved by the local ethics committee. T&T olfactometry was done in all subjects. The results showed that all of the normosmic subjects and three patients with PD had normal olfactory function. However, four patients with PD had olfactory dysfunction (grade 2 to grade 4). T&T olfactometry tests categorize the grade from one to five. Normal olfactory function is grade 1. T&T olfactometry is widely used for clinical olfactory testing in Japan (Kondo et al, 1984).

Table 1.
Subject information
Normosmic subjects
SubjectsSexAgeSubjective olfactory dysfunctionT&T olfactogram
Sub1Female25NoGrade 1
Sub2Male24NoGrade 1
Sub3Male24NoGrade 1
Sub4Male39NoGrade 1
Sub5Male28NoGrade 1
Sub6Female22NoGrade 1
Sub7Male31NoGrade 1
Sub8Male38NoGrade 1
Sub9Female25NoGrade 1
Sub10Female22NoGrade 1
Patients with PD
SubjectsSexAgeSubjective olfactory dysfunctionT&T olfactogram
Sub1Female58noGrade 1
Sub2Male77noGrade 2
Sub3Male61noGrade 1
Sub4Male59noGrade 1
Sub5Female75noGrade 4
Sub6Female67yesGrade 4
Sub7Male71noGrade 3

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