Correlation between Progressive Changes in Piriform Cortex and Olfactory Performance in Early Parkinson’s Disease

Abstract

Objectives: The mechanism underlying olfactory dysfunction in Parkinson’s disease (PD) remains unknown. The current study aims to investigate the relationship between sequential changes of volume change of cortex associated with olfactory function and degree of deficiency of olfactory performance in PD. Methods: Based on the arbitrary cut-off score of olfactory performance measured by ‘five odors olfactory detection arrays’, subjects were classified into three groups: PD patients with olfactory impairment (OPD, n = 12), PD without olfactory impairment (NPD, n = 14), and healthy controls without olfactory impairment (NC, n = 26). A morphometric analysis of magnetic resonance images (voxel-based morphometry; VBM) was used to investigate cortical volume change. Results: The scores of olfactory performance were higher in both NPD and OPD groups than in the NC group independent of age and disease duration, indicating that NPD subjects did have board line deficiency of olfaction though not meet the cut-off score for abnormal olfactory function. Both NPD and OPD had cortical atrophy in the parahippocampal gyrus (PCG), but only OPD also had change in orbitofrontal cortex (OFC). Correlation analysis revealed that decrement of volumes of PCG and right OFC was associated with decreased olfactory detection sensitivity, and the right OFC was also correlated to olfactory identification. However, no correlation was found between structural changes and the severity of the disease measured by UPDRS score. Conclusions: The results confirmed that atrophy in piriform cortex and orbitofrontal cortex is associated with olfactory dysfunction in early PD. Atrophy of the orbitofrontal cortex becomes significant as olfactory damage progresses. Volume measurement of olfaction-associated areas together with the assessment of olfactory function may be a sensitive indicator for the early diagnosis of PD.

Anterior Temporal Atrophy and Posterior Progression in Patients with Parkinson's Disease

“…For instance, olfactory dysfunction is considered as a relatively early or even preclinical sign in PD [3], while in later stages pathological changes in olfaction-related brain areas have been described [4]. Cortical atrophy has been demonstrated to correlate with olfactory dysfunction in PD [5]. Especially in later stages, cognitive impairment, including visuospatial dysfunction and alterations in executive functions, occurs relatively often in PD [6].…”

Cortical thickness analysis – The methods

“…Cortical thickness analysis has already been used to look at the normal thinning of the cortex with age (Salat et.al 2004), to see the changes in the brain after a sensory loss (Li et.al 2004), or if the brain differs from a control when one of the senses was never there (Frasnelli et.al 2013). It has been used to explore how diseases such as Parkinson's disease (Wu et.al 2011) and Alzheimer's disease (Li et.al 2012) affects the brain, and how an early start at life may affect the development of gray matter (Nagy, Lagercrantz & Hutton 2011, Kapellou et.al 2006, Martinussen et.al 2005, Nosarti et.al 2014.…”

“…Together all of these methods have been used to examine the effect of loss of a sense like hearing or smell (Li et.al 2012, Frasnelli et.al 2013, the effect of Alzheimers disease (Li et.al 2012), Parkinsons disease (Wu et.al 2011), and aging (Salat et.al 2004, Van Velsen et.al 2013. It has also been used to see the effect of a premature birth (Nagy, Lagercrantz & Hutton 2011, Kapellou et.al 2006, Martinussen et.al 2005, Nosarti et.al 2014, as well as the effect of psychiatric disorders such as bipolarity (Oertel -Knöchel et.al 2015, Giakoumatos et.al 2015, schizophrenia (Zugman et.al 2015), ADHD (Fernández-Jaén et.al 2015) and autism (Richter et.al 2015).…”

Olfactory Dysfunction in Parkinson’s Disease Patients with the LRRK2 G2385R Variant

“…The ''five-odor olfactory detection array'', one of the Chinese olfactory tests, was applied [13][14][15]. The sensitivity of this test was 74.0% and the specificity was 91.7% as calculated in a previous study [16].…”

“…The score was recorded as 3.5 and labeled as anosmia if the participant could not identify any odor. The severity of olfactory dysfunction was represented by the mean value of the combination of TOD and TOI scores for all five odors, based on which the participants were classified as normal (B1), mild hyposmia ([1, B2), and severe hyposmia ([2) [13,16].…”