Objective: To characterize the pattern of the olfactory deficit in a group of Parkison’s disease (PD) patients and compare it with hyposmic patients of other non-neurodegenerative etiologies.

Background: Olfactory dysfunction is present in up to 90% of PD patients. It is usually assessed by means of objective standardized tests; however the olfactory dysfunction has not been well characterized. Degree of olfactory dysfunction does not seem to vary with disease duration or severity, nor does it improve with antiParkinsonian medication.

Methods: We evaluated 36 PD patients, 20 patients with hyposmia secondary to acute respiratory infection (ARI), and 19 patients with olfactory dysfunction secondary to traumatic brain injury (TBI). For comparison purposes, we also included a group of 15 healthy controls matched for age and sex with the PD patients. PD patients were classified into 3 groups based on disease duration and severity: De novo PD, PD with and without chronic levodopa therapy-related complications. The Barcelona Smell Identification test (BAST-24), that consists of 24 odours scoring smell detection, definition, identification, recognition, and forced choice, was applied to all the participants.

Results: For the first cranial nerve odours, PD patients scored lower than controls on smell detection (85.28 vs 97.67 %, p=0.006), definition (79.58 vs 93.33 %, p=0.007), recognition (63.33 vs 81 %, p=0.020) and forced choice (58.06 vs 82 %, p<0.001). No differences were found regarding odour identification (p=0.068). Comparing with ARI patients, forced choice was significantly better in PD patients (p <0.001), but no differences were found regarding the other olfactory characteristics. TBI patients showed significantly lower scores than PD patients, ARI and controls, in all the olfaction items (p< 0.001). For the fifth cranial nerve odours, smell detection, definition and forced choice were similar between study groups but recognition (p=0.003) and identification (p=0.019) was lower in the TBI group than in the other groups. No differences were found among the three PD subgroups regarding any of the olfactory characteristics.

Conclusions: PD patients showed a different pattern of olfactory impairment compared to other non-neurodegenerative etiologies of hyposmia. The pattern of the olfaction deficit in PD seems to keep stable as the disease progresses. Further studies with larger sample size are needed to corroborate these findings.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/olfactory-deficit-characterization-in-parkinsons-disease/