Clinical utility of visualisation of nigrosome-1 in patients with Parkinson's disease.

OBJECTIVE

To determine the diagnostic characteristics of poor visualisation of nigrosome-1 as a neuroimaging biomarker in Parkinson's disease (PD) and to explore the relationship of poor visualisation of nigrosome-1 and clinical asymmetry.

METHODS

High-resolution gradient-echo sequences of 67 patients with PD and 63 healthy controls were reviewed by two radiologists blinded to the clinical details. A three-tier classification system was used to categorise the scans based on the visualisation of nigrosome-1, and inter-rater reliability was calculated at each level of classification. Other diagnostic properties such as sensitivity, specificity and predictive values were calculated. The relationship between poor visualisation of nigrosome-1 and clinical asymmetry was also assessed.

RESULTS

Poor visualisation of nigrosome-1 had high sensitivity (98.5%), specificity (93.6%), positive-predictive value (94.3%), negative-predictive value (98.3%), accuracy (96%) and inter-rater reliability (k = 0.75-0.92). Poorly visualised nigrosome-1 was significantly associated with higher motor asymmetry in the contralateral side in 64.8% of subjects (p = 0.004).

CONCLUSIONS

Poor visualisation of nigrosome-1 in PD had good diagnostic properties as a neuroimaging biomarker in PD. There was also a significant agreement on clinical asymmetry and poor visualisation of nigrosome-1.

KEY POINTS

• Nigrosome-1 represents the largest collection of dopaminergic neurons in dorso-lateral substantia nigra. • Loss of nigrosome-1 is being studied as a biomarker in Parkinson's disease. • Visualisation of nigrosome-1 had good diagnostic properties as a biomarker. • There was a contralateral relationship between nigrosome-1 lateralisation and clinical asymmetry. • We also highlight the potential limitations of nigrosome-1 visualisation as a biomarker.