Objective: To test the hypothesis that SN hyperechogenicity seen in transcranial sonography (TCS) can be used as a reliable disease progression marker from stage I (unilateral parkinsonism) to stage II (bilateral parkinsonism) in EOPD patients.

Background: EOPD patients require close monitoring for disease progression since they are at a higher risk for treatment related complications. SN hyperechogenicity, an established biomarker to differentiate PD from other forms of parkinsonism, has been shown to remain stable with an area >0.2cm2 in advanced PD patients (≥H&Y stage II).

Method: 44 EOPD patients in Hoehn and Yahr (H&Y) Stage I as determined by the Unified Parkinson’s Disease Rating Scale (UPDRS) in the “off” or drug naïve state (performed by a rater blinded to the TCS) were followed every 6 months. All UPDRS sessions were videotaped and verified by a blinded second movement disorders specialist with nearly 100% interrater reliability for H&Y staging.The sonographer was screened from knowing the patient’s clinical condition. A video z-stack of each SN was obtained and largest area of SN hyperechogenicity was quantitated on de-identified clips by a blinded technologist. SN hyperechogenicity >0.2 cm2 were classified as significant on each side.

Results: At V1, hyperechogenicity that met >0.2cm2 was found exclusively on the contralateral SN of 44 subjects. Mean contralateral and ipsilateral SN hyperechogenicity was 0.268 ± 0.0582 cm2 and 0.146 ± 0.0493 cm2 respectively. Mean side-specific UPDRS Part III score was 7.034 ± 2.716 on the affected side and 0.1818 ± 0.4458 on the unaffected side. By 540 days post V1, 67.57% of the patients (N=37) had hyperechogenicity >0.2cm2 ipsilaterally and 13.51% (N=37) were classified as Stage II. By 720 days, 37 subjects had bilateral SN hyperechogenicity, whereas only 17 subjects had clinically progressed to stage II. It was also observed that ipsilateral SN hyperechogenicity gradually increased >0.2cm2 prior to developing stage II disease on UPDRS testing in the “practically defined off state” in all subjects as determined by the blinded rater.

Conclusion: Our findings demonstrate the usefulness of SN hyperechogenicity as a biomarker for EOPD progression from stage I to stage II providing a useful surrogate to test disease modification therapies and for predictive counselling of patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/substantia-nigra-sn-hyperechogenicity-as-seen-in-transcranial-sonography-tcs-is-a-reliable-disease-progression-marker-from-stage-i-to-stage-ii-in-early-onset-parkinsons-disease-eopd/