Abstract Details

Title Levodopa Responsiveness Subtypes of Freezing of Gait: Results Using a Levodopa Test

Topic Movement Disorders

Presentation(s) P5 - Poster Session 5 (5:30 PM-6:30 PM)

Poster/Presentation
Number 10-027

Objective To characterize FOG subtypes based on response to a levodopa test.

Background Levodopa responsiveness of freezing of gait (FOG) in Parkinson’s disease (PD) is heterogeneous. This suggests the existence of subtypes. Previously, using subtypes determined from patient interview, we found that the levodopa unresponsive FOG subtype, in contrast to the responsive subtype, was associated with cognitive impairments involving visuospatial ability and executive functioning.

Design/Methods N=53 subjects were evaluated OFF medications (>12 h) using MDS-UPDRS and timed-up-and-go tests. They were then given an adequate levodopa dose and examined in the same way when ON. Serum levodopa levels were measured. Based on responsiveness they were categorized into: No FOG (NFOG); Responsive FOG (RFOG; FOG when OFF only); and Unresponsive FOG (URFOG; any FOG when ON). Demographics, N-FOGQ responses, change in MDS-UPDRS and serum levodopa levels from OFF to ON were compared across groups.

Results Subjects were categorized as NFOG (n=16), RFOG (n=14), or URFOG (n=23). The groups did not differ in age, gender, education, family history, OFF or ON UPDRS scores, or OFF or ON serum levodopa levels. NFOG had a shorter disease duration (p=.04), decreased use of assistive devices (p=.002), and decreased prevalence of falls (p=.002) than either RFOG or URFOG, which did not differ from each other. RFOG and URFOG groups had the same duration of FOG (~3 y). RFOG had a lower N-FOGQ score compared to URFOG (p=<.01). Change in FOG subscore from OFF to ON was significantly less in the URFOG group (p<0.05).

Conclusions FOG in PD has at least two subtypes, levodopa responsive or unresponsive, which appear to occur independently. URFOG is more troublesome (based on NFOGQ) than RFOG. These represent separate entities, not a contiguous course, with different pathophysiology. A levodopa test should be utilized to categorize FOG when developing therapies and studying pathophysiology.

Authors/Disclosures
Stewart A. Factor, DO, FAAN (Emory University School of Medicine) PRESENTER	Dr. Factor has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Neurocrine. Dr. Factor has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Biogen. Dr. Factor has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Takeda. The institution of Dr. Factor has received research support from Biohaven. The institution of Dr. Factor has received research support from Neurocrine. The institution of Dr. Factor has received research support from Supernus. The institution of Dr. Factor has received research support from Sun Pharmaceuticals Advanced Research Company. The institution of Dr. Factor has received research support from Aspen. The institution of Dr. Factor has received research support from RHO. Dr. Factor has received publishing royalties from a publication relating to health care. Dr. Factor has received publishing royalties from a publication relating to health care. Dr. Factor has received publishing royalties from a publication relating to health care. Dr. Factor has received publishing royalties from a publication relating to health care.
Garrett E. Alexander, MD (Emory University School of Medicine)	No disclosure on file
	No disclosure on file
Douglas Bernhard	No disclosure on file
Johnathan L. McKay, PhD (Emory University)	The institution of Dr. McKay has received research support from NIH. The institution of Dr. McKay has received research support from the McCamish Foundation.
	No disclosure on file
	No disclosure on file
Felicia Goldstein	No disclosure on file

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