A month has gone by since the last earnings report for Acorda Therapeutics (ACOR). Shares have lost about 6% in that time frame, underperforming the S&P 500.Will the recent negative trend continue leading up to its next earnings release, or is Acorda due for a breakout? Before we dive into how investors and analysts have reacted as of late, let's take a quick look at its most recent earnings report in order to get a better handle on the important drivers. Acorda Q4 Earnings and Revenues Surpass EstimatesAcorda announced fourth-quarter 2018 earnings per share of 45 cents, significantly beating the Zacks Consensus Estimate of a loss of 60 cents. However, the figure declined from the year-ago earnings of 61 cents.Acorda generated total revenues of $69.1 million in the fourth quarter, comprehensively outshining the Zacks Consensus Estimate of $41 million. However, sales tumbled a massive 63.3% year over year.Quarter in DetailMajority of Acorda’s net product revenues were drawn from the company’s key multiple sclerosis (MS) drug Ampyra, which raked in sales of $64.2 million in the reported quarter. Sales of Ampyra plunged 61.6% year over year and 53.4% sequentially due to generic launches including Mylan's authorized generic version.Also, on fourth-quarter conference call, the company stated that Ampyra sales will see a steady decline in the quarters ahead in 2019.Notably, in the quarter under consideration, royalty revenues plummeted 82.6% to $2.8 million from the year-ago figure of $16.1 million.Acorda’s research and development (R&D) expenses (excluding share-based compensation expenses) were $25.9 million, reflecting a decrease of 21.2% year over year.Selling, general and administrative (SG&A) expenses (excluding share-based compensation expenses) were $33 million, representing a 3.2% year-over-year dip.2019 GuidanceThe company will no longer provide any outlook for Ampyra due to declining revenues, resulting from the entrance of generics.The company expects full-year R&D and SG&A expenses (excluding share-based compensation) for 2019 in the band of $70-$80 million and $200-$210 million, respectively.How Have Estimates Been Moving Since Then?In the past month, investors have witnessed an upward trend in fresh estimates.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Acorda Therapeutics, Inc. (ACOR): Free Stock Analysis Report To read this article on Zacks.com click here.