Background
In late 2014, Sam McDonald suffered a compensable workplace injury when the hood of a car fell on him during the course of his work as a mechanic, injuring his head. The Wyoming Department of Workforce Services, Workers’ Compensation Division found the injury compensable and began providing benefits including permanent impairment and temporary total disability (TTD) payments. One lasting consequence of the head injury was severe, debilitating migraines. McDonald’s treating neurologist, Dr. Zinkhan, began seeing him in February 2015 and noted that McDonald had been taking Depakote (divalproex sodium) at 500 mg three times daily since 2012 for preexisting bipolar disorder and depression. Because Depakote is also used to treat migraines, Dr. Zinkhan recommended McDonald continue the same dosage for both conditions. In June 2016, Dr. Zinkhan recommended increasing the Depakote to 750 mg three times daily to better control the migraines. The Division eventually approved the increase, and Dr. Zinkhan wrote the prescription at McDonald’s April 2018 appointment.
In December 2019, McDonald presented to an emergency room with severe abdominal pain and was diagnosed with acute pancreatitis. He suffered recurring episodes that ultimately required removal of his gallbladder, insertion of a feeding tube, and extensive additional medical procedures. He discontinued Depakote around this time, but pancreatitis recurred even after discontinuation. McDonald filed applications for TTD benefits, arguing that his pancreatitis was a second compensable injury causally linked to his 2014 workplace injury through the Division-approved Depakote dosage increase ordered to treat his compensable migraines.
The Division denied benefits following an independent medical examination by gastroenterologist Dr. Fishman, who concluded that because McDonald had been taking Depakote before the 2014 injury, the pancreatitis was not causally related to the workplace injury. The Wyoming Medical Commission upheld the denial after an initial contested case hearing, and again after the case was remanded to receive additional expert testimony from Dr. Brodis and a supplemental report from Dr. Fishman. The Sweetwater County District Court affirmed. McDonald then appealed to the Wyoming Supreme Court.
The Court’s Holding
The Wyoming Supreme Court, in an opinion by Justice Hill joined by all five justices, affirmed under Wyoming’s substantial evidence standard. Wyoming’s second compensable injury rule allows a subsequent injury or condition to be compensable when it is causally linked to an initial compensable workplace injury. The claimant bears the burden of proving, by a preponderance of the evidence, that the subsequent condition was caused by the first injury. The Supreme Court reviews the Medical Commission’s denial of benefits by asking whether the conclusion to reject the claimant’s evidence was contrary to the overwhelming weight of the record as a whole.
The Medical Commission was presented with conflicting testimony from four medical experts. Dr. Fishman, retained by the Division for an IME, found no causal connection to the workplace injury: McDonald had been taking Depakote before the 2014 accident, and Dr. Fishman testified that pancreatitis episodes occur both with and without dosage adjustments. Dr. Zinkhan, the treating neurologist, believed Depakote caused the pancreatitis but testified that Depakote-induced pancreatitis is an idiosyncratic reaction—meaning it can occur at any time and at any dose, with the same risk whether a patient takes the drug for six months or for years. The increased dosage thus did not increase McDonald’s risk. Dr. Eskelson concluded Depakote caused the pancreatitis but had not reviewed the full medical history, was unaware of when McDonald began taking Depakote, and based his opinion partly on another treating physician’s views rather than his own independent analysis. Dr. Brodis testified that the increased Depakote dose caused the pancreatitis because it occurred within two months of the increase—placing the increase in October 2019.
The Medical Commission rejected Dr. Brodis’s timeline as inconsistent with the record. McDonald himself testified he began the higher dose after his April 2018 appointment, eighteen months before the pancreatitis attack, not two months. Other records suggested the increase began in June 2019, six months before the attack. Additionally, McDonald discontinued the increased dosage approximately a month before the pancreatitis occurred. Because Dr. Brodis’s causation opinion was expressly premised on a two-month proximity that the record did not support, the Commission found his testimony unpersuasive. The Commission also found that literature and publications Dr. Brodis cited were not entered into the record. The Supreme Court found the Commission acted within its province: it is precisely the Commission’s function to resolve conflicting expert testimony and weigh credibility, and it fully explained its reasons for discounting each opinion it rejected.
McDonald’s principal argument—that two of three experts supported his position and therefore he should prevail—was squarely rejected. No legal authority establishes that a numerical majority of expert witnesses satisfies the preponderance-of-the-evidence standard. McDonald’s arbitrary-and-capricious challenge also failed: the Commission admitted all relevant evidence, produced an eleven-page remand order incorporating a thirty-five-page original decision, and provided adequate findings of fact and conclusions of law. Because the substantial evidence determination was sufficient to affirm, the Supreme Court did not address the Medical Commission’s alternative conclusion that McDonald was ineligible for TTD benefits even if causation had been established, given that he had obtained Social Security disability benefits and his own treating physician had documented in 2018 an expectation that McDonald would never return to work.
Key Takeaways
- Under Wyoming’s second compensable injury rule, a claimant seeking benefits for a subsequent condition must prove by a preponderance of the evidence—not by a numerical majority of expert witnesses—that the condition was causally linked to the initial compensable workplace injury.
- The Wyoming Medical Commission is empowered to resolve conflicting expert testimony, weigh credibility, and disregard expert opinions it finds unreasonable or not adequately supported by the facts on which they rest; the Supreme Court does not substitute its judgment for the Commission’s credibility determinations.
- An expert opinion premised on a factual timeline that the record—including the claimant’s own testimony—contradicts can be disregarded by the Commission without legal error.
- Depakote-induced pancreatitis is characterized in the record as an idiosyncratic reaction with equivalent risk at any dosage and any duration of use, creating a significant causal-chain challenge for workers’ compensation claimants attempting to link the condition to a dose increase ordered for a compensable injury.
- The arbitrary-and-capricious standard under Wyoming’s Administrative Procedures Act provides a safety net only when the agency failed to admit clearly admissible evidence or failed to provide adequate findings; it is inapplicable when a claimant’s arguments are based entirely on record evidence that the Commission considered and weighed.
Why It Matters
McDonald v. State illustrates the high bar Wyoming workers’ compensation claimants face when pursuing a second compensable injury claim through a pharmaceutical causal chain. Where the connecting mechanism between a workplace injury and a subsequent condition is a medication prescribed to treat a compensable symptom, the claimant must establish not just that the medication can cause the subsequent condition, but that the specific circumstances of the prescription—here, the dosage increase—more probably than not caused the condition in this claimant. When the primary experts testify that the risk of the adverse drug reaction is the same at any dose and at any duration of use, the causal chain is broken regardless of how sympathetic the facts are.
The decision also reinforces the breadth of the Medical Commission’s discretion as fact-finder. Claimants and their counsel should understand that winning a headcount of experts is not winning under Wyoming law. The Commission’s credibility assessments—including its prerogative to reject an expert whose factual premise is contradicted by the claimant’s own testimony—are highly deferential on review. Building a winning case before the Commission requires accurate and internally consistent medical records, and counsel should scrutinize the factual assumptions underlying supporting expert opinions before the contested case hearing, not on appeal. For Division defense counsel, McDonald illustrates the value of an IME that focuses not only on ultimate causation but on the pharmacological characteristics of the drug at issue—evidence that the adverse reaction occurs idiosyncratically without regard to dosage proved decisive here.