The employee appeals from the compensation judge’s determination that the employee failed to prove she sustained a traumatic brain injury resulting in cognitive impairment, memory loss, recurrent headaches, chronic fatigue, trauma-induced narcolepsy, and injury to the cervical spine as the result of a work-related injury on November 5, 2008.  We affirm.

Jewel A. Schmidt, the employee, sustained a personal injury on November 5, 2008, arising out of her employment with Churches United in Ministry, the employer, when she slipped in a puddle of water and fell backward, hitting the back of her head on the floor.  The employer and its insurer accepted liability for the employee’s personal injury and paid various workers’ compensation benefits including wage loss benefits and medical expenses.

The employee was seen in the emergency room at St. Mary’s Medical Center on the day of her injury.  She denied any loss of consciousness but complained of a headache, nausea, and neck pain.  CT scans of the head and cervical spine were normal.  The emergency room doctor diagnosed a closed head injury and multiple contusions.

The employee sought care at Lempi Chiropractic Clinic on November 7, 2008, complaining of neck pain, headache, and upper back pain following a fall at work.  Dr. Lempi diagnosed a cervical sprain/strain, myofascitis, neck pain and a cervicobrachial syndrome.  The employee received chiropractic treatment from Dr. Lempi through March 2009.^[1]  In December 2009, Dr. Lempi referred the employee to Dr. Wolcott Holt, a neurologist, noting complaints of mental confusion, loss of short-term memory, and falling asleep during the day.

The employee was seen by Dr. Holt on January 9, 2009, with a chief complaint of headaches following a fall at work.  The doctor diagnosed “post-concussive syndrome, classic, now improving.”  (Ex. D.)  The doctor requested an MRI scan of the brain, which was read as normal, and referred the employee for psychometric testing.  A neuropsychological evaluation was completed by Dr. Gregory Murrey in late January 2009.  The doctor diagnosed status post closed head injury, cognitive disorder not otherwise specified, and mild to moderate depression secondary to the head injury.  Dr. Murrey recommended referral to a rehabilitation psychologist for supportive therapy, cognitive retraining, and treatment for depression.

The employee saw her primary care physician, Dr. Ingrid Nisswandt-Larsen, on February 8, 2009.  The employee complained of headaches, neck pain, fatigue, and poor short-term memory, as well as problems staying awake during the day and falling asleep at night.  The doctor assessed unspecified concussion and ordered an EEG which was normal.

The employee began seeing a therapist, Mary McHardy, in March 2009.  Ms McHardy noted the employee presented with a cognitive disorder and a mood disorder, including both depressive and anxiety symptomology, with a pre-injury history of depression, anxiety and panic attacks.  The therapy included adjustment counseling to address her mood disorder and cognitive remediation addressing the residual effects of her closed head injury.  The employee continued to see Ms. McHardy through July 2010.

The employee returned to see Dr. Holt in March 2009 with continued complaints of headaches.  The doctor again diagnosed a post-concussive syndrome, likely to improve, but stated that depression appeared to be the major contributing factor to the employee’s current symptoms.  The employee continued to follow up with Dr. Holt and Dr. Nisswandt-Larsen in 2009 and 2010.

In late January 2010, the employee underwent a second neuropsychological evaluation with Dr. Murrey.  The doctor concluded the employee showed intact and expected levels of performance in areas of short-term memory in both the visual and auditory modalities, and also showed intact abilities in all executive functions such as planning, problem solving, and mental flexibility.  He further noted the employee showed weakness in auditory processing and processing speed, difficulties with working memory, and general speed of processing, stating “[s]uch weaknesses are likely at least partially a result of her mood difficulties [and] fatigue, as well as possible residual deficits from her concussion.”  (Ex. E.)

On July 16, 2010, at the request of Dr. Holt, the employee saw Dr. Brian Konowalchuk, an occupational medicine specialist.  Dr. Konowalchuk diagnosed a cognitive disorder, not otherwise specified, daytime somnolence, depression, emotional lability including suicidal ideation, and possible postconcussive syndrome.  Dr. Konowalchuk noted there seemed to be significant emotional overlay in the employee’s description of her work difficulties that was difficult to quantify or to separate from potential cognitive difficulties.  He recommended a sleep study, repeat neuropsychological testing, and further psychological evaluation.

In September 2010, Dr. Thomas Misukanis, a licensed clinical psychologist, and Dr. Thomas Gratzer, a psychiatrist, performed independent evaluations as requested by Dr. Konowalchuk.^[2]  By report dated October 11, 2010, Dr. Misukanis stated that neuropsychological testing of the employee suggested mild residual brain impairment with deficits including executive functioning, processing speed, and complex attentional processes.  He diagnosed a mild brain injury as a result of the November 2008 slip and fall, a cognitive disorder, not otherwise specified, and depressive personality disorder, by history.  The doctor observed that most individuals who sustain a mild brain injury experience a resolution of symptoms in three to six months, but the employee appeared to be one of the unfortunate few who did not recover.  Dr. Misukanis subsequently reviewed some pre-injury medical records, including the treatment records of therapist Todd Kneebone, who provided counseling to the employee from December 2006 through May 2008.  By report dated February 22, 2011, the doctor noted Mr. Kneebone’s records reflected a pre-fall history of attention deficit disorder [ADHD] with documented problems with concentration, orientation and impulse control.  He noted that patients with ADHD exhibit weaknesses in attention, processing speed, and high-order executive functions consistent with the employee’s test results.  In light of the new documentation, Dr. Misukanis revised his initial opinion, stating it was now his opinion that the employee’s cognitive difficulties more likely represented symptoms of ADHD, and were not the consequence of a mild brain injury on November 5, 2008.

Dr. Thomas Gratzer performed a psychiatric evaluation and prepared a report dated October 11, 2010, following which the doctor reviewed additional pre-injury medical records and wrote a second report dated November 15, 2010.  In June 2011, Dr. Gratzer was deposed.  He testified the employee’s medical records documented underlying mixed personality traits with a pre-injury history of chronic low-grade depression, anxiety, and attention deficit disorder.  The doctor diagnosed an undifferentiated somatoform disorder that was not related to her personal injury.  He further agreed with Dr. Misukanis that the mild abnormalities in the neuropsychological testing were best explained by ADHD.  He opined the employee sustained a very mild head injury as a result of her fall, and that if there were any cognitive difficulties, they would have been mild and would have resolved very soon after the personal injury.  Dr. Gratzer opined the employee was capable of working on a full-time basis without restrictions.  Finally, Dr. Gratzer opined the employee had reached MMI from the effects of her personal injury and had sustained no permanent partial disability.

In November 2010, the employee asked to have her care transferred from Dr. Holt to Dr. Konowalchuk.  Dr. Konowalchuk noted the employee had been seen for a sleep study and was diagnosed with narcolepsy.  In a November 12, 2010, chart note, Dr. Konowalchuk observed there did not appear to be significant anatomical impairment or a traumatic brain injury to account for the employee’s current poor functioning and noted the inconsistency of her cognitive function testing compared to what was seen with a typical traumatic brain injury.  That left, he stated, psychosocial factors as a very large contributor to the employee’s current situation.  He limited the employee to a four-hour work day, observing additionally, that emotionally and psychologically it might not be prudent for the employee to return to work that required high level functioning.

Richard Duus, a licensed psychologist, evaluated the employee in November 2010.  The doctor diagnosed psychological factors secondary to her personal injury, major depression secondary to the dysfunction she was experiencing, generalized anxiety, and loss of consciousness of less than 30 minutes.  Dr. Duus commenced a regime of psychological treatment including compensatory procedures to address cognitive dysfunction and psychophysiological interventions to address her narcolepsy.  In a brief report dated December 23, 2010, Dr. Duus stated the employee should not work for four to six months to facilitate the psychological healing and adjustment necessary as a result of her significant cognitive disabilities.

In a note dated December 22, 2010, Dr. Nisswandt-Larsen stated the employee suffered a severe traumatic brain injury/head concussion on November 5, 2008, and developed severe memory issues.  The doctor stated the employee had been unable to function at her job despite reduced hours, and that the employee had been on disability since December 3, 2010.  Dr. Nisswandt-Larsen opined the employee was unable to work due to her traumatic brain injury and severe memory issues.

An independent medical examination was conducted in May 2011 by Dr. Khalafalla Bushara, a neurologist, at the request of the employer and insurer.  By report dated June 2, 2011, Dr. Bushara opined that the employee sustained a closed head injury with a scalp contusion and cervical sprain/strain on November 5, 2008.  The doctor noted the employee had a history of headaches and neck pain, and opined that her current symptoms were related to her preexisting headaches and chronic neck problems and were not related to her head injury.

By report dated June 23, 2011, Dr. Nisswandt-Larsen provided a diagnosis of a traumatic brain injury secondary to a concussion resulting in chronic headaches, fatigue, severe memory loss, cognitive impairment, and traumatic brain injury-induced narcolepsy.  The doctor opined these conditions resulted from the employee’s personal injury.  Dr. Nisswandt-Larson further stated the employee had reached maximum medical improvement [MMI], that her long-term prognosis was guarded, and that she was totally disabled from all employment.

On February 11, 2011, the employer and insurer filed a petition to discontinue workers’ compensation benefits on the basis that the employee’s somatoform disorder was not work-related, that the employee’s November 5, 2008, injury was temporary in nature, and that the employee had reached MMI, was capable of working, and that any disability was non-work-related.  In a Findings and Order, served and filed on September 9, 2011, the compensation judge found the employee sustained a mild head injury on November 5, 2008, from which she recovered by February 5, 2009; that the employee’s symptoms of memory loss, somnolence, fatigue, and problems with executive functions were more likely the result of her preexisting attention deficit disorder and mood disorders; that the employee failed to prove she developed severe short term memory impairment, severe fatigue, recurrent headaches or trauma-induced narcolepsy as a substantial result of her November 5, 2008, slip and fall; and that the employee failed to prove she sustained a personal injury to her cervical spine as a result of the November 5, 2008, work injury.  In reaching his decision, the compensation judge accepted the opinions of Dr. Gratzer and Dr. Misukanis, finding them well-reasoned and supported by the evidence, further explaining that he did not find persuasive the opinions of the employee’s physicians, Dr. Duus and Dr. Nisswandt-Larsen.  The employee appeals.

The employee argues that her functional limitations are a direct result of cognitive deficits and trauma-induced narcolepsy resulting from a traumatic brain injury on November 5, 2008, and not the manifestation of depression or ADHD.  She asserts the opinions of Dr. Gratzer and Dr. Misukanis lack foundation, and that the compensation judge improperly ignored the copious records and multiple findings and opinions of the employee’s treating physicians.

The employee contends, in support of her argument that Dr. Gratzer’s opinion lacks foundation, that the compensation judge erroneously found “noteworthy” that Dr. Gratzer was asked to examine the employee by the employee’s treating physician, Dr. Konowalchuk; that Dr. Gratzer’s diagnosis of a somatoform disorder, with no objective findings, is contrary to the findings and opinions of all of the other doctors; that Dr. Gratzer failed to consider Dr. Duus’s treatment notes which, as her treating psychologist, should be given greater weight than a one-time evaluation; and that Dr. Gratzer’s adoption of ADHD as a contributing cause is inconsistent with his own medical review.  We are not persuaded.

First, we note that the compensation judge, while finding “noteworthy” the fact that Dr. Gratzer was asked to examine the employee by the treating physician, also correctly observed that Dr. Konowalchuk recommended repeat neuropsychological testing through an outside group, and that the referral was made to BMI who arranged for the examinations with both Dr. Gratzer and Dr. Misukanis.  (Mem. at 6.)  Regardless, the judge’s observation is not of such significance as to render Dr. Gratzer’s opinion without foundation.

In rendering his opinion, Dr. Gratzer reviewed the employee’s treatment records both before and after the work injury and summarized them at length in his reports.  The doctor obtained a medical history and history of symptoms and complaints from the employee and performed an examination.  We have stated on numerous occasions that this level of knowledge about the subject matter establishes a doctor’s competence to render an expert opinion.  See Grunst v. Immanuel-St. Joseph Hospital, 424 N.W.2d 66, 68, 40 W.C.D. 1130. 1132-33 (Minn. 1988).  Nor does the fact that Dr. Gratzer performed a one-time evaluation, or that his opinion was contrary to the findings and opinions of the employee’s treating doctors, render his opinion without foundation.  These concerns relate to the persuasiveness or weight accorded the medical opinions, but they are insufficient to establish lack of foundation.  Drews v. Kohl’s, 55 W.C.D. 33, 39-39 (W.C.C.A. 1996).  While a finder of fact may choose to afford greater weight to the opinion of a treating physician, the judge is not required to do so.  Caven v. Ag-Chem Equip. Co., Inc., slip op. (W.C.C.A. Sept. 14, 1993).  Finally, Dr. Gratzer explained, at his deposition, the basis for his adoption of Dr. Misukanis’s opinion that the mild cognitive abnormalities observed on testing were more easily explained on the basis of preexiting ADHD, as well as the basis for his separate psychological diagnosis of mixed personality traits and undifferentiated somatoform disorder.  The compensation judge found Dr. Gratzer’s opinions well-reasoned and persuasive, additionally explaining why he rejected the opinions of the employee’s treating physicians.  Ultimately, the issue involves a choice between the conflicting testimony of medical experts.  It is the compensation judge’s responsibility, as the trier of fact, to resolve such conflicts.  A judge’s choice between expert opinions must be upheld unless the facts assumed by the expert in rendering his opinion are not supported by the evidence.  See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  The facts assumed by Dr. Gratzer are not inconsistent with the evidence submitted.  We must, therefore affirm.

The appellant additionally contends that the compensation judge erroneously ignored Dr. Misukanis’s initial report, instead adopting the opinions expressed in the doctor’s less credible amended report, and failed to explain his reasons for doing so.  We disagree.  The judge clearly outlined, in his memorandum, Dr. Misukanis’s initial diagnosis and the basis for his revised opinion - - that is, the pre-injury records of Todd Kneebone who diagnosed ADHD in 2006.  Dr. Misukanis explained in his second report that the cornerstones of his initial opinion  - - that the employee had suffered residual cognitive impairment from a mild brain injury on November 5, 2008 - - were her denial of ADHD symptoms and neuropsychological findings reflecting mild cognitive difficulties.  The doctor noted the employee’s symptoms were atypical for an individual experiencing a mild brain injury, and further observed that research documented that patients with ADHD exhibit the same pattern of cognitive difficulties described in the employee’s October 11, 2010 evaluation.  Dr. Misukanis opined, therefore, in light of the additional pre-injury medical records, that it was more plausible that the employee’s cognitive deficits were the result of ADHD rather than the residuals of a mild brain injury.  There is nothing in the law that requires a compensation judge to view as less credible a revised medical report, and the compensation judge did not err in adopting Dr. Misukanis’s adequately founded amended opinion.

The employee also argues that the compensation judge ignored the multiple findings and opinions of the employee’s numerous treating physicians as well as copious medical and vocational evidence, and that these records provide substantial evidence to support the employee’s claim.  The compensation judge wrote a memorandum describing in some detail the evidence in the case, and it is evident the judge did consider the records and reports of the employee’s treating providers.  We acknowledge that different inferences could be drawn from the evidence in this case.  The issue, however, is not whether the evidence would support a contrary result, but whether there is substantial evidence, in the record as a whole, to support the findings that the compensation judge made.  In this case, the opinions of Dr. Gratzer and Dr. Misukanis provide that substantial evidence.  Minn. Stat. § 176.421; Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).

The employee additionally argues that her functional limitations significantly increased after the November 5, 2008, personal injury.  The compensation judge accepted the testimony of Kim Randolph, her direct supervisor, and Greg Kvam, the employer’s finance director, that the employee’s job performance did not change significantly after her slip and fall.  The employee contends the testimony provided by Mr. Kvam and Ms. Randolph is founded on speculation and hearsay and did not constitute substantial evidence regarding her ability or lack of ability to do her job before and after the injury.  It is not the function of this court to reevaluate the credibility and probative value of witness’s testimony, Even v. Kraft, Inc., 445 N.W.2d 831, 835, 42 W.C.D. 220, 225 (Minn. 1989); Redgate v. Sroga’s Standard Serv., 421 N.W.2d 729, 734 (Minn. 1988), and we see nothing in the testimony of these witnesses that requires a reversal by this court.

Finally, the employee asserts the employer and insurer failed to submit any medical evidence addressing the employee’s claim of a cervical injury and that the compensation judge had no basis on which to find the employee failed to prove a personal injury to her cervical spine as a result of the November 2008 slip and fall.  We disagree.  There is substantial evidence in the record of preexisting complaints and treatment for chronic headaches and neck and upper back pain.  Additionally, in his report of June 2, 2011, Dr. Bushara, who performed an independent medical examination on behalf of the employer and insurer, opined that the employee’s current symptoms were related to her preexisting headaches and chronic neck problems and were not related to her head injury.  The employee does not contend that Dr. Bushara lacked foundation for his opinion.  As there is evidence in the record from which the compensation judge could reasonably conclude that the employee’s cervical problems, if any, were not causally related to the work injury, we must affirm.

We acknowledge that different inferences could be drawn from the evidence in this case.  However, it is the compensation judge’s responsibility, as the trier of fact, to judge the credibility of witnesses, to weigh the evidence, and to resolve conflicts in expert medical testimony.  See Nord, at 342, 37 W.C.D. at 372; Hengemuhle, at 59-60, 37 W.C.D. at 237-240.  “Whether we . . . might have viewed the evidence differently is not the point, but whether the findings of the compensation judge are supported by evidence that a reasonable mind might accept as adequate.”  Redgate at 734, 40 W.C.D. at 957 (Minn. 1988).  Having carefully reviewed the record, we conclude the evidence is adequate to support the decision of the compensation judge, and affirm.