The employer and insurer appeal from the compensation judge’s finding that the employee’s left upper extremity condition, and her related medical treatment, are casually related to her work injury, and from the award of medical expenses for mental health treatment.  We affirm.

This appeal relates to an admitted injury that Ms. Wendy Ruby, the employee, sustained on May 3, 2005.  She injured her left foot and ankle, and later developed left upper extremity symptoms which required medical treatment.  The employee also developed anxiety and depression, for which she received mental health treatment.  At issue on this appeal is whether the employee’s left upper extremity condition developed as a substantial result of her 2005 work injury.  Also at issue on appeal is whether the mental health treatment the employee has received, including psychological counseling and medication, was reasonable, necessary and causally related to her 2005 work injury.

The employee began working on a part-time basis at Casey’s General Store, the employer, in March 2004. In January 2005, she began working on a full-time basis, working as a cashier and pizza preparation worker, and performing various duties at the convenience store.  On May 3, 2005, the employee injured her left lower extremity, which resulted in pain and swelling in her left ankle and swelling in her foot and calf area.  She has remained off work almost entirely since then, although she has been able to assist her family with babysitting, and has undergone extensive medical treatment for her left lower extremity.  The employer and its insurer, CCMSI, have paid ongoing benefits to the employee, including temporary disability benefits, rehabilitation assistance, and payment of medical expenses.

Within a few months after her work injury, the employee experienced overall diffuse pain in her body and, specifically, symptoms in her left upper extremity; as documented by voluminous medical records in evidence, the employee has since undergone treatment for both her left upper and lower extremities.

By August 2005, Dr. Eric Watson, at the Orthopedic Institute, diagnosed reflex sympathetic dystrophy (RSD) in the employee’s left lower extremity; he recommended physical therapy and a pain clinic evaluation, and prescribed Neurontin for pain relief.  Dr. Jerry Blow, a physiatrist, examined the employee in September 2005; at that time she reported diffuse pain throughout her body, including burning pain in her left lower extremity.  Dr. Blow diagnosed and referred to the employee’s ankle strain as RSD or complex regional pain syndrome of her left lower leg, as well as left greater trochanteric bursitis and left infrapatellar bursitis.  Dr. Blow prescribed pain medication, including Lyrica, a Clonidine patch, and Mobic, and a continuation of Neurontin, as an aggressive attempt to control the employee’s pain.  He recommended various treatments including pain and anti-inflammatory medication, sympathetic nerve blocks, pool therapy, the use of a TENS unit and an electrical device designed to stimulate muscle contraction.

At a consultation with Dr. Blow in January 2006, the employee reported continued pain, swelling and sweating in her left foot and ankle, fatigue, difficulty sleeping and body aches.  Dr. Blow concluded that the employee had reached maximum medical improvement (MMI) from her work injury.  He assigned permanent physical work restrictions and limitations on the hours that she could drive a car; he also recommended that the employee continue to use a heat lamp and perform home exercises, and recommended that she gradually discontinue certain prescription medications.

In March 2006, at the employer and insurer’s request, the employee was examined by Dr. William Bell, orthopedic surgeon.  Dr. Bell diagnosed chronic regional pain syndrome (CRPS), and concurred that the employee’s injury of May 3, 2005, substantially contributed to that condition and her current restrictions.  He disagreed with other physicians’ diagnoses of RSD, however, as he detected no findings supportive of that diagnosis.^[1]  Dr. Bell concluded that the employee’s reports of pain were out of proportion to her objective findings, and commented that it was “unlikely that any treatment at any time in the foreseeable future will ameliorate her subjective complaints of pain.”  Dr. Bell recommended that the employee work within the physical work restrictions as outlined by Dr. Blow.  He also concurred with Dr. Blow’s determination that the employee had reached MMI from the physical effects of her 2005 injury.

Within a few months of the injury, the employee developed depression and anxiety conditions.  The records indicate that the employee had no history of any mental health treatment before her injury, and also reflect the employee’s report of pain and emotional concerns she experienced following her work injury.  Dr. Blow prescribed Lyrica for peripheral neuropathy and diffuse pain complaints, and later prescribed antidepressant medications, primarily as a sleep aide but also to assist with pain management.  Dr. Blow also encouraged the employee to seek counseling and referred her for a mental health evaluation.  Since that time, she has taken some form of antidepressant medication almost continuously; she has undergone counseling and psychological evaluations, and has continued to undergo treatment for pain control.

In 2006, litigation ensued concerning a dispute over whether the employee had reached MMI, whether the employer and insurer could discontinue payment of temporary total disability benefits, and whether the employee had unreasonably refused a job offer.  In October 2006, an evidentiary hearing was held before a compensation judge to address the dispute.  In the findings and order served and filed November 6, 2006, the compensation judge found that benefits could be discontinued on the basis of the expiration of the 90-day period post-MMI, and also found that the employee did not unreasonably refuse the written job offer.  Following an appeal by the employer and insurer, this court affirmed the findings and order.^[2]

In May 2007, additional litigation ensued on the issue of whether the employee had developed a psychological condition as a consequence of her 2005 injury, and whether the medication she was prescribed for that condition was compensable.

Dr. Thomas Gratzer conducted a medical record review on behalf of the employer and insurer to address the cause of the employee’s mental health symptoms and her need for treatment.  In a December 2007 report, Dr. Gratzer outlined his opinion that the employee’s generalized anxiety disorder either began or worsened after the employee’s 2005 injury, and that her symptoms from October 2005 to December 2005 could reasonably be attributed to the physical stresses of the 2005 injury.  In Dr. Gratzer’s opinion, any adjustment disorder the employee may have experienced thereafter was unrelated to the injury and was not psychiatrically limiting, impairing, or restricting.  Dr. Gratzer concluded that the employee had developed situational depression due to family issues that had resolved by September 2006, and concluded that the employee did not require any ongoing mental health treatment as a result of her work injury.

In April 2008, an evidentiary hearing was held before a compensation judge to address, in part, a claim for expenses incurred for mental health treatment.  In a Findings and Order, served and filed April 23, 2008, the compensation judge concluded that the employee had developed anxiety and depression as a result of her 2005 work injury and awarded payment for medical expenses related to treatment for that condition.  The compensation judge accepted the opinion rendered by a treating therapist that the employee had an adjustment disorder with depressed mood related to a general medical condition of RSD.  The judge concluded that it was reasonable for the insurer to pay for antidepressant and anti-anxiety medications to assist the employee with coping with her depression and anxiety that had accompanied her chronic pain and decreased physical abilities.

The employee’s symptoms in her left upper and lower extremities continued.  In December 2007, the employee’s family physician referred her for a pain management consultation with Dr. Sam Elghor at the Center for Pain Management.  Dr. Elghor confirmed earlier diagnoses of neuropathic pain in the employee’s left lower extremity indicative of RSD.  In response to the employee’s concern that her symptoms seemed to have migrated from her left lower extremity to her left upper extremity, Dr. Elghor provided his opinion that, in some cases, RSD symptoms have “a tendency to spread to distant areas in the body.”  He referred to a journal article, later submitted into evidence, which he considered in forming his opinion.

In view of the 2½ year duration of employee’s pain, Dr. Elghor recommended spinal cord stimulation through implantation of a stimulator; he requested but was denied insurance approval for that procedure.  In October 2008, the employee returned to Dr. Elghor, reporting continued symptoms such as hypersensitivity extending from her left shoulder into her hand, which the employee described as feeling like sunburn.  At that point, Dr. Elghor noted that the employee did not exhibit autonomic signs expected in RSD in her left upper extremity even though such symptoms had been detected in her left lower extremity.  Dr. Elghor reiterated his recommendation for spinal cord stimulation, to treat the employee’s symptoms in both her left upper and lower extremities, as an alternative to lifelong maintenance on neuropathic medications.

Records in evidence document ongoing treatment the employee received for pain medication and for stress and anxiety.  In July 2008, the employee was evaluated by Robert Packard, Ph.D., licensed psychologist, who assessed her level of depression as severely limiting her functioning.

In July 2008, Dr. Gratzer conducted an independent psychiatric examination of the employee.  Based on his testing and interview of the employee, Dr. Gratzer diagnosed generalized anxiety disorder, under good pharmacological control; and adjustment disorder with depressed mood, resolved.  He reiterated his opinion that the employee’s anxiety had been in remission as of December 2005, and that her later symptoms, such as depression, were unrelated to her May 2005 injury.  Dr. Gratzer also concluded that the employee had no psychiatric limitations or restrictions, and that she did not require any further mental health treatment.  He also expressed his opinion that the employee had relative psychiatric contraindications for implantation of a spinal cord stimulator, such as had been recommended by Dr. Elghor, and recommended a second opinion before approval for that procedure.

In August 2008, the employee underwent an independent neurological evaluation with Dr. Miles Belgrade.  He diagnosed chronic left lower extremity pain with neuropathic features, but no objective or clinical evidence of RSD; left upper extremity pain of unknown etiology; and history of signs and symptoms consistent with mild RSD.  Dr. Belgrade found no basis for the conclusion that the employee’s RSD in her left lower extremity had transferred to her upper left extremity.  Dr. Belgrade later provided his opinion that the employee’s prescriptions for Lyrica, Tramadol, and Propranolol were related to her work injury, but that her Paxil and BusSpar, for depression and anxiety, were unrelated to her work injury.  He recommended against a spinal cord stimulator.

In mid-March 2009, Dr. Packard evaluated the employee to help determine her appropriateness for the spinal cord stimulator implantation recommended by Dr. Elghor.  The employee reported ongoing difficulty with climbing stairs, lifting, balancing, and occasionally dropping things, and also reported ongoing burning pain.  She reported that she had not yet been able to secure employment because her pain made her work attendance unreliable.  Dr. Packard noted that the employee had made significant improvement in her psychological condition and her overall level of functioning, to the point that he felt the employee was psychologically capable of undergoing an implantation of a spinal cord stimulator.

The employee’s symptoms continued, including pain radiating into her left shoulder and arm, and from her left thigh to her foot.  She eventually began using a cane for walking.  By mid-January 2010, evidently after approval had been extended by the insurer, Dr. Elghor implanted a trial - - and later a permanent - - nerve stimulator to treat the employee’s upper and lower extremity symptoms.  The employee reported good relief of her symptoms from this procedure.

By claim petition and medical request, the employee claimed that her left upper extremity symptoms and need for related treatment, and her need for mental health treatment, were causally related to her 2005 work injury.  The employer and insurer denied the causal connection between the employee’s injury and those conditions, relying on the opinions of Dr. Blow, who had treated the employee, and Drs. Belgrade and Gratzer, who had conducted independent medical examinations of the employee.

The employee’s claim petition and medical request were consolidated and were addressed at an evidentiary hearing held before a compensation judge on June 17, 2010.  The issues at hearing were whether the employee’s left upper extremity condition developed as a substantial result of her 2005 work injury and whether the employee’s mental health treatment was reasonable, necessary and causally related to her 2005 work injury.

Evidence introduced at hearing included the employee’s testimony, her medical records, and video surveillance investigation conducted on the employee by the employer and insurer in 2008 and 2009.  In a findings and order, served and filed August 11, 2010, the compensation judge concluded that the employee’s left upper extremity neuropathic pain developed as a consequence of her admitted left lower extremity injury of May 3, 2005.  The compensation judge found Dr. Elghor’s opinion persuasive, and rejected the opinions of Drs. Blow and Belgrade on that issue.  She stated, as follows:

The compensation judge also found that the employee’s treatment for her psychological problems from April 2008 through the hearing, and her use of certain medications for anxiety and depression, were related to her work injury.  The compensation judge relied on the opinion of Dr. Packard, as well as the counseling records, in reaching that conclusion.  The judge also determined that medications including Lyrica, Tramadol, Propanolol, and Ambien were reasonable and necessary to cure and relieve the effects of the employee’s injury.  To that end, the compensation judge relied on the opinion of Dr. Belgrade, who had advised that those particular medications were within the “typical parameters for a patient with intractable neuropathic pain.”

Finally, the compensation judge specifically stated that she found the employee to be a credible witness, and that she did not find that the surveillance conducted by an investigator provided persuasive evidence of any fabrication or malingering by the employee concerning her left upper and lower extremity pain.  The compensation judge ordered payment of the employee’s reasonable and necessary medical bills for treatment of her upper extremity, including bills incurred at the Center for Pain Management and Douglas County Hospital, and ordered reimbursement to the intervenor.  The employer and insurer appeal.

The employer and insurer contend that the compensation judge erred by finding that the employee’s left arm condition was causally related to her work injury, based on several different arguments.  The employer and insurer first argue that there are no medical opinions indicating that the employee meets the requirements of the permanent partial disability schedules for RSD under Minn. R. 5223.0430, subp. 6.  The employee, however, is not claiming permanent partial disability under the schedules.  Further, the compensation judge specifically noted that Dr. Elghor had not opined that the employee’s left arm condition was RSD, and concluded that a finding that all diagnostic criteria for RSD have been met was not necessary for determining causation of the employee’s left arm condition.  We agree.  The lack of a medical opinion stating that the employee has been diagnosed with RSD of her left arm is not determinative in this case.

What is determinative is that the compensation judge relied on a medical expert opinion, submitted into evidence, in reaching her conclusions that the employee’s neuropathic pain in her left upper extremity is causally related to her work injury.  The compensation judge relied on Dr. Elghor’s opinion in reaching that conclusion.  The employer and insurer, however, argue that Dr. Elghor’s opinion is unfounded, in large part because he relied on a particular journal article, to which they objected but which the judge allowed into evidence, when rendering his opinion.

To be of evidentiary value, an expert medical opinion must be based on adequate foundation.  Welton v. Fireside Foster Inn, 426 N.W.2d 883, 41 W.C.D. 109 (Minn. 1988).  The competence of a witness to render expert medical testimony depends upon both the degree of the witness’s scientific knowledge and the extent of the witness’s practical experience with the matter at issue.  Reinhardt v. Colton, 337 N.W.2d 88 (Minn. 1983).  Dr. Elghor, who is a medical doctor, conducted physical examinations of the employee, took a history from her, and reviewed her medical records.  As a general rule, this level of knowledge establishes a doctor’s competence to render an expert opinion.  See Grunst v. Immanuel-St. Joseph’s Hosp., 424 N.W.2d 66, 40 W.C.D. 1130 (Minn. 1988).  Dr. Elghor had adequate foundation for his medical opinion. 

As the compensation judge advised the parties during the evidentiary hearing, she would consider the employer and insurer’s objections to inclusion of the contested journal article into evidence but would evaluate the weight she would accord to that article.  “Evidentiary rulings are generally within the sound discretion of the compensation judge.”  Ziehl v. Vreeman Constr. Co., slip op. at 5 (W.C.C.A. Oct. 15, 1991).  We agree that Dr. Elghor’s reliance on the article goes to the weight to be given it, not to its admissibility into evidence, and that his reliance on the article does not negate the overall foundation he had for his opinion.  In addition, it is the compensation judge's responsibility, as trier of fact, to resolve conflicts in expert testimony.  Nord v. City of Cook, 360 N.W.2d 337, 342, 37 W.C.D. 364, 372 (Minn. 1985).  This court will generally affirm a compensation judge’s decision which is based on a choice between competing medical opinions.  Perry v. ADB Constr., Inc., 68 W.C.D. 491 (W.C.C.A. 2008).

The employer and insurer also argue that the compensation judge misconstrued the relevance of the surveillance videos they submitted into evidence.  The surveillance videos show the employee using her left arm in various circumstances and holding various objects.  The employer and insurer argue that they submitted the videos to show that the employee did not display symptoms of RSD in her left arm.  The compensation judge found that the videos were not persuasive in showing that the employee was fabricating or malingering regarding her left arm or left leg complaints.  Since the compensation judge did not decide the causation issue based on a finding of RSD, the compensation judge did not err by failing to make a finding on whether the surveillance videos indicated symptoms of RSD.

On appeal, the Workers' Compensation Court of Appeals must determine whether “the findings of fact and order [are] clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted.”  Minn. Stat. § 176.421, subd. 1 (2010).  Substantial evidence supports the findings if, in the context of the entire record, “they are supported by evidence that a reasonable mind might accept as adequate.”  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).  On the issue of causation of the employee’s left upper extremity condition, the record contains adequate evidence, including expert medical opinion, to support the compensation judge’s finding and we, therefore, affirm.  Id. at 60, 37 W.C.D. at 240.

The employer and insurer also argue that the compensation judge erred by holding that the findings issued in 2008 - - that the employee had sustained a psychological injury as a consequence of her 2005 work injury, and that prescribed medication was reasonable medical treatment - - were the law of the case.  In her 2010 findings and order, at issue in this appeal, the compensation judge stated that the employer and insurer needed to show that something significant had changed to make the previous decision no longer controlling on the issue of whether the employee’s ongoing medication was causally related to her work injury.  The employer and insurer claim that the compensation judge therefore improperly shifted the burden of proof to the employer and insurer by applying principles of res judicata to the employee’s claim for medical treatment.

Res judicata is a doctrine bringing finality to legal proceedings in which “a final judgment on the merits bars a second suit for the same claim” by the same parties.  Kaiser v. Northern States Power Co., 353 N.W.2d 899, 902 (Minn. 1984).  Principles of res judicata are applicable in workers’ compensation proceedings.  See, e.g., Alexander v. Kenneth R. LaLonde Enters., 288 N.W.2d 18, 31 W.C.D. 407 (Minn. 1980).  However, res judicata applies in workers’ compensation cases only with respect to issues specifically litigated and decided in prior proceedings.  See, e.g., Fischer v. Saga Corp., 498 N.W.2d 449, 450, 48 W.C.D. 368, 369 (Minn. 1993).

The res judicata effect of a prior workers' compensation determination is limited to those issues and facts material to, and determinative of, benefit eligibility and events or circumstances previously at issue and in existence as of the date of the prior hearing.  Generally, no substantial change in condition or circumstances need be proven and principles of res judicata primarily govern with respect to the periods of benefits at issue.  Lindberg v. J & D Enters., 543 N.W.2d 90, 90, 54 W.C.D. 44, 52 (Minn. 1996) (order opinion).  Issues involving the need for, or the reasonableness or effectiveness of, medical treatment are among those which may be affected by changed circumstances so as to preclude a res judicata effect on determinations for subsequent periods.  See Cook v. Lloyd's Food Prods., Inc., slip op. (W.C.C.A. Sept. 22, 1992) (prior finding denying need for surgery was not res judicata for later periods); Gullickson v. Commonwealth Elec. Co., slip op. (W.C.C.A. Nov. 28, 1989) (medical restrictions determined for a prior period were not res judicata for a subsequent period).

While we agree that res judicata does not apply in this case, we conclude that the compensation judge’s findings and ultimate conclusion are supported by substantial evidence.  The judge considered the medical records from the period after the 2008 hearing, and the current medical opinions provided since that hearing, and found that the employee’s mental health condition and related medication continued to be related to her work injury.  There is no indication that the compensation judge erroneously shifted the burden of proof to the employer and insurer in making this determination.

In a corresponding argument, the employer and insurer argue that the compensation judge erred by concluding Dr. Gratzer’s opinion was based on an incorrect foundation.  The compensation judge reached this conclusion because Dr. Gratzer’s earlier causation opinion had been rejected by a compensation judge at the time of the 2008 evidentiary hearing, and his later opinion remained unchanged.  Because Dr. Gratzer’s current causation opinion contradicted the 2008 adjudication that the employee’s psychiatric conditions were related to her work injury, the compensation judge rejected the same.

We agree that Dr. Gratzer had adequate foundation for his medical opinion, even though it contradicted the earlier adjudication.  See Grunst v. Immanuel-St. Joseph’s Hosp., 424 N.W.2d 66, 40 W.C.D. 1130 (Minn. 1988).  Dr. Gratzer’s statements go to the weight to be given the opinion, not to its admissibility.  See Drews v. Kohl’s, 55 W.C.D. 33, 39 (W.C.C.A. 1996); see also Bossey v. Parker Hannifin, slip op. (W.C.C.A. Mar. 14, 1994); Trego v. Associated Leasing, slip op. (W.C.C.A. Jan. 9, 1998); Stuhr v. Northwestern Travel Serv., Inc., 57 W.C.D. 352 (W.C.C.A. 1997); summarily aff’d (Minn. Dec. 15, 1997).  And it is clear to us that the compensation judge did not exclude Dr. Gratzer’s opinion from admission or consideration due to what she considered to be a lack of foundation.  She considered his opinion and found it less persuasive due to Dr. Gratzer’s insistence that the employee’s earlier anxiety and depression were not related to her work injury.  Again, it is the compensation judge's responsibility to resolve conflicts in expert testimony.  Nord, 360 N.W.2d at 342, 37 W.C.D. at 372.

Finally, the employer and insurer claim that the compensation judge erred by failing to sufficiently explain her findings.  This court has stated that a compensation judge should “state with clarity and completeness the facts essential to the ultimate decision so that a reviewing court can determine from the record whether these facts support the judge’s decision” and “should not leave to the reviewing court the obligation to seek or spell out the facts supporting the judge’s decision or to choose between conflicting testimony and inferences.”  Mendez-Merino v. Farmstead Foods, slip op. (W.C.C.A. Aug. 7, 2001); see also Barbknecht v. Americ Disc, Inc., of Minn., slip op. (W.C.C.A. Mar. 3, 2005).  This court has remanded decisions where we have been unable to discern the basis or underlying facts upon which the compensation judge’s decision was based.  This is not such a case.  The question on appeal is not whether there was evidence by which the judge might have reached a different conclusion, but whether there is sufficient support in the record to support the decision.  The judge is not required to discuss all evidence in her decision.  See Regan v. VOA Nat’l Housing, 61 W.C.D. 142 (W.C.C.A. 2000) (a compensation judge is not required to refer to or discuss every piece of evidence introduced at the hearing).  The judge made sufficient findings, on all issues, for this court to review her decision, and the basis for her decision was clearly articulated.

We have affirmed the compensation judge’s findings related to the cause of the employee’s upper extremity condition.  We also affirm her finding that the employee’s psychological problems dating from the hearing in April 2008 through the hearing in 2010, and her medications for that condition, continued to be related to her work injury.