The employee appeals from the compensation judge’s denial of benefits on causation grounds.  We affirm.

In December of 2001, the employee began working as a phlebotomist for the American Red Cross [the employer].  In this job, the employee traveled with a team throughout the Upper Midwest, assisting with the employer’s blood donation program.  Some of the work could be classified as moderately heavy, such as loading and unloading machines and other equipment from vans or trucks.  During the hours of the blood drive itself, the employee and other team members rotated various duties, including taking donors’ vital signs, drawing blood, performing computer data entry work, marking tubes of blood, and operating equipment, such as the “double red cell” machine.

Sometime in 2005, the employee allegedly began to experience sensations of heaviness and tingling in her arms and fingers as well as pain and numbness in the back of her neck.  She noted hand symptoms during a gynecological exam on November 8, 2005, indicating that she thought she had strained her right hand stripping tubing at work.  On November 28, 2005, following an evaluation for complaints of right hand tingling and numbness, Dr. Patrick Ryal, the employee’s family physician, assessed the employee as having a paresthesia of the fingers “that is multi-dermatomal in distribution,” likely related to “metabolic issues.”

In an office note from December 12, 2005, Dr. Ryal indicated that the employee was still experiencing fingertip numbness in all of her fingers, which was not in a median nerve distribution, and, concerned about a “central lesion of some type,” he ordered an MRI of the head and neck.  The brain scan, performed on December 27, 2005, was normal; the cervical scan showed only a disc protrusion with slight cord impingement at T3-T4.

Dr. Ryal eventually referred the employee to the Mayo Clinic for further evaluation and treatment.  On March 6, 2006, Dr. Terrance Lagerlund, of Mayo’s neurology department, saw the employee for complaints of “numbness and tingling in [her] hands and feet.”  In the history portion of his treatment notes, Dr. Lagerlund recorded that the employee had noticed constant tingling in the tips of all fingers on both hands, as well as aching in her right arm and the sides of her neck, around September of 2005 and that, in February of 2006, she had developed numbness in the toes and some burning in the balls of her feet, as well as low back pain with shooting pain down the left thigh.  Neurologic exam showed diffuse symmetric hyperreflexia without pathologic reflexes but was otherwise normal.  Dr. Lagerlund offered several possible explanations for the employee’s symptoms, including a peripheral neuropathy or some type of central nervous system disease, leaving the diagnosis for the time as “indeterminate paresthesias.”

Following additional testing, including an EMG, Dr. Lagerlund concluded that the employee “did appear to have a right carpal tunnel syndrome” and, possibly, a small fiber neuropathy, which he felt might explain the paresthesias in the employee’s fingertips and feet.  No specific cause for small fiber neuropathy was ascertained.  Dr. Lagerlund also concluded that the thoracic disc protrusion shown on the prior MRI was “almost certainly asymptomatic.”

On March 30, 2006, the employee was seen by Dr. Marco Rizzo, in Mayo’s hand clinic.  After examination, Dr. Rizzo concluded that the employee was suffering from right carpal tunnel syndrome and peripheral neuropathy.  He administered an injection, in part to determine which of the employee’s symptoms were coming from the carpal tunnel, as opposed to the peripheral neuropathy.

In May of 2006, the employee was seen by several Mayo physicians for several different conditions.  Dr. Shawn Oxtenenko, of Mayo’s spine center, saw the employee for “midline neck pain with no radiation to the arms,” which had reportedly begun in “October of 2005 without injury.”  Dr. Oxtenenko diagnosed the employee as having mechanical neck pain with a myofascial component, which was not “necessarily related to her . . . likely small fiber neuropathy,” and he prescribed physical therapy.  During this same period, the employee was also treated by Dr. Christopher Klein, in Mayo’s neurology department, for Bell’s palsy.  While additional testing did not definitively confirm physicians’ suspicions that the employee was suffering from the effects of a small fiber neuropathy,^[1] treatment notes continued to contain that diagnosis.

On June 8, 2006, a first report of injury was completed, indicating that the employee has experienced pain in her arms, wrists, and hands, while loading and unloading supplies in her job.  The report designated June 8, 2006, as the date of that injury.

The employee underwent right carpal tunnel release surgery on August 14, 2006, and left carpal tunnel release surgery on September 12, 2006, both performed by Dr. Rizzo.  The employer and its insurer admitted liability for the employee’s carpal tunnel condition and paid medical expenses and temporary total disability benefits from mid-August 2006 into November of that same year, when the employee returned to work.

Also in November of 2006, the employee was seen again, for neck pain, by Dr. Oxentenko, who noted that the employee had a “complex history.”  Dr. Oxentenko’s impression, as to the employee’s neck, was that the employee was suffering from a “regional myofascial pain syndrome.”  He ordered physical therapy but indicated that the employee could work without any restrictions as to “her neck pain only,” noting that the employee had been scheduled by Dr. Rizzo to have an EMG later that day.  That EMG was interpreted as a “normal study,” with no evidence of a right cervical radiculopathy, and, compared to her pre-surgery EMG, “there [was] no longer evidence of a median mononeuropathy.”

The employee last saw Dr. Rizzo on March 21, 2007.  At that time, Dr. Rizzo indicated that the employee was still experiencing numbness in her thumbs and index fingers and that, “while working, she does have pain in both arms and neck all the way down to the hands.”  Observing that it was “difficult to pinpoint where any potential nerve problem is,” given the normal EMG, Dr. Rizzo wrote that the employee had “persistent bilateral upper extremity pain, which may be related to her neck symptoms.”

In April of 2007, Dr. Keith Bengtson reiterated that the employee’s post-surgical EMG showed “complete normalization of the median nerve,” indicating that the employee was nevertheless off work because the employer could not accommodate the employee’s “temporary” 25-pound lifting restriction.  In May of 2007, the employee saw Dr. Klein again, in neurology.  In the section describing the history of the employee’s present illness, Dr. Klein wrote as follows:

The employer terminated the employee from employment effective May 15, 2007, based on an inability to accommodate the employee’s then 30-pound lifting restriction.  The employee subsequently worked with a QRC to find alternate employment, also expressing an interest in pursuing retraining as a dental assistant.

The employee was examined again by Dr. Bengtson, in the hand clinic, in September of 2007.  Dr. Bengtson’s impression was “[b]ilateral hand numbness of uncertain etiology, possible small fiber peripheral neuropathy.”  At that time, he relaxed the employee’s restrictions so as to allow her to lift up to 40 pounds.

The matter came on for hearing before a compensation judge on February 3, 2009, for resolution of the employee’s claim for wage loss and rehabilitation benefits.  Issues included whether the employee had sustained a work-related injury on October 1, 2005, and the nature of the employee’s June 8, 2006, injury.  The employer and insurer admitted liability for the employee’s bilateral carpal tunnel condition but alleged that the employee’s continuing symptoms and need for restrictions were unrelated to that condition.  Evidence included the employee’s medical records, the employee’s testimony, and the report of Dr. Joseph Tamborino, the employer and insurer’s independent medical examiner.

In a decision issued on April 2, 2009, the compensation judge determined that the employee had not sustained a work-related injury culminating in October 2005 and that the employee’s June 8, 2006, injury was in the nature of carpal tunnel syndrome.  The judge also concluded that the employee had not established that her June 8, 2006, injury had substantially contributed to her wage loss and need for rehabilitation services for the period claimed.  The employee appeals.

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 (2008).  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).  Where evidence conflicts or more than one inference may reasonably be drawn from the evidence, the findings are to be affirmed.  Id. at 60, 37 W.C.D. at 240.  Similarly, findings of fact should not be disturbed, even though the reviewing court might disagree with them, “unless they are clearly erroneous in the sense that they are manifestly contrary to the weight of evidence or not reasonably supported by the evidence as a whole.”  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

The judge denied the employee’s claim for benefits on causation grounds, concluding that the employee did not establish that her ongoing symptoms and need for restrictions were related to her June 8, 2006, work injury, which the judge defined as carpal tunnel syndrome.^[2]  On appeal, the employee argues, essentially, that the judge erred by rejecting her claim based solely on a lack of medical opinion evidence, contending that her symptoms have been consistent since the date of injury^[3] and “have no explanation or root history but for the injuries at hand.”  The employee also argues that her testimony and treatment records contain sufficient evidence to support a finding of causation, despite the lack of any “magic letter of causation.”  We find no error in the judge’s denial of the employee’s claim.

The employee’s bilateral carpal tunnel condition is admittedly work-related.  However, the employee’s post-surgical EMG was normal, showing no evidence of any continuing median nerve problem.  Numerous Mayo Clinic physicians have expressed uncertainty as to the cause of the employee’s hand (and foot) paresthesias, and no physicians have linked any of those continuing symptoms either to the employee’s carpal tunnel condition or to her work activities.  The most frequent diagnosis, as to those symptoms, is a small fiber neuropathy, and there is no evidence whatsoever relating that diagnosis to the employee’s work or admitted work injury.  As for the employee’s neck symptoms, the tentative diagnosis appears to be myofascial pain syndrome, but, again, no physician has expressly indicated that the employee’s neck symptoms are causally related to the employee’s work.  Similarly, while the employee has been advised to observe a 40-pound lifting limit, no physician has indicated that that restriction is a result of the employee’s carpal tunnel syndrome, as opposed to one of the employee’s other conditions.

The employee is correct in noting that medical opinion evidence is not always required to establish medical causation.  See, e.g., Bender v. Dongo Tool Co., 509 N.W.2d 366, 367, 49 W.C.D. 511, 513 (Minn. 1993).  However, the present case cannot be characterized as involving one of the “commoner afflictions,” for which expert opinion is unnecessary.  Id.  Rather, as the compensation judge observed, the employee’s medical history is very complex, involving considerable doubt by the employee’s own treating physicians about the source of her symptoms.  Certainly the compensation judge was not required to simply assume, under these circumstances, that all of the employee’s various symptoms are related to her injury of June 8, 2006.  The compensation judge did not err in denying the employee’s claim on causation grounds, for lack of expert opinion.  See Westling v. Untiedt Vegetable Farm, slip op. (W.C.C.A. Apr. 29, 2004).  We therefore affirm the judge’s decision in its entirety.