The self-insured employer appeals the compensation judge’s finding that the employee’s work-related low back condition and subsequent use of medications are substantial contributing causes of the employee’s gastroesophageal reflux disease symptoms and need for the use of the medication Protonix. The employer also claims that the compensation judge did not address the issue of whether the employee’s use of Protonix was reasonable and necessary. We affirm.

On May 31, 2001, Charles Anderson, the employee, sustained a work-related low back injury while working as a delivery person for Upper Lakes Foods, the employer, which was self-insured for workers’ compensation liability. The employer accepted liability for the injury and paid temporary total disability benefits, rehabilitation expenses, and medical expenses.

The employee initially treated with his family physician, Dr. Thomas Osborne, on June 4, 2001. Dr. Osborne diagnosed low back strain, and prescribed medication and exercise. On June 15, 2001, Dr. Osborne referred the employee for physical therapy. The employee attended physical therapy from June 20, 2001, through August 2001. A July 12, 2001, x-ray indicated mild disc space narrowing at the L5-S1 level. On July 25, 2001, the employee consulted Dr. Jacob Kammer, a physical medicine specialist with St. Luke’s Occupational Medicine. Dr. Kammer diagnosed mechanical low back pain with functional overlay and left shoulder pain, and recommended physical therapy. In August 2001, Dr. Kammer recommended a work hardening program, which the employee attended from September 7, 2001, through November 12, 2001.

The employee treated with Dr. Kammer in October 2001, reporting increasing low back pain and radiating pain down his left leg. An October 18, 2001, MRI indicated a bulge at the L4-5 vertebral level with mild encroachment of the neuroforamina and mild degenerative changes, but with no nerve root compression or displacement. Dr. Kammer reviewed the MRI and read it as normal. On December 11, 2001, Dr. Kammer released the employee to return to work with restrictions and concluded that the employee had reached maximum medical improvement (MMI) from his low back injury.

In February 2002, Dr. Kammer referred the employee to Dr. Lynn Quenemoen, in the department of occupational medicine at the Duluth Clinic. Dr. Quenemoen ordered a discogram which indicated concordant pain and abnormal morphology or tears at the L4-5 and L5-S1 levels, and referred the employee for surgical consultations with Dr. James Callahan, Dr. Scott Dulebohn, and Dr. Timothy Garvey. None of these doctors found that the employee was a surgical candidate. Dr. Dulebohn recommended a chronic pain program.

On June 7, 2002, the employee was examined by Dr. John Dowdle at the self-insured employer’s request. Dr. Dowdle diagnosed a mild ligamentous injury to the cervical spine and pre-existing mild to moderate degenerative disc disease at L4-5 and L5-S1. Dr. Dowdle found that the employee had reached MMI from the effects of his low back injury and had not sustained any permanent partial disability, and that he was not in need of any further ongoing medical care or treatment.

On January 29, 2003, the employee again treated with Dr. Quenemoen, reporting chronic back pain, bilateral lower extremity pain and dysesthesias, and left groin pain. Dr. Quenemoen thought the employee was developing depression and referred the employee to a chronic pain program, advising that since “surgery does not appear to be an option, I think his only other treatment would be a chronic pain program.” The employee returned to Dr. Quenemoen on June 20, 2003, reporting increased pain and burning pain in his legs and into his feet, increased upper back and shoulder pain, and increased headaches. Dr. Quenemoen adjusted the employee’s medication, in part to attempt to reduce his edema and to improve his sleep, and recommended a neurology consultation. On July 2, 2003, the employee saw Dr. Gary Beaver for a neurology consultation in view of his persistent symptoms of severe low back pain, bilateral lower extremity and neuropathic-type pain, severe headaches, and ankle clonus. Dr. Beaver assessed chronic pain syndrome, tension headaches, and lower extremity paresthesias, and recommended an EMG. After the EMG, Dr. Beaver diagnosed mild demyelinating polyneuropathy. On July 3, 2003, the employee was examined by Dr. Martin Grune, a urologist, for urination difficulty complaints. Dr. Grune indicated that the employee could have bladder dysfunction, which could be neurologic in nature.

On July 14, 2003, the employee was evaluated by Dr. Thomas Elliot for a pain management consultation and possible participation in the pain management program at the Duluth Clinic. The employee reported low back pain, leg pain, paresthesia and dysesthesias with associated weakness, bladder dysfunction, neck and shoulder pain, tension headaches, and migraine headaches. The employee’s medications at that time included OxyContin, Neurontin, Alprazolam, Bextra, Phenergan, Imitrex, Pepcid, Nortriptyline, and Furosemide. Dr. Elliot diagnosed chronic low back pain due to degenerative disc disease and myofascial pain syndrome, and recommended that the employee participate in a pain management program.

The employee continued to experience tension headaches, which improved with use of ibuprofen. The employee reported to Dr. Elliot and Dr. Muhammad Azam that he was experiencing indigestion and gastroesophageal reflux disease (GERD) symptoms, which improved with the use of Protonix. On November 3, 2003, the employee was reevaluated by Dr. Dowdle at the employer’s request. Dr. Dowdle opined that the employee’s work injury was a temporary aggravation of his underlying degenerative disc disease and recommended a psychiatric evaluation to determine whether any of the employee’s ongoing symptoms were psychogenic in origin in view of his lack of substantial improvement even with narcotic medication. Dr. Dowdle concluded that the employee had sustained 10% permanent partial disability of the whole body relative to his pre-existing degenerative disc disease.

In his January 12, 2004, report, Dr. Quenemoen opined that the employee had suffered annular tears at L4-5 and L5-S1 and had developed chronic pain syndrome and leg pain and dysesthesias, that the employee had reached MMI from the effects of his work injury, and that he had sustained 10% permanent partial disability of the whole body relative to that injury. He also opined that the employee had sustained permanent bladder impairment, but could not relate it to his work injury.

In 2004, the parties reached a settlement whereby the employee accepted payment of $107,000.00 in exchange for settlement on a full, final, and complete basis, with his claim for future medical expenses left open. An award on stipulation was served and filed on April 27, 2004.

The employee continued to treat with Dr. Quenemoen for headaches, stomach problems, and back pain. In August 2004, Dr. Quenemoen assessed chronic low back pain and urinary and sexual dysfunction related to back pain. The employee’s conditions persisted. He did not take Protonix between September 2004 and September 2005, but by September 2005 he reported to Dr. Quenemoen that he was experiencing reflux symptoms after taking Neurontin. Dr. Quenemoen prescribed resumption of Protonix to treat the employee’s reflux symptoms. This prescription was renewed in July 2006 and November 2006 by Dr. Les Reiss, who treated the employee following Dr. Quenemoen’s retirement from the practice of medicine.

On November 22, 2006, the employee filed a medical request for payment of expenses for electrodes for a muscle stimulator and prescription medications for erectile dysfunction (Cialis), sleep disorder (Ambien), and gastroesophageal reflux disorder (Protonix). The employer agreed to pay for the electrodes and Ambien, but denied payment for Cialis and Protonix, arguing that these medications were prescribed for conditions which were not related to the employee’s work-related low back injury. On March 6, 2007, Dr. Reiss opined that the employee’s medications could make his GERD symptoms worse. On April 10, 2007, Dr. Dowdle opined that the employee’s GERD and use of Protonix were not related to his work injury.

A hearing was held on May 17, 2007, to address the employee’s medical request. The compensation judge found that the employee’s work-related injury was a substantial contributing cause of the employee’s gastroesophageal reflux disease and awarded the employee’s claim for Protonix. The compensation judge denied the employee’s claim for Cialis, finding that the employee had failed to establish a causal connection between the employee’s work injury and his need for that medication. The self-insured employer appeals the award of payment for the Protonix; the employee did not cross-appeal the denial of payment for the Cialis.

The employer argues that substantial evidence does not support the compensation judge’s finding that the employee’s work-related low back condition and subsequent use of medications are substantial contributing causes of the employee’s gastroesophageal reflux disease symptoms and need for the use of the medication Protonix. An employee has the burden of proving that claimed medical expenses are reasonable, necessary, and causally related to his work injury. Adkins v. University Health Care Ctr., 405 N.W.2d 233, 39 W.C.D. 898 (Minn. 1987). The ultimate determination of medical causation is within the province of the compensation judge. Felton v. Anton Chevrolet, 513 N.W.2d 456, 50 W.C.D. 181 (Minn. 1994). The compensation judge accepted the employee’s testimony that he noticed his GERD symptoms when he began taking more and stronger medications, and that he had not experienced any GERD symptoms before his injury. “Assessment of witness credibility is the unique function of the factfinder.” Tews v. Geo. A. Hormel & Co., 430 N.W.2d 178, 180, 41 W.C.D. 410, 412 (Minn. 1988); Brennan v. Joseph G. Brennan, M.D., 425 N.W.2d 837, 839-40, 41 W.C.D. 79, 82 (Minn. 1988). It is not the role of this court to evaluate the credibility and probative value of witness testimony and to choose different inferences from the evidence than the compensation judge. Krotzer v. Browning-Ferris/Woodlake Sanitation Serv., 459 N.W.2d 509, 513, 43 W.C.D. 254, 260-61 (Minn. 1990). We therefore defer to the compensation judge’s assessment of the credibility of the employee’s testimony.

Dr. Reiss opined that the employee’s medications could make his GERD symptoms worse, but did not specify which particular medication could have this effect. Dr. Dowdle opined that the employee’s GERD and use of Protonix were not related to his work injury. The employer argues that the employee is taking numerous medications for other conditions and that Dr Reiss’s opinion does not specify which of the employee’s medications contributed to the employee’s GERD conditions. We note that the employer’s expert medical opinion does not indicate which other medications could contribute to the employee’s GERD condition. 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). The compensation judge referred to Dr. Quenemoen’s chart note of September 27, 2005, in which he noted that the employee experienced reflux symptoms primarily after taking Neurontin. The compensation judge found that the employee’s use of numerous medications to obtain relief from his low back injury had been a substantial contributing cause of the employee’s gastroesophageal reflux disease, and that this disease was substantially controlled by the use of Protonix.

In reviewing cases 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 (2006). 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). We conclude that, in view of the record as a whole, including medical records and the employee’s testimony, substantial evidence supports the compensation judge’s findings, and we therefore affirm.

The employer also argues that the compensation judge failed to address the employer’s assertion that the employee’s ongoing use of Protonix was not reasonable and necessary. Minn. Stat. § 176.135, subd. 1(a), states that an employer is to furnish “any medical, psychological, chiropractic, podiatric, surgical and hospital treatment, including nursing, medicines, medical, chiropractic, podiatric, and surgical supplies, . . . as may reasonably be required at the time of the injury and any time thereafter to cure and relieve from the effects of the injury.” An employee has the burden of proving that medical expenses are reasonable, necessary, and causally related to her work injury. See Adkins v. University Health Care Ctr., 405 N.W.2d 233, 39 W.C.D. 898 (Minn. 1987). Generally, the reasonableness and necessity of medical treatment is a question of fact for the compensation judge. See Hopp v. Grist Mill, 499 N.W.2d 812, 48 W.C.D. 450 (Minn. 1993).

The question for this court is whether substantial evidence exists to support the decision of the compensation judge. See Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 37 W.C.D. 235 (Minn. 1984). The employee testified that he experienced GERD symptoms when he took Neurontin. Dr. Reiss opined that Protonix provided relief of the employee’s symptoms that were aggravated by his medications. The compensation judge found that the employee’s use of numerous medications to obtain relief from his low back injury has been a substantial contributing cause of the employee’s gastroesophageal reflux disease, and that this disease was substantially controlled by the use of Protonix. The compensation judge specifically found that the medication was very helpful in alleviating the symptoms of the esophageal reflux. The compensation judge did not fail to address the issue of the reasonableness and necessity of the employee’s Protonix medication. Substantial evidence supports the compensation judge’s findings, and we affirm.