The Commission determined that claimant’s preexisting nerve root tumor on his back was aggravated when the construction vehicle he was operating hit a large hole. As a result of this aggravation, claimant required surgery to remove the tumor.

Claimant, a shuttle car operator, testified that on April 18, 1992, he was operating a vehicle similar to a dump truck when he hit a large hole and felt pain in his low back. He was diagnosed with a lumbar strain. On May 2, 1997, claimant’s doctor recorded that the results of an MRI revealed a soft tissue nodule in claimant’s back. He recommended that claimant remain off work and referred him to a second doctor. The second doctor saw claimant on one occasion and opined that he did not think the tumor noted in the diagnostic tests was related to the incident at work. Claimant then saw a neurosurgeon, who performed surgery to remove the benign spinal tumor. The neurosurgeon did not believe that the traumatic event at work caused the neurofibroma but opined that the trauma caused the neurofibroma to move.

The surgeon concluded that the tumor was irritated or aggravated by the work accident. Defendant’s expert opined that the tumor was not caused by the work trauma and that the surgery to remove the tumor was not necessitated by the trauma.

The arbitrator found that claimant sustained a work-related lumbar strain arising out of his employment, but that the spinal nerve root tumor was not aggravated or caused by the accident.

The Commission modified the decision of the arbitrator to find that as a result of the work accident, claimant sustained both a lumbar strain and an aggravation of the preexisting nerve root tumor or neurofibroma, and that these conditions, as well as the subsequent need for surgery to remove the tumor, were causally related to the work accident. The Commission based this finding on the chain of events-particularly the evidence of an asymptomatic tumor prior to the accident, followed by complaints of back and leg pain thereafter-as well as the opinion of the treating neurosurgeon to the effect that claimant sustained an irritation or aggravation of the neurofibroma he eventually removed.