Testing protocol unlocks mystery of chronic pain

Research may hold the key to reducing disability

Would you like to avoid paying thousands in disability costs to employees with chronic pain? Early research results from a new testing protocol developed by a researcher currently in practice at the Comprehensive Pain and Headache Treatment Centers at Griffen Hospital in Derby, CT, may offer the first real tool for diagnosing a neurological condition that may predispose people to chronic pain conditions. (For information about protecting your staff against back injuries, see story, p. 73.)

"I started with a clinical impression that patients with reflex sympathetic dystrophy [RSD] and complex regional pain syndrome seemed to manifest similar subtle characteristic abnormalities of sensation of the head and neck. This suggested an underlying neurological condition that predisposed them to chronic pain conditions," says Mark Thimineur, MD, with the Comprehensive Pain and Headache Treatment Centers and previously assistant professor at Yale University School of Medicine in New Haven, CT.

"The MRIs [magnetic resonance imaging] on these patients were usually normal. We had a difficulty convincing anybody, even ourselves, that these clinical similarities were real," he says. This led to the development of a protocol using six noninvasive tests of neurological function on the pathways in the central nervous system which are important in transmitting pain signals and controlling motor function.

The six tests used by Thimineur to quantitatively evaluate neurologic function of chronic pain patients initially cost about $900 and could be done in one day. Thimineur hopes to streamline the testing process and decrease the cost to about $600 and the testing time down to two hours. The six tests in the protocol include:

• quantitative somatosensory thermotest;

• Semmes-Weinstein filament test;

• pressure algometry;

• taste studies;

• isokinetic strength evaluation;

• isometric evaluation.

The six tests are structured into a standard protocol designed to evaluate brainstem and spinal cord function. Using this protocol, the evidence began to support Thimineur’s theory. Of 133 RSD patients tested, 67% met the criteria for cervicomedullary dysfunction. This included a specific pattern of sensory loss of the face and tongue with same side sensory derangement of the body, which was always on the side that the RSD was located. "In fact, the syndrome compares favorably with neurologic deficits seen in certain types of brainstem vascular events, or stroke. The changes are just more subtle."

Only seven of the 133 patients with sensory derangement had abnormal MRIs. "All seven had abnormalities of the lower brainstem," says Thimineur.

Thimineur has observed similar findings in many patients with chronic low back pain. "In back pain patients, we see more evidence of cervical spine disease and confirmatory MRIs. We often find that leg symptoms such as weakness in low back pain are attributable to unrecognized cervical cord compression."

The evidence Thimineur is gathering about the underlying cause of chronic pain holds enormous implications for agencies and for payers. "We believe that with further research we will be able to identify patients that are at high risk for developing chronic pain and disability," he says. "Right now, we are seeing patients after they have already had several surgeries and therapy. If we could see them earlier, we may be able to identify a significant number of patients who are predisposed to bad outcomes."

Thimineur adds that identifying the cause of chronic pain helps physicians structure realistic treatment plans. "We have seen a common pattern of functional decline and a spreading of pain and weakness in these patients with presumed brainstem abnormalities. We also see rather consistent symptoms of brainstem dysfunction develop such as headaches and nausea. Knowing this, we are more capable of helping the patient and are less overwhelmed by these confusing symptoms."

Understanding the condition also makes physicians more comfortable and compassionate in treating patients, he says. "In the past, many of these patients were assumed to be manifesting psychiatric symptoms. If we understand better the natural evolution of these neurological chronic pain states, we can further benefit people by acting preventively and doing things like restructuring work environments or removing at-risk patients from potentially harmful work situations — perhaps avoiding a certain amount of permanent disability."

In the future, Thimineur hopes that the testing protocol can be adapted into a screening tool for employees who may be predisposed to chronic pain and disability. "What if we could identify patients at risk for disability? This would allow meaningful preventive measures such as ergonomic changes for at-risk employees, or perhaps, earlier vocational retraining," he says.

Thimineur has already started to test the general population of healthy working individuals in comparison to his chronic pain patients. "Among our healthy working colleagues, there are about 7% who manifest similar changes to those identified in our chronic pain population," he says. "Of that 7%, many have reported chronic pain conditions, such as bursitis, which have not kept them off work, but have kept them returning to the doctor."

"They might be the future disabled person," he adds. "Eventually they could get a worse injury that will become more painful than it should be and that would fail surgery."

(Editor’s note: Mark Thimineur, MD, was formerly with the Yale Center for Pain Management in New Haven, CT.)