Neurophysiologic tests for CP/CPPS show promise

The neurophysiologic tests that Claire C. Yang, MD, has performed on CP/CPPS patients are demonstrating that phenomenon and are showing potential for assessing the effectiveness of therapies and, possibly, even for diagnosis. She detailed some of those tests and results in CP/CPPS patients here at the NIDDK-sponsored Chronic Pelvic Pain/Chronic Prostatitis Scientific Workshop. Dr. Yang is associate professor of urology at the University of Washington, Seattle.

Neurophysiologic evaluations

Dr. Yang and her team performed thermosensory analysis in 36 men with CP/CPPS and 66 healthy control men, using thermal bursts starting at 35 degrees Celsius and going up to 48 degrees Celsius on the perineum, the point of maximal pain, and on the right anterior thigh, which was considered a neutral area but not too neuroanatomically distant from the perineum. The CP/CPPS group reported consistently higher pain scores on the perineum, which Dr. Yang believes represents a hypersensitivity that reflects central sensitization (J Urol 2003; 170:823-6).

But it is alteration of the autonomic nervous system that is thought to be involved in maintaining pain in many chronic pain syndromes, such as complex regional pain syndrome (CRPS). Alterations in the system can be evidenced by cardiac irregularities, vasomotor instability, and sudomotor instability, or disorders of sweating. The different ways to assess these types of disorders include monitoring these symptoms.

Measuring the RR intervals on ECGs in 20 men with CP/CPPS and 21 controls, Dr. Yang and her team found no differences between the groups.

"This is actually a good finding because it means that there is no severe dysautonomia in men with CP/CPPS," she noted.

Infrared thermography, however, proved to be revealing. This technique, which measures cutaneous blood flow, has been used to diagnose CRPS and peripheral neuropathy in the extremities. Patterns of asymmetry indicate a pathologic state that causes vasomotor instability. Dr. Yang showed an image with obvious temperature asymmetry in a man with left groin and testicular pain, a thermal difference that, in other parts of the body, would be diagnostic of CRPS.

Sympathetic skin response, a test used frequently for sympathetic dysautonomias, assesses sudomotor or sweating function by measuring skin potentials resulting from sweat release after a sympathetic discharge. Typically, the test is performed on extremities with one electrode on the dorsal surface and another on the palmar surface, in the case of the hand, to measure the potential between the two surfaces. Then a neutral nerve, such as the median nerve, is stimulated with a brief electric shock to startle the subject. People with sympathetic dysautonomias don't show a response or have an altered latency of onset of response.