Elderly patients with carpal tunnel syndrome (CTS) who have pain and demonstrate severe conduction velocity readings before surgery are at higher risk of incurring painful reinnervation paresthesias postoperatively.

These were the results of a study presented at the 2010 annual meeting of the American Society for Surgery of the Hand by Michael Y. Papaloïzos, MD, of the Center for Hand Surgery and Therapy in Geneva, Switzerland.

A small but significant percentage of elderly patients develop paresthesias, with potentially long-lasting neuralgia, Dr. Papaloïzos noted. Data about the influence of age on patient outcome after CTS surgical release are inconsistent. Another topic of debate is the significance of severe electrodiagnostic disturbances. The combination of advanced age, preoperative neuralgic symptoms, and severe conduction disturbance has been characterized as the “bad triad.”

“We know that patients with preoperative reduced sensory amplitude recover more slowly than patients with reduced nerve conduction velocity only. But which of the electroneuromyographic parameters—or at which threshold—are of predictive value is still unclear,” Dr. Papaloïzos said.

His retrospective cohort study sought to better define electrodiagnostic parameters associated with poor outcome after surgical release in this subset of patients and, specifically, to relate the postoperative onset of painful reinnervation symptoms to characteristics of preoperative nerve conduction values.

The authors identified 276 patients older than 75 years (329 hands) who received CTS release with an open technique at a single institution during a 10-year period. Clinical nerve conduction variables—sensory conduction velocity (SCV), amplitude of sensory action potential (SAP), and motor terminal latency (MTL)—were recorded preoperatively. More than 90 percent of the hands (307) exhibited paresthesias and 34 percent (111) had neurogenic pain.

After surgery, paresthesias disappeared within the first 4 days in 246 hands (75 percent) and later than 4 days in 61 additional hands (18 percent). In 22 hands (7 percent), the patient experienced reinnervation paresthesias that lasted an average of 4.1 months. True neurogenic pain was associated with reinnervation paresthesias in 13 of these instances.

Factors from the medical history—such as diabetes, hypothyroidism, and wrist fracture—were not found to be associated with outcome. However, an association was found with age, sex, preoperative pain, and wasting of thenar muscles (Table 1). Of the electrodiagnostic parameters, SCV and MTL were significantly associated with the outcome (p = 0.03). Subsequent multivariate logistic analysis demonstrated that SCV was the strongest predictor of reinnervation paresthesias.

Although the study had several limitations, the authors concluded that surgeons treating a patient older than 75 years with preoperative pain and SCV greater than 15 m/s should inform the patient of the implications and balance the benefits of surgery with the risks.

Dr. Papaloïzos’s coauthors for “Electrodiagnostic Predictors of Postoperative Neuralgia after Surgical Release for Severe Carpal Tunnel Syndrome in Elderly Patients” are Nicolas Dunand, MD, and Christiane Ruffieux, MD, PhD. The authors report no conflicts.

The AAOS clinical practice guidelines on the diagnosis and treatment of carpal tunnel syndrome can be found at www.aaos.org/guidelines

Bottom line

• Patients older than age 75 who have preoperative pain and sensitive conduction velocity <15 m s are more at risk of painful reinnervation paresthesias.>
• Surgeons should provide this information to patients and balance the benefits of surgery with the risks.