Median Nerve and Carpal Tunnel Morphology Before and After Endoscopic Carpal Tunnel Release: A 6-Year Follow-up Study

BACKGROUND

Our purpose was to describe structural and morphological features of the median nerve and carpal tunnel on magnetic resonance imaging (MRI) studies obtained before, immediately after, 6 weeks after, and 6 years after endoscopic carpal tunnel release (ECTR).

METHODS

In this prospective cohort study, 9 patients with a diagnosis of carpal tunnel syndrome (CTS) underwent ECTR. Standardized MRI studies were obtained before ECTR, immediately after ECTR, and 6 weeks and 6 years after surgery. Structural and morphological features of the median nerve and carpal tunnel were measured and assessed for each study with comparisons made between each time point.

RESULTS

All 9 patients had complete symptom resolution postoperatively. On the immediate postoperative MRI, there was a discrete gap in the transverse carpal ligament in all patients. There was retinacular regrowth noted at 6 weeks in all cases. The median nerve cross-sectional area and the anterior-posterior dimension of the carpal tunnel at the level of the hamate increased immediately after surgery and these changes were maintained at 6 years.

CONCLUSIONS

We defined structural and morphological changes on MRI for the median nerve and carpal tunnel in patients with continued symptom resolution 6 years after ECTR. Changes in median nerve and carpal tunnel morphology that occur immediately after surgery remain unchanged at mid-term follow-up in asymptomatic patients. Established imaging criteria for CTS may not apply to postoperative patients. Magnetic resonance imaging appears to be of limited clinical utility in the workup of persistent or recurrent CTS.

The Use of Preoperative Dynamic Ultrasound to Predict Ulnar Nerve Stability Following In Situ Decompression for Cubital Tunnel Syndrome

PURPOSE

To assess the use of preoperative, dynamic ultrasound to predict ulnar nerve instability following in situ decompression for cubital tunnel syndrome.

METHODS

Prior to undergoing in situ decompression, 43 consecutive patients underwent dynamic ultrasound to assess the stability of the ulnar nerve during elbow flexion. The dynamic ultrasound findings were compared with the intraoperative assessment of nerve stability following in situ decompression.

RESULTS

The preoperative dynamic ultrasound agreed with intraoperative findings in 38 of 43 patients (88%). Physical examination of ulnar nerve stability agreed with the intraoperative findings in 5 of 43 patients (12%). For the 5 of 43 cases in which the dynamic ultrasound did not correlate with the degree of ulnar nerve stability after in situ decompression, dynamic ultrasound overestimated the degree of ulnar nerve stability in 4 cases.

CONCLUSIONS

Preoperative dynamic ultrasound can be used to accurately predict the degree of ulnar nerve instability following in situ decompression.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Magnetic resonance imaging after endoscopic carpal tunnel release

PURPOSE

To determine with magnetic resonance imaging (MRI) the morphologic changes in the carpal tunnel and median nerve 3 months after endoscopic carpal tunnel release (ECTR).

METHODS

We enrolled patients who had complete resolution of numbness and pain by 6 weeks after ECTR. Patients who met these inclusion criteria received an MRI at 3 months after surgery. Images were analyzed to determine whether median nerve morphology changes and discrete gap or separation of the flexor retinaculum could be appreciated on MRI.

RESULTS

There were 17 patients screened and 15 met the inclusion criteria. Three-month MRI in all patients demonstrated changes in the flexor retinaculum over the median nerve. In all 15 patients, a distinct gap or separation in the fibers of the flexor retinaculum overlying the median nerve could not be appreciated. Median nerve width-to-height ratios at the level of the pisiform and at the hook of the hamate were 2.4 and 2.1, respectively. Median nerve cross-sectional area was 14.1 at the pisiform and 13.3 at the hook of the hamate.

CONCLUSIONS

MRI of patients 3 months after successful ECTR does not demonstrate a discrete gap or separation in the flexor retinaculum overlying the median nerve but may be useful for evaluating median nerve morphology.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Chemoprophylaxis for Pneumocystis carinii pneumonitis: outcome of unstructured delivery

Sulfamethoxazole-trimethoprim was administered prophylactically to 786 patients judged to be at sufficient risk for development of Pneumocystis carinii pneumonitis. The selection of patients, administration of the agents, and surveillance for compliance were the responsibility of the attending oncologists rather than specialists in infectious diseases, as in an earlier trial at this center. The recommended dosage was trimethoprim, 150 mg/sq m/day, and sulfamethoxazole, 750 mg/sq m/day. Over a three-year study period, nine cases of P carinii pneumonitis occurred at this institution, with none attributable to drug failure. Adverse reactions, skin rashes mainly, were noted in 43 patients, and one patient died with Stevens-Johnson syndrome. These results confirm the efficacy of sulfamethoxazole-trimethoprim in preventing P carinii pneumonitis in childhood cancer patients and illustrate the feasibility of large-scale unstructured delivery of the combination to patients with malignant diseases frequently associated with this pneumonia.