Imaging of peripheral nerve lesions in the lower limb

Lower limb peripheral neuropathy may have a variety of causes. This article focuses on focal neural lesions because of neural entrapment associated with static mechanical compression or dynamic compression/stretching. Mechanical compression may relate to direct blunt trauma, surgical injury, mass effect associated with adjacent mass lesions, and frictional effects associated with fibrous bands. Stretching neural injury may be associated with abnormalities in alignment such as plano-valgus hindfoot and hindfoot pronation. Recurrent inversion ankle injuries may also cause neural injury. Neural injury may be associated with denervation of the muscles supplied by the nerve. Electromyography (EMG) remains the gold standard for diagnosis of denervation. Diagnostic imaging plays a complementary role to EMG in difficult cases, the anticoagulated patient, and in clarifying the etiology of an EMG-demonstrated neuropathy. Magnetic resonance imaging and ultrasound can be used in peripheral nerve imaging to demonstrate extrinsic compressive lesions, focal neural lesions such as neural edema and swelling, focal neural scarring (posttraumatic neuroma in continuity) and intraneural ganglia. Imaging can also demonstrate the effects of muscle denervation. Focal areas of tenderness can be highlighted using skin markers for magnetic resonance imaging and by transducer palpation on ultrasound. Ultrasound can be particularly useful in assessing for intrinsic lesions in small peripheral nerves because of the superior spatial resolution of ultrasound in assessing superficial structures. Plain x-rays (and sometimes computed tomography scanning) may show significant bone changes and should be the initial imaging modality.

The relationship between %HRpeak and %VO2peak in patients with chronic obstructive pulmonary disease

PURPOSE

The relationship between the percent peak oxygen consumption (%VO2peak) and percent peak heart rate (%HRpeak) has been suggested as a method for exercise prescription. According to the American College of Sports Medicine (ACSM), 50, 60, 80, and 85% of VO2peak represent 62, 70, 85, and 90% of HRpeak, respectively. Recent research with young healthy adults has shown that this relationship is not as ACSM suggests. Furthermore, it has been suggested that this relationship be examined in populations with low functional capacity.

METHODS

The present study evaluated the relationship between %HRpeak and %VO2peak in 125 patients with chronic obstructive pulmonary disease before and then after 3 months of exercise intervention.

RESULTS

The mean percentages of HRpeak for the COPD patients at baseline were 70, 76, 87, and 90% at 50, 60, 80, and 85% of VO2peak. Percentages of HRpeak at 50, 60, and 80% of VO2peak were significantly different from those suggested by ACSM. The mean percentages of HRpeak after the 3-month exercise intervention were 71, 77, 87, and 90% at 50, 60, 80, and 85% of VO2peak. Percentages of HRpeak at 50, 60, and 80% of VO2peak were significantly different from those suggested by ACSM. There were no significant differences between the slopes and the intercepts of the two equations used to describe the relationship between %HRpeak and %VO2peak. Therefore, we pooled the data from the pre- and post-intervention tests to form the following equation to describe the relationship between %HRpeak and %VO2peak for COPD patients: %HRpeak = 0.55 (+/- 0.01)%VO2peak + 43.2 (+/- 1.4).

CONCLUSION

In conclusion, the relationship between %HRpeak and %VO2peak described by ACSM is not applicable to patients with COPD. Furthermore, this relationship does not change with exercise training and can be described by a single equation.