ABSTRACT
Mycobacterium leprae infection of peripheral nerves and the subsequent nerve function impairment (NFI), especially in response to reactional episodes, are hallmarks of leprosy. Improved treatments for M. leprae-induced nerve injury are needed, as most if not all of the disability and stigma associated with leprosy arises from the direct or indirect effects of NFI. Nine-banded armadillos (Dasypus novemcinctus), like humans, exhibit the full clinical spectrum of leprosy and extensive involvement of the peripheral nerves. In this study, state-of-the-art technology was used to compare nerve function between uninfected and M. leprae-infected armadillos. Motor nerve conduction velocity (MNCV) and compound muscle action potential (cMAP), which measure changes in the rate of impulse conduction velocity and amplitude, revealed a progression of impairment that was directly correlated with the duration of M. leprae infection and enabled development of an objective nerve impairment scoring system. Ultrasonography accompanied by color Doppler imaging detected enlargement of the M. leprae-infected nerves and increased vascularity, possibly due to inflammation. Assessment of epidermal nerve fiber density (ENFD), which shows a length-dependent innervation in armadillos that is similar to humans, identified small fiber degeneration early after M. leprae infection. Staining for neuromuscular junction (NMJ) integrity, which is an indicator of signal transduction efficiency into skeletal muscle, discerned a markedly lower number and structural integrity of NMJ in M. leprae-infected armadillo footpads. These tools for assessing nerve injury were used to monitor the effects of intervention therapy. Two potential neuro-protective drugs, ethoxyquin (EQ) and 4-aminopyridine (4-AP), were tested for their ability to ameliorate peripheral nerve injury in M. leprae-infected armadillos. 4-AP treatment improved MNCV, cMAP, and EFND compared to untreated animals, while EQ had less effect. These results support the armadillo as a model for M. leprae-induced peripheral nerve injury that can provide insights toward the understanding of NFI progression and contribute to the preclinical investigation of the safety and efficacy of neuro-preventive and neuro-therapeutic interventions for leprosy.
ABSTRACT
BACKGROUND AND PURPOSE: Mycobacterium leprae complex affects peripheral nerves, causing nerve enlargement. This proof-of-concept pilot study was conducted to determine if a small hand-held ultrasound device can accurately identify nerve involvement in individuals with leprosy. METHODS: Peripheral nerve ultrasound was conducted of the bilateral median (wrist, forearm, elbow, and mid-humerus), ulnar (wrist, forearm, elbow, 4 cm proximal to the elbow, and mid-humerus), C5 root, and greater auricular nerves with a standard ultrasound device (15 Mhz) and a hand-held ultrasound device (5 MHz). Nerve cross-sectional areas were compared using the two devices. RESULTS: Eight individuals with leprosy were examined. Strong correlation was found between the standard and hand-held ultrasound devices (r = .76, P < .001). A certain amount of variability between ultrasound devices may occur for multiple reasons. CONCLUSION: A hand-held ultrasound device can readily identify nerve enlargement in individuals with leprosy. This type of device may assist in the diagnosis of leprosy in areas with limited healthcare resources because of the portability and low-cost nature of such devices.
