Abstract
BackgroundLeprosy is an endemic infectious disease caused by Mycobacterium leprae that predominantly attacks the skin and peripheral nerves, leading to progressive impairment of motor, sensory and autonomic function. Little is known about how this peripheral neuropathy affects corticospinal excitability of handgrip muscles. Our purpose was to explore the motor cortex organization after progressive peripheral nerve injury and upper-limb dysfunction induced by leprosy using noninvasive transcranial magnetic stimulation (TMS).MethodsIn a cross-sectional study design, we mapped bilaterally in the primary motor cortex (M1) the representations of the hand flexor digitorum superficialis (FDS), as well as of the intrinsic hand muscles abductor pollicis brevis (APB), first dorsal interosseous (FDI) and abductor digiti minimi (ADM). All participants underwent clinical assessment, handgrip dynamometry and motor and sensory nerve conduction exams 30 days before mapping. Wilcoxon signed rank and Mann-Whitney tests were performed with an alpha-value of p<0.05.FindingsDynamometry performance of the patients’ most affected hand (MAH), was worse than that of the less affected hand (LAH) and of healthy controls participants (p = 0.031), confirming handgrip impairment. Motor threshold (MT) of the FDS muscle was higher in both hemispheres in patients as compared to controls, and lower in the hemisphere contralateral to the MAH when compared to that of the LAH. Moreover, motor evoked potential (MEP) amplitudes collected in the FDS of the MAH were higher in comparison to those of controls. Strikingly, MEPs in the intrinsic hand muscle FDI had lower amplitudes in the hemisphere contralateral to MAH as compared to those of the LAH and the control group. Taken together, these results are suggestive of a more robust representation of an extrinsic hand flexor and impaired intrinsic hand muscle function in the hemisphere contralateral to the MAH due to leprosy.ConclusionDecreased sensory-motor function induced by leprosy affects handgrip muscle representation in M1.
Highlights
Leprosy, known as Hansen's disease, is a chronic human granulomatous bacilliferous infection caused by the obligate intracellular organism Mycobacterium leprae [1]
This study employed a cross-section design where a transcranial magnetic stimulation (TMS) mapping protocol was used to evaluate the cortical representation of selected hand muscles in M1 contralateral and ipsilateral to the most affected hand in chronic leprosy patients and healthy subjects in Hospital Federal Clementino Fraga Filho, RJ, Brazil, over the period of 2009 to 2013
We found a significant difference in motor threshold (MT) for the flexor digitorum superficialis (FDS) muscle between the most affected hand (MAH) and the control group (p = 0.041) as well as between the less affected hand (LAH) and the control group (p = 0.019, Fig 2A)
Summary
Known as Hansen's disease, is a chronic human granulomatous bacilliferous infection caused by the obligate intracellular organism Mycobacterium leprae [1]. The bacillus has a predisposition to infect cutaneous and peripheral nervous tissues, which allows infiltration into Schwann cells, resulting in nerve inflammation, most frequently in the eyes, hands and feet. This causes partial or total loss of sensory, motor and autonomic functions in the territory of the affected nerve resulting in skin anesthesia and dryness, as well as a decrease in proprioception and muscle paresis/hypotrophy [4]. Since 1985, 14 million individuals have received MDT [5] Despite these efforts, every year, many patients develop upper limb disabilities and are in need of rehabilitation services to control the chronic consequences of neural damage, such as claw hand, neuropathic pain and burns, requiring technical and scientific advances and a deeper understanding of the outcomes of either short or long-term rehabilitation. Our purpose was to explore the motor cortex organization after progressive peripheral nerve injury and upper-limb dysfunction induced by leprosy using noninvasive transcranial magnetic stimulation (TMS)
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