The corticomotor projection to liminally-contractable forearm muscles in chronic spinal cord injury: a transcranial magnetic stimulation study

Abstract

Corticomotor conduction and cortical topography were appreciably normal despite only liminal activation of the target muscle with voluntary effort. Muscles with these characteristics may benefit from a targeted rehabilitation program even in the chronic phase after SCI.

Alterations in Motor Cortical Representation of Muscles Following Incomplete Spinal Cord Injury in Humans

“…However, it is possible that responses to TMS may be due to activation in surrounding associated motor regions, particularly at the edges of the grid space. Further, we include a sample size of 9 participants that, while exceeding the sample sizes of previous reports [1,6,7,8,9,10], is relatively small, limited mainly by the availability of participants. This small sample size has prevented us from drawing inferences about the relationship between factors including age, time since injury, physical activity, and rehabilitation program with changes in muscle representations.…”

“…Similarly, motor practice improves hand function and expands the M1 representation of a thumb muscle [5]. In complete SCI, cortical territory is expanded for spared muscles rostral to the level of injury [1,6,7] but does not appear to change following incomplete SCI [8,9]. Similarly, somatotopic shifts occur in SCI [10] but not always [1,6,7,8,9].…”

“…In complete SCI, cortical territory is expanded for spared muscles rostral to the level of injury [1,6,7] but does not appear to change following incomplete SCI [8,9]. Similarly, somatotopic shifts occur in SCI [10] but not always [1,6,7,8,9]. Notably, previous investigations have been performed on SCI groups with varying injury severity and without consideration of hand dominance, although multiple studies have shown interhemispheric differences in motor cortex organization based on laterality [11,12,13,14,15].…”

“…To date, there is a paucity of research examining bilateral M1 reorganization in SCI. Previous TMS studies have mainly investigated muscle representations in one hemisphere following SCI [5,6,7,8,9,10], and therefore it is unknown whether reorganizational changes exist within both hemispheres and whether or not symmetry between hemispheres exists. Therefore, important unanswered questions regarding somatotopy, expansion, and symmetry remain.…”

Optimization of the navigated TMS mapping algorithm for accurate detection of plasticity and abnormalities in cortical muscle representations

“…Its ability to localize motor eloquent cortical areas has found successful applications in preoperative planning [4,5]. Additionally, a growing body of literature is concerned with the use of nTMS mapping for assessing the state of the motor system and its plastic changes during learning of new skills [6–9], in neurological diseases, such as stroke [10], dystonia [11], spinal cord injury [12,13], amyotrophic lateral sclerosis [14], as well as in the course of treatment [15]. For identifying the possibly subtle differences in motor maps, it is essential to make the method precise and reliable.…”