Cortical plasticity causes useless hand syndrome in multiple sclerosis: a neurophysiological study in a rare case

Short-latency afferent inhibition is reduced in people with multiple sclerosis during fatiguing muscle contractions

Understanding how inhibitory pathways influence motor cortical activity during fatiguing contractions may provide valuable insight into mechanisms associated with multiple sclerosis (MS) muscle activation. Short-latency afferent inhibition (SAI) reflects inhibitory interactions between the somatosensory cortex and the motor cortex, and although SAI is typically reduced with MS, it is unknown how SAI is regulated during exercise-induced fatigue. The current study examined how SAI modulates motor evoked potentials (MEPs) during fatiguing contractions. Fourteen people with relapsing-remitting MS (39 ± 6 years, nine female) and 10 healthy individuals (36 ± 6 years, six female) participated. SAI was induced by stimulation of the median nerve that was paired with TMS over the motor representation of the abductor pollicis brevis. A contraction protocol was employed that depressed force generating capacity using a sustained 3-min 15% MVC, immediately followed by a low-intensity (15% MVC) intermittent contraction protocol so that MEP and SAI could be measured during the rest phases of each duty cycle. Similar force, electromyography and MEP responses were observed between groups. However, the MS group had significantly reduced SAI during the contraction protocol compared to the healthy control group (p < .001). Despite the MS group reporting greater scores on the Fatigue Severity Scale and Modified Fatigue Impact Scale, these scales did not correlate with inhibitory measures. As there were no between-group differences in SSEPs, MS-related SAI differences during the fatiguing contractions were most likely associated with disease-related changes in central integration.

Transverse myelitis in children and adults

Transverse myelitis is a noncompressive myelopathy of inflammatory origin. The causes are broad, ranging from infective or toxic to immuno-mediated etiology. They can be manifestations of systemic diseases, such as sarcoidosis and systemic lupus erythematous, or phenotypes of neuroinflammation; in a portion of cases, the etiology remains unknown, leading to the designation idiopathic. The clinical presentation of transverse myelitis depends on the level of spinal cord damage and may include sensorimotor deficits and autonomic dysfunction. The age of onset of the disorder can impact the symptoms and outcomes of affected patients, with differences in manifestation and prognosis between children and adults. Spinal cord magnetic resonance imaging and cerebrospinal fluid examination are the main diagnostic tools that can guide clinicians in the diagnostic process, even though the search for antibodies that target the structural components of the neural tissue (anti-aquaporin4 antibodies and anti-myelin-oligodendrocyte antibodies) helps in the distinction among the immune-mediated phenotypes. Management and outcomes depend on the underlying cause, with different probabilities of relapse according to the phenotypes. Hence, immunosuppression is often recommended for the immune-mediated diseases that may have a higher risk of recurrence. Age at onset has implications for the choice of treatment.