Mohamed Nasreldin Thabit

Human Motor Plasticity Induced by Mirror Visual Feedback

The clinical use of mirror visual feedback (MVF) was initially introduced to alleviate phantom pain, and has since been applied to the improvement of hemiparesis following stroke. However, it is not known whether MVF can restore motor function by producing plastic changes in the human primary motor cortex (M1). Here, we used transcranial magnetic stimulation to test whether M1 plasticity is a physiological substrate of MVF-induced motor behavioral improvement. MVF intervention in normal volunteers using a mirror box improved motor behavior and enhanced excitatory functions of the M1. Moreover, behavioral and physiological measures of MVF-induced changes were positively correlated with each other. Improved motor performance occurred after observation of a simple action, but not after repetitive motor training of the nontarget hand without MVF, suggesting the crucial importance of visual feedback. The beneficial effects of MVF were disrupted by continuous theta burst stimulation (cTBS) over the M1, but not the control site in the occipital cortex. However, MVF following cTBS could further improve the motor functions. Our findings indicate that M1 plasticity, especially in its excitatory connections, is an essential component of MVF-based therapies.

Recovery of upper-limb function due to enhanced use-dependent plasticity in chronic stroke patients

Patients with chronic stroke often show increased flexor hypertonia in their affected upper limbs. Although an intervention strategy targeting the extensors of the affected upper limb might thus be expected to have benefits for functional recovery, conventional repetitive motor training has limited clinical utility. Recent studies have shown that repetitive transcranial magnetic stimulation could induce motor recovery. The present study tested whether 5 Hz repetitive transcranial magnetic stimulation of the upper-limb area of the primary motor cortex, combined with extensor motor training, had a greater effect on motor recovery than either intervention alone in stroke hemiparesis. Nine patients with chronic subcortical stroke and nine age-matched healthy subjects completed the crossover study. In separate sessions, we examined the single intervention effect of repetitive wrist and finger extension exercises aided by neuromuscular stimulation, the single intervention effect of 5 Hz repetitive transcranial magnetic stimulation and the combined effect of the two interventions. The motor functions were evaluated behaviourally in patients (Experiment 1) and electrophysiologically in healthy subjects (Experiment 2), both before and after the intervention. In addition, we tested the long-term effect by repeating the combined interventions 12 times in patients (Experiment 3). The motor functions were measured again 2 weeks after the end of the repetitive intervention period. In Experiment 1, the combined intervention, but neither of the single interventions, resulted in an improvement of extensor movement (P < 0.0001) and grip power (P < 0.05), along with a reduction of flexor hypertonia (P < 0.01), in their paretic upper limbs. In Experiment 2, only the combined intervention resulted in selective plastic changes of cortico-spinal excitability (P < 0.01), motor threshold (P < 0.001) and silent period (P < 0.01) for the extensors. In Experiment 3, we also confirmed long-term beneficial effects of the combined intervention in patients. These findings indicate that combining motor training with repetitive transcranial magnetic stimulation can facilitate use-dependent plasticity and achieve functional recovery of motor impairments that cannot be attained by either intervention alone. This method could be a powerful rehabilitative approach for patients with hemiparetic stroke.

Movement-Related Cortical Stimulation Can Induce Human Motor Plasticity

Repeated paired associative stimulation combining peripheral nerve stimulation and transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) can produce human motor plasticity. However, previous studies used paired artificial stimuli, so that it is not known whether repetitive natural M1 activity associated with TMS can induce plasticity or not. To test this hypothesis, we developed a movement-related cortical stimulation (MRCS) protocol, in which the left M1 was stimulated by TMS at specific timing with respect to the mean expected reaction time (RT) of voluntary movement during a simple reaction time task using the right abductor pollicis brevis (APB) muscle. Seventeen normal volunteers were subjected to repeated MRCS intervention (0.2 Hz, 240 pairs). Motor function was assessed before and after MRCS. When TMS was given 50 ms before the RT of movement [MRCS(−50)], motor-evoked potential (MEP) amplitude of the right APB, but not other muscles, increased for up to 15 min post-MRCS. The RT of the right APB was also shortened. However, spinal excitability measured by F-wave did not change. When TMS was given 100 ms after the RT [MRCS(+100)], MEP amplitude was decreased. These findings show that this new MRCS protocol can produce timing-dependent motor associative plasticity, which may be clinically useful.

Momentary reward induce changes in excitability of primary motor cortex.

OBJECTIVE To investigate the human primary motor cortex (M1) excitability changes induced by momentary reward. METHODS To test the changes in excitatory and inhibitory functions of M1, motor-evoked potentials (MEPs), short-interval intracortical inhibition (SICI) and short-latency afferent inhibition (SAI) were tested in the abductor pollicis brevis (APB) muscle of non-dominant hand in 14 healthy volunteers by transcranial magnetic stimulation (TMS) during a behavioral task in which subjects were pseudorandomly received either reward target or non-target stimuli in response to a cue. To control sensorimotor and attention effects, a sensorimotor control task was done replacing the reward target with non-reward target. RESULTS The SICI was increased, and the SAI was decreased significantly during the presentation of the reward target stimuli. Those changes were not evident during non-reward target stimuli in the sensorimotor control task, indicating that this change is specific to momentary reward. CONCLUSIONS Momentary rewarding is associated with change in intracortical inhibitory circuits of M1. SIGNIFICANCE TMS may be a useful probe to study the reward system in health and in many diseases in which its dysfunction is suspected.

Writing's shadow: Corticospinal activation during letter observation

We can recognize handwritten letters despite the variability among writers. One possible strategy is exploiting the motor memory of orthography. By using TMS, we clarified the excitatory and inhibitory neural circuits of the motor corticospinal pathway that might be activated during the observation of handwritten letters. During experiments, participants looked at the handwritten or printed single letter that appeared in a random order. The excitability of the left and right primary motor cortex (M1) was evaluated by motor-evoked potentials elicited by single-pulse TMS. Short interval intracortical inhibition (SICI) of the left M1 was evaluated using paired-pulse TMS. F waves were measured for the right ulnar nerve. We found significant reduction of corticospinal excitability only for the right hand at 300–400 msec after each letter presentation without significant changes in SICI. This suppression is likely to be of supraspinal origin, because of no significant alteration in F-wave amplitudes. These findings suggest that the recognition of handwritten letters may include the implicit knowledge of “writing” in M1. The M1 activation associated with that process, which has been shown in previous neuroimaging studies, is likely to reflect the active suppression of the corticospinal excitability.

Community-based epidemiological study of epilepsy in the Qena governorate in Upper Egypt, a door-to-door survey.

BACKGROUND The aim of this study is to estimate the epidemiological features of epilepsy in a representative governorate of Upper Egypt. MATERIALS AND METHODS A door-to-door community-based survey study was performed using a sample of 10 areas among various districts of the Qena governorate in Upper Egypt. Six were classified as rural areas, and the remaining four were classified as urban areas, with a total population of 8027 inhabitants. The population was screened using an epilepsy-screening questionnaire. Positive cases with suspected epilepsy were referred to Qena University Hospital to be further evaluated by a qualified neurologist and for further investigations, such as neuroimaging and electroencephalography. RESULTS One hundred patients had a confirmed diagnosis of epilepsy, with a lifetime prevalence of 12.46/1000. The active prevalence rate of epilepsy was 2.12/1000, while the incidence rate was 123/100000. Seventy-six percent of the patients had idiopathic epilepsies, while 24% had symptomatic epilepsy. Generalized epilepsies were more common (70.1%) than partial epilepsy (26.3%), meanwhile epilepsies with mixed seizure types were 2.6%. The most common seizure type was generalized tonic clonic seizures (51.8%). The age-specific prevalence rate of epilepsy was much higher in infancy and early childhood (62.5 and 37.04/1000, respectively), which regressed steadily with age. Idiopathic epilepsies were significantly more common in urban areas than in rural areas (P=0.01), while symptomatic epilepsies were more common in rural areas than in urban areas (P<0.005). CONCLUSION Upper Egypt is characterized by a relatively high incidence and prevalence of epilepsy and epilepsy-related medical service, and more cultural education should be directed to those areas in Egypt.

Combined central and peripheral stimulation for treatment of chronic tinnitus: a randomized pilot study.

Background. Tinnitus is a common untreatable condition that originates from central maladaptive plasticity initiated by peripheral injury. Repetitive transcranial magnetic stimulation (rTMS), direct cochlear low-level laser therapy (LLLT), and acupuncture were tried for tinnitus treatment, but the results of these methods were clinically unsatisfactory. Objective. This study aimed to test the combined effect of the 3 methods targeting both peripheral and central auditory areas as a new therapeutic strategy for tinnitus. Methods. For this, 30 patients were randomized to 3 equal groups receiving 3 different interventions: inhibitory rTMS to the left auditory cortex, LLLT (which includes a combination of direct cochlear LLLT and laser acupuncture) to the affected ear(s), and finally, a combination of rTMS and LLLT. The Tinnitus Handicap Inventory (THI) and Visual Analogue Scale (VAS) were assessed before, immediately after, and at 2 weeks and 4 weeks after 10 consecutive every-other-day sessions for each intervention type. Results. We found that combined stimulation was effective in tinnitus treatment. This effect remained for 4 weeks after the end of the treatment. However, each of rTMS and LLLT alone had no significant effect. Repeated-measures ANOVA showed a significant effect of Time and Time × Intervention interaction for THI and VAS scores. The post hoc t test for different time points per intervention revealed a significant difference between baseline and all postintervention measurements of both THI and VAS for the combination intervention. Conclusion. Combined central rTMS and peripheral LLLT is more beneficial as a new method for management of tinnitus rather than these two used separately.

Idiopathic Carpal Tunnel Syndrome: Evaluation of the Depth of the Carpal Tunnel by Ultrasonography.

The objective of the work described here was to evaluate the depth of the carpal tunnel (DCT) in patients with idiopathic carpal tunnel syndrome (CTS) and healthy volunteers by ultrasonography (US), through measurement of the distance from the flexor retinaculum to the surface of the capitate bone at the carpal tunnel outlet, and compare it with other ultrasonographic and electrophysiologic parameters in CTS. The study was conducted in 60 non-diabetic patients with idiopathic carpal tunnel syndrome (unilateral n = 37, bilateral n = 23) evidenced by electrophysiologic diagnosis according to the criteria of the American Association of Electrodiagnostic Medicine (AAEM). Furthermore, 40 hands from 20 healthy volunteers were examined. Median nerve cross-sectional area (CSA); flattening ratio (FR), the ratio of the length to the width of the median nerve; and DCT at the canal outlet were measured for all participants. The mean age was 35.6 ± 9.48 y. The female-to-male ratio was 47:13 in the CTS patients. The sensitivity and specificity were 82% and 95% for CSA, 75% and 60% for FR and 75% and 87.5% for DCT, respectively. Differences between patients and healthy controls were significant for all three parameters, greatest for DCT, followed by CSA and then FR. We conclude that DCT increased in CTS and this new parameter is comparable in sensitivity and specificity to CSA and FR. DCT increased independently of the cause of the CTS (decrease in size of canal or increase in contents).

Evaluation of knowledge about epilepsy and attitudes towards patients with epilepsy among university students in Upper Egypt

PURPOSE Epilepsy is a major public health problem worldwide. There are many misconceptions about peoples knowledge and attitudes about epilepsy, which influence peoples behavior towards patients with epilepsy. METHODS We conducted a cross-sectional study in Sohag University, a public Egyptian University, in Upper Egypt. We used an Arabic language designed questionnaire to assess peoples knowledge about epilepsy and their attitudes towards patients with epilepsy. We included a total of 920 students in the study. RESULTS 12.4% of study respondents had never heard of or read about epilepsy. Moreover, there was much misunderstanding about the etiology of epilepsy, as 68.2% of epileptic and 74.5% of nonepileptic respondents believe epilepsy is caused by evil spirits and evil eyes or due to psychiatric disorders. There were also many people who held negative attitudes towards patients with epilepsy in regards to major life milestones such as marriage and having children. Among nonepileptics, 54.5% believe epileptics should not marry and 49.9% believe they should not have children. Among patients with epilepsy, these percentages are 27.3% and 36.4% respectively. CONCLUSIONS Knowledge about epilepsy is insufficient and should be increased. The attitudes towards patients with epilepsy are negative and should be changed in Upper Egypt.

61. Human M1 excitability changes depending on letter recognition

acute sensory ataxia. The positive anti-Hu antibody suggested that he had anti-Hu-associated paraneoplastic subacute sensory neuropathy. The conventional nerve conduction studies and somatosensory evoked potentials revealed severe sensory neuropathy. For magnetic cerebellar stimulation, the test magnetic stimulus over the left primary motor cortex (M1) was preceded by the conditioning stimulus over the right cerebellum. Motor evoked potential was recorded from the right first dorsal interosseous muscle. The suppressive effect of magnetic cerebellar stimulation on the contralateral M1 was abnormally reduced. The results indicated that cerebellar efferent pathway or dentatothalamocortical pathway was involved in this patient, although cerebellar signs could not be evaluated due to severe sensory neuropathy. Magnetic cerebellar stimulation might be useful to reveal cerebellar dysfunction masked by coexisting sensory ataxia in patients with paraneoplastic sensory neuropathy.