Objectives: Prolongation of the cortical silent period (CSP) following transcranial magnetic stimulation has been reported in patients with partial epilepsy involving the primary motor cortex (M1). ...This study aimed to investigate the relationship between the expected intraindividual variations in risk factors for seizures and CSP duration.
Methods: We studied a 59-year-old woman with a rolandic meningioma and simple motor partial seizures and a 71-year-old woman with a parietal/occipital meningioma and complex partial seizures. Both patients had seizure as their initial symptom with complete postsurgical remission. Repeated pre- and postoperative CSP recordings were made from both first dorsal interosseous muscles. We compared the results to those obtained in 13 normals.
Results: In the patient with simple motor partial seizures, the CSP was significantly prolonged in preoperative recordings and 3 weeks after surgery. This CSP lengthening partly subsided 3 months after surgery. Finally, the CSP was normal 6, 8, and 18 months after surgery. In the patient with complex partial seizures, no CSP change was observed.
Conclusions: In our patient with a rolandic meningioma, CSP prolongation was observed when the risk of seizure relapse was supposed to be higher (preoperative and early postoperative periods). This supports the view that CSP changes reflect compensatory mechanisms in M1 epilepsy.
Abnormal branching of corticospinal fibers from the unaffected motor cortex is responsible for mirror movements in patients with congenital hemiparesis, but it is unknown which mechanisms enable ...these patients to lateralize motor activity. Using multiunit electromyographic analysis and transcranial magnetic stimulation, the authors provide evidence for nonbranched crossed and uncrossed corticospinal projections and intracortical inhibition of the mirror hand. They propose that this remarkable reorganization of the unaffected motor cortex helps these patients to reduce mirror movements.
Growing evidence points toward involvement of the human motor cortex in the control of the ipsilateral hand. We used focal
transcranial magnetic stimulation (TMS) to examine the pathways of these ...ipsilateral motor effects.
Ipsilateral motor-evoked potentials (MEPs) were obtained in hand and arm muscles of all 10 healthy adult subjects tested.
They occurred in the finger and wrist extensors and the biceps, but no response or inhibitory responses were observed in the
opponens pollicis, finger and wrist flexors and the triceps.
The production of ipsilateral MEPs required contraction of the target muscle. The threshold TMS intensity for ipsilateral
MEPs was on average 1.8 times higher, and the onset was 5.7 ms later (in the wrist extensor muscles) compared with size-matched
contralateral MEPs.
The corticofugal pathways of ipsilateral and contralateral MEPs could be dissociated through differences in cortical map location
and preferred stimulating current direction.
Both ipsi- and contralateral MEPs in the wrist extensors increased with lateral head rotation toward, and decreased with head
rotation away from, the side of the TMS, suggesting a privileged input of the asymmetrical tonic neck reflex to the pathway
of the ipsilateral MEP.
Large ipsilateral MEPs were obtained in a patient with complete agenesis of the corpus callosum.
The dissociation of the pathways for ipsilateral and contralateral MEPs indicates that corticofugal motor fibres other than
the fast-conducting crossed corticomotoneuronal system can be activated by TMS. Our data suggest an ipsilateral oligosynaptic
pathway, such as a corticoreticulospinal or a corticopropriospinal projection as the route for the ipsilateral MEP. Other
pathways, such as branching of corticomotoneuronal axons, a transcallosal projection or a slow-conducting monosynaptic ipsilateral
pathway are very unlikely or can be excluded.
Endothelins (ETs) are vasoactive peptides evolutionary well conserved that exert their effects through two specific receptors (ET
A and ET
B) widely distributed in all vertebrates. In snakes, the ...presence and function of endothelins and their receptors are still scarcely described. We have recently demonstrated the presence of ET
A and ET
B2 receptors in the snake
Bothrops jararaca (Bj). In the present work we showed that distinctively from Bj, the vascular contraction induced by endothelin in
Oxyrhopus guibei (Og) snake is mediated only by ET
A receptors. Selective ET
B agonists (SRTX-c and IRL
1620) and antagonists (IRL
1038 and BQ
788) were ineffective in Og preparations of isolated aorta. We also showed that ET-1 response on Og arterial blood pressure was monophasic hypertensive as opposed to biphasic (hypotension followed by hypertension) in Bj. Furthermore, we characterized the relaxing properties of endothelin receptor ET
B1 in pre-contracted aorta preparations. We showed that IRL
1620 induced relaxation of pre-contracted Bj aorta but was ineffective in relaxing Og preparations. IRL
1620 relaxing effect on Bj aorta was abolished by
l-NAME, indicating involvement of NO release, and was reduced by selective ET
B antagonists. Our findings suggest that Og snake has a more primitive spectrum of ET receptors (only ET
A receptor) than Bj (presence of ET
A, ET
B1 and ET
B2 receptors).
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