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Onset Latency of Motor Evoked Potentials in Motor Cortical Mapping with Neuronavigated Transcranial Magnetic Stimulation.

Kallioniemi E, Pitkänen M, Säisänen L, Julkunen P - Open Neurol J (2015)

Bottom Line: As expected, the latency and amplitude CoGs were congruent and were located in the centre of the maps but in a few subjects, instead of a single centre, several loci with short latencies were observed.In conclusion, MEP latencies may be useful in distinguishing the cortical representation areas with the most direct pathways from those pathways with prolonged latencies.However, the potential of latency mapping to identify stressed motor tract connections at the subcortical level will need to be verified in future studies with patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland ; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.

ABSTRACT
Cortical motor mapping in pre-surgical applications can be performed using motor evoked potential (MEP) amplitudes evoked with neuronavigated transcranial magnetic stimulation. The MEP latency, which is a more stable parameter than the MEP amplitude, has not so far been utilized in motor mapping. The latency, however, may provide information about the stress in damaged motor pathways, e.g. compression by tumors, which cannot be observed from the MEP amplitudes. Thus, inclusion of this parameter could add valuable information to the presently used technique of MEP amplitude mapping. In this study, the functional cortical representations of first dorsal interosseous (FDI), abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles were mapped in both hemispheres of ten healthy righthanded volunteers. The cortical muscle representations were evaluated by the area and centre of gravity (CoG) by using MEP amplitudes and latencies. As expected, the latency and amplitude CoGs were congruent and were located in the centre of the maps but in a few subjects, instead of a single centre, several loci with short latencies were observed. In conclusion, MEP latencies may be useful in distinguishing the cortical representation areas with the most direct pathways from those pathways with prolonged latencies. However, the potential of latency mapping to identify stressed motor tract connections at the subcortical level will need to be verified in future studies with patients.

No MeSH data available.


Related in: MedlinePlus

MEP latencies shown from FDI as absolute values from the group shortest latency (pooled data from both hemispheres). Bars are shown at 1.5 ms latency intervals.
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Figure 2: MEP latencies shown from FDI as absolute values from the group shortest latency (pooled data from both hemispheres). Bars are shown at 1.5 ms latency intervals.

Mentions: The distribution of the MEP latencies for FDI is presented in Fig. (2) (pooled data from both hemispheres). The majority of the latencies had an approximate delay of 3 to 6 ms from the shortest latency. The shortest latencies were located in the centre of the latency maps, whereas the longest latencies were associated with the edges of the latency maps (Fig. 3). In a few maps, separate distinct centers of short latencies could be observed (Fig. 4). The individual and group characteristics of latencies and amplitudes of FDI muscle, as well as the inter-hemispheric differences evaluated with a paired t-test, are shown in Table 1.


Onset Latency of Motor Evoked Potentials in Motor Cortical Mapping with Neuronavigated Transcranial Magnetic Stimulation.

Kallioniemi E, Pitkänen M, Säisänen L, Julkunen P - Open Neurol J (2015)

MEP latencies shown from FDI as absolute values from the group shortest latency (pooled data from both hemispheres). Bars are shown at 1.5 ms latency intervals.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4627389&req=5

Figure 2: MEP latencies shown from FDI as absolute values from the group shortest latency (pooled data from both hemispheres). Bars are shown at 1.5 ms latency intervals.
Mentions: The distribution of the MEP latencies for FDI is presented in Fig. (2) (pooled data from both hemispheres). The majority of the latencies had an approximate delay of 3 to 6 ms from the shortest latency. The shortest latencies were located in the centre of the latency maps, whereas the longest latencies were associated with the edges of the latency maps (Fig. 3). In a few maps, separate distinct centers of short latencies could be observed (Fig. 4). The individual and group characteristics of latencies and amplitudes of FDI muscle, as well as the inter-hemispheric differences evaluated with a paired t-test, are shown in Table 1.

Bottom Line: As expected, the latency and amplitude CoGs were congruent and were located in the centre of the maps but in a few subjects, instead of a single centre, several loci with short latencies were observed.In conclusion, MEP latencies may be useful in distinguishing the cortical representation areas with the most direct pathways from those pathways with prolonged latencies.However, the potential of latency mapping to identify stressed motor tract connections at the subcortical level will need to be verified in future studies with patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland ; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.

ABSTRACT
Cortical motor mapping in pre-surgical applications can be performed using motor evoked potential (MEP) amplitudes evoked with neuronavigated transcranial magnetic stimulation. The MEP latency, which is a more stable parameter than the MEP amplitude, has not so far been utilized in motor mapping. The latency, however, may provide information about the stress in damaged motor pathways, e.g. compression by tumors, which cannot be observed from the MEP amplitudes. Thus, inclusion of this parameter could add valuable information to the presently used technique of MEP amplitude mapping. In this study, the functional cortical representations of first dorsal interosseous (FDI), abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles were mapped in both hemispheres of ten healthy righthanded volunteers. The cortical muscle representations were evaluated by the area and centre of gravity (CoG) by using MEP amplitudes and latencies. As expected, the latency and amplitude CoGs were congruent and were located in the centre of the maps but in a few subjects, instead of a single centre, several loci with short latencies were observed. In conclusion, MEP latencies may be useful in distinguishing the cortical representation areas with the most direct pathways from those pathways with prolonged latencies. However, the potential of latency mapping to identify stressed motor tract connections at the subcortical level will need to be verified in future studies with patients.

No MeSH data available.


Related in: MedlinePlus