Elsevier

Clinical Neurophysiology

Volume 113, Issue 10, October 2002, Pages 1536-1543
Clinical Neurophysiology

Transcranial magnetic stimulation after pure motor stroke

https://doi.org/10.1016/S1388-2457(02)00255-9Get rights and content

Abstract

Objectives: The objective of this study was to assess the sensitivity of motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) in demonstrating the possible subclinical impairment of the corticospinal pathway after recovery, in patients with a clinical history of pure motor stroke (PMS) due to a single lacunar infarct detectable by magnetic resonance imaging (MRI).

Methods: MEPs were recorded from the first dorsal interosseous muscle of 20 healthy subjects and 40 patients, 6 months or more after PMS onset. Patients were evaluated clinically by means of the NIH stroke scale, the Medical Research Council (MRC) scale and the Barthel Index. The patients with full hand strength recovery and the normal controls were also tested by means of the 9-hole peg test.

Results: Motor threshold (MT), MEP amplitude and central motor conduction time (CMCT) of the affected side were significantly different from those of the normal side and of the control subjects. MT, MEP amplitude and CMCT obtained after stimulation of the affected hemisphere were significantly correlated with the MRC scale values of the affected hand. Eighty-six percent of patients with persistent hand strength deficit showed MEP abnormalities. In 21 patients with complete clinical recovery, a significant increase in MT and decrease in MEP amplitude on the affected side were observed.

Conclusions: After PMS, neurophysiological changes may persist despite complete clinical recovery. TMS represents a sensitive tool that enables to demonstrate objectively the clinical and subclinical impairment of the corticospinal pathway.

Introduction

Lacunar infarcts are small infarcts (less than 1.5–2 cm diameter) of the deeper non-cortical part of the cerebrum and brainstem, resulting from occlusion of small penetrating cerebral arteries (Fisher, 1982). They can be asymptomatic or determine a clinical syndrome when strategically located in a sensory or motor tract (Fisher, 1982). Pure motor stroke (PMS) is one of the most common expression of lacunar infarcts. Transcranial magnetic stimulation (TMS) has been widely used to study the involvement of the corticospinal tract in stroke patients (Berardelli et al., 1991, Heald et al., 1993a, Heald et al., 1993b, Arac et al., 1994, Catano et al., 1995, Rapisarda et al., 1996, Escudero et al., 1998, Pennisi et al., 1999). In some cases, patients with lacunar infarcts have been included in the series of stroke patients (Heald et al., 1993a, Heald et al., 1993b, Escudero et al., 1998), but, as far as we know, a homogeneous group of patients with lacunar syndromes has not yet been investigated by TMS. Only Abbruzzese et al. (1991) have specifically studied lacunar infarcts, but by means of transcranial electrical stimulation (TES).

The aim of the present work was to study the modifications of motor-evoked potentials (MEPs) to TMS in patients with PMS due to a lacunar infarct. The patients were investigated 6 months or more after the onset of the neurological impairment. The modifications of the MEP were related to the clinical data at the moment of the study, in order to assess the sensitivity and the possible clinical relevance of TMS in the lacunar syndromes. Moreover, we tried to establish to what extent TMS was able to reflect possible, remaining subclinical abnormalities in corticospinal pathway after recovery.

Section snippets

Stroke patients

The study was approved by the local Ethics Committee and informed consent was obtained from all the patients.

Forty right-handed patients (15 men; 25 women; mean age 64.05±11SD years; range 38–79 years) with a pure motor hemiparesis or hemiplegia due to a lacunar infarct were investigated between 6 and 18 months after the onset of symptoms (chronic stage). They were all out-patients of the Cerebrovascular Diseases Centre of our Department of Neurology. The diagnosis of lacunar infarct was

Results

In the 20 normal subjects, no significant difference in MT, MEP amplitude and CMCT was detected between left and right sides; so, the results of both sides were aggregated by calculating the mean values for each subject.

In normal controls, the mean 9HPT time for the right hand was 16.1±1.8 s (upper normal limit, 20.6 s) while it was 17.5±1.7 s (upper normal limit, 21.7 s) for the left one.

Clinical and electrophysiological data obtained from the 40 patients are shown in Table 1.

Over the affected

Discussion

PMS is one of the most common syndromes that occur due to lacunar infarct and generally has an excellent functional prognosis (Fisher, 1982). In the present work, we have studied patients with PMS 6 months or more after the onset of symptoms. We have only included patients with lacunar infarct detectable by MRI and location compatible with the motor deficit. This choice was made in order to minimize the risk of studying patients with motor disturbances due to other causes. At the moment of the

Acknowledgements

The authors express their appreciation to Mr Santi Lorito for his excellent technical assistance.

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