Combination of TMS and fMRI reveals a specific pattern of reorganization in M1 in patients after complete spinal cord injury.

PURPOSE: After a spinal cord injury (SCI), which was complete, deafferentation of the body representation caudal to the lesion height results in drastic changes in the cortical representation. The underlaying processes are poorly understood. METHODS: We investigated cortical representation sites of upper limb muscles using functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) in five patients suffering from thoracic complete SCI and one with an incomplete SCI in the height of L1. RESULTS: In comparison to healthy controls fMRI demonstrated a displacement of elbow movement representations in the precentral gyrus in patients with complete SCI into the direction of the deafferented cortical thoracic representation. Changes increased with time after the incidence of SCI. TMS revealed reduced excitability and prolonged silent periods for muscles more distant to the deafferented area. CONCLUSIONS: Whereas fMRI demonstrated changes in representation sites adjacent to the deafferented area, TMS excitability changes were also observed more distant to the deafferented area and silent periods were prolonged in comparison to healthy controls. TMS changes might depend on both: the distance to the deafferented area and the time of persistence of deafferentation.

[Laboratory diagnosis of hyperkinetic movement disorders in adulthood]. / Labordiagnestik hyperkinetischer Bewegungsstörungen des Erwachsenenalters.

Hyperkinetic movement disorders such as dystonia, chorea, ballism, myoclonus, tics, and tremor may be idiopathic or symptomatic in origin. Symptomatic movement disorders need further diagnostic testing in order to identify their etiology. In addition to clinical findings, imaging techniques, and electrophysiological testing, laboratory studies are required. Here, we review the prevalence of diseases presenting with symptomatic hyperkinetic movement disorders and discuss the diagnostic relevance of laboratory studies.

Motor thresholds in humans: a transcranial magnetic stimulation study comparing different pulse waveforms, current directions and stimulator types.

OBJECTIVES: To evaluate the stimulation effectiveness of different magnetic stimulator devices with respect to pulse waveform and current direction in the motor cortex. METHODS: In 8 normal subjects we determined motor thresholds of transcranial magnetic stimulation in a small hand muscle. We used focal figure-of-eight coils of 3 common stimulators (Dantec Magpro, Magstim 200 and Magstim Rapid) and systematically varied current direction (postero-anterior versus antero-posterior, perpendicular to the central sulcus) as well as pulse waveform (monophasic versus biphasic). The coil position was kept constant with a stereotactic positioning device. RESULTS: Motor thresholds varied consistently with changing stimulus parameters, despite substantial interindividual variability. By normalizing the values with respect to the square root of the energy of the capacitors in the different stimulators, we found a homogeneous pattern of threshold variations. The normalized Magstim threshold values were consistently higher than the normalized Dantec thresholds by a factor of 1.3. For both stimulator types the monophasic pulse was more effective if the current passed the motor cortex in a postero-anterior direction rather than antero-posterior. In contrast, the biphasic pulse was weaker with the first upstroke in the postero-anterior direction. We calculated mean factors for transforming the intensity values of a particular configuration into that of another configuration by normalizing the different threshold values of each individual subject to his lowest threshold value. CONCLUSIONS: Our transformation factors allow us to compare stimulation intensities from studies using different devices and pulse forms. The effectiveness of stimulation as a function of waveform and current direction follows the same pattern as in a peripheral nerve preparation (J Physiol (Lond) 513 (1998) 571).

Motor reorganization after spinal cord injury: evidence of adaptive changes in remote muscles.

Purpose: Given that SCI leads to substantial changes in biomechanical properties of the body and to widespread postlesional reorganization of the motor system as determined by functional imaging studies, we sought to identify neurophysiological correlations and time course of reorganization affecting muscles more distant to a SCI. Methods: Two arm muscles distant to a SCI (T2-L3), M.biceps brachii (BIC), M.abductor pollicis brevis (APB), were studied in 13 SCI-patients and 15 controls. Motor thresholds at rest (MT), facilitatory effects on MEP-amplitudes (FE) with voluntary activation, MEP-amplitudes with maximal stimulation (MA) and recruitment curves (RC) were measured and correlated with level, age and severity of the lesion. Follow-up studies (t2) were performed in five patients with clinical recovery. Results: Patients exhibited smaller MA from activated BIC, a tendency towards smaller FE and smaller RC-slopes at t1. With clinical recovery, activated BIC-FE, MA and RC-slopes tended to normalize. Conclusions: Our data support the hypothesis that postlesional reorganization of the motor system also involves remote muscles. Considering pattern and time course of reorganization, we speculate that they appear as sequelae of the trauma, possibly representing an adaptation of the motor system to an altered biomechanical status after SCI.

Reorganization in the primary motor cortex after spinal cord injury - A functional Magnetic Resonance (fMRI) study.

Activation maps in the primary motor cortex (M1) were investigated in three patients with complete spinal cord injury (SCI) at level TH3, TH7 and TH9 and in one patient with an incomplete spinal cord injury at level L1 during right elbow (4 patients), right thumb (4 patients), bilateral lip (2 patients) and right foot (3 patients during imagined, 1 patient during executed) movements using functional Magnetic Resonance Imaging (fMRI). Compared to controls fMRI activation maps of patients with complete paraplegia showed a cranial displacement of the activation maxima in the contralateral primary motor cortex during elbow movement of 13.3mm, whereas the maxima of thumb and lip movements were not altered. The patient with an incomplete spinal cord injury revealed no displacement of elbow activation maxima. The reorganization is likely to occur on the cortical and not on the spinal level.

Reorganization in the primary motor cortex after spinal cord injury - A functional Magnetic Resonance (fMRI) study.

Activation maps in the primary motor cortex (M1) were investigated in three patients with complete spinal cord injury (SCI) at level TH3, TH7 and TH9 and in one patient with an incomplete spinal cord injury at level L1 during right elbow (4 patients), right thumb (4 patients), bilateral lip (2 patients) and right foot (3 patients during imagined, 1 patient during executed) movements using functional Magnetic Resonance Imaging (fMRI). Compared to controls fMRI activation maps of patients with complete paraplegia showed a cranial displacement of the activation maxima in the contralateral primary motor cortex during elbow movement of 13.3mm, whereas the maxima of thumb and lip movements were not altered. The patient with an incomplete spinal cord injury revealed no displacement of elbow activation maxima. The reorganization is likely to occur on the cortical and not on the spinal level.