No effect of a levodopa single dose on motor performance and motor excitability in chronic stroke. A double-blind placebo-controlled cross-over pilot study

PURPOSE

Drugs that modulate neuronal transmission can influence motor recovery after stroke. Here, we tested if a single dose of levodopa could improve motor functions and change motor excitability in a group of chronic stroke patients.

METHODS

Ten patients > 6 months after their stroke participated in a placebo-controlled double-blind trial. On two different occasions, they received either 100 mg levodopa or placebo in a randomized order. After drug intake, they participated in one hour of physiotherapy aimed at an improvement of dexterity. Motor functions were tested by application of the Nine-Hole-Peg Test, a dynamometer measuring grip strength and the Action Research Arm Test. In addition, transcranial magnetic stimulation (TMS) was applied to study intracortical excitability, stimulus response curves and silent periods. TMS studies and motor function measurements were performed before drug intake, 45 minutes after drug ingestion and after the physiotherapy.

RESULTS

Compared to placebo, levodopa neither improved motor functions nor changed motor excitability as tested by TMS.

CONCLUSION

These findings suggests that a single levodopa dose is not sufficient to improve motor function in chronic stroke. However, it cannot be excluded that the lack of a beneficial effect is related to the small study sample.

Transcranial grey-scale sonography of subdural haematoma in adults

AIM

Transcranial high-resolution grey-scale sonography reliably allows diagnosis and monitoring of subdural haematoma (SDH) and extra-cerebral intracranial fluid collections in infants but has not been evaluated thoroughly in adults up to now. Because of rapid development of ultrasound systems, the depiction of intracerebral haemorrhage (ICH) has now become feasible. The presented study evaluated the sonographic appearance of SDH in adults.

METHOD

We performed transcranial grey-scale sonography (TGS) in 25 consecutive patients with SDH confirmed by cranial computed tomography (CCT) or MRI. According to paediatric TGS, the dural border of the arachnoid was depicted as a highly echogenic membrane, and the distance between the skull and the echogenic membrane was measured. SDH was measured by CCT/MRI and by TGS in corresponding axial planes. The rate of identification of SDH in TGS was evaluated, and the extent of SDH as assessed by CCT/MRI and TGS was compared.

RESULTS

TGS reliably detected SDH in 22 of the 25 patients with confirmed SDH (88 %). In the remaining 3 patients, the temporal bone window was insufficient for TGS investigation. Extent of SDH measured by CCT and TGS correlated linearly (r= 0.849).

CONCLUSION

TGS allows imaging of SDH in patients with CCT/MRI confirmed SDH, and the extent of SDH correlates significantly between TGS and CCT/MRI. Therefore, TGS may be a possible alternative to serial CCT imaging in monitoring SDH, since in contrast to CCT, TGS is a non-invasive bedside method. So far, TGS is not suitable for the diagnosis of SDH.

The amount of solid cerebral microemboli during carotid stenting does not relate to the frequency of silent ischemic lesions

BACKGROUND AND PURPOSE

Carotid artery stent placement (CAS) may be associated with clinically silent cerebral lesions. We prospectively evaluated the association of the number of solid cerebral microemboli during unprotected CAS with the frequency of silent cerebral lesions as detected by diffusion-weighted MR imaging (DWI).

METHODS

We performed multifrequency transcranial Doppler detection of solid microemboli in the ipsilateral middle cerebral artery (MCA) during CAS in 27 consecutive patients with symptomatic high-grade carotid stenoses. No embolus protection was used in any of the cases. DWI before and 24 +/- 2 hours after CAS was used to detect new ischemic lesions.

RESULTS

We detected 484 solid microemboli in 17 patients (63%). On MR imaging 24 +/- 2 hours after CAS, 6 patients (22%) had developed 13 new clinically silent DWI lesions within the ipsilateral MCA territory. In patients with Doppler evidence of solid emboli during CAS, the incidence of new DWI lesions was higher (29%) than in patients without Doppler evidence of solid emboli during the procedure (10%); this difference was not statistically significant (P = .25). The number of solid microemboli during CAS in patients with new ipsilateral DWI lesions was not significantly different from that in patients without new ipsilateral DWI lesions.

CONCLUSIONS

Solid microembolism is a common event during unprotected CAS; however, the frequency of procedure-related silent cerebral lesions appears to be independent of the number of solid cerebral microemboli during the procedure.

Mechanisms of placebo analgesia: rACC recruitment of a subcortical antinociceptive network

Placebo analgesia is one of the most striking examples of the cognitive modulation of pain perception and the underlying mechanisms are finally beginning to be understood. According to pharmacological studies, the endogenous opioid system is essential for placebo analgesia. Recent functional imaging data provides evidence that the rostral anterior cingulate cortex (rACC) represents a crucial cortical area for this type of endogenous pain control. We therefore hypothesized that placebo analgesia recruits other brain areas outside the rACC and that interactions of the rACC with these brain areas mediate opioid-dependent endogenous antinociception as part of a top-down mechanism. Nineteen healthy subjects received and rated painful laser stimuli to the dorsum of both hands, one of them treated with a fake analgesic cream (placebo). Painful stimulation was preceded by an auditory cue, indicating the side of the next laser stimulation. BOLD-responses to the painful laser-stimulation during the placebo and no-placebo condition were assessed using event-related fMRI. After having confirmed placebo related activity in the rACC, a connectivity analysis identified placebo dependent contributions of rACC activity with bilateral amygdalae and the periaqueductal gray (PAG). This finding supports the view that placebo analgesia depends on the enhanced functional connectivity of the rACC with subcortical brain structures that are crucial for conditioned learning and descending inhibition of nociception.

[Hypothalamic deep brain stimulation in patients with chronic cluster headaches. Suggestions for patient selection]

Cluster headaches involve a stereotypic symptomatic and belong to the most severe primary pain syndromes. Imaging studies have demonstrated functional and structural changes in the inferior-posterior hypothalamus ipsilateral to the pain. These changes are highly specific to the syndrome, strongly suggesting that this anatomical region is the trigger or generator of the acute attacks and/or determine the duration of the acute pain. These findings have led to the successful therapy of 19 not or difficult to treat patients with hypothalamic deep brain stimulation, resulting in long-term periods without pain and without significant side effects. Recently, however, a patient was reported who died after the operation due to increased blood pressure leading to the rupture of a previously non-diagnosed aneurysm. This article offers a translated summary of the recently published criteria of an international consensus group, which, in addition to a positive ethics vote, should be fulfilled before such deep brain stimulation of the hypothalamus is carried out in such patients.

Motor cortex excitability after thalamic infarction

OBJECTIVE

We examined 8 patients with hemihypesthesia due to an ischemic thalamic lesion to explore the effects of a central sensory dysfunction on motor cortex excitability.

METHODS

Motor excitability was assessed using transcranial magnetic stimulation techniques and electrical peripheral nerve stimulation. Motor function was evaluated by the Nine-Hole-Peg Test and measurement of hand grip strength. The affected side was compared with the non-lesioned side and with an age-matched control group.

RESULTS

Patients had a loss of inhibition and an increase of facilitation in the motor cortex of the affected side. The silent period was prolonged and motor function was impaired on the affected side.

CONCLUSIONS

A thalamic lesion can modulate motor cortical excitability.

SIGNIFICANCE

This study suggests that, under normal conditions, somatosensory afferents influence inhibitory and excitatory properties in the motor cortex.

Time course of wallerian degeneration after ischaemic stroke revealed by diffusion tensor imaging

Wallerian degeneration (WD) after ischaemic stroke is a well known phenomenon following a stereotypical time course. Whereas conventional magnetic resonance imaging fails to detect signal intensity changes until four weeks after stroke, diffusion tensor imaging (DTI) reveals changes related to WD only after days. DTI was used to monitor the time course of Wallerian degeneration of the pyramidal tract from the early subacute to the late chronic stage of ischaemic stroke in two patients. A progressive decrease of fractional anisotropy was found along the pyramidal tract in the cerebral peduncle below the primary lesion resulting from progressive changes in the principal diffusivities, as well as a slight increase in the orientationally averaged diffusivity in the chronic phase. These signal changes reflect the progressive disintegration of fibre structures resulting from WD.

Abnormal excitability of premotor-motor connections in de novo Parkinson's disease

The dorsal premotor cortex (PMd) is abnormally active in patients with idiopathic Parkinson's disease. This has been interpreted as a functional correlate of adaptive plasticity within the motor system to compensate for deficient activation of striato-mesial-frontal projections in these patients. Whether abnormal PMd activity influences excitability in the primary motor cortex (M1) in untreated Parkinson's disease patients and how this premotor-motor interaction might be altered by l-dopa is unclear. To this end, we studied the effects of 1 Hz premotor repetitive transcranial magnetic stimulation (rTMS) on M1 excitability in 10 previously untreated non-tremulous Parkinson's disease patients before (day 1) and after (day 8) their first ever l-dopa treatment and compared the results with those of a group of nine age- and sex-matched healthy controls. In each rTMS session, 1200 pulses of 1 Hz rTMS were applied at an intensity of 80% active motor threshold (AMT) to the PMd contralateral to the clinically more affected side in Parkinson's disease patients and to the left PMd in healthy controls. Intracortical paired pulse excitability of ipsilateral M1 was probed using a TMS paired pulse paradigm where subthreshold conditioning pulses (80% of AMT) were given 2-15 ms prior to a suprathreshold test pulse. In Parkinson's disease patients, abnormal baseline intracortical excitability at an interstimulus interval (ISI) of 5 ms was normalized by premotor rTMS. In contrast, rTMS led to an increased excitability at an ISI of 5 ms in healthy controls. Premotor rTMS effects lasted longer (for at least a week) in patients. These results show that the modifiability of premotor-motor connections is abnormal in untreated Parkinson's disease. A single dose of l-dopa reversed, i.e. normalized, the direction of excitability changes in M1 following premotor rTMS in Parkinson's disease patients, suggesting that dopamine depletion directly or indirectly influences premotor-motor interactions in Parkinson's disease. The rTMS conditioning approach described here provides a promising tool to delineate further the excitability changes in frontal motor areas in response to progressive degeneration of nigrostriatal dopaminergic neurons and also to chronic l-dopa treatment in Parkinson's disease.

Motor cortex excitability after cerebellar infarction

BACKGROUND AND PURPOSE

The cerebellum has an influence on motor excitability. We investigated if the location of a cerebellar infarction was crucial for changes of motor cortex excitability and if the electrophysiological findings were correlated with motor performance.

METHODS

Transcranial magnetic stimulation was applied to study intracortical inhibition (ICI), intracortical facilitation (ICF), motor thresholds, and corticospinal excitability. Dexterity as a measure of motor performance was tested with the Nine-Hole-Peg Test (9HPT). Ratios (affected/unaffected) were also calculated.

RESULTS

ICI and ICF ratios were negatively correlated with 9HPT ratios in all patients (n=9). Compared with an age-matched control group, patients with lesions in the territory of the superior cerebellar artery (SCA) (n=3) or a lesion rostral of the dentate nucleus (n=1) had abnormally enhanced ICI and a loss of ICF (3 patients). Dexterity was impaired in all 4 patients. Motor excitability and motor performance normalized over the subsequent weeks. Patients with an infarct either in the territory of the anterior inferior cerebellar artery (n=2) or in the territory of the posterior inferior cerebellar artery (n=3) displayed motor excitability and motor performance within the normal range.

CONCLUSIONS

The superior part of the cerebellum has a strong influence on motor cortex excitability. We suggest that the enhancement of motor inhibition and reduction of motor facilitation is mediated by an impairment of the deep cerebellar nuclei.