Abstract 14: Effects of Lesion Laterality on Post-Stroke Motor Performance: An ENIGMA Stroke Recovery Analysis

The laterality of the lesioned hemisphere is often overlooked in stroke recovery research due to small sample sizes. Here, we used a well-powered dataset from ENIGMA Stroke Recovery (a consortium that harmonizes post-stroke MRIs and behavioral data worldwide; http://enigma.usc.edu) to analyze the effects of left (LHL) versus right (RHL) hemisphere lesions on motor performance. Given the different functional roles of each hemisphere, we hypothesized that the LHL group should show better motor performance, and, consequently, different brain-behavior relationships, compared to the RHL group. Data from over 2000 stroke patients across 20 sites worldwide has been committed. To date, structural T1-weighted MRIs from n=343 (10 sites) have been analyzed (LHL n=174; RHL n=169). ENIGMA protocols extracted volumes of subcortical regions of interest and provided quality control. Regression analyses examined brain volumes as predictors of motor outcomes. Motor scores were combined across scales/sites, with each score expressed as a percentage of the maximum score. Covariates (e.g., age, sex, intracranial volume) and manually marked lesion effects were also modeled. Statistical significance was assessed nonparametrically by permutation. As anticipated, the LHL group had better motor performance compared to the RHL group (t(1,341)=3.07, p=0.0023). In addition, while the combined LHL+RHL analyses showed significant associations between motor scores and volumes of the basal ganglia/lateral ventricles, separate group analyses showed strong associations for the LHL group, but only one association for the RHL group (Table 1). This may suggest that motor recovery following RH lesions is more heterogeneous or relies more on cortical regions/networks that were not assessed here. While further research is needed, these results suggest that laterality of the lesioned hemisphere affects neural patterns related to motor recovery and should be carefully examined.

Effects of combined peripheral nerve stimulation and brain polarization on performance of a motor sequence task after chronic stroke

BACKGROUND AND PURPOSE

Recent work demonstrated that application of peripheral nerve and cortical stimulation independently can induce modest improvements in motor performance in patients with stroke. The purpose of this study was to test the hypothesis that combining peripheral nerve stimulation (PNS) to the paretic hand with anodal direct current stimulation (tDCS) to the ipsilesional primary motor cortex (M1) would facilitate beneficial effects of motor training more than each intervention alone or sham (tDCS(Sham) and PNS(Sham)).

METHODS

Nine chronic stroke patients completed a blinded crossover designed study. In separate sessions, we investigated the effects of single applications of PNS+tDCS, PNS+tDCS(Sham), tDCS+PNS(Sham), and PNS(Sham)+tDCS(Sham) before motor training on the ability to perform finger motor sequences with the paretic hand.

RESULTS

PNS+tDCS resulted in a 41.3% improvement in the number of correct key presses relative to PNS(Sham)+tDCS(Sham), 15.4% relative to PNS+tDCS(Sham), and 22.7% relative to tDCS+PNS(Sham). These performance differences were maintained 1 and 6 days after the end of the training.

CONCLUSIONS

These results indicate that combining PNS with tDCS can facilitate the beneficial effects of training on motor performance beyond levels reached with each intervention alone, a finding of relevance for the neurorehabilitation of motor impairments after stroke.

Obstipation as a paraneoplastic presentation of small cell lung cancer: case report and literature review

Paraneoplastic symptoms caused by abnormal gastrointestinal motility may be the initial manifestation of small cell lung cancer (SCLC). We report a case of a 63-year-old woman who presented with progressive constipation culminating in obstipation, and associated symptoms of more widespread dysmotility. A paraneoplastic syndrome was suspected. The only abnormality on chest computed tomography was a minimally enlarged paratracheal lymph node. Positron emission tomography demonstrated increased activity in the lymph node. The antinuclear neuronal antibody titer was elevated. Bronchoscopy with transtracheal biopsy confirmed the diagnosis of SCLC. One year after diagnosis, the patient had progressive symptoms of intestinal obstruction, and ultimately feculent vomiting. On abdominal radiography, colonic sitz markers ingested a year earlier were in virtually the same positions as after ingestion. Palliative colectomy with ileostomy was performed. The myenteric plexus in the terminal ileum and colon showed infiltration by a mixture of B-cell and T-cell lymphocytes and plasma cells, and no gross neuronal abnormalities. We review the clinical and pathologic features, clinical course, and management of paraneoplastic pseudoobstruction.

Cortical control of voluntary blinking: a transcranial magnetic stimulation study

OBJECTIVE

To investigate cortical regions related to voluntary blinking.

METHODS

Transcranial magnetic stimulation (TMS) was applied to the facial motor cortex (M1) and the midline frontal region (Fz) in 10 healthy subjects with eyes opened and closed. Motor-evoked potentials were recorded from the orbicularis oculi (OOC), orbicularis oris (OOR), abductor digiti minimi and tibialis anterior using surface and needle electromyography electrodes. Facial M waves and blink reflex were measured using supramaximal electrical stimulation of the facial and supraorbital nerves.

RESULTS

TMS at Fz elicited 3 waves in OOC with no response in other tested muscles except for the early wave in OOR. Facial M1 stimulation produced only early and late waves. Because of their latencies, shapes, and relationship to coil position and stimulation intensity, early and late waves appeared to be analogous to the facial M wave and R1 component of the blink reflex. The intermediate wave at 6-8 ms latency was elicited in OOC by Fz stimulation with eyes closed.

CONCLUSIONS

Since its latency matches the central conduction time of other cranial muscles and it has characteristic of muscle activation-related facilitation, the intermediate wave is presumably related to cortical stimulation. This result provides evidence that the cortical center for the upper facial movements, including blinking, is not principally located in the facial M1, but rather in the mesial frontal region.