Comparison of hemispheric dominance and correlation of evoked speech responses between functional magnetic resonance imaging and navigated transcranial magnetic stimulation in language mapping.

BACKGROUND: Non-invasive language mapping is commonly facilitated via two different approaches, functional magnetic resonance imaging (fMRI) and navigated transcranial magnetic stimulation (nTMS). The aim of our examination was to compare both methods regarding hemispheric dominance and detection of involved cortex in speech-processing. METHODS: Since 2015, patients with language eloquent tumors received both fMRI and nTMS language mapping in our facility. Hemispheric dominance for fMRI (word pairing task) and nTMS (picture naming) was defined according to activation/response predominance between hemispheres. For a detailed comparison of methods, we used a cortical parcellation system and correlated activations of each gyrus. Statistical analysis was performed using Sign test, Spearman's rank correlation coefficient and Mann-Whitney-U test. RESULTS: Twenty-three patients with predominantly frontal and temporal tumors were enrolled. fMRI and nTMS predicted the same hemispheric dominance in 67% of examinations. No significant difference was found between the tests (P=0.63). When examining the correlation of anatomical areas with speech relevance between the two methods, we found significant differences in activation patterns of language relevant areas when comparing patients inter-individually. Using 2/3 rule for evoked language errors in nTMS improved congruence in perisylvian regions. CONCLUSIONS: fMRI and nTMS lead to comparable results in determining hemispheric dominance, however they show significantly different results in predicting language relevant areas. We recommend using 2/3 rule for nTMS to improve congruence. Both tools seem to be valuable methods for preoperative planning. However, surgical decision making concerning resectability of language eloquent lesions should be based on awake craniotomy, furthermore.

Super-selective cervical nerve root stimulation in contralateral C7 transfer: An intraoperative study.

OBJECTIVE: We designed this study using super-selective intraoperative cervical nerve root stimulation aiming to support decision making about complete or partial contralateral C7 (cC7) nerve root transfer in patients with multiple cervical root avulsion injury. METHODS: Super-selective intraoperative stimulations of anterior, lateral, medial and posterior aspect of C5-C8 nerve roots were performed. Compound muscle action potentials (CMAP) were recorded in the lateral part of the deltoid (DM), long head of biceps brachii (BCM), brachioradial (BRM), long head of triceps brachii (TCM), and extensor digitorum communis (EDC) muscle. Muscle strength was documented immediately after cC7 transfer procedures and on scheduled follow-up visits according to the Medical Research Council (MRC) scale. RESULTS: In the DM, stimulation of the posterior aspect of C5 resulted in the largest CMAP amplitudes (2.0 mV ±â€¯1.9; 80% ±â€¯28.3). The BCM CMAPs induced by the different aspects of C6 all revealed homogenous stimulation results. Stimulation of the lateral aspect of C7 induced the largest amplitude of TCM CMAPs (1.3 mV ±â€¯1.0; 67.1% ±â€¯43.3). CMAP amplitudes of individual muscles and individual contributions of cervical nerve roots to the TCM varied between subjects. Overall donor side morbidity was low, no permanent motor deficit occurred. CONCLUSION: A super-selective intraoperative cervical nerve root stimulation may help minimize donor side morbidity in transfer procedures. Individual differences of cervical nerve root innervation pattern need to be addressed in future electrophysiological studies. SIGNIFICANCE: Our study outlines individual differences of cervical nerve root innervation pattern.

Mechanisms, Treatment, and Patient Outcome of Iatrogenic Injury to the Brachial Plexus-A Retrospective Single-Center Study.

BACKGROUND: Injury to the brachial plexus is a devastating condition, with severe impairment of upper extremity function resulting in distinct disability. There are no systematic reports on epidemiology, causative mechanisms, treatment strategies. or outcomes of iatrogenic brachial plexus injury (iBPI). METHODS: We screened all cases of iatrogenic nerve injuries recorded between 2007 and 2017 at a single specialized institution. Mechanism of iBPI, type of previous causative intervention, location and type of the lesion as well as the type of revision surgery and functional patient outcome were analyzed. RESULTS: We identified 14 cases of iBPI, which all presented with significant impairment of upper extremity motor function (at least 1 muscle Medical Research Council grade 0). Neuropathic pain was present in most patients (11/14). Orthopedic shoulder procedures such as rotator cuff fixation, arthroplasty, and repositioning of a clavicle fracture accounted for iBPI in 7 of 14 patients. Other reasons for iBPI were resection or biopsy of a peripheral nerve sheath tumor in 3 patients or lymph node situated at the cervicomediastinal area in 2 patients. Mechanisms also included transaxillary rib resection in one and sternotomy in another patient. The treatment of iBPI was conducted according to each individual's needs and included neurolysis in 4, nerve grafting in 9, and nerve transfers in 1 patient. We found improved symptoms after treatment in most patients (11/14). CONCLUSIONS: Most common causes for iBPI were shoulder surgery and resection or biopsy of peripheral nerve sheath tumor and lymph nodes. Early referral to specialized peripheral nerve centers may help to improve functional patient outcome.