Schwannoma in the Thenar Eminence: a Case Report.

This report describes a rare presentation of schwannoma in the thenar aspect of a surgeon and reviews the literature. A 35-year-old surgeon had a slow-growing swelling in his left thenar eminence. Clinical and radiological findings suggested it was a well-encapsulated mass within the abductor pollicis brevis muscle. A complete surgical excision was done, and the histopathological findings confirmed schwannoma, a benign peripheral nerve tumor. The surgeon remained symptom-free and had no recurrence at 1 year of follow-up. Though a benign peripheral nerve tumor is rare in the hand, it remains one of the differential diagnoses for a thenar eminence swelling. Surgical enucleation preserving the nerve fascicles achieves an excellent functional outcome.

Functional MRI vs. navigated TMS to optimize M1 seed volume delineation for DTI tractography. A prospective study in patients with brain tumours adjacent to the corticospinal tract.

BACKGROUND: DTI-based tractography is an increasingly important tool for planning brain surgery in patients suffering from brain tumours. However, there is an ongoing debate which tracking approaches yield the most valid results. Especially the use of functional localizer data such as navigated transcranial magnetic stimulation (nTMS) or functional magnetic resonance imaging (fMRI) seem to improve fibre tracking data in conditions where anatomical landmarks are less informative due to tumour-induced distortions of the gyral anatomy. We here compared which of the two localizer techniques yields more plausible results with respect to mapping different functional portions of the corticospinal tract (CST) in brain tumour patients. METHODS: The CSTs of 18 patients with intracranial tumours in the vicinity of the primary motor area (M1) were investigated by means of deterministic DTI. The core zone of the tumour-adjacent hand, foot and/or tongue M1 representation served as cortical regions of interest (ROIs). M1 core zones were defined by both the nTMS hot-spots and the fMRI local activation maxima. In addition, for all patients, a subcortical ROI at the level of the inferior anterior pons was implemented into the tracking algorithm in order to improve the anatomical specificity of CST reconstructions. As intra-individual control, we additionally tracked the CST of the hand motor region of the unaffected, i.e., non-lesional hemisphere, again comparing fMRI and nTMS M1 seeds. The plausibility of the fMRI-ROI- vs. nTMS-ROI-based fibre trajectories was assessed by a-priori defined anatomical criteria. Moreover, the anatomical relationship of different fibre courses was compared regarding their distribution in the anterior-posterior direction as well as their location within the posterior limb of the internal capsule (PLIC). RESULTS: Overall, higher plausibility rates were observed for the use of nTMS- as compared to fMRI-defined cortical ROIs (p < 0.05) in tumour vicinity. On the non-lesional hemisphere, however, equally good plausibility rates (100%) were observed for both localizer techniques. fMRI-originated fibres generally followed a more posterior course relative to the nTMS-based tracts (p < 0.01) in both the lesional and non-lesional hemisphere. CONCLUSION: NTMS achieved better tracking results than fMRI in conditions when the cortical tract origin (M1) was located in close vicinity to a brain tumour, probably influencing neurovascular coupling. Hence, especially in situations with altered BOLD signal physiology, nTMS seems to be the method of choice in order to identify seed regions for CST mapping in patients.

High-resistance strength training does not affect nerve cross sectional area - An ultrasound study.

OBJECTIVE: The aim was to study the effect of high-resistance strength training on peripheral nerve morphology, by examining properties of peripheral nerves as well as distal and proximal muscle thickness with ultrasound, comparing healthy individuals who perform and do not perform high-resistance strength training. METHODS: Neuromuscular ultrasound was used to examine cross sectional area (CSA) of the median and musculocutaneous nerves, and muscle thickness of the abductor pollicis brevis muscle, biceps brachii muscle, quadriceps muscle and extensor digitorum brevis muscle, in 44 healthy individuals, of whom 22 performed regular high-resistance strength training. RESULTS: No difference in nerve CSA was found between trained and untrained individuals although trained individuals had thicker biceps brachii muscles. The CSA of the median nerve in the forearm correlated with participants' height and was significantly larger in men than women. CONCLUSIONS: In this cohort, CSA of the median and musculocutaneous nerves was not affected by strength training, whereas gender had a prominent effect both on CSA and muscle thickness. SIGNIFICANCE: This is the first study to examine the effect of high-resistance strength training on peripheral nerves with neuromuscular ultrasound.

Improved nTMS- and DTI-derived CST tractography through anatomical ROI seeding on anterior pontine level compared to internal capsule.

Imaging of the course of the corticospinal tract (CST) by diffusion tensor imaging (DTI) is useful for function-preserving tumour surgery. The integration of functional localizer data into tracking algorithms offers to establish a direct structure-function relationship in DTI data. However, alterations of MRI signals in and adjacent to brain tumours often lead to spurious tracking results. We here compared the impact of subcortical seed regions placed at different positions and the influences of the somatotopic location of the cortical seed and clinical co-factors on fibre tracking plausibility in brain tumour patients. The CST of 32 patients with intracranial tumours was investigated by means of deterministic DTI and neuronavigated transcranial magnetic stimulation (nTMS). The cortical seeds were defined by the nTMS hot spots of the primary motor area (M1) of the hand, the foot and the tongue representation. The CST originating from the contralesional M1 hand area was mapped as intra-individual reference. As subcortical region of interests (ROI), we used the posterior limb of the internal capsule (PLIC) and/or the anterior inferior pontine region (aiP). The plausibility of the fibre trajectories was assessed by a-priori defined anatomical criteria. The following potential co-factors were analysed: Karnofsky Performance Scale (KPS), resting motor threshold (RMT), T1-CE tumour volume, T2 oedema volume, presence of oedema within the PLIC, the fractional anisotropy threshold (FAT) to elicit a minimum amount of fibres and the minimal fibre length. The results showed a higher proportion of plausible fibre tracts for the aiP-ROI compared to the PLIC-ROI. Low FAT values and the presence of peritumoural oedema within the PLIC led to less plausible fibre tracking results. Most plausible results were obtained when the FAT ranged above a cut-off of 0.105. In addition, there was a strong effect of somatotopic location of the seed ROI; best plausibility was obtained for the contralateral hand CST (100%), followed by the ipsilesional hand CST (>95%), the ipsilesional foot (>85%) and tongue (>75%) CST. In summary, we found that the aiP-ROI yielded better tracking results compared to the IC-ROI when using deterministic CST tractography in brain tumour patients, especially when the M1 hand area was tracked. In case of FAT values lower than 0.10, the result of the respective CST tractography should be interpreted with caution with respect to spurious tracking results. Moreover, the presence of oedema within the internal capsule should be considered a negative predictor for plausible CST tracking.

Relationship between excitability, plasticity and thickness of the motor cortex in older adults.

The relationship between brain structure, cortical physiology, and learning ability in older adults is of particular interest in understanding mechanisms of age-related cognitive decline. Only a few studies addressed this issue so far, yielding mixed results. Here, we used comprehensive multiple regression analyses to investigate associations between brain structure on the one hand, i.e., cortical thickness (CT), fractional anisotropy (FA) of the pyramidal tract and individual coil-to-cortex distance, and cortical physiology on the other hand, i.e. motor cortex excitability and long-term potentiation (LTP)-like cortical plasticity, in healthy older adults (mean age 64 years, 14 women). Additional exploratory analyses assessed correlations between cortical physiology and learning ability in the verbal domain. In the regression models, we found that cortical excitability could be best predicted by CT of the hand knob of the primary motor cortex (CT-M1HAND) and individual coil-to-cortex distance, while LTP-like cortical plasticity was predicted by CT-M1HAND and FA of the pyramidal tract. Exploratory analyses revealed a significant inverse correlation between cortical excitability and learning ability. In conclusion, higher cortical excitability was associated with lower CT and lower learning ability in a cohort of healthy older adults, in line with previous reports of increased cortical excitability in patients with cortical atrophy and cognitive deficits due to Alzheimer's Disease. Cortical excitability may thus be a parameter to identify individuals at risk for cognitive decline and gray matter atrophy, a hypothesis to be explored in future longitudinal studies.

Superficial portion of abductor pollicis brevis muscle, morphological study and literature review: case report / Fascículo superficial del músculo abductor corto del pulgar, estudio morfológico y revisión de la literatura. reporte de caso

Abductor pollicis brevis muscle (APB) belongs to the foreground of the subfascial muscle thenar region, which is of great importance in the movement of the thumb on its two-joint arrangement. In this article, we report the presence of a superficial portion of the APB muscle and its relationship and discuss the available literature and the clinical implications of the presence of this variation.

El músculo abductor corto del pulgar (ACP) pertenece al primer plano muscular subfascial de la región tenar de gran importancia en los movimientos del pulgar por su disposición biarticular. En el presente artículo reportamos la presencia de un fascículo superficial del músculo ACP y sus relaciones, se analiza la literatura disponible y se discuten las implicancias clínicas de la presencia de esta variación.

Effects of sevoflurane on transcranial electrical motor evoked potential monitoring elicted from four-limb muscles / 复旦学报（医学版）

Objective To compare the influence of different end-tidal concentrations of sevoflurane on transcranial electrical four-limb muscle motor evoked potential (MEP) monitoring. Methods Twenty ASA Ⅰ-Ⅱpatients aged 23-62 years undergoing craniotomy were enrolled. Triangular muscle, biceps brachii muscle, triceps brachii muscle, brachioradialis muscle, extensor digitorum communis muscle, abductor pollicis brevis abductor digiti minimi muscle, rectus femoris muscle, tibialis anterior muscle, gastrocnemius muscle and abductor hallucis were selected for MEPs recording. Sevoflurane was introduced at 0.5, 0.75, 1.0 and then 1.3 MAC (15 min each), and the effects on MEPs were studied. Results ①Maximum MEP amplitude was observed at abductor pollicis brevis muscle in upper limb and abductor hallucis muscle in lower limb at baseline and 0.5 MAC. Up to 1.0 MAC, there was no significant difference in MEP amplitude among extensor digitorum communis muscle, abductor pollicis brevis and abductor digiti minimi muscle. ②The success rate of MEP recording from abductor pollicis brevis muscle and abductor hallucis muscle was 100% during the administration of 0.5-1.0 MAC sevoflurane. ③The MEP amplitude was decreased and the latency was increased in a sevoflurane dose-dependent manner. Conclusions Abductor pollicis brevis muscle and abductor hallucis muscle were suitable for MEP monitoring during the administration of 0.5-1.0 MAC sevoflurane.