Contribution of different somatosensory afferent input to subcortical somatosensory evoked potentials in humans

ObjectivesTo investigate the subcortical somatosensory evoked potentials (SEPs) to electrical stimulation of either muscle or cutaneous afferents.MethodsSEPs were recorded in 6 patients suffering from Parkinson’s disease (PD) who underwent electrode implantation in the pedunculopontine (PPTg) nucleus area. We compared SEPs recorded from the scalp and from the intracranial electrode contacts to electrical stimuli applied to: 1) median nerve at the wrist, 2) abductor pollicis brevis motor point, and 3) distal phalanx of the thumb. Also the high-frequency oscillations (HFOs) were analysed.ResultsAfter median nerve and pure cutaneous (distant phalanx of the thumb) stimulation, a P1-N1 complex was recorded by the intracranial lead, while the scalp electrodes recorded the short-latency far-field responses (P14 and N18). On the contrary, motor point stimulation did not evoke any low-frequency component in the PPTg traces, nor the N18 potential on the scalp. HFOs were recorded to stimulation of all modalities by the PPTg electrode contacts.ConclusionsStimulus processing within the cuneate nucleus depends on modality, since only the cutaneous input activates the complex intranuclear network possibly generating the scalp N18 potential.SignificanceOur results shed light on the subcortical processing of the somatosensory input of different modalities.     

Altered supraspinal motor networks in survivors of poliomyelitis: A cortico-muscular coherence study

ObjectivePoliomyelitis results in changes to the anterior horn cell. The full extent of cortical network changes in the motor physiology of polio survivors has not been established. Our aim was to investigate how focal degeneration of the lower motor neurons (LMN) in infancy/childhood affects motor network connectivity in adult survivors of polio.MethodsSurface electroencephalography (EEG) and electromyography (EMG) were recorded during an isometric pincer grip task in 25 patients and 11 healthy controls. Spectral signal analysis of cortico-muscular (EEG-EMG) coherence (CMC) was used to identify the cortical regions that are functionally synchronous and connected to the periphery during the pincer grip task.ResultsA pattern of CMC was noted in polio survivors that was not present in healthy individuals. Significant CMC in low gamma frequency bands (30–47 Hz) was observed in frontal and parietal regions.ConclusionThese findings imply a differential engagement of cortical networks in polio survivors that extends beyond the motor cortex and suggest a disease-related functional reorganisation of the cortical motor network.SignificanceThis research has implications for other similar LMN conditions, including spinal muscular atrophy (SMA). CMC has potential in future clinical trials as a biomarker of altered function in motor networks in post-polio syndrome, SMA, and other related conditions.     

Reprint: Sehnentransfers in der Vorfußchirurgie

The aim of the current forefoot surgery is to retain function or to restore lost function. In contrast, in the past resection arthroplasty or amputation of the lesser toes were common. Included in the repertoire of every specialist are different operation techniques especially the tendon surgery, in addition to experience in indication and rehabilitation. It is important, that the focus during history taking, clinical examination and choice of treatment should not only be on the forefoot but also on the axis of the leg and the hindfoot position and function. As an example, the recruitment of the extensor digitorum longus – meaning the excessive support by the toe extension for forefoot extension – over time results in hammer toes. In some cases this excessive recruitment is the result of the rupture of the tibialis anterior tendon. Therefore, one should address the cause and repair the tibialis anterior tendon by suture and/or augmentation and not operate on the hammer toes in isolation.     

Early axonal loss predicts long-term disability in chronic inflammatory demyelinating polyneuropathy

ObjectiveTo investigate early pre-treatment nerve fiber loss as a predictor of long-term clinical outcome in chronic inflammatory demyelinating polyneuropathy (CIDP).MethodsIn 14 patients, motor and sensory conduction studies of the median, fibular, and sural nerves were performed at pre-treatment and follow-up 11–28 years later. Z-scores of amplitudes were combined as biomarkers of axonal loss and Z-scores of conduction properties as demyelination scores. The axonal loss was further examined by electromyography (EMG) and motor unit number estimation. Axonal and demyelination scores were compared to clinical outcomes in the Inflammatory Rasch-built Overall Disability Scale, the Neuropathy Impairment Score, and dynamometry.ResultsAt follow-up 12 patients walked independently, one needed support and one could not walk. The initial and follow-up axonal and demyelination scores were markedly abnormal. The initial axonal loss but not demyelination was strongly associated with both the follow-up axonal loss and the clinical measures. Moreover, delay of treatment initiation negatively influenced the axonal scores and clinical outcomes.ConclusionIn this hypothesis generating limited study, we found that axonal loss at early CIDP was highly predictive for long-term nerve fiber loss and disability.SignificanceThe study indicates that prompt initiation of treatment to prevent nerve fiber loss is necessary for outcome in CIDP.     

Peroneus longus tendon transfer; prospective study of treatment outcome of recurrent fixed clubfoot deformities in children after failed surgical treatment

BackgroundIn childhood, for flexible clubfoot deformity, the transfer of the tendon of the tibialis anterior muscle is widely used. In contrast, extensive surgical procedures are required for fixed clubfoot deformities.MethodsWe describe the peroneus longus tendon transfer to the peroneus brevis tendon, additionally to full surgical release, in cases of recurrent fixed clubfoot deformities. The purpose of this surgical technique was to restore and maintain the dynamic balance of foot inversion-eversion during the gait cycle by augmenting the muscular strength of the weak peroneus brevis tendon. We report the prospective study of treatment outcome of twenty recurrent fixed clubfoot deformities in twelve children (20 feet) after failed surgical treatment they had. Anteroposterior and lateral radiographs under full-body weight-bearing and the AOFAS score pre-and postoperatively were used in all patients. For the estimation of the severity of the recurrent clubfoot deformity in each child and to increase the credibility of the AOFAS rating scale, we additionally used a clubfoot sheet score preoperatively and postoperatively (maximum score 100 points for normal foot appearance clinically and radiologically).ResultsThe mean age at surgery was 6,85 (±1,81; 5–11) years. The mean follow-up time was 5,4 (±1,7; 2–8) years. The mean AOFAS ankle-hindfoot rating score increased from 69,85 (±9,51; 53–82) points preoperatively to 94,4 (±2,43; 91–97) points postoperatively. The mean clubfoot sheet rating score increased from 43,00 (±12,18; 15–55) points, preoperatively to 90,0 (±4,58; 80–95) points postoperatively. The two-tailed p-value was < 0,0001.ConclusionsThe transfer of the peroneus longus tendon to the peroneus brevis tendon is a minimal surgical procedure that acts collaboratively in maintaining the correction of foot deformity, achieved by the complete surgical release. Level of Evidence: IV.     

New classification of the distal attachment of the fibularis brevis — Anatomical variations and potential clinical implications

BackgroundAlthough the lateral compartment of the leg is characterized by a high degree of morphological variation, very little information exists on the morphological variability of the fibularis brevis muscle (FBM) and fibularis digiti quinti (FDQ). The main aim of the study was to characterize the morphology of the FBM tendon and its accessory bands, to classify them and to determine the incidence of FDQ. The work attempts to determine the relationship between the types of the insertion of the FBM tendon and the occurrence of FDQ.MethodsClassical anatomical dissection was performed on 102 lower limbs fixed in 10% formalin solution. The morphology of the insertion of the FBM and of the FDQ was evaluated.ResultsThe FBM was present in all specimens. Two types of insertion were observed, the most common being Type I (70.6%): a single distal attachment in which the tendon inserts into the tuberosity at the base of the fifth metatarsal bone. The second most common was Type II (29.4%); this group was divided into three subtypes (A–C). The FDQ was present in 17.7% of specimens and always with Type I FBM.ConclusionBoth the FBM tendon and FDQ present significant morphological variation. Two main types of the FBM tendon determine the presence of the FDQ.Level of evidenceII Basic Science Research.