Maria Grosheva

Factors limiting motor recovery after facial nerve transection in the rat: combined structural and functional analyses

It is believed that a major reason for the poor functional recovery after peripheral nerve lesion is collateral branching and regrowth of axons to incorrect muscles. Using a facial nerve injury protocol in rats, we previously identified a novel and clinically feasible approach to combat axonal misguidance – the application of neutralizing antibodies against neurotrophic factors to the injured nerve. Here, we investigated whether reduced collateral branching at the lesion site leads to better functional recovery. Treatment of rats with antibodies against nerve growth factor, brain‐derived neurotrophic factor, fibroblast growth factor, insulin‐like neurotrophic factor I, ciliary neurotrophic factor or glial cell line‐derived neurotrophic factor increased the precision of reinnervation, as evaluated by multiple retrograde labelling of motoneurons, more than two‐fold as compared with control animals. However, biometric analysis of vibrissae movements did not show positive effects on functional recovery, suggesting that polyneuronal reinnervation – rather than collateral branching – may be the critical limiting factor. In support of this hypothesis, we found that motor end‐plates with morphological signs of multiple innervation were much more frequent in reinnervated muscles of rats that did not recover after injury (51% of all end‐plates) than in animals with good functional performance (10%). Because polyneuronal innervation of muscle fibres is activity‐dependent and can be manipulated, the present findings raise hopes that clinically feasible and effective therapies could be soon designed and tested.

An example of neural plasticity evoked by putative behavioral demand and early use of vibrissal hairs after facial nerve transection.

Abnormally associated movements inevitably occur after surgical repair of the facial nerve. The reason for this postparalytic syndrome is poor navigation of regrowing axons. Despite the valuable functional advantage provided by the easily detected movement of vibrissae in rats, the major investigative tools for establishing the degree of misdirected reinnervation are still electrophysiologic recordings and retrograde tracing. In the present study we complemented data from pre- and postoperative retrograde labeling (FluoroGold, Fast Blue, DiI) of facial motoneurons with an evaluation of whisker movements. Using a video-based motion analysis system, we compared the recovery of vibrissae motor performance in visually normal and blind rats of the Sprague-Dawley strain. The analysis of whisker movement after facial nerve surgery revealed a striking discrepancy between morphologic and functional estimates. Whereas retrograde labeling displayed poor accuracy of target reinnervation and supernumerary axonal branching in both groups, the video-based motion analysis showed a perfect recovery of vibrissae movements in the blind rats. Attributing the complete recovery of whisker movement in the blind rats to an extraordinary plasticity of the facial motoneurons induced by putative behavioral demand and forced overuse, we conclude that the video-based analysis of whisker movement is a valuable tool for studying the progress in functional recovery.

The axotomy-induced neuropeptides galanin and pituitary adenylate cyclase-activating peptide promote axonal sprouting of primary afferent and cranial motor neurones

The neuropeptides galanin and pituitary adenylate cyclase‐activating peptide (PACAP) are markedly up‐regulated in response to peripheral nerve lesion. Both peptides are involved in neuronal differentiation and neurite outgrowth during development. In this study, we investigated the effects of galanin and PACAP on axonal elongation and sprouting by adult rat sensory neurones in vitro and facial motor neurones in vivo. Dissociated rat dorsal root ganglion neurones were plated on laminin substrate and analysed morphometrically. Both the mean axonal length and the number of branch points significantly increased in the presence of galanin or PACAP (2–5 µm). Effects on axonal collateralization were investigated in the rat facial nerve lesion model by direct application of the peptides to collagen‐filled conduits entubulating the transected facial nerve stumps. Triple retrograde labelling of brainstem neurones confirmed that the peptides potently induce axonal sprouting of cranial motor neurones. The number of neurones regenerating into identified rami of the facial nerve increased up to fivefold. Biometrical analysis of whisking behaviour revealed that galanin and PACAP impaired the functional outcome when compared with vehicle‐treated animals 8 weeks after surgery. In conclusion, although galanin and PACAP have been established as neurotrophic molecules with respect to axonal development and regeneration, their potential as treatments for peripheral nerve lesions appears limited because of the extensive stimulation of collateral axon branching. These branches are misrouted towards incorrect muscles and cause impairment in their coordinated activity.

Prognostic Value of Electroneurography and Electromyography in Facial Palsy

Objectives: To compare the prognostic value of electroneurography (ENG) and needle electromyography (EMG) to estimate facial function outcome after acute facial palsy.

Manually-stimulated recovery of motor function after facial nerve injury requires intact sensory input

We have recently shown in rat that daily manual stimulation (MS) of vibrissal muscles promotes recovery of whisking and reduces polyinnervation of muscle fibers following repair of the facial nerve (facial-facial anastomosis, FFA). Here, we examined whether these positive effects were: (1) correlated with alterations of the afferent connections of regenerated facial motoneurons, and (2) whether they were achieved by enhanced sensory input through the intact trigeminal nerve. First, we quantified the extent of total synaptic input to motoneurons in the facial nucleus using synaptophysin immunocytochemistry following FFA with and without subsequent MS. We found that, without MS, this input was reduced compared to intact animals. The number of synaptophysin-positive terminals returned to normal values following MS. Thus, MS appears to counteract the deafferentation of regenerated facial motoneurons. Second, we performed FFA and, in addition, eliminated the trigeminal sensory input to facial motoneurons by extirpation of the ipsilateral infraorbital nerve (IONex). In this paradigm, without MS, vibrissal motor performance and pattern of end-plate reinnervation were as aberrant as after FFA without MS. MS did not influence the reinnervation pattern after IONex and functional recovery was even worse than after IONex without MS. Thus, when the sensory system is intact, MS restores normal vibrissal function and reduces the degree of polyinnervation. When afferent inputs are abolished, these effects are eliminated or even reversed. We conclude that rehabilitation strategies must be carefully designed to take into account the extent of motor and/or sensory damage.

Evaluation of Peripheral Vocal Cord Paralysis by Electromyography

Objective: To analyze the predictive value of electromyography (EMG) after peripheral vocal cord paralysis and to estimate regeneration time.

Manual stimulation of facial muscles improves functional recovery after hypoglossal-facial anastomosis and interpositional nerve grafting of the facial nerve in adult rats.

The facial nerve in humans is often prone to injuries requiring surgical intervention. In the best case, nerve reconstruction is achieved by a facial-facial anastomosis (FFA), i.e. suture of the proximal and distal stumps of the severed facial nerve. Although a method of choice, FFA rarely leads to a satisfactory functional recovery. We have recently devised and validated, in an established experimental paradigm in rats, a novel strategy to improve the outcome of FFA by daily manual stimulation (MS) of facial muscles. This treatment results in full recovery of facial movements (whisking) and is achieved by reducing the proportion of functionally detrimental poly-innervated motor end-plates. Here we asked whether MS could also be beneficial after two other commonly used surgical methods of clinical facial nerve reconstruction namely hypoglossal-facial anastomosis (HFA) and interpositional nerve grafting (IPNG) which, however, seem to have a poorer outcome compared to FFA. Compared to FFA, daily MS for 2 months after HFA and IPGN did not completely restore function but, nevertheless, significantly improved the amplitude of whisker movements by 50% compared with untreated animals. Functional improvement was associated with a reduction in the proportion of polyinnervated end-plates. MS did not reduce the extent of axonal branching at the lesion site nor the subsequent misdirected axonal regrowth to inappropriate targets. Our data show that a simple approach leading to improved quality of muscle fiber reinnervation is functionally beneficial after different types of clinically relevant surgical interventions.

Manual stimulation, but not acute electrical stimulation prior to reconstructive surgery, improves functional recovery after facial nerve injury in rats.

UNLABELLED The outcome of peripheral nerve injuries requiring surgical repair is poor. Recent work suggested that electrical stimulation (ES) of the proximal nerve stump to produce repeated discharges of the parent motoneurons for one hour could be a beneficial therapy if delivered immediately prior to reconstructive surgery of mixed peripheral nerves. PURPOSE We tested whether ES has a positive influence on functional recovery after repair of a purely motor nerve, the facial nerve. METHODS Electrical stimulation (20 Hz) was delivered to the proximal nerve stump of the transected facial nerve for 1 hour prior to nerve reconstruction by end-to-end suture (facial-facial anastomosis, FFA). For manual stimulation (MS), animals received daily rhythmic stroking of the whisker pads. Restoration of vibrissal motor performance following ES or MS was evaluated using video-based motion analysis. We also assessed the degree of collateral axonal branching at the lesion site, by counting motoneuronal perikarya after triple retrograde labeling, and estimated the quality of motor end-plate reinnervation in the target musculature. Outcomes at 4 months were compared to animals receiving sham stimulation (SS) or MS. RESULTS Neither protocol reduced the degree of collateral sprouting. ES did not improve functional outcome and failed to reduce the proportion of polyinnervated motor end-plates. By contrast, MS restored normal whisking function and reduced polyinnervation. CONCLUSION Whereas acute ES is not beneficial for facial nerve repair, MS provides long-term benefits.

Manual stimulation of the orbicularis oculi muscle improves eyelid closure after facial nerve injury in adult rats

We have shown that manual stimulation of rat whisker‐pad muscles following facial–facial‐anastomosis (FFA) restores normal whisking by lowering the proportion of polyinnervated motor endplates. Here we examined whether manual stimulation of the orbicularis oculi muscle (OOM) after FFA would also improve outcome. Blink responses to standardized air puffs were analyzed using video‐based motion analysis. Two months after FFA, blink capacity was impaired, as indicated by a largely increased minimum distance between the eyelids after air‐puff stimulation compared with intact rats (2.7 ± 0.4 vs. 0.2 ± 0.01 mm). Manual stimulation reduced this deficit by a factor of two (1.3 ± 0.5 mm). The functional improvement after manual stimulation was associated with a 2‐fold decrease in the proportion of polyinnervated OOM endplates (21 ± 10% vs. 42 ± 10% without manual stimulation, 0% in intact rats). We conclude that manual stimulation is a noninvasive and simple procedure with immediate potential for clinical rehabilitation of eyelid closure following facial nerve injury. Muscle Nerve, 2008

Sialoendoscopy: prognostic factors for endoscopic removal of salivary stones.

OBJECTIVE To detect prognostic factors for successful sialoendoscopic removal of salivary stones. DESIGN Retrospective case series. SETTING Tertiary referral hospital. PATIENTS Forty-nine consecutive patients who underwent sialoendoscopy for sialolithiasis between January 1, 2008, and January 1, 2010, at University Hospital of Cologne, Cologne, Germany. INTERVENTIONS Diagnostic and interventional sialoendoscopy using local anesthesia. MAIN OUTCOME MEASURES Stone removal rate, size, mobility, shape, and location, as well as clinical follow-up data. RESULTS Sixty-one percent (39 of 64) of all salivary stones were removed endoscopically. The cutoff point for endoscopic removal was between 5 and 6 mm in stone diameter. Small size, good mobility, round or oval, and distal location of a salivary stone were positive prognostic factors for sialoendoscopic removal, with sialolith mobility having the greatest effect in multivariate analysis. CONCLUSION Small size, good mobility, round or oval, and distal location of a salivary stone in the main duct predict significantly greater probability of endoscopic removal and consequently are positive prognostic factors.