Postparalytic Syndrome Research Articles

Facial Nerve Repair by Muscle-Vein Conduit in Rats: Functional Recovery and Muscle Reinnervation.

The facial nerve is the most frequently damaged nerve in head and neck traumata. Repair of interrupted nerves is generally reinforced by fine microsurgical techniques; nevertheless, regaining all functions is the exception rather than the rule. The so-called "postparalytic syndrome," which includes synkinesia and altered blink reflexes, follows nerve injury. The purpose of this study was to examine if nerve-gap repair using an autologous vein filled with skeletal muscle would improve axonal regeneration, reduce neuromuscular junction polyinnervation, and improve the recovery of whisking in rats with transected and sutured right buccal branches of the facial nerve. Vibrissal motor performance was studied with the use of a video motion analysis. Immunofluorescence was used to visualize and analyze target muscle reinnervation. The results taken together indicate a positive effect of muscle-vein-combined conduit (MVCC) on the improvement of the whisking function after reparation of the facial nerve in rats. The findings support the recent suggestion that a venal graft with implantation of a trophic source, such as autologous denervated skeletal muscle, may promote the monoinnervation degree and ameliorate coordinated function of the corresponding muscles.

Effect of surgically guided axonal regrowth into a 3-way-conduit (isogeneic trifurcated aorta) on functional recovery after facial-nerve reconstruction: Experimental study in rats.

The "post-paralytic syndrome" after facial nerve reconstruction has been attributed to (i) malfunctioning axonal guidance at the fascicular (branches) level, (ii) collateral branching of the transected axons at the lesion site, and (iii) intensive intramuscular terminal sprouting of regenerating axons which causes poly-innervation of the neuromuscular junctions (NMJ). The first two reasons were approached by an innovative technique which should provide the re-growing axons optimal conditions to elongate and selectively re-innervate their original muscle groups. The transected facial nerve trunk was inserted into a 3-way-conduit (from isogeneic rat abdominal aorta) which should "guide" the re-growing facial axons to the three main branches of the facial nerve (zygomatic, buccal and marginal mandibular). The effect of this method was tested also on hypoglossal axons after hypoglossal-facial anastomosis (HFA). Coaptational (classic) FFA (facial-facial anastomosis) and HFA served as controls. When compared to their coaptation (classic) alternatives, both types of 3-way-conduit operations (FFA and HFA) promoted a trend for reduction in the collateral axonal branching (the proportion of double- or triple-labelled perikarya after retrograde tracing was slightly reduced). In contrast, poly-innervation of NMJ in the levator labii superioris muscle was increased and vibrissal (whisking) function was worsened. The use of 3-way-conduit provides no advantages to classic coaptation. Should the latter be impossible (too large interstump defects requiring too long interpositional nerve grafts), this type of reconstruction may be applied. (230 words).

Facial nerve injury in neurosurgery: a rehabilitation potential of botulinum therapy

Surgical treatment of posterior cranial fossa and cerebellopontine angle tumors is associated with a risk of facial nerve dysfunction. The causes for facial muscle paresis include nerve compression by the tumor, destruction of the nerve structure by the tumor growing from nerve fibers, nerve injury during surgical removal of the tumor, etc. The first 3 months after facial nerve injury are a potential therapeutic window for the use of botulinum toxin type A (BTA). During this period, the drug is introduced both in the healthy side to improve the facial symmetry at rest and during mimetic movements and in the affected side to induce drug-induced ptosis. Post-paralytic syndrome develops 4-6 months after facial nerve injury. At this stage, administration of BTA is also an effective procedure; in this case, drug injections are performed on the affected side at small doses and symmetrically on the healthy side at doses doubling those for the affected side. BTA injections are mandatory in complex treatment of facial muscle paralysis.

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.

Transplantation of olfactory mucosa minimizes axonal branching and promotes the recovery of vibrissae motor performance after facial nerve repair in rats.

The occurrence of abnormally associated movements is inevitable after facial nerve transection. The reason for this post-paralytic syndrome is poor guidance of regrowing axons, whereby a given muscle group is reinnervated by misrouted axonal branches. Olfactory ensheathing glia have been shown to reduce axonal sprouting and stimulate axonal regeneration after transplantation into the spinal cord. In the present study, we asked whether transplantation of olfactory mucosa (OM) would also reduce sprouting of a damaged peripheral pure motor nerve. The adult facial nerve was transected, and the effect of the OM placed at the lesion site was analyzed with regard to the accuracy of target reinnervation, axonal sprouting of motoneurons, and vibrissal motor performance. Accuracy of target reinnervation and axonal sprouting were studied using preoperative/postoperative labeling and triple retrograde labeling of facial motoneurons, respectively. The vibrissal motor performance was monitored using a video-based motion analysis. We show here that implantation of OM, compared with simple facial-facial anastomosis, (1) improved the protraction, amplitude, angular velocity, and acceleration of vibrissal movements up to 80% of the control values, (2) reduced the percentage of branching motoneurons from 76 to 39%, and (3) improved the accuracy of reinnervation from 22 to 49%. Moreover, we present evidence, that transplanted OM but not buccal mucous membrane induced a sustained upregulation of trophic factors at the lesion site. It is concluded that transplantation of OM to the transected facial nerve significantly improves nerve regeneration.

The use of curare-like agents in resuscitation

To analyse current data on use of neuromuscular blocking agents (NBA) in the intensive therapy unit (ITU) patients and to propose practice guidelines. We did a Medline search of French and English language articles on NBA administration in ITU patients from 1960 to 1998. Data were also selected from our own collection of articles and books. Original articles, clinical cases, letters to the editor and review articles were considered. Data on pharmacology of NBA in the ITU patient were extracted, as well as data on administration patterns and cost. The indications for myorelaxation in ITU patients include either short term use, as in anaesthesia, or long term administration for facilitation of mechanical ventilation, control of increased intracranial pressure, status epilepticus, tetanus and oxygen demand in case of muscular hyperactivity, diagnostic and therapeutic procedures facilitation. A beneficial effect of NBA on the prognosis of the disease for which these agents have been used is not yet proven. Suxamethonium, because for its short onset time and duration of action, is the agent of choice for endotracheal intubation if myorelaxation is required. Among the benzylisoquinolines, atracurium and besilate of cisatracurium are convenient agents in ITU patients, whereas mivacurium is of no special interest. Among the aminosteroids, pancuronium and vecuronium are the most often used agents in the ITU. Rocuronium has not yet been extensively assessed. Myorelaxants carry risks for morbidity and mortality. The difficulty to assess the neurological status and the level of sedation is a recognised adverse effect. An accidental disconnection from the circuit and the resulting asphyxia is nowadays recognised without delay by the ventilator. NBAs increase the rate of bronchopulmonary infections. Cardiovascular complications include extreme bradycardia or sinus arrest following vecuronium administration, and cardiac arrest after suxamethonium injection mainly in burned or traumatised patients. Conversely to anaesthesia, NBAs do not carry a significant risk for anaphylactic or anaphylactoid complications in the ITU. Tachyphylaxis occurs mainly in burns and other pathologies modifying acetylcholine receptors. Neuromuscular complications include myopathy from steroids, postparalytic syndrome, deconditioning syndrome and intensive care polyneuropathy. Prolonged curarisation after discontinuation of NBA administration has a multifactorial origin and must be differentiated from neuromuscular complications. For prolonged neuromuscular blockade, pancuronium, vecuronium and atracurium are the agents of choice. The association with an adequate sedation is essential. Assessment of depth of neuromuscular blockade is not based on clinical symptoms but on train-of-four (TOF) twitch monitoring. A convenient basic relaxation is usually obtained with the suppression of the two last responses to TOF. The use of NBA in ITU patient should result from a rational decision making procedure, the blockade titrated with a TOF monitor and maintained as superficially and shortly as possible.

Nerve-plasty interventions on the facial nerve in the elderly patient--morphological evaluation of disappointing functional results

Nerve sutures such as facial-facial anastomosis are helpful methods for recovery of facial movements after peripheral nerve lesions. Most of the results on neuronal regeneration were based on experiments with young or young adult animals. In contrary the vast majority of the diseases (cholesteatoma or tumors of the parotid gland) causing facial nerve lesions are in aged patients. Therefore, we compared the original data from two recently published articles concerning the axonal outgrowing process after facial-facial-anastomosis in young-adult and aged rats. In additional, we tried to explain the clinically observed postparalytic syndrome (synkinesia, autoparalytic syndrome,...) after surgical interventions on the facial nerve with the experimental results in the rat. As an important result, we could not find spontaneous loss of facial motoneurons on the control side in the aged rats. On the operated side, two results have to be emphasized. The initial regeneration (10-42 days after the operation) showed a significant faster reinnervation in the group of young rats. The aged rats showed an apparent hyperinnervation after axonal outgrow to the mimic muscles has been accomplished. Both experimental observations are in agreement with our clinical experiences. After facial nerve surgery, aged patients show a delayed recovery of the mimic functions and a more pronounced postparalytic syndrome. A morphological explanation one can bear is that the delayed reinnervation causes the extreme hyerinnervation, which leads to a simultaneous innervation of different muscles by same facial motoneurons.