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Facial nerve injury and microsurgical repair: Experimental and clinical studies
Linköping University, Department of Biomedicine and Surgery, Cell biology. Linköping University, Department of Biomedicine and Surgery, Plastic Surgery, Hand Surgery and Burns. Linköping University, Faculty of Health Sciences.
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Facial palsy is a relatively common clinical condition with a variety of causes. Irrespective of its etiology, facial palsy always represents a very serious problem for the patient. This underlines the need for more effective treatment procedures. Retrospective evaluation of a clinical material of 16 patients with facial palsy treated at the University Hospital of Linköping during the period 1990-2000 showed that to improve the results of microsurgical nerve repair experimental research - controlled studies on homogeneous materials - is imperative.

To produce relevant experimental data we used a rat model. Dissections showed that the mandibular branch (MB) of the rat facial nerve is suitable for experimental studies. Electron rnicroscopy revealed that the normal rat MB contains some 2,200 axons, 1,825 of which are myelinated and show a unimodal size distribution with a mode at 4.5 µm. It was also found that the normal rat MB contains myelinated and unmyelinated sympathetic axons and that about half the C-fibers in the normal rat MB belong to capsaicin-sensitive putative polymodally nociceptive sensory neurons. Importantly, repair of the MB through transmedian grafting in one stage and in two stages, respectively, had largely similar outcomes in terms of anatomy.

These data evoked questions concerning the functional outcome of the two types of repair. Electrophysiological analysis (force recordings andelectromyography) revealed that repair of the rat MB through transmedian grafting in one stage gives a somewhat better functional restoration than repair in two stages.

The observations on the rat MB called for experimental studies on the effects of denervation and repair on mimic muscle. We found that the rat dilator naris muscle (DNM) is suitable for that purpose. The normal DNM contains 1,200 fast MyHC fibers with MyHC IIB fibers predominating. It is a very fast contracting muscle without static functions. A brief denervation of the DNM followed by spontaneous reinnervation by the MB did not influence fiber number, had long-term effects on fiber diameter, and had little effect on fiber types. Fiber number, fiber diameter, and occurrence of fiber types in the DNM remained abnormal both after immediate and delayed surgical repair of the MB. Long-term denervation of the DNM had severe effects on qualitative histology, fiber number, fiber diameter and fiber type distribution. Hence, a long delay between facial nerve injury and repair reduces the chances of restoring normal facial muscle function.

Conventional cross facial grafting includes division of a facial nerve branch (the donor nerve) on the intact side of the face. This non-optimal situation prompted us to test cross-facial grafting with a less traumatic end-to-side procedure in the rat. After coaptation of a sural nerve graft to the rat MB in an end-to-side fashion, including opening of a perineurial window, axons in the donor nerve emitted myelinated and umnyelinated sprouts into the graft. A predegenerated graft did not stimulate sprouting more than a fresh graft. Retrograde tracing with fast blue and fluoro-ruby showed that many sprouts originate from facial motor axons. Of all traced facial motoneurons 50% projected exclusively into the graft, 45% projected into the graft and the donor MB and 5% projected exclusively into the donor MB. This shows that the end-to- side procedure can be used for cross-facial repair of the rat MB.

Altogether these results provide new experimental data, which hopefully will contribute to improvements of the microsurgical treatment of patients with facial palsy.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2002. , 97 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 716
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-25666Local ID: 10042ISBN: 91-7373-159-5 (print)OAI: oai:DiVA.org:liu-25666DiVA: diva2:246214
Public defence
2002-02-22, Berzeliussalen, Hälsouniversitetet, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-09-18Bibliographically approved
List of papers
1. Microsurgical treatment of facial palsy: 10 years of clinical experience
Open this publication in new window or tab >>Microsurgical treatment of facial palsy: 10 years of clinical experience
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The aim of this study is to analyse retrospectively the outcome of microsurgical treatment of patients with facial palsy at the University Hospital of Linköping during the period 1990-2000. Ten patients with facial palsy during 1 year or more completed the evaluation.

Patients subjected to cross facial nerve grafting (CFNG) only included 3 females. The CFNGs appeared to be fimctional in all patients. The measurements revealed good symmetry of the eye rim at rest and at eye closure. All three patients had an asymmetric angle of the mouth with a mean dropping of 2.3 mm at rest and 5.5 mm when smiling. The House-Brackmann grade was 4-5. The average Facial Grading System score was 33. The mean decrease in quality of life was 34%. The mean improvement after treatment was 48%. The degree of post-lesional impairment and the degree of postoperative satisfaction were inversely related. All patients were aware of their disability but they had not completely accepted the current facial status.

The group of patients with CFNG and a free muscle flap transfer included six females and one male. The transferred muscle flaps were activated by the CFNGs. Symmetry of the eye rims at rest was observed in 4 cases and with closure in 3 cases. In asymmetric cases, the mean difference was 1. 8 mm at rest. With eyes closed the mean difference was 4.4 mm. The angle of the mouth was asymmetric in all patients, the mean lowering being 3 mm at rest and 7.5 mm at smile. The House Brackmann grade was 4-5 and the average Facial Grading System score was 31. Four patients with early or congenital facial palsy could not provide data on impairment of quality of life. In the others, the post-lesional impairment was 63%. For all patients in this group the average postoperative improvement was 76%. The patients expressed a rather good acceptance of the achieved status after reconstruction.

Surgical methods to correct facial paresis should be directed towards achieving a symmetric resting tone on the injured side as well as symmetric movements. At present, our methods, when utilised on proper indications and with a precise timing, can give the patient a reasonably good but not perfect result. Further refinements of the technique are needed and should be sought through experimental studies.

Keyword
facial palsy, clinical study, cross facial nerve graft, free microneurvascular muscle flap
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-81517 (URN)
Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2012-09-18Bibliographically approved
2. Repair of the mandibular branch of the rat facial nerve through transmedian grafting in one or two stages: Morphological evaluation
Open this publication in new window or tab >>Repair of the mandibular branch of the rat facial nerve through transmedian grafting in one or two stages: Morphological evaluation
1997 (English)In: Journal of the peripheral nervous system, ISSN 1085-9489, E-ISSN 1529-8027, Vol. 2, no 2, 181-188 p.Article in journal (Refereed) Published
Abstract [en]

This study examined by electron microscopy the normal fibre composition of the mandibular branch (MB) of the rat facial nerve and the outcome of axon regeneration in the MB after transmedian grafting in one or two stages. The average normal MB contained 2,185 axons, 17 % of which were unmyelinated. The myelinated axons had a unimodal diameter distribution (range 1.5-9.5 μm, mode 4.5 μm). After superior cervical ganglionectomy, the MB lost 1/3 of the C-fibres and 10% of the myelinated axons. In neonatally capsaicin-treated rats the occurrence of unmyelinated axons was reduced by about 50%. After repair in one or two stages the MB contained more myelinated and unmyelinated axons than normal. The myelinated axons showed a unimodal size distribution with a subnormal diameter range. Statistical comparisons showed that MBs from both experimental groups were significantly abnormal with respect to total axon number as well as numbers of unmyelinated and myelinated axons. In these respects the grafted MBs did not differ significantly from each other. However, the myelinated axons in MBs from one-stage cases showed larger mean and maximum diameters compared to MBs from two-stage cases. These data suggest that the normal MB of the rat contains myelinated and unmyelinated sympathetic axons and that about half the C-fibres in the normal MB come from capsaicin-sensitive sensory neurons. The comparison of the two reparative procedures used provides evidence in favor of the one-stage alternative.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-81518 (URN)10959232 (PubMedID)
Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2017-12-07Bibliographically approved
3. Repair of the mandibular branch of the rat facial nerve through transmedian grafting in one or two stages: Functional evaluation
Open this publication in new window or tab >>Repair of the mandibular branch of the rat facial nerve through transmedian grafting in one or two stages: Functional evaluation
1998 (English)In: Journal of the peripheral nervous system, ISSN 1085-9489, E-ISSN 1529-8027, Vol. 3, no 1, 54-62 p.Article in journal (Refereed) Published
Abstract [en]

A previous study examined the morphological outcome of axonal regeneration in the mandibular branch (ramus marginalis mandibulae) of the rat facial nerve after transmedian nerve grafting in one or two stages. The present study supplements the morphological data with a functional evaluation. Recordings of the force of tetanic muscle contractions elicited through stimulation of the mandibular branch showed that upper and lower lip data obtained from animals grafted in one stage did not differ significantly from control data. However, animals grafted in two stages exhibited significantly lower muscle forces compared to one-stage data and to control data. Electromyographic recordings of the M-response showed multiple prolonged potential fluctuations with subnormal amplitudes in grafted cases. In both groups of grafted rats, the mean voltage amplitudes recorded from the upper lip were weaker than the amplitudes seen at the angle of the mouth or the lower lip. The two-stage cases exhibited the most obvious deficit. In conclusion, the present results show that, with respect to the functional restoration achieved three months after nerve injury, repair through transmedian grafting in one stage gives better results than repair in two stages. This finding, which conforms with previous morphological data, suggests that the one-stage procedure should be considered for clinical use.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-81519 (URN)10959238 (PubMedID)
Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2017-12-07Bibliographically approved
4. Changes in a rat facial muscle after facial nerve injury and repair
Open this publication in new window or tab >>Changes in a rat facial muscle after facial nerve injury and repair
Show others...
2001 (English)In: Muscle and Nerve, ISSN 0148-639X, E-ISSN 1097-4598, Vol. 24, no 9, 1202-1212 p.Article in journal (Refereed) Published
Abstract [en]

This study describes changes in a rat facial muscle innervated by the mandibular and buccal facial nerve branches 4 months after nerve injury and repair. The following groups were studied: (A) normal controls; (B) spontaneous reinnervation by collateral or terminal sprouting; (C) reinnervation after surgical repair of the mandibular branch; and (D) chronic denervation. The normal muscle contained 1200 exclusively fast fibers, mainly myosin heavy chain (MyHC) IIB fibers. In group B, fiber number and fiber type proportions were normal. In group C, fiber number was subnormal. Diameters and proportions of MyHC IIA and hybrid fibers were above normal. The proportion of MyHC IIB fibers was subnormal. Immediate and delayed repair gave similar results with respect to the parameters examined. Group D rats underwent severe atrophic and degenerative changes. Hybrid fibers prevailed. These data suggest that spontaneous regeneration of the rat facial nerve is superior to regeneration after surgical repair and that immediacy does not give better results than moderate delay with respect to surgical repair. Long delays are shown to be detrimental.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25077 (URN)10.1002/mus.1133 (DOI)9507 (Local ID)9507 (Archive number)9507 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13Bibliographically approved
5. Collateral and terminal sprouting of rat facial nerve axons into fresh or predegenerated nerve grafts after end-to-side neurorrhaphy
Open this publication in new window or tab >>Collateral and terminal sprouting of rat facial nerve axons into fresh or predegenerated nerve grafts after end-to-side neurorrhaphy
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In spite of a continuous technical refinement the results of microsurgical facial nerve repair remain unsatisfactory. This situation prompted the present study, which evaluates axonal regeneration into a rat facial nerve branch after crossfacial end-to-side neurorrhaphy in adult rats. A fresh (group A, 12 rats) or predegenerated (group B, 12 rats) sural nerve graft (SNG) was sutured to a perineurial window in the mandibular branch (MB) of the right facial nerve. It was then tunneled under the chin and sutured to the distal stump of the cut left MB. Twelve weeks after grafting some rats were prepared for electron microscopy (EM). EM examination showed that distal to the window the right MB contained mainly myelinated axons with relatively thick sheaths. Aberrant small-diameter axons with thin sheaths were also observed in most specimens. The counts revealed a total average of about 1 800 axons (14 % unmyelinated) in both groups. In the SNG thin myelinated and unmyelinated axons predominated. The counts showed 900-1 000 axons (63-68% unmyelinated) with no significant difference between the groups. The left MB contained some thin myelinated axons and many unmyelinated axons. The number of axons was 1 200-1300 (81-83% unmyelinated). Again, the two groups did not differ. Other rats were subjected to retrograde tracing. The SNG-right MB coaptation was exposed and each nerve was cut off. Two or 3 days after application of fast blue (FB) to the right MB and fluoro-ruby (FR) to the SNG the animals were perfused with paraformaldehyde and the brain stem was transversely cryosectioned. Counts of labeled motoneurons were used to calculate the percentage of motoneurons with different tracer combinations. The results showed FBlabeling only (motoneurons with axons in the right MB distal to the coaptation) in 5-11% of the counted profiles, FR-labeling only (motoneurons with axons in the SNG) in 43-54% of the profiles, and a combined FB- and FR-labeling (motoneurons with axons in the right MB as well as in the SNG) in 41-46% of the profiles. The two groups did not differ statistically in this respect. We conclude that (i) coaptation of a SNG to the MB of the facial nerve in an end-toside fashion is followed by growth of myelinated and unmyelinated axons from the donor nerve into the graft; (ii) these axons originate from facial motor axons; (iii) some 50% of the traced facial neurons project into the SNG only, 45% project into the SNG and into the MB and 5% project into the MB only; (iv) predegeneration of the SNG does not enhance the number of axons in the graft.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-81520 (URN)
Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2012-09-18Bibliographically approved

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