The problem of synkinesis and contracture in cases of hemifacial spasm and Bell's palsy

Blink reflex excitability in patients with Hemifacial spasm exhibiting different abnormal discharge patterns: from early isolated discharges to later grouped bursts or tonic spasms

OBJECTIVE

We studied blink reflex (BR) and BR excitability recovery (BRER) in patients with hemifacial spasm (HFS) exhibiting different abnormal discharge patterns. We hypothesized that patients with groups of clonic or tonic burst activities appear later in the disease course and may have more excitability of the BR circuit at the brainstem compared to patients with isolated twitchings, which occur earlier.

METHODS

We included 124 patients with botulinum toxin-naive HFS (mean age 50.6 ± 13.3 years) and 40 healthy subjects. We performed surface polymyography on facial muscles in patients and classified them according to the abnormal discharge pattern: isolated discharges, grouped bursts forming random sequences, tonic spasms, and a combination of these activities. Then, we recorded BR and BRER at 200, 600, and 1000 ms interstimulus intervals. We compared disease duration, R1 and R2 latencies, R2 area-under-the-curve (AUC), and BRER% (i) between healthy subjects and patients and (ii) among groups of patients with different abnormal discharge patterns.

RESULTS

There were isolated discharges in 28 patients, grouped bursts forming random sequences in 42, and continuous muscle activity with tonic spasms in one. The remaining patients had combinations. Mean R1 and R2 latencies were significantly longer, and mean R2 AUC was significantly higher on the symptomatic side of patients compared to healthy subjects. The mean BRER was enhanced on both sides in patients than in healthy subjects (p < 0.001). However, it was similar among patient groups with different abnormal discharge patterns (p > 0.05). The mean disease duration in patients with isolated discharges was shorter (3.3 ± 2.0 years) than those with grouped bursts or tonic spasms (p = 0.002; Kruskal-Wallis test).

CONCLUSION

Our study observed that excitability at the brainstem was similar in HFS patients with different abnormal discharge patterns, suggesting that the difference in discharge patterns in HFS may be due to a reason other than the difference in BR excitability.

Therapeutic strategies in post-facial paralysis synkinesis in pediatric patients

Synkinetic movements comprise abnormal involuntary contractions of one or more facial muscle groups which follow the desired contraction of another facial muscle group. They are frequently encountered in patients with long standing facial paralysis and seriously affect their psychological status due to the impairment of their facial appearance, function and emotional expressivity.

PATIENTS AND METHODS

Eleven pediatric patients (2 male and 9 female) presenting with post-facial paralysis synkinesis were included in the study. Mean age was 10.3±4 years and mean denervation time 72.5 months.

RESULTS

Patients underwent the following types of treatment: --Cross facial nerve grafting (CFNG) and secondary microcoaptations with botulinum toxin injection which had an improvement of 100% (3 in the 3 grade synkinesis scale) (n=2). --Cross facial nerve grafting (CFNG) and secondary microcoaptations without botulinum toxin injection which had an improvement of 66%(2 in the 3 grade synkinesis scale) (n=5). --CFNG and direct muscle neurotization with (n=2) or without (n=1) botulinum toxin injection where the improvement was 33%. --Contralateral nasalis muscle myectomy was performed in one patient along with CFNG and secondary microcoaptations which resulted in 66% synkinesis improvement. Biofeedback was invariably undertaken by all patients. Postoperative improvement in eye closure and smile was also noted in the respective cases treated for synkinesis ranging from 25 to 50%, with all patients achieving optimum functional return.

CONCLUSION

CFNG with secondary microcoaptations and botulinum toxin injections was found to be a very efficient surgical modality addressing post-facial palsy synkinesis with high improvement in facial function and symmetry. Facial neuromuscular re-education contributes considerably in the treatment.

Effects of antineoplastic agents on the peripheral nerves under a surgical tissue expansion procedure: An experimental study

BACKGROUND

Elongation of peripheral nerve by the use of a tissue expander is helpful to repair nerve defects. This study was designed to investigate the effects of some antineoplastic agents on the peripheral nerves under a surgical tissue expansion procedure.

MATERIALS AND METHODS

Twenty-five Wistar rats were used in this study. Following the exposition of the sciatic nerve and placement of two 10/0-nylon sutures in the epineurium 20 mm apart, a tissue expander was then placed under it. Inflation of the expander was immediately accomplished by the separate percutaneous injections of 6, 6, and 8 ml for every 3 min under general anesthesia. The expander was fully deflated at the end of each 3 min The distance between two sutures was measured 1 h later to measure the rate of elongation. Rats were randomly divided into five groups (according to the administered drugs), each consisting of five rats (10 sciatic nerves). Normal saline (1 ml) in the control group (group I), cyclophosphamide (15 mg/kg) in the group II, cisplatinum (3 microg/kg) in the group III, mitomycin-C (0.5 mg/kg) in the group IV and 5-fluorouracil (10 mg/kg) in the group V were injected intravenously. Intravenous injections of drugs were performed via the tail vein 30 min before expansion, 48 and 96 h after removal of expander. The incision was reopened on the third and seventh postoperative days, and five sciatic nerves of each group were exposed and then the pinching test was performed to measure regeneration distance. Electroneurographic changes were recorded. The expanded portion of the sciatic nerve between two sutures was harvested for histological evaluation.

RESULTS

There is no significant difference between the elongation rates of all groups (P < 0.05). Histologic evaluation showed that inflammatory changes, vacuolization, intraneural edema, demyelination, axonal changes in the control group, the cisplatinum group, and the mitomycin-C group. These changes were significantly decreased in the cyclophosphamide group and the 5-fluorouracil group. In the cyclophosphamide group and the 5-fluorouracil group, the amplitude of compound action potential (CAP) values were significantly higher and the latency was significantly shorter (P > 0.05).

CONCLUSION

We believed that cyclophosphamide and 5-fluorouracil may be helpful in tissue expansion of peripheral nerves, by decreasing the effects of the ischemia-reperfusion injury on the expanded peripheral nerves.

Role of postoperative magnetic resonance imaging after microvascular decompression of the facial nerve for the treatment of hemifacial spasm

OBJECTIVE

This study was performed to investigate the role of postoperative three-dimensional short-range magnetic resonance angiography in the prediction of clinical outcomes after microvascular decompression (MVD) for the treatment of hemifacial spasm.

METHODS

We examined pre- and postoperative magnetic resonance imaging scans obtained between March 1999 and May 2000 for 122 patients with hemifacial spasm, to evaluate the degree of detachment of the vascular contact and changes in the positions of offending vessels. The degree of vascular decompression of the facial nerve root was classified into three groups, i.e., contact, partial decompression, or complete decompression. Contact was defined as unresolved compression, as indicated by postoperative three-dimensional short-range magnetic resonance angiography. Partial decompression was defined as incompletely resolved compression; vascular indentation of the facial nerve was improved, but contact with the facial nerve remained. Complete decompression was defined as completely resolved compression. These findings were compared with the surgical findings and clinical outcomes.

RESULTS

Of 122 patients with MVD, complete decompression of offending vessels at the root entry zone of the facial nerve was observed for 106 patients (86.9%), partial decompression was observed for 10 patients (8.2%), and contact with offending vessels was observed for 6 patients (4.9%) by using postoperative three-dimensional short-range magnetic resonance angiography. Our study demonstrated that the types of offending vessels affected neither the degree of decompression of the root entry zone of the facial nerve nor surgical outcomes (P > 0.05). Also, there was no significant relationship between the degree of decompression and improvement of symptoms (P > 0.05). Furthermore, there was no significant relationship between the degree of decompression and the timing of symptomatic improvement (P > 0.05).

CONCLUSION

Our data suggest that MVD of the facial nerve alone may not be sufficient to resolve symptoms for all patients with hemifacial spasm. Therefore, unknown factors in addition to vascular compression may cause symptoms in certain cases, and it may be necessary to remove those factors, simultaneously with MVD, to obtain symptom resolution.

Electroneurography during facial nerve expansion

With the use of tissue-expansion techniques, it is possible to elongate the facial nerve without impairing its function. The rate of expansion is limited by ischemic events imposed by stretching of the nerve and by anatomic characteristics of the nerve segment. In this study, we used various electroneurography techniques to determine the first sign of facial dysfunction during expansion. The main objective of the study was to ascertain test-retest variability of electroneurography techniques. Facial nerves were expanded in 16 cats with the use of a tissue expander secured more deeply to the main trunk. We conducted electroneurography measurements with the use of surface electrodes, temporary needle electrodes, and permanently implanted electrodes. Technique-dependent variations encountered with the surface electrodes made this method unreliable. Using implanted electrodes, we noted gradual worsening of the compound-action potential amplitude with increasing expansion. During acute expansion, reduction in compound-action potential amplitude was correlated with clinically observed deterioration of facial-nerve function. In this study, electroneurography with implanted electrodes was found to be the most reliable predictor of the rate of successful facial nerve expansion.

Plasticity of the extracranial facial nerve

Although the expansion properties of peripheral nerves have been a matter of considerable study in recent years, investigations of the plasticity of cranial nerves, including the facial nerve, have been lacking. Clinicians, however, have long recognized the tenacity of facial nerve function in patients with slow-growing benign tumors that enormously distort the nerve. An experimental study was designed to assess whether tissue expansion techniques can be applied to the extracranial portion of the facial nerves of cats. In eight cats the frontozygomatic branch of the facial nerve was expanded by stages in seven sessions over a period of 40 days. The length of the nerve increased an average of 95% without significantly impairing nerve function. Pressure changes in the expander averaged 75 mm Hg during each stage of expansion. Electroneurography was performed after each injection of the expander. Statistical analysis of these data did not show consistent evidence of demyelination or denervation, and all but one cat exhibited a normal blink reflex and had normal electromyographic findings at the end of the experiment. Histologic examination of the expanded nerves, however, did show inflammatory changes, intraneural edema, and occasional demyelination.

Hemifacial spasm: a review

Hemifacial spasm can be diagnosed by observation and clinical history. It is thought to arise primarily from compression of the facial nerve at the pons, usually by an adjacent artery. Although many approaches to treatment have been tried, the most effective is microvascular decompression of the facial nerve at the pons. That operation has well-recognized risks, including ipsilateral deafness. The latter complication ordinarily can be avoided by the use of intraoperative monitoring of auditory evoked potentials.

The cranial nerve vascular compression syndrome: II. A review of pathophysiology

The various hypotheses regarding the pathophysiologies of trigeminal neuralgia and hemifacial spasm are reviewed, and the results of recent physiological studies on the pathogenesis of hemifacial spasm are discussed. Evidence is presented that strongly supports the hypothesis that the symptoms and signs of hemifacial spasm are caused by hyperactivity in the facial motonucleus. Some of the contradictions regarding the prevalence of vascular conflicts in the cerebellopontine angle and the symptoms of vascular compression are discussed, and a hypothesis is presented that assumes that a suitable substrate must be present, in addition to vascular compression of the respective cranial nerve root, for the symptoms and signs of a cranial nerve vascular compression disorder to develop. Finally, it is discussed how this hypothesis can explain some of the differences between the disorders that can be cured by microvascular decompression of respective cranial nerves.

Ephaptic transmission in hemifacial spasm: a single-fiber EMG study

In two patients with hemifacial spasm (HFS), single-fiber EMG recordings in facial muscles demonstrated low jitter in the late responses produced by stimulation of peripheral branches to other facial muscles. Surgical decompression of the facial nerve in one patient was followed by clinical improvement and disappearance of the abnormal late responses. These observations are consistent with the hypothesis that there is ephaptic transmission among peripheral branches of the facial nerve at the site of compression in HFS.

Physiological abnormalities in hemifacial spasm studied during microvascular decompression operations

The pathophysiology of hemifacial spasm was studied using electrophysiologic recordings made during neurosurgical operations to relieve it by microvascular decompression of the facial nerve near its entrance into the brain stem. Electrical stimulation of the temporal or the marginal mandibular branch of the facial nerve resulted in a response not only from the muscles that were innervated by the branch of the facial nerve that was stimulated, but also from other muscles, as evidenced by EMG recordings. This "lateral spread" of antidromic activity was facilitated by stimulation at a high rate (50 pps): the response increased five- to tenfold within a few seconds. When the repetition rate was reduced to the initial low stimulus rate (2 to 5 pps), facilitation continued for periods lasting from a few seconds to several minutes. The amplitude of the response of the supraorbital reflex (blink reflex), which can be elicited in patients with hemifacial spasm intraoperatively on the affected side despite the use of inhalation anesthesia, also increased after brief stimulation at a high rate (50 pps). After the facial nerve had been decompressed, both the lateral spread response and the blink reflex response were absent. These results support the hypothesis that hemifacial spasm is the result of hyperexcitability of the facial motor nucleus and facilitation of cross-transmissions between cells in the nucleus that innervate different parts of the face.

The identification of neuroapraxia, axonostenosis and trigger zone in facial nerve pathology

The classical electromyographic investigations and simultaneous recordings of voluntary activity and M responses from muscles of both the upper and lower branch of the facial nerve were carried out in 5 patients with Bell's palsy. R1 responses were also recorded. All investigations were extended to the healthy side. With the aim of localizing the point of axonostenosis with axonal atrophy we investigated the following parameters: conduction velocity (c.v.) in the fallopian canal, c.v. in the external facial nerve, side difference of R1-M. In one case of amyotrophic lateral sclerosis with previous Bell's palsy signs of collateral sprouting and of ephaptic transmission were detected.

Abnormal facial movements. Guide to differential diagnosis

Spontaneous facial movements are disturbing to those who have them, yet some such movements are benign and cause no more than cosmetic embarrassment. Other abnormal facial movements, however, are more serious and can be associated with neurologic disorders such as multiple sclerosis, brainstem tumor, peripheral neuropathy, and Guillain-Barré syndrome. Occasionally, an abnormal movement of the face is the first sign of such an underlying disorder. Accurate differential diagnosis of these perplexing movement disorders is imperative in determining prognosis.

Electrophysiology of the facial nerve in hemifacial spasm: ectopic/ephaptic excitation

Pathologic and pathophysiologic findings in hemifacial spasm are reviewed in connection with recent theoretical and experimental studies of ectopic/ephaptic excitation. The intracranial segment of the normal facial nerve is ensheathed by an arachnoid membrane only and shows no fascicular organization. In hemifacial spasm, this segment shows signs of demyelination. Several electrical phenomena relating to ectopic excitation, ephaptic transmission between facial nerve fibers, and autoexcitation can be reproduced in clinical electrophysiologic studies of hemifacial spasm. These abnormalities gradually disappear after facial nerve decompression in the cerebellopontine recess. It is concluded that the normal facial nerve is vulnerable to minor compression, the primary pathophysiologic mechanism in hemifacial spasm is ectopic/ephaptic excitation due to compression and demyelination of the intracranial segment of the facial nerve, and the facial nerve in hemifacial spasm is a useful model for the study of ephaptic transmission, which has provided new information about the resolution of abnormal electrical events after decompression.

On the origin of synkinesis in hemifacial spasm: results of intracranial recordings

Recordings were made from facial muscles and the facial nerve near its entrance into the brain stem in patients with hemifacial spasm (HFS). The purpose of this study was to determine if the synkinesis commonly seen in patients with HFS could be linked to ephaptic transmission at the presumed site of the lesion (at the root entry zone (REZ) of the facial nerve). When the mandibular branch of the facial nerve was electrically stimulated, a response could be recorded from the orbicularis oculi muscles during the operation. The latency of the earliest response was 11.03 +/- 0.66 msec (mean response of seven patients +/- standard deviation (SD]. With equivalent stimulation a response could also be recorded from the facial nerve near the REZ; the latency of this response was 3.87 +/- 0.36 msec. Stimulation of the facial nerve at the same location yielded a response from the orbicularis oculi muscle, with a latency of 4.65 +/- 0.25 msec. The latency of the earliest response from the orbicularis oculi muscle to stimulation of the marginal mandibular branch of the facial nerve (11.3 msec) is thus larger than the sum of the conduction times from the points of stimulation of the marginal mandibular branch to the REZ of the facial nerve and from the REZ of the facial nerve to the orbicularis oculi muscle (8.52 +/- 0.38 msec). It is therefore regarded as unlikely that the earliest response of the orbicularis oculi muscle to stimulation of the mandibular branch of the facial nerve is a result of "crosstalk" in the facial nerve at a location near the REZ, and it seems more likely that HFS caused by injury of the facial nerve is a result of reverberant activity in the facial motonucleus, possibly caused by mechanisms that are similar to kindling.

Masticatory spasm in facial hemiatrophy

Spontaneous spasms began in the left masseter muscle six years following the onset of facial hemiatrophy in a young woman. A dental procedure had preceded the original facial wasting by four weeks. The electromyographic findings were similar to those described in hemifacial spasm and consisted of brief bursts of one to four morphologically different potentials, each firing at rates of up to 200 Hz. The findings demonstrate that spontaneous activity due to nerve injury can arise in muscles innervated by the trigeminal nerve.

Hemifacial spasm and the facial nucleus

Spontaneous and associated hyperkinetic facial movements and contracture which follow injury to the seventh cranial nerve (postparalytic hemifacial spasm) or arise without known previous injury (cryptogenic hemifacial spasm) are pathological motor phenomena not found in the distribution of other cranial or somatic motor nerves. The commonly expressed hypotheses of pathogenesis--aberrant regeneration and fiber excitation by false synapse formation (ephapses) at the site of injury--cannot account for all aspects of these phenomena or for the uniqueness of such movements to the distribution of the seventh nerve. The suggestion is made that the existing diversity of facial motor behavior, which encompasses voluntary, emotional, and especially automatic, associated, and reflexive movements, is based on a unique central organization that sets it apart from other motor groups. I hypothesize that because of this organization, the changes following axonal injury--which include selective deafferentation, glial response, axonal sprouting, functional reconnection, and hyperexcitability from dendritic spike generation--can unmask and augment automatic, associated, and reflexive movements already present in the facial neuronal network to result in facial hyperkinesia.