Intra-operative monitoring by facial electromyographic responses during microvascular decompressive surgery for hemifacial spasm

The facial electromyographic response was monitored intraoperatively in 40 patients with hemifacial spasm who were operated on by microvascular decompression of the facial nerve. All 40 patients showed an abnormal facial electromyographic response (lateral spread response) with a latency of about 10 msec after stimulation. The abnormal response resolved before decompression in 22, resolved immediately with decompression in 16, and failed to resolve in two. Of the 38 patients in whom the abnormal response disappeared during surgery, 36 were postoperatively free from hemifacial spasm and two had mild hemifacial spasm. The two patients in whom the lateral spread response did not disappear during surgery showed persistent hemifacial spasm. In conclusion. Disappearance of the lateral spread response during surgery correlated with the absence of hemifacial spasm in the early postoperative period. The prognosis of hemifacial spasm was good in cases in whom the lateral spread response disappeared. Therefore, the authors think that intra-operative facial electromyography is very useful in assessing the efficacy of microvascular decompression and in predicting the prognosis of hemifacial spasm.

Electrophysiological investigation of hemifacial spasm: F-waves of the facial muscles

In patients with hemifacial spasm (HFS), the spasm is due to cross-compression of the facial nerve by a blood vessel. There are currently two hypotheses for the mechanism of HFS: 1) the spasm is caused by ephaptic transmission and an increase in excitability at the site of compression; and 2) the spasm is caused by hyperexcitability in the facial nerve nucleus. In peripheral nerves, F-waves, which result from the backfiring of antidromically activated anterior horn cells, have been proposed as indices of proximal motoneuron conduction and anterior horn cell excitability. Enhancement of the F-waves indicates increased anterior horn cell excitability. We have therefore measured F-waves in the facial muscle of HFS patients in order to investigate the excitability of the facial nerve nucleus. The authors obtained facial nerve evoked responses from 20 HFS patients before microvascular decompression (MVD), 10 HFS patients after MVD and 10 healthy controls. The F-waves, obtained with surface electrodes from the mentalis muscle, were the second response after the M-wave. On the patient's spasm side, the F-wave duration, F/M amplitude ratio and frequency of F-wave appearance significantly increased compared with those of the normal side or healthy controls; minimum latency and chronodispersion did not significantly differ between these groups. In patients whose spasm disappeared completely following MVD, the abnormal muscle response (lateral spread), which is a characteristic sign of HFS, and the enhancement of the F-wave eventually also disappeared. Because of the correlation between HFS and F-waves, the authors' study supports the hypothesis that the cause of HFS is hyperexcitability of the facial motonucleus.

Facial nerve neuromas: diagnosis and management

Facial nerve neuromas are uncommon tumors that involve the facial nerve. There is no classic presentation of these tumors. This study presents a series of 22 patients with facial neuromas managed from 1977 to 1993. Facial nerve dysfunction was the most common complaint, present in 90.5% of cases. Hearing loss was the second most common complaint and was found in 76.2% of cases. High resolution computed tomography and magnetic resonance imaging with gadolinium proved to be the most accurate methods of preoperative assessment of these tumors and are complementary in selected cases. Different surgical approaches were performed according to tumor location and preoperative hearing level. In all cases long-term follow-up showed no tumor recurrence, and acceptable return of facial function was noted in 80% of cases.

Intracranial facial neuromas: total tumor removal with facial nerve preservation: a new surgical technique

Neuromas of the facial nerve are uncommon tumors. The majority of cases involve the intratemporal and parotid areas. Since their description in 1930, there have been only 26 cases of intracranial facial neuroma reported in the world literature. Of these, 19 involved the middle cranial fossa, and only seven tumors extended into or originated in the posterior cranial fossa. In this location, the seventh nerve is surrounded by a very delicate and thin arachnoid casing. Thus, although these tumors are encapsulated, there is usually no obvious plane of separation between the tumor and perineurium. As a result, the seventh nerve has been sacrificed routinely. Two patients with posterior fossa facial neuromas underwent total tumor removal with a new surgical technique permitting preservation of the nerve fascicles via a translabyrinthine approach. Each patient has good recovery of seventh nerve function with no evidence of recurrence six and nine years later, respectively. Leaving the nerve fascicles intact appears to result in good reinnervation following total tumor removal. The potential value of this technique is best considered in the context of diagnostic and therapeutic options for facial neuromas in general. Neurotologists should find this a useful addition to their surgical armamentarium for selected cases.

Segmental myoclonus in Whipple's disease

A patient suffering from Whipple's disease, presenting with segmental myoclonus in the muscular distribution of the muscles of the right facial nerve, which is one of the first neurological findings of the disease is described. Patients suffering from segmental myoclonus and Whipple's disease are reported and the possible anatomical sites of the injury, responsible for the presence of this symptom is discussed.

Facial nerve involvement in patients with acoustic neurinomas. Examination with magnetic single- and bi-stimulation

The diagnosis of acoustic neurinomas is usually made by auditory and vestibular testing and magnetic resonance imaging. As clinical involvement of the facial nerve is infrequent, occurring only in large tumours, only little is known about the subclinical involvement of the facial nerve. Transcranial magnetic stimulation of the VIIth cranial nerve in the temporal bone, adjacent to acoustic neurinoma growth, seems to be an adequate instrument for electrophysiological measurements of minimal nerve lesions without clinically obvious facial palsy. In 70% out of 97 patients with surgically and histologically confirmed acoustic neurinomas, obvious elongation of the intratemporal conduction time of the facial nerve was found. This affection was dependent on tumour size. No correlation was found to preoperative or postoperative facial nerve function and hearing function. The latencies of the conduction time showed a tendential increase in patients with a more difficult grade of surgery and of facial nerve preparation due to fibrous adhesions and nerve spreading on the tumour capsule. A completely new stimulation modality, the application of two magnetic stimuli in quick succession, was applied for the first time in acoustic neurinoma patients, and revealed facial nerve involvement by acoustic neurinoma growth. Facial nerve involvement in acoustic neurinoma can be detected by transcranial magnetic stimulation even in patients with small and medium sized tumours but with clinically normal facial function.

Chronic vascular irritation of the facial nerve causes facial spasm in rats

The abnormal muscle response, elicited by electrical stimulation of one branch of the facial nerve and recorded from muscles innervated by another branch, has been used previously as an objective sign of hemifacial spasm in the development of animal models of this disorder. In the present study we recorded spontaneous electromyographic activity from the orbicularis oculi muscle from both sides in rats in which a demyelination of the peripheral portion of the facial nerve and vascular contact had been made previously. The root mean square value of the electromyographic activity on the affected side was significantly larger than that on the unaffected side in all rats in which the vascular irritation had caused the abnormal muscle response to appear. The results support our earlier finding that vascular contact together with demyelination of the peripheral facial nerve can cause the development of signs of hemifacial spasm, including involuntary muscle contractions.

Unusual synkinetic movements between facial muscles and respiration in hemifacial spasm

We describe two cases of hemifacial spasm (HFS) with unusual synkinetic movements between facial muscles and respiratory activity. Patient 1 developed an idiopathic HFS. She underwent microvascular decompression surgery, followed by transitory facial nerve palsy; she recovered but later developed a facial synkinesia characterized by involuntary and forced eyelid closure on spontaneous and deep breathing; the orbicularis oculi muscle was active also when her mouth was open (the so-called Marin-Amat syndrome). Patient 2, 1 year after a peripheral facial nerve palsy (Bell's palsy), developed an HFS together with synkinetic movements between the orbicularis oculi muscle and respiration. In both cases electrophysiological studies showed pathological synkinetic electromyographic activity. An enhanced hyperexcitability of brain stem interneurons and facial motoneurons could be suggested to explain the phenomenon.

Facial nerve demyelination and vascular compression are both needed to induce facial hyperactivity: a study in rats

It is generally assumed that hemifacial spasm (HFS) is caused by vascular compression of the facial nerve at the root exit zone (REZ), but the mechanism for the development of HFS is not known. Evidence has been previously presented that the signs of HFS are caused by hyperactivity of the facial motonucleus that is caused by the irritation to the facial nerve from the vascular contact. This assumption has been supported by the finding that daily electrical stimulation of the facial nerve in the rat facilitates the development of an abnormal muscle response that is a characteristic sign of HFS in man and is an indication of an abnormal cross-transmission that makes it possible to elicit a contraction of muscles innervated by one branch of the facial nerve by electrically stimulating another branch of the facial nerve. In the present study we show that close contact between a peripheral branch of the facial nerve and an artery also facilitates the development of an abnormal muscle response, but only if the facial nerve has previously been slightly injured (by a chromic suture) at the location of the arterial contact. We also show that blocking neural conduction in the facial nerve proximal to the artificial vascular compression abolishes the abnormal muscle contraction, which supports the assumption that the anatomical location of cross-transmission that is causing the abnormal muscle response is central to the vascular compression, most likely in the facial motonucleus. These findings may explain why the facial nerve is only susceptible to vascular compression near its REZ, where an injury to its myelin is more likely to occur than where the nerve is covered with schwann cell myelin.

Familial hemifacial spasm

Two brothers developed hemifacial spasm at 63 and 70 years of age. Spasms occurred on the left and right sides of the face, respectively. Computed tomography scan and magnetic resonance imaging failed to show any abnormality. In addition, a third sibling reported a history of a peripheral facial palsy, which remitted spontaneously without sequelae. This is the fourth description of familial hemifacial spasms. This family is unique in that hemifacial spasm presented on different sides in the two brothers, and involvement was limited to one generation. Age at onset was later than for other familial cases and similar to sporadic cases.

Indication, technique and results of facial nerve reconstruction

160 patients with various intra- or extracranial pathologies were treated by microsurgical facial nerve reconstruction at Nordstadt Neurosurgical Clinic between 1978 and 1993. Facial nerve reconstruction was accomplished along the anatomical course of the facial nerve from its origin at the brainstem, within the mastoid, at the stylomastoid foramen and within the face. Mostly, reconstruction was indicated because of nerve discontinuity (n = 61), whereas facial nerve reanimation with a donor nerve such as the contralateral facial nerve or the ipsilateral hypoglossal nerve was indicated in 99 cases of loss of a proximal nerve stump. Depending on the site of the lesion reinnervation started at 5 to 15 months postoperatively lasting for 2 to 3 years with overall satisfactory results. 69% of all the patients regained good symmetry on rest, complete eye closure equivalent to House-Brackmann-Score III: Patients with complete failures either suffered of non-related diseases such as cancer leading to death before the estimated time of recovery or were exposed to radiation or received facial nerve reconstruction after long-standing facial deficit and marked muscular atrophy. The indication of the adequate method depends on the clinical course with or without preexisting facial paresis, on considering the intraoperative state of the facial nerve, the identification and microsurgical preparation of adequate nerve stumps, as well as on the adaptation techniques and the postoperative guidance of the patient. We conclude that facial nerve reconstruction by transplantation at either site of the nerve course or by reanimation with a donor nerve are effective and reliable procedures of treatment leading to satisfactory functional and cosmetic results.

Simultaneous quantitation of facial movements: the maximal static response assay of facial nerve function

An assay is described that enables the simultaneous measurement of bilateral facial movements within zones relevant to facial nerve function. The assay allows the accurate quantitation of movement of the eyebrows, radix, lower eyelids, philtrum, mentum, and oral commissures relative to these points on the resting face. Global or region-specific facial nerve dysfunction is detectable using this assay, as shown in examples of patients having single branch facial nerve palsy and bilateral facial palsy (Möbius syndrome variant). Because facial movement is tested by region, with the remainder of the face relaxed, synkinesis can be detected when present. The assay has potential to be used as an adjunct to the presently used ordinal scales of facial nerve function, by allowing actual quantitation of region-specific facial movement. This feature may prove helpful in vector planning for reanimation procedures and may allow the tracking of functional responses after such procedures, thereby providing a measurement of their efficacy.

Anastomosis of the intratemporal facial nerve using fibrin tissue adhesive

This work aimed at studying the results obtained by the repair of complete lesions of the facial nerve in its intratemporal portions. Clinical, electrophysiological and surgical techniques were studied. Twenty-three patients with traumatic facial nerve lesions were operated. Nerve grafts were made in 10, and end-to-end anastomosis in thirteen. The surgical technique performed was the coaptation of the stumps and stabilization with fibrin tissue adhesive. Sixteen months after surgery, a clinical and electrophysiological evaluation was made. The use of fibrin tissue adhesive to stabilize intratemporal anastomosis of facial nerve showed clinical and electrophysiological evidence of axonal growth and reinnervation of mimical muscles of the face. These results were similar to that obtained by other authors that used other methods of microanastomosis. The use of fibrin tissue adhesive is an effective technique to utilize in intratemporal anastomosis of the facial nerve.

Transcranial magnetic stimulation excites the root exit zone of the facial nerve

The actual site of excitation of the facial nerve by transcranial magnetic stimulation was investigated in five patients with hemifacial spasm who underwent microvascular decompression. The facial nerve was stimulated preoperatively and intraoperatively by transcranial magnetic stimulation and intraoperatively by electrical stimulation at its root exit zone with a minimum of surgical invasion of the facial nerves. The onset latency of compound muscle action potentials recorded from the nasalis muscle was 5.06 +/- 0.44 ms by magnetic stimulation and 5.08 +/- 0.43 ms by electrical stimulation. The latency difference was 0.06 +/- 0.08 ms. Therefore, transcranial magnetic stimulation was basically the same as electrical stimulation in onset latency. From this study, it appears that the root exit zone of the facial nerves is stimulated by transcranial magnetic stimulation.

Hemifacial spasm: early postoperative normalization of blink reflex latency

Electrophysiological improvement in the blink reflex latency after neurovascular decompression of the facial nerve in patients with hemifacial spasm is believed to be related to remyelination and occurs 2-8 months after surgery. We report a patient with hemifacial spasms for 3 years, in whom the increased blink reflex latency returned to normal within a week after surgery. This suggests that compression without demyelination may be responsible for increased blink reflex latency in some of the patients with hemifacial spasms.

Time course of distant effects of local injections of botulinum toxin

Botulinum toxin A (btx) is used to treat focal dystonias. From accidental intoxications it is known that btx can cause generalized pathologic single-fiber electromyography (SFEMG) findings. We monitored the onset and course of these disturbances in eight patients who received a small dose of btx (2-22 ng) for therapy of focal dystonias in the head/neck region for the first time via repeated SFEMG investigations at days 0, 3, 6, 9, 12, 28, and 56. Recordings were performed in the extensor digitorum brevis muscle, and in two patients additionally in the tibialis anterior muscle. In six of these patients we found an increase of jitter and blocking. The onset of these changes was in the range of 3-13 days after injection. Fiber density showed a tendency to increase. There was no correlation between SFEMG findings and the dose of injected btx. Possible mechanisms for these observations may be either a very efficient local uptake and retrograde axonal transport via the spinal motor neurons or a systemic distribution via the blood circulation.

Result of decompression surgery in late-stage severe facial paralysis

We investigated the usefulness of decompression surgery in the treatment of the facial nerve in 23 patients with severe complete facial paralysis regardless of etiology. All patients were followed up for at least one year after onset. Nine patients underwent decompression surgery within a month of onset (Group A), 10 underwent surgery at a later time (Group B), and 4 did not receive surgery (Group C). In Group A, 2 patients showed satisfactory recovery and 2 fair recovery. In Group B, 4 patients showed satisfactory outcome, and one patient who underwent surgery 131 days after onset showed fair outcome. No patient in Group C showed satisfactory or fair recovery. There were no significant differences among the three groups in the percentage showing sequelae after treatment. We conclude that decompression surgery is indicated even for patients with severe facial paralysis who have a history of palsy of 2 months' or more duration.

[Somatosensory evoked potentials in peripheral diseases of the facial nerve: a new investigation method]

In 1988, at the Facial Nerve Congress in Rio de Janeiro, results of facial nerve somatosensory evoked potentials (SEPs) by electrical stimulation of the Ramsay-Hunt zone were presented. In the clinical phase of this work, we have tested 8 normal subjects and 5 patients with unilateral peripheral facial palsy by the SEP method. Significant and reproducible responses were obtained in the normal nerves; general wave-form and different parameters are described: latency of different activities, differences inter and intra-subjects. In one case, we performed a brain mapping by stimulation of the Ramsay-Hunt zone to improve the localization of the different activities and to differentiate them from a possible auditory response to the electrical stimulation. In the pathological nerves, we observed significant changes in the morphology of the cortical waves with regards to the healthy nerves. Detailed results are presented in two cases with a long-term follow-up. We concluded that the electrical stimulation of the Ramsay Hunt zone evokes a cortical response like the electrical stimulation of other cutaneous zones. This response is significantly altered in peripheral facial palsy. Following studies should define the prognostic value of such modifications.

A case of bilateral alternating hemifacial spasms

We report a 24-year old woman who developed bilateral hemifacial spasm alternating from one side to the other. The spasms followed a left peripheral facial palsy 2 years previously. This unusual type of bilateral hemifacial spasm was possibly due to lesions of multiple sclerosis in the brainstem.

Intratemporal facial nerve neurinoma without facial paralysis

A 38-year-old man was referred by his general practitioner to our department on 28 October 1991, with a 2-week history of vertigo. A left aural polyp was identified. The audiogram showed a moderate conductive loss on the left side. Computed tomography (CT) and magnetic resonance imaging (MRI) confirmed the presence of the expanding lesion in the descending portion of the facial nerve. However, there was no seventh nerve paresis. At operation, the neurinoma (Schwannoma) filled the middle ear cleft and extended from the genu to the stylomastoid foramen. The floor of the middle ear had been eroded, exposing the jugular bulb. Facial nerve paresis is the usual presenting feature of a facial neurinoma. The case is presented for the reason that the absence of facial palsy as a presenting feature is rather rare, especially in the cases with large tumor and extensive bone erosion.

Testing facial nerve function

A variety of facial nerve tests are now available. These tests can aid the clinician in discerning the site of lesion, estimating prognosis, assessing evidence of neoplastic or infectious involvement, and assisting in intraoperative facial monitoring.