Transcranial Magnetic Stimulation Excites the Root Exit Zone of the Facial Nerve

Tokimura, Hiroshi; Yamagami, Masayuki; Tokimura, Yoshika; Asakura, Tetsuhiko; Atsuchi, Masayuki

doi:10.1097/00006123-199303000-00012

Cited by 3 publications

(5 citation statements)

References 7 publications

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“…to 5 mm distal to the REZ in man. 31 This interindividual variability in both of these experimental series makes it impossible to estimate the excitation site for the facial nerve with any degree of certainty.…”

Section: Conclusion I Precise Coil Positioning and Orientationmentioning

confidence: 99%

Transcranial magnetic stimulation of the trigeminal nerve: Intraoperative study on stimulation characteristics in man

1995

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We studied responses from the masseter and nasalis muscles following magnetic stimulation (magStim) and compared these responses with those obtained by direct electrical stimulation of the trigeminal (NV) and facial (NVII) nerve near the root exit zone during microvascular decompression operations of NVII. We found that (1) magStim threshold to excite the nerve is high for NV and low for NVII; (2) excitation of all motor fibers is impossible for NV, and easy for NVII; (3) optimal coil placement is critical for NV, but not critical for NVII; and (4) between and within subjects, the excitation site is variable on NV, but stable on NVII. We estimated that the anatomical location of magStim to be either within or outside the cerebrospinal fluid for NV, and to be in the labyrinthine segment of the facial canal for NVII. Physical models explain and clinical lesion models support these differences found between NV and NVII.

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Section: Conclusion I Precise Coil Positioning and Orientationmentioning

confidence: 99%

Transcranial magnetic stimulation of the trigeminal nerve: Intraoperative study on stimulation characteristics in man

1995

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“…Eventually, scientists and clinicians began focusing on the evolution and possible clinical applications of the transcranial magnetic stimulation system in facial nerve disorders. 2,3,16–28 …”

Section: Introductionmentioning

confidence: 99%

“…In the past 12 years several studies have focused on determining the exact site where magnetic stimulation excites the facial nerve, 3,17,19–27,29–32 but the location of the site remains controversial. Centrally (supranuclear) activated motor responses by magnetic stimulation vary in amplitude, latency and waveforms, depend on the stimulus conditions, and are facilitated by voluntary contractions.…”

Section: Introductionmentioning

confidence: 99%

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Transcranial Magnetic Stimulation in Acute Facial Nerve Injury

Har‐El¹,

McPhee²

2000

The Laryngoscope

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Objective/Hypothesis Available electrodiagnostic tests that are used to evaluate facial nerve injury examine the nerve distal to the stylomastoid foramen; because most facial nerve injuries are within the temporal bone, the tests cannot evaluate the nerve at or across the injury site. The interpretation of these tests depends on the predictability (or unpredictability) of distal degenerative process. Transcranial magnetic stimulation may be able to stimulate the nerve proximal to the injury site. The hypothesis of the present study is that in cases of mild traumatic facial nerve injury where axonal integrity is maintained, proximal stimulation of the nerve using higher than normal stimulus intensities to “overcome” the block at the injury site result in recordable facial nerve activity. Study Design A prospective controlled animal study comparing response to transcranial magnetic stimulation of the facial nerve in the following groups: mild injury, severe injury/transection, and control. Methods We studied 44 facial nerves in 22 cats. Fifteen nerves were subjected to mild trauma. Five nerves were severely crushed, 2 nerves were completely transected, and 22 nerves were not traumatized. All nerves were examined with the transcranial magnetic stimulation system before the trauma, immediately after the trauma, and at 3, 8, and 12 weeks after trauma. Results All nerves in the mild and severe trauma groups showed complete clinical paralysis immediately after trauma. The nerves in the mild trauma group showed significant increase in threshold as well as significant increase in latency for recordable facial muscle response to transcranial magnetic stimulation. Thresholds and latencies decreased gradually within 3 to 12 weeks and returned almost to preinjury levels. This paralleled the return of clinical facial muscle movement. In the severe trauma/transection group, the nerves had no facial muscle response to transcranial magnetic stimulation after trauma. Neither facial muscle response to transcranial magnetic stimulation nor facial muscle movements recovered. Conclusions In cats transcranial magnetic stimulation can assess the integrity of the facial nerve after trauma and predict its potential for regeneration. This technique can excite the nerve proximal to the injury site and may play a role in the clinical evaluation of the acute traumatic facial nerve paralysis. It can be used immediately after trauma, because it does not depend on wallerian degeneration to occur.

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“…Schmid et al 6 suggested that the nerve is stimulated just proximal to its entrance into the porus of the facial canal, or the porus acousticus internus, because the average latency observed corresponded best with the value obtained by electrically stimulating the facial nerve at the porus acousticus internus. Tokimura et al 7 used intraoperative intracisternal stimulation but exposed only the facial nerve root exit zone. The results strongly suggested that the site of stimulation is, in fact, in the cistern.…”

mentioning

confidence: 99%

Assessing the Clinical Utility of the Magnetic Stimulator for Measuring Response Latencies in the Laryngeal Muscles

Sims

Yamashita

Rhew

et al. 1996

Otolaryngol.--head neck surg.

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Our purpose was to assess the use of magnetic stimulation for measuring conduction time of the recurrent and superior laryngeal nerves in 10 normal volunteers (7 male, 3 female). Subjects underwent laryngeal electromyography and magnetic stimulation of the vagus nerve bilaterally at the mastoid tip with a figure 8 coil. Mean muscle response latencies were measured and examined for consistent differences. Thyroarytenoid muscle response latencies were consistently longer than those in the cricothyroid muscle. Left thyroarytenoid muscle latencies were consistently longer than those on the right in agreement with bilateral asymmetry of these nerves. No appreciable differences were observed in cricothyroid muscle latencies when the right side was compared with the left. Results were consistent and reproducible within a broad range, but appreciable intersubject variability was observed. The limited sample size was unable to support a correlation with anthropometric variables, although an association was indicated. Magnetic stimulation with this technique has great potential for use in neurolaryngologic studies.

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Transcranial Magnetic Stimulation Excites the Root Exit Zone of the Facial Nerve

Cited by 3 publications

References 7 publications

Transcranial magnetic stimulation of the trigeminal nerve: Intraoperative study on stimulation characteristics in man

Transcranial magnetic stimulation of the trigeminal nerve: Intraoperative study on stimulation characteristics in man

Transcranial Magnetic Stimulation in Acute Facial Nerve Injury

Assessing the Clinical Utility of the Magnetic Stimulator for Measuring Response Latencies in the Laryngeal Muscles

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