Intraoperative findings of abnormal muscle response for hemifacial spasm following botulinum neurotoxin treatment.

OBJECTIVE: This study aimed to investigate the effect of preoperative botulinum toxin (BTX) injection on intraoperative abnormal muscle response (AMR) in patients with hemifacial spasm (HFS). METHODS: A total of 104 patients (32 men, 72 women) who underwent microvascular decompression (MVD) for HFS were included in this study. A total of 62 patients without and 42 patients with preoperative BTX treatments were assigned to group A and group B, respectively. AMR recordings were obtained from the orbicularis oculi and mentalis muscles by stimulation of the marginal mandibular branch and zygomatic branch of the facial nerve, respectively. The intraoperative AMR monitoring findings and therapeutic effects were compared between groups A and B. RESULTS: The rates of the patients with unavailable AMRs recorded from the orbicularis oculi muscles in group B (38.1%) were significantly higher than those in group A (14.5%, p = 0.006). Moreover, in cases with over 4 times BTX injection, the recordings of AMR from the orbicularis oculi muscles were poorer than the cases with less BTX injection (p = 0.001). There were no significant differences in the rates of the patients with unavailable AMRs recorded from the mentalis muscles between the two groups. There were no significant differences in the surgical results obtained between the two groups. CONCLUSIONS: Preoperative BTX injections should be less than 4 times to ensure effective AMR monitoring. MVD using AMR monitoring is useful for patients with HFS who were previously treated by BTX as well as those who were not treated.

[Abnormal muscle response monitoring during microvascular decompression for hemifacial spasm and long term results].

OBJECTIVE: There is some debate over the reliability of intraoperative abnormal muscle response (AMR) monitoring as an indicator of postoperative long-term outcome in patients with hemifacial spasm (HFS). We investigated whether AMR findings obtained during microvascular decompression reflect postoperative long-term outcome. MATERIAS AND METHODS: Subjects were 51 HFS patients who underwent AMR monitoring during surgery. AMR recordings were obtained from the mentalis muscle by electrical stimulation of the temporal branch of the facial nerve and from the orbicularis oculi muscles by stimulation of the marginal mandibular branch. Postoperative follow-up was more than 5 years (range 61-118 months, mean 87 months). RESULTS: In 37 patients, AMR disappeared after vascular decompression. Among those patients, only one presented with spasm at the final follow-up examination. In 6 of 7 patients with AMR that disappeared early before the completion of decompression, hemifacial spasm resolved completely. Five of six patients in whom AMR still remained but with decreased amplitude at the end of surgery experienced complete resolution. CONCLUSIONS: Our findings suggest that intraoperative cessation including prior to decompression or decreased amplitude of AMR at the end of surgery indicates a high likelihood of postoperative long-term relief of HFS. We believe that intraoperative AMR monitoring is useful in MVD surgery for HFS.

Unstable stenosis of the internal carotid artery caused by a craniofacial nail-gun injury-case report-.

A 30-year-old carpenter suffered accidental piercing of his jaw by a 3-inch nail from a nail gun. No neurological deficits were found on admission. Computed tomography showed that the tip of the nail had reached the foramen lacerum. Cerebral angiography revealed severe stenosis at the C(4) portion of the left internal carotid artery (ICA) and marked decrease in the flow of the distal ICA. He had developed right hemiparesis and sensory aphasia by the following morning. T(2)-weighted and fluid-attenuated inversion recovery magnetic resonance imaging showed a focal hyperintense signal in the left central region indicating cerebral infarction. Repeat angiography demonstrated that the antegrade blood flow from the occluded point on the admission day had partially resumed, and endovascular trapping of the ICA was successfully carried out. The nail was then removed safely without problematic bleeding. The patient suffered no additional deficit, and his sensory aphasia and right hemiparesis gradually improved. The fluctuating blood flow through the unstable stenosis of the ICA related to nail movement possibly caused the delayed cerebral infarction. To avoid the occurrence of such events, rapid treatment after necessary investigations is recommended in patients with craniofacial penetrating injuries that affect the ICA.

Lateral spread response elicited by double stimulation in patients with hemifacial spasm.

In patients with hemifacial spasm (HFS), a lateral spread response (or abnormal muscle response) is recorded from facial muscles after facial nerve stimulation. The origin of this response is not completely understood. We studied the lateral spread responses elicited by double stimulation in 12 patients with HFS during microvascular decompression. The response was recorded from the mentalis muscle by electrical stimulation of the temporal branch of the facial nerve or from the orbicularis oculi muscles by stimulation of the marginal mandibular branch. The interstimulus intervals (ISIs) of double stimulation ranged from 0.5 to 7.0 ms. R1 was defined as the response elicited by the first stimulus, and R2 as the response elicited by the second stimulus. R1 had a constant latency and amplitude regardless of the ISI, whereas R2 appeared after a fixed refractory period without facilitation or depression in a recovery curve of latency and amplitude. From these findings, we consider that the lateral spread response is due to cross-transmission of facial nerve fibers at the site of vascular compression rather than arising from facial nerve motor neurons.