Factors Promoting a Good Outcome in a Second Microvascular Decompression Operation When Hemifacial Spasm is Not Relieved After the Initial Operation.

Background: Microvascular decompression (MVD) has become the best treatment for hemifacial spasm (HFS); however, some patients do not obtain complete relief after the initial MVD. We analyzed a group of patients who underwent a second MVD, to identify the factors that prevented relief after the initial MVD and those that promote the success of the second procedure.
Methods: Of a group of 1400 patients with typical primary unilateral HFS treated with MVD between January 2014 and October 2015, we focused on 42 patients with poor postoperative outcomes. All patients underwent abnormal muscle response (AMR) monitoring again the day after surgery. Of those patients, 35 underwent a second MVD surgery within a week. We analyzed their AMRs after each operation.
Results: After the first operation, AMR was positive in 40 patients and negative in 2 patients. The latter 2 patients reported spontaneous relief within 1 week. Among the 40 positive patients, 35 and 4 patients underwent a second MVD within a week and 6-11 months, respectively. Thirty-nine patients reported relief after the second MVD; 1 patient remained unchanged at follow-up (<12 months).
Conclusions: When initial MVD does not provide relief, a repeat MVD should be performed as soon as possible. In 2/42 cases, relief was delayed enough that AMR had a false-negative result. Combinative monitoring of AMR and Z-L responses was important in identifying the real cause of HFS.
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