Bell's palsy is a relatively common, unilateral facial paralysis of unknown etiology. The purpose of this study was to evaluate the prognostic value of several electrophysiologic tests in Bell's palsy.
Blink reflex (BR), side-to-side compound muscle action potential (CMAP) amplitude comparison, and side-to-side nerve excitabiliry test(NET) threshold difference have been studied during the first 2 weeks in 66 patients with Bell's palsy.
According to the early response of BR(R1), the patients wee divided into 3 groups: R1≤13ms (17cases); R1>13ms(22cases), and absent BR(27cases). There was a remarkable tendency towards a satisfactory recovery from paralysis if BR occurred during
the
first 2 weeks from onset(p<0.001). In patients with normal BR, 88.2% had a satisfactory recovery, when the reflex was absent a bad prognosis was given in 59.3% of the patients.
According to side-to-side CMAP amplitude comparison, the patients were divided into 2 groups; CMAP amplitude comparison≥25%(35cases), and CMAP amplitude comparison <25%(31cases). There was a tendency towards a satisfactory recovery from
paralysis
if
side-to-side CMAP amplitude comparison was more than 25%(p<0.003). In patients with more than 25% of CMAP amplitude comparison, 82.9% of the patients had a satisfactory recovery, but in patients with less than 25% of CMAP amplitude comparison,
51.6% of
the patients had a bad prognosis.
According to side-to-side NET threshold difference, the patients were divided into 2 groups, NET threshold difference≤3.5mA(43cases), and NET threshold difference >3.5mA(23cases). When the threshold of electrical excitability on both sides
differs
3.5mA or more an unsatisfactory recovery has strongly to be expected(p<0.001). In patients with less than 3.5mA of NET threshold, 81.4% had a satisfactory recovery, but in patients with more than 3.5mA of NET threshold, 60.9% had a bad prognosis.
BR, side to side CMAP amplitude comparison, and side-to-side NET threshold difference seem to be useful independent indices for predicting the prognosis in an early stage of the paralysis.
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