The role of lateral spread response in differentiation of hemifacial spasm with various reasons and tumors in the brainstem and surrounding areas

Abstract

Objective \nTo investigate the role of lateral spread response (LSR) in differentiation of hemifacial spasm caused by Bell s palsy, compression of the nerve by blood vessels, tumors in the brainstem or its surrounding areas. \n \n \nMethods \nWe retrospectively analyzed 128 patients who had LSR examination at Neuroelectrophysiological Center of Guizhou Provincial People s Hospital from January 2010 to December 2017. The patients were divided into group with hemifacial spasm caused by Bell s palsy (Bell s palsy group, n=37), group with hemifacial spasm due to intracranial blood vessel compression (vascular compression group, n=69) and group with tumors in the brainstem or its surrounding areas (n=22, mild facial spasm in 5 cases) according to surgical confirmation, brain MRI findings and case history. Electromyography, bilateral nerve conduction velocity and LSR examination were performed in all patients. \n \n \nResults \nDecreased conduction velocity of facial nerve was observed in 5 cases in Bell s palsy group. A little denervation potential was seen in 3 cases in this group. No abnormalities were observed in the all examined muscles of the other patients. LSR was induced on the affected side in 37 cases with Bell s palsy and 69 cases with vascular compression. The positive rate was 100.0%. LSR waves were induced on ipsilateral side of the lesion in 10 cases (45.4%, including 5 facial spasm patients) and on both sides in 3 cases among 22 cases in group with tumors in the brainstem and its surrounding areas. The LSR latent periods were 6.4±2.3 ms, 10.6±3.7 ms and 16.4±5.1 ms in Bell s palsy group, vascular compression group and group with tumors in the brainstem and its surrounding areas, respectively(P<0.01). \n \n \nConclusions \nLSR could be induced in patients with hemifacial spasm by various causes, which could be present in patients with tumors in the brainstem and its surrounding areas having no clinical manifestations of facial spasm. LSR test might help distinguish the etiology of hemifacial spasm and suggest that there may be tumors in the brainstem and its surrounding areas. \n \n \nKey words: \nHemifacial spasm;\xa0Lateral spread response;\xa0Brain stem neoplasms