Abstract

An unusual vasomotor reaction was observed following an interscalene nerve block. The patient's face appeared divided symmetrically into a pale ipsilateral half and a vividly flushed contralateral half. The two halves were divided by a sharp line running through the center of the patient's head. An ipsilateral Horner's syndrome on the side of the block was also present. The most likely explanation for this phenomenon is an extension of the nerve block to the ipsilateral facial nerve and block of facial vasomotor fibers causing unilateral abolition of vasodilation. Evidence supporting this conclusion is presented.