According to the classical textbooks of neurological semeiology, unilateral facial paralysis due to upper motor neuron damage is characterized by the sparing of frontal muscle of the involved side. However, a small lesion affecting the facial nucleus at the level of pontine tegmentum which causes lower motor neuron type facial paralysis also spares the frontal muscle. The frontal muscle sparing in nuclear type of facial paralysis might be explained by the hypothetical decussation of facial nerve roots innervating frontal muscle at the level of facial genu. The validity of the hypothesis should be confirmed further clinical studies on facial paralysis.
東京女子医科大学雑誌 78 (Extra), E6-E9, 2008-02-25