Facial nerve palsy at sternomastoid canal can cause:
Ans. A Loss of Corneal reflex at the side of lesionCourse of Facial NerveBelow stylomastoid formen, facial nerve gives following branches: Posterior auricular branch, muscular branches (stylohyoid and posterior belly of diagastric) and terminal (peripheral) branches.Lesion at sternomastoid forameni. Will spare:- Greater superficial petrosal nerve -7 Lacrimation present.- Nerve to stapedius -7 Normal stapedial reflex and no hyperacusis.- Chorda tympani -7 Normal salivation and taste sensation in anterior 2/3 of tongue.ii. Will involve:Terminal (peripheral) branches -7 Paralysis of muscles of facial expression. Corneal reflex will also be lost because efferent fibres of corneal reflex are derived from peripheral branches of facial nerve (it is a LMN type lesion).Remember:Corneal Reflex: Afferent: Trigeminal nerveEfferent: Peripheral branches of facial nerve
Loss of corneal reflex at side of lesion
Loss of corneal taste sensation anterior 2/3 of ipsilateral tongue
Loss of lacrimation at side of lesion
Hyperacusis