Page 49 - Edited - Webster HEAD AND NECK - part 2-Merge PDF

ΗΝ 247

Facial palsy may also be caused by a neurofibroma (a Schwann cell tumour, otherwise benign) - a
so-called "acoustic neuroma" - of the eighth (vestibulo-cochlear) cranial nerve, because of the close
association of these two cranial nerves from the brainstem to the bottom of the facial canal in the petrous
temporal bone. (I well remember a patient with a "ponto-cerebellar angle" Schwannoma: his presenting
symptoms were vestibulo-auditory, i.e. eighth nerve; he subsequently developed a facial palsy - after the
surgery...)
Recovery from facial palsy is usually complete and uneventful. Occasionally, however, it is
marred by misrouting of peripheral axons which maintain their central connections (presumably the
endoneurial tubes have been disturbed): when the patient tastes something, the homolateral eye floods with
tears . . . . i.e. some sensory axons from taste buds now connect centrally to those brainstem neurons
providing pre-synaptic parasympathetic innervation of the lacrimal gland. A similar effect is sometimes
seen among wine-tasters - but it is bilateral, and just all in a day's work, whether they be tears of sorrow or
bliss…

Upper Motor Neuron (or "supranuclear") facial palsy is due to des uction of fibres from the motor cortex
anywhere above the pons - usually following a stroke. It is less severe than lower motor neuron facial
palsy, and characteristically affects only the muscles of facial expression of the lower half of the
contralateral side of the face - compare HN 252, Fig. A(iii) with (i). (See Neuro notes, Vol. II, Fig. 130 for
explanation. Remember: upper motor neuron lesion means paralysis of lower face.) Peculiarly, the
paralysis is not spastic and, moreover, is not manifest during "social" facial responses (smiling, etc.) as
opposed to attempting to respond to a request ("Show me your teeth", i.e. "Grin").

K.E.W.

\NewCMedPhysSc\26 HN 246 FacialNerve.