Facial Weakness

Visceral efferent and visceral afferent fibres arise and terminate in the superior salivary nucleus and nucleus/tractus solitarius respectively.

They run together as the nervus inter-medius and accompany the facial nerve to the internal auditory meatus. The parasympathetic fibres (visceral efferent) pass in the greater petrosal nerve to the sphenopalatine ganglion and thence to the lacrimal gland to produce tears and in the chorda tympani nerve to the submandibular ganglion.

Facial nerve

Visceral afferent

Parasympathetic efferent

Facial nerve

„ Superior salivatory nucleus

-- Nucleus and tractus solitarius

Nervus intermedius

„ Superior salivatory nucleus

-- Nucleus and tractus solitarius

Visceral afferent

Parasympathetic efferent

Sublingual gland -

Nervus intermedius

The chorda tympani nerve contains both parasympathetic efferent and visceral afferent fibres. Parasympathetic fibres are responsible for salivation.

• Visceral afferent fibres convey sensations of taste from the anterior two-thirds of the tongue. The geniculate ganglion contains the bipolar cell bodies of these afferent fibres.

Supranuclear control of facial muscles

The muscles in the lower face are controlled by the contralateral hemisphere, whereas those in the upper face receive control from both hemispheres (bilateral representation). Hence a lower motor neuron lesion paralyses all facial muscles on that side, but an upper motor neuron (supranuclear) lesion paralyses only the muscles in the lower half of the face on the opposite side.

Clinical examination of the facial nerve (see page 15)

In addition to examining for facial weakness and taste impairment, also note whether the patient comments on reduced lacrimation or salivation on one side, or hyperacusis (exaggeration of sounds due to loss of the stapedius reflex).

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