Functional Systems

The voluntary component of facial expression is mediated by the precentral cortex, in which the face is somatotopically represented. Only the upper facial muscles have bilateral supranuclear innervation; thus, a central supranuclear facial palsy does not affect eye closure or the ability to knit one's brow. Yet facial palsy that spares the upper face is not necessarily of supranuclear origin: because the facial nucleus and nerve are also somatotopically organized, incomplete lesions of these structures may also produce a similar appearance. An important and sometimes helpful distinguishing feature is that a su-pranuclear palsy may affect facial expression in the lower face in a dissociated fashion. Supranu-clear facial palsy due to a cortical lesion impairs voluntary facial expression, but tends to spare emotional expression (laughing, crying); that due to a subcortical lesion (e. g., in Parkinson disease or hereditary dystonia) does just the opposite.

The following reflexes are ofclinical significance (A = afferent arm, E = efferent arm): orbicularis oculi reflex (blink reflex; A: V/1; E: VII); corneal reflex (A: V/1; E: VII); sucking reflex (A: V/2, V/3, XI; E: V, VII, IX, X, XII), palmomental reflex (A: thenar skin/muscles; E: VII), acoustic blink reflex (A: VIII; E: VII), visual blink reflex (A: II; E: VII), orbicularis oris reflex (snout reflex; A: V/2; E: VII).

Peripheral pathway

Corticonuclear tract Nucleus of the solitary tract Superior salivatory nucleus Nucleus abducens Inner genu of facial nerve

Motor nucleus of VII

Corticonuclear tract Nucleus of the solitary tract Superior salivatory nucleus Nucleus abducens Inner genu of facial nerve

Nervus intermedius

- Motor fibers

Superior salivatory nucleus

Motor nucleus of V

Nuclear region

Lacrimal gland —

Otic ganglion —

Pterygopalatine -ganglion

Chorda tympani

Lingual nerve

Motor fibers -

Taste fibers

Submandibular ganglion Sublingual gland Submandibular gland

Nervus intermedius

Superior salivatory nucleus

Motor nucleus of V

Submandibular Gland Marginal Mandibular

Peripheral tracts

Motor nucleus of VII

Peripheral pathway

Temporal-

branches

External genu of facial nerve

Pterygopalatine ganglion

Lingual nerve

Subman-dibular ganglion

Marginal mandibular branch

The Human Pterygopalatine Ganglion

Digastric branch Stylohyoid branch Cervical branch

Branches of facial nerve

Peripheral tracts

Motor nucleus of VII

Digastric branch Stylohyoid branch Cervical branch

Branches of facial nerve

Temporal branches-

Posterior auricular n.

Parotid plexus, parotid gland

Parotid Plexus

Motor branches

Cervical branch

Motor branches

Cervical branch

Examination. Motor function is assessed at rest (asymmetry of face/skin folds, atrophy, spontaneous movements, blink rate) and during voluntary movement (forehead, eyelids and brows, cheeks, mouth region, platysma). Trigeminal nerve dysfunction (V/1) causes unilateral or bilateral absence of the blink reflex; facial palsy may impair or abolish the blink response, but lagophthalmos persists, because the extraocular muscles are unimpaired. Similar logic applies to

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