lesions may involve the facial nucleus or intrapontine facial nerve fascicles
(Figure 181.1). They produce an ipsilateral facial musculature deficit
that equally affects the corner of the mouth, the nasolabial fold, the
lower eyelid, the upper eyelid, and the forehead. When crying, the mouth
deviates toward the normal side and the eyelid remains open or closes
less tightly on the affected side.
Schematic representation of the intrapontine trajectory of the facial
nerve. N: nucleus; CN: cranial nerve; C: location of intrapontine lesion.
facial nerve motor nucleus may be involved in Moebious syndrome and autosomal
dominant congenital facial palsy; and by cerebrovascular accidents and
tumors. Moebious syndrome has been described with degeneration, agenesis,
and hypoplasia of the nucleus of the sixth and seventh cranial nerves.
Moebious syndrome is characterized by bilateral but asymmetrical facial
weakness (Figure 181.2). More
Autosomal dominant congenital facial palsy is characterized by facial
motor nucleus hypocellularity, neighboring structures are not involved.
lesions of the facial nerve fascicle are strictly unilateral. The intrapontine
fibers of the facial nerve may be affected by cerebrovascular accidents
In addition to facial musculature involvement, they produce: (1) ipsilateral
sixth cranial nerve palsy; (2) ipsilateral Horner syndrome and hypohydrosis
and vasodilatation of the ipsilateral body; (3) ipsilateral decreased
tearing; and (4) contralateral upper motor neuron hemiparesis.
Magnetic resonance imaging is the study of choice to evaluate the facial
nucleus and intrapontine fibers.
Figure 181.2— Moebious syndrome.
[A] At rest, no asymmetry is noted. [B] During crying, the facial asymmetry