Descriptions of the anatomy of the facial nerve throughout its course can be
tound in any textbook. There are also the excellent papers by Lathrop 2 3 , Sullivan
and Smith 42 and Tschiassny 45.
In Bell's palsy the facial nerve is affecied in its intratemporal course between
the posterior end of the lateral semicircular canal and the stylomastoid foramen.
Certain details of the pathway should be stressed.
In its peripheral part the nerve is superficially situated, but in its temporal
course becomes enclosed by the rigid Fallopian canal, connected with the wall by
fibrous strands running to the nerve sheath. Within the stylomastoid foramen and
at its exit the nerve is compactly bound down and intimately surrounded by a
cíense periosteal sheath, which leaves it very little space to expand
A description of the blood supply is important for clinical reasons. The intratympanic
part of the nerve, the mastoid cells, the semicircular canals and the
tympanic cavity are mainly nourished by the stylomastoid artery, a branch of the
posterior auricular, which enters the Fallopian canal at the stylomastoid foramen
and runs proximally. There are two principal anastomoses. At the knee of the
facial canal, posterior to the tympanum, the stylomastoid artery anastomoses with
the superior petrosal branch of the middle meningeal, which enters the canal by
the hiatus facialis. The second anastomosis concerns the posterior tympanic branch
of the stylomastoid artery; this follows the chorda tympani in the posterior part
of the tympanic cavity and on the tympanum before joining with branches to
the tympanum from the internal maxillary, ascending pharyngeal, middle meningeal
and carotid arteries.