Nk. Sinsel et al., THE EFFECT OF UNILATERAL PARTIAL FACIAL PARALYSIS AND MUSCLE ABLATIONON CRANIOFACIAL GROWTH AND DEVELOPMENT - AN EXPERIMENTAL-STUDY IN THERABBIT, Plastic and reconstructive surgery, 102(6), 1998, pp. 1894-1912
The effect of unilateral partial facial nerve ablation anti unilateral
partial midface muscle ablation on craniofacial growth and developmen
t was investigated. New Zealand White rabbits (12 days old) were rando
mly assigned to three experimental groups: control group, to study nor
mal craniofacial growth and development (n = 15); nerve ablation group
, surgically induced unilateral paralysis of the buccal branches of th
e facial nerve (n = 15); and muscle ablation group, surgical unilatera
l ablation of the facial muscles innervated by the buccal branches of
the facial nerve (n = 12). All animals cere operated on at the age of
12 days; follow-up evaluations were performed at the ages of 2 months
and 6 months. The age of 2 months represents the endpoint of the prepu
bertal craniofacial growth and development. At the age of 6 months, th
e animals are fully grown; therefore, the time period between 2 and 6
months is regarded as the pubertal growth period. Computerized dorsove
nural roentgencephalometric (measurement of distances and angles) and
computer tomographic (three-dimensional volumetric measurements) inves
tigations were per-formed at both ages. Additional dry skull measureme
nts were Der formed to determine more precisely the bone segments invo
lved in the craniofacial growth alterations studied. The obtained resu
lts indicated the following. Unilateral partial facial paralysis invol
ving the midface resulted in growth alterations analogous to those see
n after unilateral total facial paralysis. The growth alterations were
not to be seen as a growth restriction (reduction in bony volume) but
as growth misdirections (alterations in shape). Major growth alterati
ons were present in those regions closely related to the facial muscul
ature, namely the nasal, maxillary, and premaxillary regions, resultin
g in a snout deviation toward the operated side. The growth alteration
s occurred during prepuberty and remained rather stable during puberty
. Morphologic signs of muscle denervation were related to the craniofa
cial growth disturbances. The growth alterations after unilateral part
ial facial paralysis were mainly biomechanically induced, as they were
analogous to those observed after unilateral midfacial muscle ablatio
n. The fact that after unilateral midfacial muscle ablation at the age
of 6 months the severity of the alterations had increased was attribu
ted to the scar formation inherent to the surgical procedure.