Correlation between structural changes of facial muscle after denervation and rehabilitation of facial muscle function

Lian HUI; Hongquan WEI; Xiaotian LI; Zhong REN

ABSTRACT

BACKGROUND:

It is of significance to imitate facial nerve paralysis of temporal trauma, establish the model of facial nerve paralysis, and study the histopathologic changes of facial muscle after denervation and the effect on rehabilitation of facial muscle function.

OBJECTIVE:

To investigate the relationship between rehabilitation of facial muscle function and the structural changes of mitochondria and succinate dehydrogenase (SDH) of oris muscles after denervation.

DESIGN:

A randomized controlled trail based on experimental animals.

SETTING:

Department of otolaryngology in a hospital of a university.MATERIALS The experiments were conducted in the Center of Animal Experiment, the Department of Histoembryology, and the Second Electron Microscope(EM) Center, China Medical University. Sixty white guinea pigs provided by the Center of Animal Experiment, China Medical University [certification No SCXK (liao) 2003-0009 ], were randomly divided into three groups, 5 s squeezed group( n = 15, 10 tested for the function of facial muscle, 5 for EM specimen 15 days after operation), 15 s squeezed group( n =20, 10 tested, 5 for EM specimen 15 days and 30 days after operation), and 30 s squeezed group( n = 25, 10 tested, 5 for EM specimen 15 days after operation and 10 for EM specimen 30 days after operation).

INTERVENTIONS:

Models of facial paralysis were established. The threshold of facial nerve was detected with electroneurogram(ENoG) before and after squeezed, and the duration of the functional recovery of facial muscle was observed with blink reflex. Orbicularis oris was taken for SDH cytochemical staining, and the ultrastructural changes of SDH positive reaction granules,mitochondria and muscle fibers were observed under transmission electroscope.MAIN OUTCOME

MEASURES:

ENoG threshold value, tine for recovery of facial muscle function, SDH positive reaction granules and ultrastructural changes of mitochondria and muscle fibers.

RESULTS:

In 5 s squeezed group, the average inhibition time of nerve excitement conduction was(35.2 ± 16.8) minutes, the structure of mitochondria and the positive reaction granules of SDH remained normal, and the muscle fiber had no pathologic changes. In 15 s squeezed group, it took an average of(47 ± 15) days for blink reflect to recover. In 15 s squeezed group of 15 days, the mitochondria showed slight bubble degeneration and the SDH granules decreased and the muscle fiber had slight pathologic changes, but recovered after 30 days. The mitochondria changed severely and SDH granules decreased significantly in 30 s squeezed group of 15 days and 30 days; no case of blink reflect recovered within' half a year.

CONCLUSION:

The longer the facial nerve is injured, the nore severely the function of facial muscles is damaged, and the more difficultly it will recover. Therefore, facial nerve decompression should be performed as early as possible.