Synaptic connectivity and ultrastructrue of the masseteric muscle spindle afferent trigeminals according to geometric location in the trigeminal motor nucleus of the cat / 대한해부학회지

The purpose of this study was to investigate any relationship between the geometric factors of synaptic contacts of muscle spindle afferent terminals and masseteric motor neurons in the trigeminal motor nucleus. Terminals from the masseteric muscle spindle afferents were stained with intra-axonal injection of HRP and were examined electronmi-croscopically with serial sections at the central and peripheral regions of trigeminal motor nucleus of the cat. The number of terminals examined were 76 in peripheral and 105 in central region. The results obtained were as follows. 1. Most of the labeled terminals showed simple synaptic connectivity. Each terminals in peripheral and central region made synaptic contact with 1 to 5 neuronal profiles. Two or three labeled terminals were occasionally seen to make synaptic contact with the same dendrite. 2. The average number of postsynaptic proximal dendrite per labeled terminal was higher in the central region than in the peripheral region. In contrast, that of postsynaptic distal dendrite per labeled terminal was higher in the peripheral region than in the central region. 3. The average diameter of postsynaptic dendrites in the central region was larger than that in the peripheral region. This imply terminals in the peripheral region contacted with further distal part of the distal dendrite than that in the central region. These results indicate that synaptic connectivity associated with the spindle afferents from masseteric muscle is different according to their geometric location within the trigeminal motor nucleus and suggest that there will be precise interrelationship between the morphology, pattern of synaptic connectivity and functions of muscle spindle afferents.

A CASE OF RHABDOMYOSARCOMA IN MASSETER, PAROTID AND MANDIBULAR AREA

MANDIBULAR SETBACK OSTEOTOMY WITH REDUCTION CHEILOPLASTY

The face and notably the lips are important structures not only of aestheticvalue but also for expression, vibrancy and vitality. Sometimes we are encountered with the functional and aesthtetic lip problems especially in the patients with mandibular prognathism, such as excessive vermilion exposure, lip incompetence and hyperactivity of mentalis muscle. The etiologic factors are usually related to excessive anterior facial height, secondary to the abnormal development of perioral muscle, salivary gland and the swelling of lymphatic gland. Sometimes orthognathic surgery (mandibular setback osteotomy) alone is not accepted regarding to aesthetic value, there is likely to be a corresponding interest in adjunctive procedures such as genioplasty and soft tissue procedures. This article urges the incorporation of reduction cheiloplasty. It is a relatively minor procedure that can be easily reproducible and yields excellent, predictatable results with few complications. We treated two patients who have excessive vermilion exposure and marked abnormal lip eversion using reduction cheiloplasty combined with mandibular setback osteotomy, followed by improved facial harmony and patients were pleased.