The Blood Supply of the Human Velum and Pharynx: Some Implications for Cleft Palate Surgery

This thesis has described in detail the blood supply of the soft palate and posterior pharyngeal wall in a series of dissections performed on human fetuses and cadavers. A variety of injection media were used in both fresh and fixed specimens to demonstrate the vascular anatomy. Adult cadavers were dissected by conventional methods. For the fetuses a dissection microscope and microsurgical instruments were required. Radiology and clearing techniques have also been used. It was found that three arteries are important in the supply of the normal soft palate - the ascending palatine, ascending pharyngeal and accessory meningeal arteries. The posterior pharyngeal wall was normally supplied by branches of the ascending pharyngeal and superior thyroid arteries. A small series of dissections has also been carried out on fetuses with cleft palate and the vascular anatomy shown to be similar to normal cases with some minor variations. This finding was confirmed by histological studies performed on several fetal heads. Detailed findings have been given of the blood supply of the velar muscles, in particular levator veli palatini and tensor veli palatini. Both these muscles were normally shown to have a dual arterial supply. The most common pattern observed was the levator receiving branches from the ascending palatine and ascending pharyngeal vessels and the tensor from the ascending palatine and accessory meningeal. Several velar muscles were also examined histochemically in a number of fresh specimens both to study the intramuscular vascular anatomy and to identify fibre types. In no case of levator was any large vessel seen entering the upper lateral portion of the muscle. In each muscle both type I and type IIb fibres were identified, with the levator appearing to have the highest proportion of fast twitch IIb fibres. The anatomical observations made have been related to cleft palate surgery including pharyngoplasty. It was observed that of different types of pharyngoplasty performed, laterally based flaps appeared to have the richest blood supply. The finding of dual blood supply of the levator and tensor veli palatini suggests that if careful cleft palate closure is performed these muscles should not suffer ischaemic damage. On the other hand, anatomical observations together with skull measurements made on a series of child and adult skulls point to the possibility that two manoeuvres commonly performed in cleft closure could be damaging to the levator and render a portion of it ischaemic: these are intravelar veloplasty and dissection posterior to the maxillary tuberosity. The author believes that extensive intravelar veloplasty, especially if carried out together with a deep lateral dissection behind the maxillary tuberosity, should be avoided. Dissection and histological findings in fetuses with cleft palates also showed that the levator has a tripartite insertion: into the cleft soft palate edge, the tensor tendon or aponeurosis, and the posterior aspect of the hard palatal shelf. Extensive intravelar veloplasty is often therefore not required on anatomical grounds as many of the fibres run in a normal direction. On the basis of observations made, a sequential series of steps is suggested for cleft palate closure in order to minimise risk of vascular damage to the palatal muscles