Info

Figure 7.96 Effective mandibular length, both sexes, 6 to 16 years. From McNamara (1984), by permission.

Maxillomandibular Differential: Cephalometric

Definition This measurement is determined by subtracting the effective midfacial length from the effective mandibular length (Fig. 7.97).

Landmarks See sections on effective midfacial length and effective mandibular length for details.

Mandible Width (Bigonial Distance)

Definition The bigonial width. The distance between the two most lateral aspects of the mandible.

Landmarks Measure from the most lateral aspect at the angle of the jaw (gonion) to the same point on the other side of the face (Fig. 7.98).

Instruments Spreading calipers.

Figure 7.97 Maxillo mandibular differential, both sexes, 6 to 16 years. From McNamara (1984), by permission.

Figure 7.97 Maxillo mandibular differential, both sexes, 6 to 16 years. From McNamara (1984), by permission.

Figure 7.98 Measuring mandible width.

Figure 7.98 Measuring mandible width.

Position The head should be held erect with the eyes facing forward.

Alternative The infant or young child may lie supine.

Remarks The mouth should be relaxed when this measurement is taken. Typical values for children age 4-16 years are shown in Fig. 7.99.

Pitfalls Marked asymmetry of the mandible or malformation of the mandible may make it difficult to define the gonial points.

Figure 7.99 Mandibular width, both sexes, 4 to 16 years. From Farkas (1981), by permission. 110

Figure 7.99 Mandibular width, both sexes, 4 to 16 years. From Farkas (1981), by permission. 110

4 5 6 7 8 9 10 11 11 12 13 14 16 Age (years)

Chapter 7 Craniofacies The Neck

Introduction

Most of the congenital malformations of the neck originate during transformation of the branchial apparatus into adult structures. Branchial cysts, sinuses, or fistulae may develop from parts of the second branchial groove, the cervical sinus, or the second pharyngeal pouch if they fail to regress. An ectopic thyroid gland results when the thyroid gland fails to descend completely from its site of origin in the tongue. The thyroglossal duct may persist, or remnants of it may give rise to thyroglossal duct cysts. These cysts, if infected, may form thyroglossal duct sinuses that open in the midline of the neck, in contrast to the branchial sinuses, which open off-center, close to the borders of the sternocleidomastoid muscle.

Torticollis (wry neck) usually is attributed to injury of the sterno-cleidomastoid muscle during delivery; however, prenatal onset of the anomaly cannot be ruled out. Torticollis can be caused by malformations of the cervical vertebrae. The right and left sides are affected equally without any sex predilection. The incidence is 0.6 per 1000 births. The presence of unequal muscle pull on the developing cranium by torticollis may lead to unequal growth of the skull, with resultant plagiocephaly. A contralateral epicanthal fold is frequently seen. In approximately one third of cases, torticollis is associated with congenital hip dislocation. Both are thought to be caused by cramped circumstances in utero, for example, due to abnormal uterine anatomy, a uterine fibroid, or oligohydramnios.

Estimation of the length and width of the neck is very subjective, and normal age-related charts are not available. The neck is generally short in the neonate and begins to elongate in the older child. The width of the neck obviously varies, increasing from a superior to an inferior aspect in general. A wide neck may be associated with marked skin folds or webs or with prominence of the trapezius muscle. Folds, webs, and prominent trapezius may be related to prenatal onset of lymphatic obstruction. An early clue in the newborn period is the presence of excess nuchal skin and posteriorly rotated auricles with an upturned lobule. The circumference of the neck may be quantified, and the charts are available in this section.

The neck should also be inspected for branchial arch remnants such as pits, sinuses, fistulae and tags.

The Neck

Definition The distance around the neck.

Landmarks Measure around the neck in a horizontal plane at the level of the most prominent portion of the thyroid cartilage (Fig. 7.100).

Instruments Tape-measure.

Position The head should be held erect (in the resting position) with the eyes facing forward.

Remarks Normal values to age 12 years are presented in Fig. 7.101. The neck may be broad because of excessive prominence of the trapezius or secondary to skinfolds or webs. Both these anatomical differences can be associated with excess nuchal skin in the newborn period and with lymphatic obstruction during prenatal development.

Pitfalls In the presence of prominent folds of skin or webs at the side of the neck, the tape-measure should carefully follow the surface of the skin to reflect circumference accurately. The horizontal plane at which measurement occurs should be carefully selected at the most prominent portion of the thyroid cartilage.

Figure 7.100 Measuring neck circumference.

Figure 7.100 Measuring neck circumference.

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