Other Morphological Anomalies Involving the Jaws










210
Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong.
© 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.
14.1 Hemimandibular hyperplasia
(Figures14.1–14.3)
Increased development of a hemimandible.
Note:
Bilaterally and symmetrically relatively prominent man-
dibles are not infrequently seen, a normal variant (class
III relationship).
Symmetric abnormal excessive growth of the mandible
can be seen in endocrine disorders such as acromegaly.
Generally considered to be developmental.
Note that facial bones are often slightly asymmetric, a nor-
mal variant.
The hyperplasia may involve the entire hemimandible or a
part of it. It may be limited to the mandibular condylar (refer
to Chapter 18) and/or coronoid (refer to Chapter 18) pro-
cesses. It can also be limited to the ramus. Other cases involve
the ramus and posterior body of the mandible.
Most common presentation is facial asymmetry.
Varying degrees of severity and rates of progression.
Growth may occasionally continue past the end of skeletal
maturity of other bones.
May be more evident in the vertical (craniocaudal) dimen-
sion or may be primarily in the transverse dimension,
where the mandibular symphysis is located contralateralto
the overall facial midline. Various combinations are seen.
There are often associated changes to the occlusion, e.g.
open bite and cross bite. Canting of the occlusal plane and
associated compensatory asymmetry of the maxillary alve-
olar process is often seen.
Sometimes, there is associated temporomandibular joint dys-
function and related symptoms.
Radiological features
When imaging is indicated, multidetector computed tomog-
raphy (MDCT)or cone beam computed tomography (CBCT)
are recommended over 2D radiography. Magnetic resonance
imaging (MRI) may be useful if there is associated joint dys-
function or other related symptoms.
Technetium bone scans, especially single‐photon emission
computed tomography, may be useful to determine condylar
growth activity. However, increased uptake is non‐specific
and many other conditions, including degenerative changes,
can contribute to this. Therefore, evaluation with MDCT or
CBCT is recommended prior to bone scans.
The affected hemimandible demonstrates variably larger
condyle, coronoid process, ramus and body of the mandible.
This increased dimension may be more evident in one plane
than another. For example, a hemimandible (or part of) may
be larger craniocaudally (vertically) or longer with asymme-
try limited to the transverse dimension or may be larger
mediolaterally (buccolingually) or there may be various
combinations.
The condylar neck may be bowed posteriorly and/or laterally
and the ramus may be bowed laterally.
The antegonial notch is usually less obvious or flattened relative
to the normal contralateral side. Occasionally, the inferior border
of the mandible in this antegonial region may appear convex.
Note that there is a large normal variation in the promi-
nence of the antegonial notches, which are sometimes
non-existent. However, these appearances should be
symmetric.
There may be remodelling of the glenoid fossa related to con-
dylar hyperplasia.
Differential diagnosis
Key radiological differences
Contralateral
hemimandibular
hypoplasia
The morphology typical of hyperplasia or
hypoplasia may be helpful. Occasionally,
differentiation can be difficult as the
hemimandibles are similar in morphology
where the difference in size is the only feature.
Conditions
contributing to
increased size of
the condyle or
hemimandible
For example, osteochondroma, osteoma,
fibrous dysplasia–these conditions present
as focal diseases and may be associated with
focal bony prominence rather than overall
enlargement.
CHAPTER 14
Other Morphological Anomalies Involving theJaws

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210Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong. © 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.14.1 Hemimandibular hyperplasia (Figures14.1–14.3)• Increased development of a hemimandible. ◦Note: ■ Bilaterally and symmetrically relatively prominent man-dibles are not infrequently seen, a normal variant (class III relationship). ■ Symmetric abnormal excessive growth of the mandible can be seen in endocrine disorders such as acromegaly.• Generally considered to be developmental. ◦Note that facial bones are often slightly asymmetric, a nor-mal variant.• The hyperplasia may involve the entire hemimandible or a part of it. It may be limited to the mandibular condylar (refer to Chapter 18) and/or coronoid (refer to Chapter 18) pro-cesses. It can also be limited to the ramus. Other cases involve the ramus and posterior body of the mandible.• Most common presentation is facial asymmetry. ◦Varying degrees of severity and rates of progression. ◦Growth may occasionally continue past the end of skeletal maturity of other bones. ◦May be more evident in the vertical (craniocaudal) dimen-sion or may be primarily in the transverse dimension, where the mandibular symphysis is located contralateralto the overall facial midline. Various combinations are seen. ◦There are often associated changes to the occlusion, e.g. open bite and cross bite. Canting of the occlusal plane and associated compensatory asymmetry of the maxillary alve-olar process is often seen.• Sometimes, there is associated temporomandibular joint dys-function and related symptoms.Radiological features• When imaging is indicated, multidetector computed tomog-raphy (MDCT)or cone beam computed tomography (CBCT) are recommended over 2D radiography. Magnetic resonance imaging (MRI) may be useful if there is associated joint dys-function or other related symptoms.• Technetium bone scans, especially single‐photon emission computed tomography, may be useful to determine condylar growth activity. However, increased uptake is non‐specific and many other conditions, including degenerative changes, can contribute to this. Therefore, evaluation with MDCT or CBCT is recommended prior to bone scans.• The affected hemimandible demonstrates variably larger condyle, coronoid process, ramus and body of the mandible. This increased dimension may be more evident in one plane than another. For example, a hemimandible (or part of) may be larger craniocaudally (vertically) or longer with asymme-try limited to the transverse dimension or may be larger mediolaterally (buccolingually) or there may be various combinations.• The condylar neck may be bowed posteriorly and/or laterally and the ramus may be bowed laterally.• The antegonial notch is usually less obvious or flattened relative to the normal contralateral side. Occasionally, the inferior border of the mandible in this antegonial region may appear convex. ◦Note that there is a large normal variation in the promi-nence of the antegonial notches, which are sometimes non-existent. However, these appearances should be symmetric.• There may be remodelling of the glenoid fossa related to con-dylar hyperplasia.Differential diagnosisKey radiological differencesContralateral hemimandibular hypoplasiaThe morphology typical of hyperplasia or hypoplasia may be helpful. Occasionally, differentiation can be difficult as the hemimandibles are similar in morphology where the difference in size is the only feature.Conditions contributing to increased size of the condyle or hemimandibleFor example, osteochondroma, osteoma, fibrous dysplasia–these conditions present as focal diseases and may be associated with focal bony prominence rather than overall enlargement.CHAPTER 14Other Morphological Anomalies Involving theJaws Flattening of the antegonialnotch of the larger left hemimandible(a) (b)Figure14.2 Left hemimandibular hyperplasia: panoramic (a) and lateral (b) radiographs.Slight lateral bowing ofthe condyle and ramusSymphysis is left of the overall facial midline, especially inferiorlyFigure14.3 Right hemimandibular hyperplasia: surface‐rendered MDCT image.Inferoposterior bowing ofthe larger left hemimandible(a) (b)Figure14.1 Left hemimandibular hyperplasia: panoramic (a) and lateral (b) radiographs. 212 Atlas of Oral and Maxillofacial Radiology14.2 AcromegalyRefer to Chapter15.14.3 Mandibular andhemimandibular hypoplasia (Figures14.4–14.6)• Reduced development of the affected mandible. ◦Note that facial bones are often slightly asymmetric, a nor-mal variant.• May be bilateral (mandibular) or unilateral (hemimandibular).• May be developmental or related to a trauma/condition interrupting mandibular growth (usually the condyle). Occasionally congenital, most of which are related to syn-dromes, e.g. Pierre Robin syndrome.• Most cases demonstrate condylar hypoplasia of the affected side. However, hypoplasia can be limited to the condyle (refer to Chapter18). While generally not considered to be a hypo-plastic condition, the bifid condyle (refer to Chapter18) may result in an overall smaller appearance of the affected condyle, especially on a panoramic radiograph.• Bilateral cases present with small hypoplastic mandibles, usu-ally symmetric.• Unilateral cases present with facial asymmetry. Associated canting of the occlusal plane and compensatory asymmetry of the maxillary alveolar process is often seen.• Sometimes associated with temporomandibular joint dys-function and related symptoms. Hypoplastic condyles often demonstrate degenerative changes earlier in life.Radiological features• When imaging is indicated, MDCT or CBCT are recom-mended over 2D radiography. MRI may be useful if there is associated joint dysfunction or other related symptoms.• The affected mandible/hemimandible is smaller than usually expected.• Almost all cases of mandibular hypoplasia demonstrate con-dylar hypoplasia (refer to Chapter18).• The affected mandible/hemimandible also demonstrates a variably smaller ramus and body of the mandible. This decreased dimension may be more evident in one plane than another. Occasionally, the hypoplasia affects the condyle and ramus much more than the body of the mandible.• The condylar neck is usually bowed anteriorly and/or medi-ally and the ramus may be bowed medially.• The antegonial notch is usually more pronounced. ◦It should be noted that there is a large normal variation in the prominence of the antegonial notch, which is some-times non‐existent.Differential diagnosisKey radiological differencesContralateral hemimandibular hyperplasia in unilateral casesThe morphology typical of hyperplasia or hypoplasia may be helpful. Occasionally, differentiation can be difficult as the hemimandibular difference in size is the only difference.Normal variant The mandible can be relatively small in normal persons, and is considered a normal variant (class II relationship). Other Morphological Anomalies Involving theJaws 213Prominent antegonialnotches bilaterallyBilaterally small posterior body, rami and condyles Figure14.5 Mandibular hypoplasia: panoramic radiograph.Prominent antegonialnotches bilaterallyBilaterally small posterior body, rami and condyles. Note the short and square appearance of the rami Figure14.4 Mandibular hypoplasia: panoramic radiograph. 214 Atlas of Oral and Maxillofacial Radiology14.4 Stafne defect (Figures14.7–14.9)• Synonyms: lingual salivary gland depression, Stafne cyst, Stafne bone cavity.• Focal corticated depression at the medial/lingual surface of the mandible.• Most commonly seen in the posterior mandible inferiorly.• It is has been historically accepted that these concavities are developmental, related to adjacent submandibular salivary glands. However, this proposed aetiology is questioned.• These defects have been seen to develop and slowly enlarge in the adult, and the vast majority do not demonstrate presence of salivary gland tissue within the depression.• Often incidentally identified. Does not require treatment. Radiological examination (optimally MDCT) is usually suf-ficient, not requiring biopsy.Radiological features• When imaging is indicated, MDCT is preferred over CBCT as the soft tissue content within the depression is poorly demon-strated with CBCT. However, CBCT may suffice, especially if there is no access to MDCT. ◦Focal, well‐corticated, round, ovoid or lobulated depression at the medial/lingual surface of the mandible. Not infre-quently, a cortical lip is seen at the lingual cortical edges of this depression. ◦When located at the inferior body of the mandible, it often involves the lingual/medial aspect of the inferior mandibu-lar cortex, preserving the lateral/buccal aspect of this infe-rior cortex. ◦The vast majority demonstrate fat within these concavities (MDCT soft tissue window or MRI). Occasionally, a part of a submandibular lymph node or salivary gland is seen within this portion of the concavity.• In the panoramic radiograph, it classically presents as a lucency with a heavily corticated superior border and a thin-ner and/or more hypodense inferior border. In a larger defect involving the inferior border of the mandible, the inferior mandibular cortex may appear absent or hypodense in this view.Differential diagnosisKey radiological differencesCystic lesions Classically presenting Stafne defects may besufficiently obvious on a panoramic radiograph. However, unless there is absolute confidence in the nature of the lucency based upon this view, MDCT or at least CBCT is suggested. The Stafne defect is almost always definitively identified on MDCT.Prominent overjetBilaterally small posterior mandible and condyles. The right condyle is smaller (a) (b)Figure14.6 Mandibular hypoplasia: panoramic (a) and lateral (b) radiographs. Well-defined lucency with heavily corticated superior borderFat-filledcorticated depression(a) (b)(c)Figure14.8 Stafne defect of the left posterior mandible: cropped panoramic radiograph (a) with axial bone and soft tissue MDCT images (b,c).(b)(a)(c)Well-defined lucencies with heavily corticated superior bordersFigure14.7 Stafne defect of the posterior mandible in three different cases: cropped panoramic radiographs (a–c). 216 Atlas of Oral and Maxillofacial Radiology14.5 Cleft lip andpalate (Figures14.10–14.13)• A group of developmental anomalies that include cleft lip, cleft palate or both.• One of the most common facial birth defects.• Failure of fusion of developmental processes.• Often divided into two groups, with different aetiologies: ◦Cleft lip with or without cleft palate ◦Cleft palate.• Variable severity, ranging from a small unilateral lip cleft to bilateral osseous and soft tissue cleft of the alveolus and also at the palatal midline. The bifid uvula is considered a mild manifestation.• There are many associated problems including speech, swal-lowing and increased risks of middle ear infections.• There are often dental anomalies at the alveolar cleft, includ-ing congenital absent, supernumerary, hypoplastic and mal-formed teeth. Dental anomalies elsewhere are also more commonly seen and there may be a slight delay in the overall dental development.• The maxilla is often relatively smaller in relation to the man-dible and is taken into account as part of the orthodontic and orthognathic evaluation and management.Radiological features• When imaging is indicated, MDCT or CBCT are recom-mended over 2D radiography.• In utero imaging for the presence of cleft lip/palate (antenatal ultrasound) is not within the scope of this atlas.Appearance of a well-defined lucency with heavily corticated superior border and thinned mandibular inferior cortexFat-filledcorticated depressionLipping of thelingual cortex(b)(c) (a)Figure14.9 Stafne defect of the left posterior mandible: cropped panoramic radiograph (a) with axial bone and soft tissue MDCT images (b,c). Other Morphological Anomalies Involving theJaws 217Lucent cleft defect which is onlypartly within the focal trough. The corticated mesial border is visualisedSupernumerary tooth Figure14.10 Left anterior maxillary cleft: cropped panoramic radiograph.Lucent cleft defect whichis partly within thefocal troughMalformed teeth Figure14.11 Left anterior maxillary cleft: cropped panoramic radiograph.• The osseous clefts appear as well‐defined corticated defects. ◦There may soft tissue bridging these osseous clefts. ◦Where there is oronasal communication an air track (MDCT or CBCT) may be seen within the bony clefts. However, an oronasal communication cannot be excluded when an air track is not seen, as the mucosal lining of the oronasal communication may be in contact.• Dental anomalies may be seen at the region of the alveolar clefts and/or elsewhere (refer to Chapter3).Differential diagnosisKey radiological differencesAnterior maxillary lucent lesionsOn panoramic and intraoral radiographs, the bony clefts may sometimes present as non‐specific lucencies. If clinically indicated, the clefts are usually obvious on CBCT and MDCT. 218 Atlas of Oral and Maxillofacial RadiologyWell-defined corticatedcleft defect. Note the presenceof soft tissue within the defect,although this does not excludepossible oronasal communication(a) (b)(c)Figure14.12 Palatal and left anterior maxillary cleft: axial and coronal (a,c) and surface‐rendered (b) MDCT images.Well-defined corticated cleft defect. Note the associated asymmetry ofthe nasal floor (a) (b)Figure14.13 Right anterior maxillary cleft: axial (a) and coronal (b) MDCT images.

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