Radiological interpretation and the differential diagnosis of radiolucencies of the jaws

Question 1

What thought process should you follow when you see a radiolucency on a radiograph?

Answer 1

Question 2

What do the submandibular fossa look like on a radiograph?

Answer 2

Question 3

What does unilocular mean?

Answer 3

having, consisting of, or characterized by only one loculus or cavity; single-chambered.

Question 4

What are the different types of cyst?

Answer 4

1. Odontogenic cysts (formed from tissues involved in odontogenesis):
   - radicular dental cyst
   - residual dental cyst
   - lateral periodontal cyst
   - dentigerous cyst
2. Non-odontogenic cysts:
   - nasopalatine duct cyst
   - bone cysts (solitary bone cysts, aneurysmal bone cyst)
   - nasolabial cyst

Question 5

What is a radicular cyst?

Answer 5

• Origin: Cell rests of Malassez from the epithelial remnants of Hertwig’s root sheath.
• Most commonly found in adults aged 2-50.
• Most common of all jaw cysts (>70%)
• Site: Apex of a non-vital tooth
• Size: 1.5 – 3cm
• Shape: Round / Oval and unilocular
• Outline: Smooth, well defined, corticated (unless infected whereby cortication is lost)
• Radiodensity: Uniformly radiolucent
• Effects: Displace teeth, antral floor, IDN canal. Buccal expansion. Can resorb teeth but rarely

Question 6

What’s the difference between a chronic and an acutely developed cyst?

Answer 6

See image

Question 7

What is a residual cyst?

Answer 7

• Origin: Refers to a radicular cyst remaining after the causative tooth has been removed
• Age: Commonly adults >20 years
• Site: Apical region of the tooth bearing portion of the jaws
• Size: 1.5 – 3cm
• Shape: Round / Oval and unilocular
• Outline: Smooth, well defined, corticated (unless infected whereby cortication is lost)
• Radidensity: Uniformly radiolucent
• Effects: Displace teeth, antral floor, IDN canal. Buccal expansion. Can resorb teeth but rarely

Question 8

What is a lateral periodontal cyst? (developmental)

Answer 8

• Origin: ? Reduced enamel epithelium
• Age: Commonly adults >30 years
• Frequency: Rare
• Site: Lateral root surface
• Size: Small
• Shape: Round and unilocular
• Outline: Smooth, well defined, corticated (unless infected whereby cortication is lost)
• Radiodensity: Uniformly radiolucent
• Effects: Displace teeth if large, rarely resorb. May cause buccal expansion

Question 9

What is a botyroid cyst?

Answer 9

A multilocular variant of a lateral periodontal cyst. It is rare and seen more in middle age to older adults.

Question 10

What is a dentigerous (follicular) cyst?

Answer 10

• Origin: Remnants of the reduced enamel epithelium after tooth formation
• Age: Usually adolescents / young adults
• Frequency: ~20% of odontogenic cysts
• Site: Crown of an unerupted and displaced tooth (3’s and 8’s)
• Size: Suspected if follicle >3-4mm can become large (several cm’s)
• Shape: Round / oval and unilocular
• Outline: Smooth, well defined, corticated
• Radiodensity: Uniformly radiolucent
• Effects: Displace teeth and resorb in ~50% May cause bony expansion displacement of the antrum

Question 11

What is an eruption cyst?

Answer 11

a bluish swelling that occurs on the soft tissue over an erupting tooth. It is usually found in children. The fluid in thecyst is sometimes clear creating a pale-coloured cyst although often they are blue. An eruption cyst (eruption hematoma) is a developmental soft-tissue cyst ofodontogenic origin that forms over an erupting tooth.

Question 12

What’s a nasopalatine duct cyst? (incisive canal cyst)

Answer 12

• Origin: Epithelial remnants of the nasopalatine duct or incisive canal.
• Age: Variable but commonly middle aged
• Frequency: Most common non odontogenic cyst ~1% of population
• Site: Midline anterior maxilla
• Size: From 6mm to several cm’s
• Shape: Round / oval and unilocular
• Outline: Smooth, well defined, corticated
• Radiodensity: Uniformly radiolucent
• Effects: Displace teeth distally, rarely resorb. Palatal expansion

Question 13

What is a solitary bone cyst?

Answer 13

Commonly seen in the young – probable trauma related

Question 14

What are the different types of multilocular radiolucencies seen in radiographs of the head and neck?

Answer 14

1. Odontogenic tumours:

• Keratocystic odontogenic tumour (Odontogenic keratocyst)
• Ameloblastoma
• Ameloblastic fibroma Ameloblastic fibro- odontoma
• Odontogenic myxoma
• Odontogenic fibroma
• Sialo-odontogenic tumour

2. Giant cell lesions:

• Central giant cell granuloma
• Cherubism
• Browns Tumour of Hyperparathyroidism
• Aneurysmal bone cyst

Question 15

What is an odontogenic keratocyst?

Answer 15

• A multilocular radiolucency.
• They are seen in Gorlin Goltz Syndrome.
• Origin: Epithelium of the dental lamina
• Age: Peak incidence 2nd to 3rd decade
• Frequency: Rare but most common (if termed an odontogenic tumour)
• Site: Posterior body / angle of mandible Anterior maxilla canine region
• Size: Variable
• Shape: Oval, extending along the body of the mandible Pseudo / multilocular
• Outline: Smooth and scalloped, well defined and corticated
• Radiodensity: Uniformly radiolucent
• Effects: Tooth displacement, rarely resorb. Extensive expansion within cancellous bone. Possible cortical perforation.

Question 16

What is Gorlin-Goltz syndrome?

Answer 16

 Multiple basal cell carcinomas of the skin

 Odontogenic keratocysts: Seen in 75% of patients and is the most common finding. There are usually multiple lesions found in the mandible. They occur at a young age (19 yrs average).

 Rib and vertebrae anomalies

 Intracranial calcification

 Skeletal abnormalities: bifid ribs, kyphoscoliosis, early calcification of falx cerebri

 Distinct faces: frontal and temporopariental bossing, hypertelorism, and mandibular prognathism

Question 17

What’s an ameloblastoma?

Answer 17

May mimic other radiolucencies.

• Origin: Remnants of the odontogenic epithelium of the enamel organ or dental lamina
• Age: 30-60 years old
• Frequency: Rare
• Site: 80% posterior body / angle / ramus of mandible Anterior mandible in black Africans
• Size: Variable – can become very large and disfiguring
• Shape: Multilocular, distinct septa dividing the lesion into compartments “soap bubble effect” Occasionally unilocular in early stages
• Outline: Smooth and scalloped, well defined and corticated
• Radiodensity: Radiolucent with Radiopaque septa
• Effects: Teeth displaced, loosened and often resorbed Extension expansion in all dimensions Extension into adjacent structures; for example maxillary sinuses, orbit. Displacement of IDN canal

Question 18

What’s a unicystic ameloblastoma?

Answer 18

Account for ~15% of Ameloblastoma. Equal distribution between maxilla and mandible. Usually unilocular associated with the crown of an un erupted tooth peak age 35 years.

Question 19

What is this?

Answer 19

An Ameloblastic fibro-odontoma

Question 20

What is an Odontogenic myxoma?

Answer 20

Origin: Odontogenic connective tissue fibroblasts of the developing tooth germ.

Age: Young adults 2nd-4th decades

Frequency: Rare

Site: Posterior maxilla or mandible

Size: Variable

Shape: Multilocular – honeycomb or soap bubble

Outline: Well defined with variable cortication

Radiodensity: Radiolucent with fine radiopaque internal septa often arranged at right angles to each other

Effects: Displaced teeth occasionally resorbed, may be associated with an un erupted tooth cortical expansion / breach.

Question 21

What is cortical expansion?

Answer 21

Cortical expansion is a radiological description which means thickening of the cortex of the bone being radiographed. It can also mean widening of the bone, with a cortex being seen. The cortex is the shell of the bone, versus the medulla which is the central spongy bone. The possible causes are numerous, and vary from trauma to infection to tumor etc.

Question 22

What are examples of giant cell lesions?

Answer 22

Central Giant Cell Granuloma

Aneurysmal Bone Cyst

Brown’s Tumour of Hyperparathyroidism Cherubism

Question 23

What is a central giant cell granuloma?

Answer 23

Age: All ages but usually young majority

Frequency: Rare

Site: Mandible – main feature often crosses midline

Size: Variable – can become large

Shape: Multilocular

Outline: Smooth and scalloped, well defined and generally not well corticated

Radiodensity: Radiolucent with Radiopaque thin septa - honeycomb

Effects: Teeth displaced, loosened and often resorbed Extension expansion in all dimensions Extension into adjacent structures; for example maxillary sinuses, orbit. Displacement of IDN canal

Question 24

What’s an aneurysmal bone cyst?

Answer 24

Age: Adolescents and young adults under 30

Frequency: Rare

Site: Commonly body / posterior mandible

Size: Can become very large

Shape: Unilocular / Multilocular – may be soap bubble appearance

Outline: Smooth and well defined

Radiodensity: Radiolucent with faint random trabeculation

Effects: Teeth displaced uncommonly resorbed Ballooning expansion Rare cortical perforation

Question 25

Hyperparathyroidism?

Answer 25

 1 0 Hyperparathyroidism – parathyroid hyperplasia / an adenoma  2 0 Hyperparathyroidism – kidney disease  Leads to increased secretion of parathormone and raised plasma calcium levels

Question 26

What is cherubism?

Answer 26

Age: Children 2-6 years old Frequency: Rare Site: Bilateral mandible and maxilla Size: Variable, May fill whole jaw Shape: Multilocular Often symmetrical Outline: Smooth and well defined and corticated Radiodensity: Radiolucent with internal radiopaque septa Effects: Teeth displaced occasionally resorbed Bucco-lingual expansion Encroachment on the antra

Question 27

What does the outline/periphery of a lesion tell you?

Answer 27

 Provides information about the nature of the lesion i.e. benign or malignant and speed of growth  A slow growing benign lesion such as a cyst is more likely to have a well defined smooth corticated outline  A more aggressive lesion is more likely to be ill defined

Question 28

What does squamous cell carcinoma of the frontal bone look like?

Answer 28

See image

Question 29

What are examples of Well Defined Non-Corticated Lesions: Punched out lesions?

Question 30

What is Langerhans cell disease?

Answer 30

Proliferation of Langherhans cells and eosinophilic granulomas. - Solitary eosinophilic granuloma - Multifocal eosinophilic granuloma (Hand Schuller – Christian disease) - Letterer – Siwe disease Frequency: Rare Site: Skull vault, posterior mandible or maxilla Multiple lesions in Hand Schuller – Christian and Letterer – Siwe disease Size: Small Shape: Round Unilocular Outline: Well defined, smooth, non corticated, punched out Radiodensity: Radiolucent Effects: Teeth not resorbed periodontal support is sometimes lost; teeth appear floating. No bony expansion

Question 31

What is Multiple Myeloma?

Answer 31

Multifocal proliferation of the plasma cell series within the bone marrow leads to overproduction of Immunoglobulins. Age: Middle aged Frequency: Uncommon Site: Skull vault, posterior mandible and other bones Size: Variable may be several cm’s and can coalesce Shape: Round Unilocular , multifocal Outline: Well defined, non corticated, punched out Radiodensity: Radiolucent Effects: May lead to pathological fracture