Atlas of Head/Neck and Spine Normal Imaging Variants

Preface
Contents
1: Head/Neck and Spine Imaging Variants: Introduction
2: Sinonasal Variants
	2.1	 Introduction, Technique, and Basic Anatomy
	2.2	 Pattern of Serial Paranasal Sinus Development and Sequential Pneumatization
	2.3	 Maxillary Sinus
		2.3.1	 Maxillary Sinus Hypoplasia
		2.3.2	 Accessory Maxillary Sinus Ostia
		2.3.3	 Maxillary Sinus Septa
		2.3.4	 Dehiscence of the Infraorbital Nerve Canal
		2.3.5	 Maxillary Sinus Teeth (“Ectopic Teeth”)
	2.4	 Sphenoid Sinus
		2.4.1	 Sphenoid Sinus Pneumatization: Aerated-Pneumatized Clinoid (Onodi Cell), Pterygoid Processes, and Dehiscent Neural Structures
		2.4.2	 Arrested Pneumatization of the Sphenoid Sinus
	2.5	 Frontal Sinus
		2.5.1	 Frontal Sinus Aplasia and Hypoplasia
		2.5.2	 Crista Galli Aeration-Pneumatization and Other Forms of Frontal Sinus Midline Extension
	2.6	 Ethmoidal Air Cells
		2.6.1	 Agger Nasi Cell, Haller Cell, Bulla Ethmoidalis, and Suprabulbar Recess
	2.7	 Nasal Cavity
		2.7.1	 Concha Bullosa and Pneumatized Uncinate Process
		2.7.2	 Paradoxical Middle Turbinate and Turbinate Sinus
		2.7.3	 Nasal Septal Deviation, Septal Spur, and Septal Pneumatization
	2.8	 Anterior Skull Base
		2.8.1	 Lateral Lamellar Dehiscence and Asymmetry of the Olfactory Fossae
		2.8.2	 The Nasal Cycle
	Suggested Reading
3: Orbital Variants
	3.1	 Introduction, Technique, and Basic Anatomy
	3.2	 Bony Orbit: Normal Orbital Sutures, Orbital Roof Thinning, and Orbital Decompression
		3.2.1	 Normal Orbital Sutures
		3.2.2	 Orbital Roof Thinning
		3.2.3	 Postoperative Orbital Decompression
	3.3	 Globe
		3.3.1	 Intraocular Lens Implant
		3.3.2	 Glaucoma Shunt Implant
		3.3.3	 Scleral Buckle
		3.3.4	 Ocular Injection of Gas or Silicone Oil
		3.3.5	 Orbital Implant and Ocular Prosthesis
		3.3.6	 Eyelid Weights
		3.3.7	 Congenital Proptosis
		3.3.8	 Pseudo-proptosis and Measurement Error Caused by Nonuniform Axial Plane
		3.3.9	 Sedation-Related Strabismus
	3.4	 Extraocular Muscles
		3.4.1	 Normal Contrast Enhancement
		3.4.2	 Physiologic FDG Uptake
	3.5	 Optic Nerve Tortuosity, Diameter, Sheath Distention, and Normal Perineural Enhancement
		3.5.1	 Optic Nerve Tortuosity
		3.5.2	 Optic Nerve Sheath Distention
		3.5.3	 Optic Perineural Enhancement: A Normal Variant
		3.5.4	 Optic Nerve Diameter and Normal Variation
	3.6	 Orbital Calcifications
		3.6.1	 Trochlear Calcifications
		3.6.2	 Drusen
		3.6.3	 Senile Scleral Plaques
		3.6.4	 Arterial Atherosclerosis
	3.7	 Orbital Venous System
		3.7.1	 Superior Ophthalmic Vein Asymmetry and Enlargement
		3.7.2	 Inferior Ophthalmic Venous Plexus
		3.7.3	 Orbital Venous Varix
	3.8	 Lacrimal Gland
		3.8.1	 Lacrimal Gland Size, Symmetry
		3.8.2	 Lacrimal Gland Cyst
	3.9	 Nasolacrimal Duct
		3.9.1	 Opacification/Aeration and Size/Morphology
	3.10	 Orbital Artifacts
		3.10.1	 Incomplete Fat Suppression
		3.10.2	 Ocular Motion Artifact
		3.10.3	 Truncation Artifact
		3.10.4	 Metallic Susceptibility Artifact from Adjacent Facial Hardware or Orbital Foreign Body
	Suggested Reading
4: Neck Soft Tissue Variants
	4.1	 Introduction, Technique, and Basic Anatomy
	4.2	 Tornwaldt Cyst (Pharyngeal Bursa)
	4.3	 Adenoidal Retention Cyst
	4.4	 Lingual Tonsillar Hypertrophy
	4.5	 Vallecular Cyst
	4.6	 Laryngocele
	4.7	 Parapharyngeal Space Lipoma
	4.8	 Medial Retropharyngeal Lymph Nodes in Children
	4.9	 Pterygoid Venous Plexus Asymmetry
	4.10	 Denervation Atrophy of Masticator Muscles and Asymmetric Masticator Uptake on PET-CT
	4.11	 Hypoglossal Denervation and Hemiglossal Atrophy
	4.12	 Retropharyngeal Carotid Artery (If Bilateral: “Kissing Carotid Arteries”)
	4.13	 Thyroid Lipoma
	4.14	 Thyroid Cartilage Lipoma
	4.15	 Thyroglossal Duct Cyst
	4.16	 Ectopic Thyroid
	4.17	 Thyroid Isthmus Agenesis
	4.18	 Thyroid Lobe Asymmetry and Agenesis
	4.19	 Pyramidal Lobe of Thyroid
	4.20	 Submandibular Gland Agenesis (Unilateral)
	4.21	 Sublingual Gland Hypertrophy
	4.22	 Parotid Gland Fatty Replacement: Unilateral and Bilateral
	4.23	 Accessory Parotid Gland
	4.24	 Pneumoparotid
	4.25	 Thymic Hyperplasia
	4.26	 Elongated Styloid Process or Calcified Stylohyoid Ligament (Eagle Syndrome)
	4.27	 Brown Fat on FDG-PET
	4.28	 Vocal Cord FDG Uptake
	4.29	 Lymphoid Tissue FDG Uptake
	Suggested Reading
5: Temporal Bone Variants
	5.1	 Introduction
	5.2	 Internal Auditory Canals: Bulbous or Asymmetric, Small Canals, and Crista Falciformis
		5.2.1	 Bulbous or Prominent Internal Auditory Canals (IACs)
		5.2.2	 Small Internal Auditory Canals (IACs)
		5.2.3	 Crista Falciformis
	5.3	 Cochlear Variants: Osseous Spiral Lamina, Cochlear Cleft, Noise, Canals, and Aqueduct
		5.3.1	 Osseous Spiral Lamina
		5.3.2	 Cochlear Cleft
		5.3.3	 Cochlear Hypoattenuation from Noise and Quantum Mottle
		5.3.4	 Cochlear Aqueduct: Normal Size and Appearance
		5.3.5	 Cochlear Nerve Canal: Normal Size and Appearance
	5.4	 Semicircular Canal Variants: Crura Relative to Thin Apices of Semicircular Canals
		5.4.1	 Vestibular Aqueduct: Normal Size and Appearance
		5.4.2	 Subarcuate Canals
		5.4.3	 Superior Petrosal Sinus Variation in Course and Supply
		5.4.4	 Facial Nerve Canal Fallopian or Geniculate Segment Subarachnoid Space Enlargement
	5.5	 Ossicular and Middle Ear Ligamentous Normal Variants
		5.5.1	 Embryology and Development
		5.5.2	 Malleal Head “Notching” and Pseudo-Clefts from the Incudomallear Joint
		5.5.3	 Notch or Fenestration (“Hole”) in the Incus
		5.5.4	 Suspensory Ligaments of the Middle Ear Ossicles
	5.6	 Aberrant Internal Carotid Artery and Internal Carotid Artery Lateralization
	5.7	 High-Riding Jugular, Jugular Diverticulum, and Jugular Dehiscence
	5.8	 Petrous Apex Fatty Marrow and Pneumatized/Aerated Petrous Apices
	5.9	 Petrous and Petrous Apex Exostoses
	5.10	 Foramen Tympanicum (Foramen of Huschke)
	5.11	 Calcified Auricular Cartilage (“Petrified Ear”)
	Suggested Reading
6: Cervical and Thoracic Spine: Normal Variants and Artifacts
	6.1	 Introduction
	6.2	 Cervical Spine Anatomy and Development
		6.2.1	 Numbering
		6.2.2	 Cervical Ribs
		6.2.3	 Thoracic Rib Variation and Supernumerary (“Lumbar”) Ribs
	6.3	 Vertebral Embryology Overview and Normal Synchondroses
	6.4	 Vertebral Body Development
		6.4.1	 Block (Fused) Vertebrae
		6.4.2	 Vertebral Clefts
	6.5	 Posterior Element Development
	6.6	 Atlantooccipital Assimilation and the Paracondylar Process
		6.6.1	 Atlantooccipital Assimilation
		6.6.2	 Paracondylar Process
		6.6.3	 Development of the Atlas (C1)
		6.6.4	 Development of the Axis (C2)
		6.6.5	 Vertebral Artery Dominance and Foraminal Variation
		6.6.6	 Arcuate Foramen (Foramen of C1)
		6.6.7	 Vascular Channels
	6.7	 Spinal Canal
		6.7.1	 Congenital Spinal Canal Narrowing
	6.8	 Spinal Cord
		6.8.1	 Normal Central Grey Matter
		6.8.2	 Ventral Median Fissure
		6.8.3	 Central Canal Prominence
	6.9	 Accessory Ossification and Ligamentous Ossification Simulating Fractures
		6.9.1	 Craniocervical Accessory Ossicles
		6.9.2	 Ossification of the Posterior Longitudinal Ligament and Diffuse Idiopathic Skeletal Hyperostosis
		6.9.3	 Ossification of the Ligamentum Flavum
		6.9.4	 Ossification of the Nuchal Ligament
		6.9.5	 Old Fractures
	6.10	 Accessory Findings
		6.10.1	 Craniocervical Rotation and Asymmetry of the Odontoid Lateral Mass Interval
		6.10.2	 Pseudosubluxation of C2 on C3
		6.10.3	 Loss (or Reversal) of Cervical Lordosis
		6.10.4	 Epidural Lipomatosis
		6.10.5	 Perineural Cysts
		6.10.6	 Pneumorrhachis
		6.10.7	 Contrast Reflux into Paraspinous Veins and Plexi
	6.11	 Artifacts That Simulate Spinal Lesions
		6.11.1	 CSF Flow Artifact
		6.11.2	 Gibbs Artifact Phenomenon
		6.11.3	 Vacuum Phenomenon
		6.11.4	 Vertebroplasty Cement
	Suggested Reading
7: Normal Variants of the Lumbar and Sacral Spine
	7.1	 Introduction, Acquisition Techniques, and Basic Anatomy
	7.2	 Epidural Lipomatosis
	7.3	 Limbus Vertebra
	7.4	 Schmorl Nodes
	7.5	 Spina Bifida Occulta
	7.6	 Retrosomatic Cleft
	7.7	 Retroisthmic Cleft
	7.8	 Pars Interarticularis Defect
	7.9	 Sacral Cleft
	7.10	 Perineural Cysts (Tarlov Cysts)
	7.11	 Dermal Sinus Tract
	7.12	 Sacralization
	7.13	 Lumbarization
	7.14	 Hemivertebrae
	7.15	 Conus Medullaris at the Level of L3
	7.16	 Ventriculus Terminalis
	7.17	 Vertebral Bone Island
	7.18	 Osteopoikilosis
	7.19	 Filum Terminale Lipoma
	7.20	 Supernumerary Ribs
	7.21	 Vertebral Hemangioma
	7.22	 Dependent Edema
	7.23	 Basivertebral Veins
	7.24	 Prominent Anterior Internal Vertebral Venous Plexus
	7.25	 Normal Age–Related Spine Changes
	7.26	 Sacral Fat Deposition
	7.27	 Retrodural Space of Okada
	7.28	 Conjoined Root
	Suggested Reading
Index