Terminology Definitions Morphogenetic fields Embryological cellular regions with potential for development into discrete anatomic structures Gradient fields Describe gradually varying potential to form specific individual bones and organs within morphogenetic field Homeobox genes Gene family complexes that regulate early embryologic differentiation Located on separate chromosomes Arranged linearly in same order as expression along craniocaudal axis Imaging Protocols Multiplanar magnetic resonance imaging best evaluates soft tissues, neural…

Imaging Anatomy There are 33 spinal vertebrae, which comprise 2 components: A cylindrical ventral bone mass, which is the vertebral body , and the dorsal arch . 7 cervical, 12 thoracic, 5 lumbar bodies 5 fused elements form the sacrum 4-5 irregular ossicles form the coccyx Arch 2 pedicles, 2 laminae, 7 processes (1 spinous, 4 articular, 2 transverse) Pedicles attach to the dorsolateral aspect of…

KEY FACTS Terminology Optic nerve sheath meningioma Also known as perioptic meningioma Benign, slow-growing tumor of optic nerve sheath Distinct entity from intracranial (spheno-orbital) meningioma that extends through orbital apex into orbit Imaging NECT “Tram-track” Ca++ on either side of optic nerve – Seen in 1/3 to 1/2 of cases CECT Tubular enhancing mass surrounding intraorbital optic nerve MR Variably hyperintense to hypointense on T2WI Uniform,…

KEY FACTS Terminology Optic pathway glioma (OPG) Primary neuroglial tumor of optic pathway 3 broad clinical subtypes Childhood syndromic [neurofibromatosis type 1 (NF1)], childhood sporadic, adult Imaging Fusiform optic nerve (ON) mass with variable posterior pathway involvement MR is preferred imaging modality Isointense to mildly hypointense on T1WI Variably hyperintense on T2WI Enhancement varies from none/minimal to intense Associated neuroimaging findings in NF1: ↑ T2 foci…

KEY FACTS Terminology Nonspecific orbital inflammation, not due to any known etiology or systemic illness Imaging Best imaging tool: Contrast-enhanced MR with fat suppression Poorly marginated mass-like enhancing soft tissue involving any area of orbit Categorized by area(s) of involvement Myositic, lacrimal, anterior, diffuse, apical Moderate diffuse enlargement, irregularity, and enhancement of involved structures Isointense or slightly hyperintense on T2WI or STIR ↓ signal compared with…

KEY FACTS Terminology Synonyms: Graves ophthalmopathy, thyroid orbitopathy Autoimmune orbital inflammatory condition associated with thyroid dysfunction Imaging CT For uncomplicated disease and surgical planning Nonuniform, symmetric, or asymmetric extraocular muscle involvement Enlargement of muscle bellies, sparing tendinous insertions “I'M SLO” mnemonic for sites of predilection – I nferior > m edial > s uperior > l ateral > o blique Increased volume of orbital fat –…

KEY FACTS Imaging Focal or segmental T2 hyperintensity of optic nerve Nerve normal in size or minimally enlarged Central or diffuse nerve enhancement ± peripheral sheath enhancement Top Differential Diagnoses Neuromyelitis optica Ischemic optic neuropathy Infectious optic neuritis (ON) Idiopathic perineuritis (pseudotumor) Granulomatous optic neuropathy (sarcoid) Optic nerve sheath meningioma Optic nerve glioma Pathology Presumed autoimmune process triggered by infection, systemic disease, or other stressor Clinical…

Imaging Approach & Indications General Approach Imaging of the orbit encompasses 2 clinically distinct areas of ophthalmology: (1) The eye or globe and (2) the bony orbit, soft tissues, and periorbita. Lesions in these 2 areas result in specific clinical profiles that affect different patient groups. When a patient is referred for imaging, it is usually clear to the clinician whether the problem involves the eye…

KEY FACTS Imaging Enhancing lesion(s) with skull/meningeal destruction/infiltration Skull, dura, leptomeninges, arachnoid/subarachnoid, pia, and subgaleal Many manifestations: Smooth thickening, nodularity, loculation, lobulation, fungating masses Top Differential Diagnoses Skull metastases: Surgical defect (burr hole, craniectomy), myeloma Dural metastases: Epidural/subdural hematoma, meningioma Leptomeningeal metastases: Subarachnoid hemorrhage, sarcoidosis, infectious meningitis Clinical Issues 18% of patients with extracranial and intracranial malignancies Primary tumor never identified in 2-4% All metastases: May…

KEY FACTS Terminology Clonal B-lymphocyte neoplasm of terminally differentiated plasma cells Solitary = plasmacytoma – Brain/CNS is extramedullary plasmacytoma Multifocal = multiple myeloma (MM) Imaging Intracranial MM rare (1% of MM) Can occur as solitary (primary) plasmacytoma or manifestation of systemic MM (secondary) Secondary – Extension from osteolytic skull lesion > hematogenous spread Primary CNS myeloma rare – Extraaxial dural-based nonosseous lesions – CNS “myelomatosis” involving…

KEY FACTS Terminology Benign intraosseous skull lesion with predominantly vascular and some avascular components Imaging Best clue Sharply marginated expansile skull lesion Frontal, temporal, parietal bone in decreasing order Most often solitary, but multiple in 15% Best imaging tool: Bone CT Sharply marginated expansile lesion Thin peripheral sclerotic rim in 1/3 Intact inner and outer table Outer table often more expanded than inner table Trabecular thickening…

KEY FACTS Terminology Typical (benign) meningioma = WHO grade I Atypical meningioma (AM) = WHO grade II Malignant meningioma (MM) = WHO grade III Imaging CT triad of MM: Extracranial mass, osteolysis, intracranial tumor MR Dural-based locally invasive lesion with areas of necrosis, marked brain edema Indistinct tumor margins (tumor invades, interdigitates with brain) Prominent tumor pannus extending away from mass = “mushrooming” Marked peritumoral edema…

KEY FACTS Imaging Intradural extramedullary mass Thoracic (80%) > cervical (16%) > lumbar (4%) Typically round or ovoid (en globe) En plaque variety pancaked or flat along dura Broad-based dural attachment Strong homogeneous enhancement Prominent “dural tail” less common than with intracranial Calcification in 1-5% No bony remodeling or hyperostosis in spine Top Differential Diagnoses Schwannoma Ependymoma, myxopapillary Lymphoma Intradural metastases Pathology Arise from arachnoid cap…

KEY FACTS Terminology Trichilemmal cyst (TC) is preferred term Sebaceous cyst commonly used but incorrect Variant = proliferating trichilemmal tumor Keratin-containing cyst Lined by stratified squamous epithelium Pathology looks like root sheath of hair follicle Imaging General features Most within dermis or subcutaneous tissue Size varies (few millimeters to several centimeters) Can be single or multiple CT Round/ovoid, well-delineated scalp mass Multifocal punctate/curvilinear/coarse Ca++ MR Isointense…

KEY FACTS Terminology Multisystem inflammatory disease characterized by noncaseating epithelioid-cell granulomas Imaging Solitary or multifocal CNS mass(es) ± abnormal CXR CXR abnormal in > 90% with neurosarcoid (NS) Wide spectrum of MR manifestations Dura-arachnoid thickening (diffuse or focal)) May coat pia, cranial nerves, fill internal auditory canals Pituitary stalk/hypothalamus thickening Can thicken, infiltrate choroid plexi Can infiltrate orbital adnexa, optic nerve Rare – Small vessel vasculitis/angiitis…

KEY FACTS Terminology Langerhans cell histiocytosis (LCH) LCH now best understood as neoplastic disease Activating somatic BRAF mutations, LCH cell clonality Imaging NECT Sharply marginated lytic skull defect – Beveled edges Mastoid: Geographic destruction, soft tissue mass MR Absent posterior pituitary “bright spot” on T1WI Thick enhancing infundibulum Enhancing masses in choroid plexus, leptomeninges, basal ganglia Sometimes cerebellar white matter disease Top Differential Diagnoses Lytic calvarial…

KEY FACTS Terminology Skull thickening (ST) Diploic space expanded ± thickened cortex Imaging Widened calvaria (skull width) Can be diffuse or focal NECT best for most causes of ST Thin-section bone CT for detailed skull base evaluation MR C+ contrast: Look for adjacent dural involvement Top Differential Diagnoses Normal variation (most common cause) Shunted hydrocephalus or infantile brain injury Neonatal meningitis or cerebritis Hypoxia/ischemia/hypoglycemia in neonatal…

KEY FACTS Terminology Chronic metabolic skeletal disorder Characterized by bony expansion with variable destruction ± sclerosis Imaging Well-circumscribed, sharply marginated defects &/or marked thickening + sclerosis Skull in 25-65% (may be isolated to skull base) Diploic widening, coarse trabecula, thick cortices “Tam-o'-shanter” skull: Marked ↑ diploic space, particularly inner table “Cotton wool” skull: Focal sclerosis within previous areas of “osteoporosis circumscripta” Platybasia Typically “hot” throughout all…

KEY FACTS Terminology Fibrous dysplasia (FD) Synonyms: Craniofacial fibrous dysplasia (CFD), osteitis fibrosa, osteodystrophy fibrosa McCune-Albright syndrome (MAS) 1 of most common FD syndromes Congenital disorder characterized by expanding lesion(s) Defect in osteoblastic differentiation, maturation Contains mixture of fibrous tissue, woven bone Imaging Best diagnostic clue: Ground-glass matrix in bone lesion on CT CFD: Majority have > 1 bone involved MR: ↓ T2WI signal throughout (if…

KEY FACTS Terminology IgG4-related disease (IgG4-RD) Chronic fibroinflammatory disease characterized by IgG4(+) plasma cell infiltrates Imaging Diffusely infiltrating enhancing mass Orbital adnexa (lacrimal gland most common) Dura-arachnoid (IgG4-related hypertrophic pachymeningitis) Pituitary gland, stalk (hypophysitis) Other: Cranial nerves (especially infraorbital nerve), brain (autoimmune-like encephalopathy) MR Isointense to brain on T1WI, hypointense on T2WI Enhances strongly, uniformly Top Differential Diagnoses Idiopathic inflammatory pseudotumor Meningioma Neurosarcoid Lymphoma Clinical Issues…