Articles
Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.
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Article
Abscess
Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
a central core consisting of necrotic inflammatory cells and local tissue
peripheral halo of viable neutrophils
surrounded by a 'capsule' with dilated blood vessel...
Article
Anterior vertebral body beaking
Anterior vertebral body beaking occurs in a number of conditions and may eminate from the central portion or the lower third of the vertebral body.
Middle third
Morquio syndrome 1 (middle for Morquio)
Lower third
Hurler syndrome 2
achondroplasia 3
pseudoachondroplasia 4
cretinism 5
Down ...
Article
Atlantodental interval
The atlantodental interval (ADI), as the name suggests, is the horizontal distance between the anterior arch of the atlas and the dens of the axis, used in the diagnosis of atlanto-occipital dissociation injuries and injuries of the atlas and axis.
It is the distance (in mm) between the posteri...
Article
Basilar invagination
Basilar invagination, also called basilar impression, is a congenital or acquired craniocervical junction abnormality where the tip of the odontoid process projects above the foramen magnum.
Terminology
The terms basilar invagination and basilar impression are often used interchangeably becau...
Article
Basion-axial interval
The basion-axial interval (BAI), as the name suggests, is the horizontal distance between the basion and the posterior cortex of the axis, used in the diagnosis of atlanto-occipital dissociation injuries.
It is the distance (in mm) between the basion and the superior extension of the posterior ...
Article
Basion-dens interval
The basion-dens interval (BDI), as the name suggests, is the distance between the basion and the tip of the dens, used in the diagnosis of atlanto-occipital dissociation injuries.
It is the distance from the most inferior portion of the basion to the closest point of the superior aspect of the ...
Article
Bone within a bone appearance
Bone within a bone is a descriptive term applied to bones that appear to have another bone within them. There are numerous causes including:
normal
thoracic and lumbar vertebrae (neonates and infants)
growth recovery lines (after infancy)
cortical splitting and new periostitis
sickle cell d...
Article
Boogard's angle
Boogard's angle is measured by drawing a line from basion to opisthion and another line along the plane of the clivus to the basion intersecting the first line - the angle between these two lines is measured .
The normal angle is 126° +/- 6°. If the angle measures more than 136° it is indicativ...
Article
Cervical spine fractures
Cervical spine fractures can occur secondary to exaggerated flexion or extension, or because of direct trauma or axial loading.
Pathology
The cervical spine is susceptible to injury because it is highly mobile with relatively small vertebral bodies and supports the head which is both heavy and...
Article
Cervical spine injury
Cervical spine injuries can involve the cervical vertebral column, intervertebral discs and cervical spine ligaments, and/or cervical spinal cord. The cervical spine accounts for ~50% of all spinal injuries.
Epidemiology
5-10% of patients with blunt trauma have a cervical spine injury 1.
Pa...
Article
Chalk stick fracture
Chalk stick or carrot stick fractures are fractures of the fused spine, classically seen in ankylosing spondylitis.
Terminology
Some authors define the chalk stick fracture as a fracture through a Pagetoid long bone (see Paget disease).
Pathology
They usually occur through the disco-vertebra...
Article
Chamberlain line
Chamberlain line is a line joining the back of hard palate with the opisthion on a lateral view of the craniocervical junction.
Significance
It helps to recognise basilar invagination which is said to be present if the tip of the dens is >3 mm above this line.
McGregor developed a modificatio...
Article
Chance fracture
Chance fractures, also referred to as seatbelt fractures, are flexion-distraction type injuries of the spine that extend to involve all three spinal columns. These are unstable injuries and have a high association with intra-abdominal injuries.
Pathology
Mechanism
They tend to occur from a fl...
Article
Coronal vertebral cleft
Coronal vertebral cleft refers to the presence of a radiolucent vertical defect on a lateral radiograph.
Epidemiology
It is most often seen in premature male infants 1,3. As they can occur as part of normal variation (especially in the lower thoracic-upper lumbar spine of premature infants) ...
Article
Craniovertebral junction anomalies
Craniovertebral junction (CVJ) anomalies can be congenital, developmental or due to malformation secondary to any acquired disease process. These anomalies can lead to cranial nerve compression, vertebral artery compression and obstructive hydrocephalus.
Pathology
The cranio-vertebral junctio...
Article
Diffusely increased bone marrow FDG uptake
A diffuse homogeneous bone marrow FDG uptake usually reflects hyperplastic bone marrow which can be seen in the following conditions:
therapy-related
granulocyte colony stimulating factor (G-CSF)
post-chemotherapy
erythropoietin
pathological process
myelodysplastic syndromes
beta thalasse...
Article
Diffuse T1 bone marrow signal loss
Diffuse T1 vertebral bone marrow signal loss has a number of causes. T1-weighted imaging without fat suppression is one of the most important sequences for distinguishing between normal and abnormal bone marrow. Given the homogeneity, this appearance can often be difficult to spot as abnormal. ...
Article
Dural ectasia
Dural ectasia refers to ballooning or widening of the dural sac which can result in posterior vertebral scalloping and is associated with herniation of nerve root sleeves.
Clinical presentation
Patients with dural ectasia may present with low back pain or radicular pain in the buttocks or legs...
Article
Erosion of the odontoid process (differential)
Erosion of the odontoid peg can result from a number of pathological entities:
inflammatory arthropathy
rheumatoid arthritis: classic 1-2
systemic lupus erythematosus
crystal arthropathy
calcium pyrophosphate arthropathy (CPPD): relatively common
gout
non-inflammatory arthropathy: osteoar...
Article
Extension tear drop fracture
Extension tear drop fracture typically occurs due to forced extension of the neck with resulting avulsion of the anteroinferior corner of the vertebral body. Extension teardrop fractures are stable in flexion, and unstable in extension as the anterior longitudinal ligament is disrupted. Extensio...
Article
Facet dislocation
Facet dislocation refers to anterior displacement of one vertebral body on another. Without a fracture, the only way anterior displacement can occur is by dislocation of the facets.
Facet dislocation can occur to varying degrees:
subluxed facets
perched facets
locked facets
The injury usua...
Article
Flexion tear drop fracture
Flexion tear drop fractures are the most severe fracture of the cervical spine, often causing anterior cervical cord syndrome and quadriplegia.
Pathology
Mechanism
It typically occurs from severe flexion and compression forces, most commonly at C5-6 (e.g. diving head first, motor vehicle coll...
Article
Gibbus deformity
Gibbus deformity is a short-segment structural thoracolumbar kyphosis resulting in sharp angulation.
Pathology
There are a number of causes which can be divided into congenital and acquired.
Congenital
achondroplasia
cretinism (congenital hypothyroidism)
Apert syndrome
Coffin-Lowry syndro...
Article
Hangman fracture
Hangman fracture, also known as traumatic spondylolisthesis of the axis, is a fracture which involves the pars interarticularis of C2 on both sides, and is a result of hyperextension and distraction.
Clinical presentation
Post-traumatic neck pain after a high-velocity hyperextension injury is ...
Article
Intervertebral disc calcification
Intervertebral disc calcification is seen with numerous conditions.
Epidemiology
It may be observed in paediatric 5 as well as adult populations.
Pathology
Causes
degenerative: relatively common and may occur in up to 6% in routine abdominal radiographs in adults
postoperative/traumatic
o...
Article
Intradural extramedullary spinal tumours
Intradural extramedullary neoplasms are located outside the spinal cord but within the dural sheath.
Clinical presentation
The most common presenting symptoms include weakness, back pain and radicular pain.
Pathology
Schwannomas are the most common intradural extramedullary spinal lesions (...
Article
Intramedullary spinal metastasis
Intramedullary spinal metastases are rare, occurring in ~1% of autopsied cancer patients, and are less common than leptomeningeal metastases.
Intramedullary lesions may result from:
growth along the Virchow-Robin spaces
haematogenous dissemination
direct extension from leptomeninges
Epidemi...
Article
Locked facet joint
Locked facet joint is a type of facet joint dislocation that results from jumping of the inferior articular process over the superior articular process of the vertebra below and becomes locked in the position.
It can be unilateral or bilateral.
Radiographic features
Plain radiograph
The tip ...
Article
Longitudinally extensive spinal cord lesion
Longitudinally extensive spinal cord lesions (LESCL), also known as longitudinally extensive transverse myelitis (LETM), represent extensive involvement of the spinal cord, with abnormal T2 signal traversing at least three vertebral body segments in length.
Differential diagnosis
They are typi...
Article
Loss of intervertebral disc space (differential)
Loss of intervertebral disc space can be due to a variety of causes:
degenerative disc disease of the spine: most common cause
trauma
discitis
neuropathic spondyloarthropathy
dialysis related spondyloarthropathy
ankylosing spondylitis
ochronosis
crystal deposition diseases
sarcoidosis
...
Article
McRae line
McRae line is a radiographic line drawn on a lateral skull radiograph or midsagittal section of CT or MRI, joining the basion and opisthion.
Normal position of the tip of dens is 5mm below this line. If the tip of the dens migrates above this line it indicates the presence of basilar invaginati...
Article
Meningocele
Meningoceles are protrusions of the meninges through a defect or weak point in the skull or spine, usually involving the soft tissues beneath the surface of the skin. They are typically categorized into congenital, iatrogenic (e.g. following a craniotomy, sinus surgery, or as a laminectomy compl...
Article
Neoplasms of the cauda equina (differential)
The differential diagnosis for masses of the cauda equina region is often considered separately to the remainder of the spinal cord. It is often difficult to determine whether masses in this region are intramedullary or intradural-extramedullary.
Most common tumours
myxopapillary ependymoma
b...
Article
Nerve root enhancement
Nerve root enhancement is phenomenon described on post contrast MRI scans that can be observed in a number of situations.
Common causes
post-operative states
post-operative nerve root enhancement
arachnoiditis
leptomeningeal metastases
disseminated spinal leptomeningeal metastases
HIV vac...
Article
Osteoarthritis of the vertebral column
Osteoarthritis of the vertebral column, also known as spondylosis deformans, is common and usually merely referred to as spinal "degenerative change". Complications such as spinal stenosis are important to recognise.
Radiographic features
The hallmark of osteoarthritis in the spine, as is the...
Article
Parasyndesmophytes
Parasyndesmophytes or floating syndesmophytes are, as the name suggests, paravertebral dystrophic soft tissue calcifications or heterotopic ossifications.
Pathology
They are known to be seen in psoriatic arthritis and reactive arthritis 4.
Radiographic features
Initially they begin at a dist...
Article
Powers ratio
Powers ratio is a measurement of the relationship of the foramen magnum to the atlas, used in the diagnosis of atlanto-occipital dissociation injuries.
The ratio, AB/CD, is measured as the ratio of the distance in the median (midsagittal) plane between the:
basion (A) and the posterior spinola...
Article
Primary bone tumours of the spine
The most common tumour of the spine is metastatic deposits. A number of both benign and malignant tumours may arise primarily from the spine.
Benign
osteoid osteoma
osteoblastoma
osteochondroma
giant cell tumour (GCT)
aneurysmal bone cyst (ABC)
eosinophilic granuloma (EG)
haemangioma
Ma...
Article
Radiation-induced MRI signal changes in bone
Radiation-induced MRI signal changes in bone are the earliest detectable changes in bone. They increase with increase in the radiation dose.
Pathology
1st week: decreased marrow cellularity with oedema and haemorrhage
2nd week: increased marrow cellularity due to influx from unirradiated area...
Article
Retropulsed fragment
A retropulsed fragment is any vertebral fracture fragment that is displaced into the spinal canal, thereby potentially causing spinal cord injury.
They usually arise from the vertebral body with or without a portion of the pedicle, and are displaced posteriorly, hence the prefix 'retro'.
Article
Scheuermann disease
Scheuermann disease (also known as juvenile kyphosis, juvenile discogenic disease 11, or vertebral epiphysitis) is a common condition which results in kyphosis of the thoracic or thoracolumbar spine. The diagnosis is usually made on plain film.
Epidemiology
occurs in ~5% (range 0.4-8%) of the ...
Article
Scoliosis
Scoliosis is defined as an abnormal lateral curvature of the spine. It is quite common in young individuals and is often idiopathic and asymptomatic. In some cases, however, it is the result of underlying structural or neurological abnormalities.
By definition, a scoliosis is any lateral spina...
Article
Spinal cord compression
Spinal cord compression is a surgical emergency, usually requiring prompt surgical decompression to prevent permanent neurological impairment.
Pathology
Aetiology
There are numerous causes of cord compression. These can be divided according to the location of the compressing mass:
interverte...
Article
Spinal dysraphism
Spinal dysraphism is a broad term given to a group of anomalies where there are malformations in the dorsum of the embryo. Neural tube defects come under this group as well.
Pathology
There is often abnormal fusion of the midline embryonic neural, vertebral and mesenchymal structures.
Sub t...
Article
Spinal epidural mass
The differential diagnosis for a spinal epidural mass includes:
epidural metastasis
epidural abscess
herniated nucleus pulposus
epidural haematoma
epidural arteriovenous malformation
epidural angiolipoma
epidural lipomatosis
Article
Spinal fractures
Spinal fractures are usually the result of significant trauma to a normally formed skeleton, or the result of trauma to a weakened spinal column. Examples include:
Jefferson fracture: ring fracture of C1
hangman fracture: bilateral pedicle or pars fracture of C2
dens fracture
flexion teardro...
Article
Spinal metastases
Spinal metastases is a vague term which can be variably taken to refer to metastatic disease to any of the following:
vertebral metastases (94%)
may have epidural extension
intradural extramedullary metastases (5%)
intramedually metastases (1%)
Each of these are discussed separately. Below...
Article
Spinal synovial cyst
Synovial cysts of the spine are cystic formations connected to the facet joint and containing synovial fluid lined by a cuboid or pseudostratified columnar epithelium. They may be result in lumbar radiculopathy in a significant number of cases.
Clinical presentation
They may be asymptomatic an...
Article
Spinal vascular malformations
Spinal vascular malformations (SVM) are rare but knowledge of them is important as if undiagnosed and untreated they can lead to serious complications.
Pathology
There are two main types of SVMs 1,2:
spinal arteriovenous fistula (AVF): 70% of SVMs
pial: small, large, or giant
dural AVF (DA...
Article
Subluxed facet joint
Subluxed facet joint is the mildest form of facet dislocation in which the ligamentous injury leads to partial uncovering of facet joint (c.f. complete uncovering in perched facet). This results in mild anterior displacement of one vertebral body on another (anterolisthesis).
Article
Syndesmophyte
Syndesmophytes are calcifications or heterotopic ossifications inside a spinal ligament or of the annulus fibrosus. They are seen in only a limited number of conditions including:
ankylosing spondylitis
ochronosis
fluorosis
Radiographic features
Appearance on plain radiographs comprises v...
Article
Torticollis
Torticollis (wryneck) is a clinical finding of head tilt with or without rotational spinal malalignment. It is not a diagnosis in itself and there are a wide range of underlying conditions. It is most common in the paediatric age group.
Pathology
Torticollis can be acute (<1 week) or chronic ...
Article
Traumatic spinal cord injury
Traumatic spinal cord injury can manifest as a wide variety of clinical syndromes resulting from damage to the spinal cord or its surrounding structures. It can result from minor injury if the spine is weakened from disease such as ankylosing spondylitis or if there is pre-existing spinal stenos...
Article
Unilateral facet dislocation
Unilateral facet dislocation is a relatively stable type of facet dislocation.
Pathology
Mechanism
Flexion/distraction associated with rotation. The inferior articular facet of vertebral above moves over the superior facet of the vertebral below and becomes locked. It usually affects C4-C5 or...
Article
Vertebral body mass
The differential diagnosis for a vertebral body mass is broad and may range from a completely benign, sclerotic enostosis (bone island) to a malignant primary bone tumour.
Classification
Broadly, these lesions can be separated into:
non-neoplastic lesions
primary bone tumours
secondary meta...
Article
Vertebral scalloping
Vertebral scalloping is a concavity to the posterior (or less commonly anterior) aspect of the vertebral body when viewed in a lateral projection. A small amount of concavity is normal, as is concavity of the anterior vertebral body (see vertebral body squaring).
Posterior scalloping
Causes of...
Article
Vertebra plana
Vertebra plana (a.k.a. pancake / silver dollar / coin-on-edge vertebra) is the term given when a vertebral body has lost almost its entire height anteriorly and posteriorly, representing a very advanced compression fracture. Plural is vertebrae planae. It can occur in a variety of settings, incl...
Article
Winking owl sign (spine)
The (absent) pedicle sign, also called the winking owl sign, occurs on plain film when a pedicle is absent.
The term, winking owl sign, where the missing pedicle corresponds to the closed eye, the contralateral pedicle to the other open eye, and the spinous process to the beak of the animal on ...