Lipiodol® (also known as ethiodized oil) is an oil-based iodinated contrast medium that was historically used for myelography and hysterosalpingography. It was later superseded by newer, less hazardous, agents, and now is used primarily as a therapeutic agent. Guerbet is now the sole manufacture...
Fatty filum terminale, also known as lipoma of the filum terminale or filar lipoma, is a relatively common finding on imaging of the lumbar spine, and in most cases is an incidental finding of no clinical concern. However, in some patients it may be associated with signs and symptoms of tethered...
Lipomyelocele is one of the most common closed spinal dysraphism. It is seen in thoracolumbar region and usually presents as a fatty subcutaneous mass.
It is twice as common as lipomyelomeningocele.
Affected individuals are usually asymptomatic at birth, but many (~ 50%)...
Lipomyelomeningoceles are one of the forms of closed spinal dysraphism. They usually present as a subcutaneous fatty mass just above the intergluteal cleft. However, some lipomyelomeningoceles may occur at other locations along the spinal canal.
Lipomyelomeningoceles may ...
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.
The tip ...
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.
They are typi...
Loss of intervertebral disk space can be due to a variety of causes:
degenerative disk disease of the spine: most common cause
dialysis related spondyloarthropathy
crystal deposition diseases
Several conditions may give vertebral endplate T1 low signal on MRI. They include:
The lumbar cistern refers to the subarachnoid space in the lower lumbar spinal canal.
The cistern is an enlargement of the subarachnoid space in the dural sac, distal to the conus medullar is. It contains cerebrospinal fluid and the nerve roots of the cauda equina. As the conus (usually) termin...
Lumbar disk disease is a very common entity with a high asymptomatic prevalence. Intervertebral disk abnormalities are found in 25% of individuals below the age of 60, and over 50% in those over the age of 60. It is therefore not enough to demonstrate a disk lesion in someone with non-specific b...
The lumbar enlargement of the spinal cord corresponds to the mild increase in cross sectional area of the cord from the T11 level to the conus medullaris. It is enlarged due to the present of spinal nerve anterior rami which contribute to the lumbar and sacral plexuses.
Lumbar epidural gas is a rare phenomenon where gas locules are observed within the central canal of the lumbar spine. It can arise from a number of factors:
due to regional degenerative disk disease with or without dorsal epidural disk migration: thought to be from gas leaking from the disk spa...
Lumbar interlaminar epidural injections are one of some possible spinal epidural injections. For an alternative approach for the same region, please refer to the article on lumbar transforaminal epidural injections.
Typically, epidural injections are performed in patients with rad...
The lumbar plexus is a complex neural network formed by the lower thoracic and lumbar ventral nerve roots (T12 to L5) which supplies motor and sensory innervation to the lower limb and pelvic girdle.
origin: ventral rami of T12 to L5
course: formed within the substance of the psoas ma...
A handy mnemonic to recall the roots of the lumbar plexus is:
2 from 1, 2 from 2, 2 from 3
2 nerves from 1 root: ilioinguinal (L1), iliohypogastric (L1)
2 nerves from 2 roots: genitofemoral (L1/L2), lateral femoral cutaneous (L2/L3)
2 nerves from 3 roots: obturator (L2/L3/L4), femo...
Lumbar (or 13th) ribs are a rare anatomical variant and represent transitional vertebrae at the thoracolumbar junction with a prevalence of ~1% 1. It presents as an additional rib coming off T13 or L1 (depending on numbering classification) and may be unilateral or bilateral. Lumbar ribs are mos...
The lumbar spine consists of five adjacent vertebrae of the lower vertebral column. They participate in the lumbar lordosis, a natural curve in the spine, that is convex anteriorly.
Articulations of the facet (zygapophyseal) joints permit flexion/extension and abduction movements. Rotation is ...
The lumbar spine AP view images the lumbar spine which consists of five vertebrae. It is utilized in many imaging contexts including trauma, postoperatively, and for chronic conditions.
the patient is erect or supine, depending on clinical history
ideally, spinal imaging sho...
The lumbar spine series is comprised of two standard projections along with a range of additional projections depending on clinical indications. The series is often utilized in the context of trauma, postoperative imaging and for chronic conditions such as ankylosing spondylosis.
Lumbar spine x...
Lumbosacral transitional vertebrae (LSTV) are a relatively common variant and can be seen in ~25% (range 15-35%) of the general population 1-3. Non-recognition of this variant and/or poor description in the report can lead to operations or procedures performed at the wrong level.
Depending on ...
Lymphoma of the spinal cord is an uncommon manifestation of lymphoma. Although lymphoma more commonly involves the vertebral body (vertebral body tumors) or epidural compartment, intramedullary lymphoma may rarely occur.
Apparent intramedullary spinal cord lymphoma may often, in fact, represe...
The Magerl classification of thoracolumbar spinal fractures is based on the three column concept by Denis, and the McAfee classification. It relies exclusively on CT findings.
A: compression injuries
A1: impaction fractures
A1.1: endplate impaction
A1.2: wedge impaction
Magnetic resonance neurography (MRN) is a relatively new non-invasive imaging technique for dedicated assessment of peripheral nerves.
It is used to assess peripheral nerve entrapments and impingements as well as localization and grading of nerve injuries and lesions.
The Matterhorn sign is a descriptive sign for a calcified disk herniation that impales the dural sac and sometimes the cord, typically located in the thoracic spine.
History and etymology
The Matterhorn sign is named after one of the most iconic mountains in the Alps: the Matterhorn.
McAfee classification of acute traumatic spinal injuries is based on the three column concept of the spine. CT is needed for accurate assessment.
wedge compression: isolated anterior column compression
stable burst: anterior and middle column compression but posterior column i...
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...
Meningeal melanocytomas are rare benign primary melanocytic tumors of the CNS that are derived from leptomeningeal melanocytes. They can occur anywhere along the neuraxis but are most commonly found in the spinal canal near the foramen magnum, as well as the posterior cranial fossa, Meckel cave,...
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...
Meningocele manqué (from French, literally "missed meningocele") is a rare condition characterized by focal dorsal tethering of the spinal cord. The term is used to designate a meningocele which failed to develop and became atretic.
It has been reported in neonates, but median age...
Modic type endplate changes represent a classification for vertebral body end-plate MRI signal, first described in 1988 1. It is widely recognised by radiologists and clinicians and is a useful shorthand for reporting MRIs of the spine.
Recently Modic type I has received renewed attention due t...
Modic type I endplate change is the most controversial and important of the three types described (see Modic endplate change). It is seen on MRI of the spine and represents the presence of low T1 and high T2 signal within the bone marrow of a vertebral body adjacent to a disk. Type 1 change can...
The modified Memphis criteria are a set of screening criteria for blunt cerebrovascular injury (BCVI) in trauma. The presence of one or more of these criteria makes necessary a complementary CTA or DSA study to exclude a BCVI.
The screening protocol criteria for BCVI are:
base of skull fractur...
Movements of the spine are possible due to intervertebral discs, and with the fulcrum of movement occurring primarily around the nucleus pulposus. Specialized motion occurs at the atlanto-occipital and atlantoaxial joints, which do not contain a disk.
The spine (vertebral column) forms the cent...
Disk degeneration can be graded on MRI T2 spin-echo weighted images using a grading system proposed by Pfirrmann 1. This classification is not used on routine spine reports, being more important for research purposes.
grade I: disk is homogeneous with bright hyperintense white signal intensity ...
Myelitis, is a collective term simply referring to any inflammation of the spinal cord. It is a form of myelopathy.
The two major sub types include:
ideopathic transverse myelitis
secondary transverse myelitis: viral, neurosyphilis...
Myelography is a form of imaging intended to evaluate the subarachnoid spaces within the spinal canal. It is now usually performed with either CT or MR imaging of the spine after injection of an intrathecal iodinated or gadolinium-based contrast agent. MR myelography may also provide evaluation ...
Myelomeningocele, also known as spina bifida cystica, is a complex congenital spinal anomaly that results in spinal cord malformation (myelodysplasia).
It is one of the commonest congenital CNS anomalies and thought to occur in approximately 1:500 of live births 5. There may be a...
The naked facet sign (also known as the hamburger sign or reverse hamburger bun sign) refers to the CT appearance of an uncovered vertebral articular facet when the facet joint is dislocated, most often in cases of locked facet.
This CT sign is characteristic of a flexion-distraction injury an...
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 tumors
Neoplasms of the spinal canal encompass a range of tumors which arise from or involve the spinal cord, theca and spinal nerves.
These can be divided according to the tissue/structure of origin within the spinal canal. Tumors of vertebral bodies are discussed separately: see vertebral...
Nerve root enhancement is phenomenon described on post contrast MRI scans that can be observed in a number of situations.
post-operative nerve root enhancement
disseminated spinal leptomeningeal metastases
The neurenteric canal or canal of Kovalevsky is the transient communication of the amnion through notochordal canal to the yolk sac during notochordal formation at day 16-17.
Abnormalities during this stage produce the neurenteric cyst spectrum.
Neuroanatomy encompasses the anatomy of all structures of the central nervous system, which includes the brain and the spinal cord, and their supporting structures.
This anatomy section promotes the use of the Terminologia Anatomica, the global standard for correct gross anatomical nomenclature.
Neurogenic bladder is a term applied to a dysfunctional urinary bladder that results from an injury to the central or peripheral nerves that control and regulate urination. Injury to the brain, brainstem, spinal cord or peripheral nerves from various causes including infection, trauma, malignanc...
Neurolymphomatosis is a rare condition characterized by the direct invasion of the cranial and peripheral nerves and roots by lymphoma, in the great majority B-cell non-Hodgkin lymphoma.
It should be differentiated from non-tumor conditions associated with lymphoma that also affect the peripher...
Neuromyelis optica (NMO) and neuromyelitis optica spectrum disorder (NMOSD) are closely related severe demyelinating diseases caused by an autoantibody to the aquaporin-4 water channel. The classic presentation of NMO is with the triad of optic neuritis, longitudinally extensive myelitis, and po...
Nitrous oxide (N2O) toxicity has serious medical sequelae including encephalopathy, myelopathy, neuropathy and endovascular effects 1. This results from demyelination and gliosis due to selective inhibition of vitamin B12.
N2O is an established and widely used anesthetic gas though also misused...
This article lists examples of normal imaging of the spine and surrounding structures, divided by region and modality.
example 1: AP, lat, obliques only
example 2: PEG view
example 3: flexion and extension views only
example 4: pediatric - 12 years old
The notochord represents the earliest fetal axial skeleton, extending from the Rathke pouch to the coccyx. It is a primitive cell line from which the skull base and vertebral column develop. The notochord is cylindrical and is replaced by sclerotomes that produce cartilage, and subsequently bone...
The nucleus pulposus is the central part of each intervertebral disk.
It is located within the annulus fibrosus and between the vertebral body endplates. It is composed of a thin lattice of collagen fibers (type II) which traverse though hydrophilic glycosaminoglycans.
A nude nerve root is perhaps not as exciting as the name would suggest. It refers to an uncommon anatomical variant where nerve roots simply exit the theca without investing dural sleeves 1. These have been associated, at least in case reports, with spontaneous craniospinal hypotension 1.
Occipital condylar fractures result from high-energy blunt trauma and is a specific and localized type of basilar skull fracture.
The exact incidence of these fractures is unknown but are reported to occur in 3-4% patients with moderate-severe traumatic brain injuries 3.
Occipital vertebrae is a very rare anatomical variant and results from incomplete or aberrant fusion of occipital bone ossification centers. There is a broad spectrum of occipital vertebrae variations and the four most common include:
third condyle (condylus tertius)
Occult intrasacral meningocele is a rare congenital lesion characterized by the presence of a cyst within the sacral thecal sac. It is an extradural sacral arachnoid cyst - Nabor type Ib meningeal cyst. It is not a true meningocele, since meninges are not involved.
It is associated with spinal ...
Ochronosis, or alkaptonuria (AKU), is a rare multisystem autosomal recessive metabolic disorder.
On imaging, the most particular presentation is on the spine, with osteoporotic bones and dense disk calcifications.
The term ochronosis usually refers to the bluish-black discolourat...
Odontoid process fracture, also known as the peg or dens fracture, occurs where there is a fracture through the odontoid process of C2.
The mechanism of injury is variable, and can occur both during flexion or extension with or without compression 5.
There are two cl...
Olisthesis, also known as the etymologically less correct listhesis, means slipping or sliding.
Oppenheimer ossicles are accessory ossicles associated with the facet joints found in ~4% (range 1-7%) 1 of lumbar spines.
Oppenheimer ossicles are thought to arise as a result of non-union of a secondary ossification center of the articular process. They predominantly occur as a single, unila...
Opticospinal multiple sclerosis (OSMS) is a demyelinating disease and has been considered a variant of multiple sclerosis (MS) encountered in Asian populations, who are generally rarely affected by normal multiple sclerosis. It has similar clinical and imaging features to neuromyelitis optica (N...
Os odontoideum is an anatomic variant of the odontoid process of C2 and needs to be differentiated from persistent ossiculum terminale and from a type 2 odontoid fracture. It can be associated with atlantoaxial instability.
Although it was originally thought to be a congenital lesion due to a ...
Ossification of the vertebral column is complex but an overview of primary and secondary ossification centers is given below:
Primary ossification centers
The C3-L5 vertebrae typically have three primary ossification centers that start appearing at 9 weeks in utero and finish primary ossificat...
Ossification of the ligamentum flavum (OLF) is a phenomenon where there is a formation of ossific-calcific components in the ligamentum flavum. It is recognised causes of myelopathy (especially in the thoracic and to a lesser degree the cervical region).
The condition as a whole i...
Ossification of the posterior longitudinal ligament (OPLL) is typically an entity seen in patients of Asian descent, although it is seen in all ethnic groups. It is characterized by, as the name suggests, ossification of the posterior longitudinal ligament.
There is a recognised g...
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 recognize.
The hallmark of osteoarthritis in the spine, as is the...
Osteoporotic spinal compression fractures occur as a result of injury, commonly fall onto the buttock or pressure from normal activities, to the weakened vertebrae due to osteoporosis.
They have a reported incidence of 1.2 per 1000 person-years after 85 years of age in the United ...
The owl's eye sign represents bilaterally symmetric circular to ovoid foci of high T2-weighted signals in the anterior horn cells of the spinal cord and is seen on axial MR imaging. The sagittal corollary is a "pencil-like" vertical linear high T2-weighted signal extending usually over a number ...
Paracondylar process is a rare anatomical variant of the occipital bone, where a bony exostosis extends caudally from the paracondylar region (lateral to the native occipital condyles), typically articulating with the superior surface of a transverse process of the atlas. This may be unilateral ...
Parasyndesmophytes or floating syndesmophytes are, as the name suggests, paravertebral dystrophic soft tissue calcifications or heterotopic ossifications.
They are known to be seen in psoriatic arthritis and reactive arthritis 4.
Initially they begin at a dist...
Perched facet joint is a vertebral facet joint whose inferior articular process appears to sit 'perched' on the ipsilateral superior articular process of the vertebra below.
Any further anterior subluxation will result in dislocation, with one facet "jumping" over the other and becoming locked ...
Peripheral nerve sheath tumors (PNSTs) are a group of primary neurogenic tumors that arise from nerve sheaths outside of the central nervous system. The vast majority are benign, however, malignant transformation is seen particularly in large tumors and those associated with neurofibromatosis ty...
The perivertebral space is one of the seven deep compartments of the head and neck.
The perivertebral space is a cylinder of soft tissue lying posterior to the retropharyngeal space and danger space surrounded by the prevertebral layer of the deep cervical fascia and extends from...
The ossiculum terminale appears as a secondary ossification center of the dens between 3-6 years and normally fuses by 12 years. Failure of fusion results in a persistent ossiculum terminale (also called Bergmann's ossicle or ossiculum terminale of Bergmann) and is considered a normal anatomical...
Picture frame vertebral body is a radiologic appearance in which the cortex of the vertebral body is thickened. This sign can be seen in patients with Paget disease.
It is a result of disorganised new cortical bone formation after excessive osteoclastic activity causes the resorption of normal...
A pine cone bladder or Christmas tree bladder is a cystographic appearance in which the bladder is elongated and pointed with a thickened, trabeculated wall. It is typically seen in severe neurogenic bladder with increased sphincter tone (detrusor sphincter dyssynergia) due to suprasacral lesion...
Pneumatic nerve root compression is a term given nerve root compression due to a presence of a juxtadiscal herniated gas locule. It is not a common occurence 2. The gas locules in these instances typically arise from herniation of intradiscal gas which occurs as part of disk degenerative change....
Pneumorrhachis refers to a rare phenomenon characterized by the presence of gas within the spinal canal (either intra- or extradural).
Patients can often be asymptomatic 3.
Pneumorrhachis can result from a number of causes:
trauma (traumatic pneumor...
Polio-like paralysis refers to a paralytic state which is similar in clinical appearance to polio, but from which poliovirus is not isolated. Like polio, the main presenting symptom is acute flaccid paralysis.
There are many causes, some of which are infective, e.g. coxsackie A9 and ...
The polka-dot sign is the result of the replacement of the normal cancellous bone by thickened vertical trabeculae surrounded by fat marrow or vascular lacunae in vertebral intraosseous hemangiomas 2. It is the axial equivalent of the corduroy sign seen on sagittal and coronal images. On CT the ...
Posterior ring apophysis fractures occur in the immature skeleton, most commonly in the lumbar spine.
Typically, adolescent males practicing sport activities.
muscle weakness related with root innervation
association with Scheuermann ...
The posterior atlanto-occipital membrane attaches the upper border of the posterior arch of the atlas (C1) to the outer margin of the foramen magnum. It is continuous with the posterior atlantoaxial membrane (inferiorly) and ligamentum nuchae (posteriorly) and lies immediately posterior to the t...
Posterior inferior cerebellar artery (PICA) is one of the three vessels that provide arterial supply to the cerebellum. It is the most variable and tortuous cerebellar artery.
Its origin is highly variable:
~20% arise extracranially, inferior to the foramen magnum
The posterior ligamentous complex acts to stabilize the vertebral column and is made up of the following structures:
facet joint capsule
In particular, it acts to hold the facet joints of the neighbouring vertebrae in fixed relat...
The posterior longitudinal ligament (PLL) is a long and important ligament located immediately posterior to the vertebral bodies (to which it attaches loosely) and intervertebral discs (to which it is firmly attached).
It extends from the back of the sacrum inferiorly and gradually broadens as ...
Posterior lumbar interbody fusion (PLIF) is a commonly performed spinal fusion procedure that can be performed at a single level or a multiple adjacent levels.
It relies on the introduction of pedicle screws with connecting rods posteriorly. A partial laminectomy is performed to gain access to ...
Posterior lumbar subcutaneous edema is a very frequent finding on MRI of the spine. Clinical correlation is almost always required to identify the significance of this.
Due to its distribution, it is sometimes referred to colloquially as "tramp-stamp edema".
It is m...
The posterior spinal arteries are a pair of arteries that supply the respective ipsilateral grey and white posterior columns of the spinal cord.
The posterior spinal arteries arise from either the posterior inferior cerebellar or vertebral arteries (V3 or V4 segments) and runs t...
Posterior spinal artery syndrome is a rare syndrome associated occlusion of the posterior spinal artery and results in a unilateral dorsal cord syndrome (since the posterior arteries are paired) 3.
The syndrome is clinically characterized by isolated loss of proprioception and vibratory sensat...
Posterior vertebral fusion anomalies are relatively common and should not be mistaken for fractures. They are thought to be both developmental and pathological (e.g. spondylolysis) but are typically asymptomatic and incidental, and considered as anatomical variants. There are six types of poster...
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...
The most common tumor of the spine is metastatic deposits. A number of both benign and malignant tumors may arise primarily from the spine.
giant cell tumor (GCT)
aneurysmal bone cyst (ABC)
eosinophilic granuloma (EG)
A pseudosinus tract is a normal fibrous cord extending from the coccyx to an overlying sacral dimple. These have no associated mass and contain no fluid (if CSF drainage is occurring via the sacral dimple, then a true dorsal dermal sinus should be considered).
Pseudosubluxation of the cervical spine is the physiological anterior displacement of C2 on C3 in children. It is common in children <7 years, and less often present in older children. Less often it is seen at C3 on C4. It is more pronounced in flexion and is of clinical significance as it can b...
The quadratus lumborum muscle is an irregular quadrilateral muscle that forms part of the posterior abdominal wall.
location: dorsal abdominal wall
attachments: medial half of inferior margins of 12th ribs and upper four lumbar transverse processes
branches of the lumba...