Medical Term Glossary
Plain-language explanations of the medical terms that appear on CT, MRI and X-ray reports — what each one means, when it matters, and what to ask your doctor.
A
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Annular fissure
A small crack or tear in the tough outer ring of a spinal disc, seen on MRI. It is a common age-related change and often causes no symptoms, though it can sometimes be a source of back pain. On its own it is not a herniation and rarely needs specific treatment.
Also: annular disc tear, annular tear, annular tear of the disc
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Anterolisthesis
Forward slippage of one spinal vertebra relative to the bone directly beneath it, so the normally straight stack of bones is thrown slightly out of alignment. Many small slips are stable and cause no symptoms, while larger ones can narrow the space around the spinal nerves and cause back or leg pain.
Also: anterior spondylolisthesis, anterior vertebral displacement, forward slippage of the spine
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Arachnoiditis
Inflammation and scarring of the arachnoid membrane, the middle layer covering the spinal nerves, often following spine surgery, an epidural injection, or infection. The scarring can bind nerve roots together inside the spinal canal, sometimes causing chronic pain, numbness, or tingling in the back and legs.
Also: adhesive arachnoiditis, arachnoid scarring, arachnoiditis of the spine
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urgent
Cauda equina
The bundle of nerve roots that fills the lower spinal canal below where the spinal cord itself ends, carrying signals to the legs, bladder, bowel, and pelvic organs. It is a normal anatomical structure, but severe compression of it is a surgical emergency.
Also: CES, cauda equina compression, cauda equina nerve bundle
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Coccyx
The tailbone — the small, triangular tip at the very bottom of the spine, just below the sacrum. It is the leftover of what would be a tail, made of a few tiny fused bones. On a report it is usually just naming the lowest point of the spine. The word itself is plain anatomy.
Also: bottom of the spine, coccygeal bone, tail bone
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Compression fracture
A break in one of the spine's bones where the front of the bone has collapsed and lost height, while the back wall typically stays intact. Most happen in the mid or lower back, and many occur from a small load — like a cough or a minor stumble — in bone that has been weakened by osteoporosis.
Also: VCF, collapsed vertebra, crushed vertebra
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Conus medullaris
This is the tapered, cone-shaped lower tip of the spinal cord, where the cord narrows and ends before splitting into a bundle of nerve roots. Reports usually note the vertebral level where it sits, since that level is checked to confirm it looks normal.
Also: conus, cord terminus, medullary cone
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urgent
CSF leak
Escape of cerebrospinal fluid, the clear liquid that cushions the brain and spinal cord, through a tear or hole in its surrounding membrane. It most often follows spine surgery, a spinal tap, or trauma, and causes a distinctive headache that typically needs medical treatment to seal.
Also: CSF fistula, cerebrospinal fluid leak, dural leak
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Degenerative changes
A general term radiologists use for the everyday wear-and-tear that accumulates in the spine over a lifetime — slightly flattened cushions between vertebrae, small bony ridges along the edges, and a bit of joint thickening. Extremely common after the mid-30s and found in plenty of people who have no back pain at all.
Also: age-related changes, degeneration, degenerative disease
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Degenerative disc disease
An umbrella term for the everyday wear and drying-out of the spine's soft cushions as we age — despite the word "disease," it describes a normal, near-universal process rather than an illness, and it is present in most people's spines by middle age.
Also: DDD, degenerative disc changes, degenerative spine disease
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Disc bulge
A gentle, broad outward swell of one of the soft cushions that sit between the bones of the spine. The cushion stays intact — nothing has torn or leaked — but its outer edge pushes a little past its usual footprint. Extremely common with age and often found in people who have no symptoms at all.
Also: annular bulge, broad-based bulge, bulging disc
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Disc desiccation
A loss of water content in one of the spine's cushioning discs, which makes it appear darker than a well-hydrated disc on MRI. It is one of the earliest and most common signs of normal disc aging, present to some degree in most adults, and usually causes no symptoms by itself.
Also: dark disc sign, degenerative disc desiccation, dehydrated disc
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Disc herniation
A small tear in the outer wall of one of the spinal cushions has let some of the soft inner core push outward into a focused lump. Unlike a broad, even bulge, this is a localized pocket that can press on a nearby nerve and cause arm or leg pain, tingling, or weakness along the nerve's path.
Also: disc extrusion, disc protrusion, herniated disc
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Disc protrusion
A focused, dome-shaped outward push of one of the spine's soft cushions, wider than a broad bulge but narrower than a herniation with a leaked fragment. The outer wall of the cushion stays intact, but the shape can crowd a nearby nerve root and trigger arm or leg pain.
Also: broad-based protrusion, contained disc herniation, disc protrusion
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Disc-osteophyte complex
A combination finding where a bulging or degenerated disc and a bony spur have grown together at the same spinal level, forming one firm ridge that pushes back toward the spinal canal. It's a common sign of long-term wear and tear, most often described in the neck, and doesn't by itself mean something is seriously wrong.
Also: bony-disc complex, disc and osteophyte complex, disc-osteophyte bar
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Discitis
Infection of one of the spinal discs, the soft cushions between the vertebrae, usually caused by bacteria that reach the disc through the bloodstream or after a recent spine procedure. It's a serious diagnosis that needs prompt antibiotic treatment, and doctors often raise or rule it out even when back pain has an ordinary cause.
Also: disc infection, disc space infection, infectious discitis
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Facet joint
One of the small paired joints at the back of each level of the spine that link one vertebra to the next. They guide and limit movement — bending, twisting, leaning back — and share load with the disc at the front. Like every joint in the body, they can show wear over time.
Also: apophyseal joint, facet, facet arthropathy
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Foraminal narrowing
A tightening of one of the small side-doors of the spine that each nerve uses to leave the spinal canal and travel out to the body. When the door is smaller than usual, the nerve passing through can be pinched, leading to pain, tingling, or weakness along that nerve's path — usually on one side.
Also: exit foramen narrowing, foraminal stenosis, narrowing of the nerve exit
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Lamina
A flat plate of bone that forms the back wall of each vertebra, completing the bony ring that protects the spinal cord. The two laminae meet in the middle and join the bump you can feel along your back. Reports often name them to locate a finding or after surgery that removes part of this bone.
Also: bony arch, laminae, spinal lamina
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Laminectomy
Back surgery that removes part or all of the lamina, the bony arch that forms the back wall of the spinal canal, to relieve pressure on the spinal cord or nerves. Seeing this term on a post-operative scan usually means the report is describing expected changes after a decompression surgery you already had, not a new problem.
Also: back decompression surgery, decompressive laminectomy, hemilaminectomy
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Lateral recess stenosis
Narrowing of a small side pocket within the spinal canal, just before a nerve root branches off toward the foramen. When this pocket tightens — usually from bone spurs, a bulging disc, or a thickened ligament — the nerve root can be pinched, often producing pain that radiates down one leg, much like sciatica.
Also: lateral canal stenosis, lateral recess compromise, lateral recess narrowing
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Ligamentum flavum hypertrophy
Thickening of a yellow, elastic ligament that runs along the back of the spinal canal, connecting one vertebra's bony arch to the next. When it thickens with age or wear, it can narrow the space around the spinal nerves. It is one of several common contributors to spinal canal narrowing.
Also: LF hypertrophy, hypertrophic ligamentum flavum, ligament flavum hypertrophy
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Loss of cervical lordosis
Straightening of the neck's normal forward curve, often seen on imaging done for neck pain or after an injury. It is frequently caused by muscle spasm or the position someone was lying in during the scan, and by itself it is a common, usually benign observation rather than a diagnosis.
Also: cervical hypolordosis, cervical lordosis reversal, flattened cervical curve
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Lumbar lordosis
The natural inward curve of the lower spine, where the row of vertebrae arcs gently forward rather than running in a straight line. Everyone has some degree of this curve, and reports usually just note whether it looks preserved, flattened, or more pronounced than typical.
Also: hyperlordosis, lordosis, lordotic curve
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Lumbar puncture
A procedure in which a thin needle is inserted into the lower back to collect a small sample of the fluid that surrounds the brain and spinal cord. It helps diagnose infections, bleeding, and certain neurological conditions, and can also be used to measure pressure or deliver medication directly into that fluid.
Also: CSF tap, LP procedure, cerebrospinal fluid tap
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Lumbosacral transitional vertebra (Bertolotti)
A variation in how the lowest bone of the lower back is shaped, where an enlarged wing-like process on one or both sides forms an extra joint or fusion with the pelvis. Present from birth in a meaningful share of people, it can be a source of one-sided low back pain.
Also: Bertolotti syndrome, LSTV, lumbarization
M
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Modic changes
A way radiologists grade wear-related signal changes in the bone right next to a spinal disc, seen on MRI. Type 1 suggests active inflammation and swelling, Type 2 a more settled fatty change, and Type 3 hardened bone. They are common with age and often unrelated to pain.
Also: endplate signal changes, modic endplate change, modic type 1
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urgent
Myelomalacia
Softening or damage within the spinal cord itself, usually caused by long-standing compression, a significant injury, or a loss of blood supply to that segment of cord. It's a finding radiologists take seriously because it can reflect real, sometimes lasting, injury to the cord's nerve tissue.
Also: cervical cord myelomalacia, cord myelomalacia, cord softening
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Myelopathy
Dysfunction of the spinal cord itself, most often caused by ongoing compression from a narrowed canal, a herniated disc, or bone spurs pressing on the cord. It can affect walking, hand coordination, and bladder control, and tends to need timely evaluation to prevent lasting nerve damage.
Also: cervical myelopathy, cervical spondylotic myelopathy, compressive myelopathy
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Nerve root compression
A spinal nerve root is being squeezed or crowded, usually by a bulging or herniated disc, bone spur, or thickened ligament nearby. It is the finding radiologists point to when explaining pain, tingling, or weakness that radiates down an arm or leg along a specific nerve's path.
Also: compressed nerve, nerve root compromise, nerve root entrapment
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Neurogenic claudication
Leg pain, heaviness, or weakness that comes on with standing or walking and eases with sitting or bending forward, caused by narrowing of the spinal canal that crowds the nerves in the lower back. It's the classic symptom pattern linked to spinal stenosis and tends to get better fairly quickly with rest, unlike leg pain from poor blood flow.
Also: lumbar stenosis leg pain, nerve claudication, neurogenic intermittent claudication
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Odontoid process
A small, tooth-shaped peg of bone rising from the second neck vertebra. The vertebra above pivots around it, letting you turn your head side to side to say no. Reports often name it when checking the upper neck after injury or to confirm the bone and its alignment look normal.
Also: C2 peg, dens, dens of C2
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Osteomyelitis
Infection of bone tissue, in the spine usually affecting a vertebra next to an infected disc. Bacteria most often reach the bone through the bloodstream, and the combination is serious enough that doctors treat it with a prolonged course of targeted antibiotics and close monitoring.
Also: bone infection, infectious osteomyelitis, osteitis
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Osteophyte
A small extra ridge of bone that grows along the edge of a joint or vertebra as the body responds to years of wear and load. Very common after middle age, usually painless on its own, and most often a marker of ageing rather than a disease — though large ones can crowd nearby nerves.
Also: bone spur, bony outgrowth, bony ridge
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Pars defect (spondylolysis)
A crack or stress fracture in a thin bridge of bone at the back of a vertebra, most often in the lower spine. It develops gradually from repeated stress rather than a single injury, and it can allow the vertebra above to gradually slip forward over the one below.
Also: pars fracture, pars interarticularis defect, pars interarticularis fracture
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Pedicle
A short, strong bridge of bone on each side of a vertebra that connects the round front body of the bone to the protective arch behind it. The pedicles form the side walls of the canal that shields the spinal cord. Reports often name them to locate a finding or to confirm the bone looks intact.
Also: bony pedicle, pedicle of vertebra, pedicles
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Pfirrmann grade
A 1-to-5 rating radiologists use to describe how worn a spinal disc looks on MRI. Grade 1 is a healthy, well-hydrated disc; grade 5 is a collapsed, dried-out one. It measures the disc's condition, not your pain, and higher grades are extremely common with normal aging.
Also: disc degeneration grade, pfirrmann classification, pfirrmann grade 4
R
S
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Sacrum
The base of the tailbone — the large, triangular bone at the bottom of the spine, wedged between the two hip bones. It is made of fused vertebrae and forms the back wall of the pelvis. On a report it is usually just naming where at the bottom of the spine or back of the pelvis a finding sits.
Also: base of the spine, lower spine bone, sacral bone
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Schmorl's node
A spot where the soft center of a spinal disc has pushed up or down into the neighboring vertebral bone, leaving a small dent. It is a very common, usually harmless finding on spine imaging, typically causes no symptoms, and generally needs no treatment on its own.
Also: endplate disc herniation, intravertebral disc herniation, schmorl node
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Scoliosis
A sideways curve in the spine, usually with some rotation of the vertebrae as well, so the spine looks like an S or C shape from the front instead of a straight line. Most cases are mild, discovered incidentally, and never cause a meaningful problem.
Also: S-shaped spine, curved spine, idiopathic scoliosis
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Spina bifida
A congenital condition where the bony arch at the back of one or more vertebrae fails to close fully around the spinal cord during early development. The mild, occult form found incidentally on adult scans is usually harmless, while the open forms diagnosed before or at birth are a very different, more serious matter.
Also: lamina defect, occult spinal dysraphism, posterior element defect
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Spinal canal stenosis
A narrowing of the bony tunnel that houses the spinal cord and nerve roots. The narrowing crowds the structures running through it, which can cause back pain, leg pain, numbness, or weakness depending on the level. Most cases develop slowly with age; the severity on imaging often correlates loosely with symptoms.
Also: central canal narrowing, central canal stenosis, cervical stenosis
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Spinal cord
The thick bundle of nerves that runs from the base of the brain down through the protective spine, carrying messages between the brain and the rest of the body. It controls movement and sensation in your limbs and trunk. Reports often name it to confirm it looks normal or to locate a finding nearby.
Also: cord, medulla spinalis, neural cord
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Spinal fusion hardware
Metal screws, rods, plates, or cage devices placed during back or neck surgery to permanently join two or more vertebrae into one solid unit, stopping motion at that level to relieve pain or stabilize the spine. Seeing it on a scan usually confirms a surgery you already had rather than a new problem.
Also: fusion hardware, interbody cage, pedicle screws and rods
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Spinous process
The bony bump that sticks out backward from each vertebra, forming the knobbly ridge you can feel down the middle of your back. Muscles and ligaments attach to it to support and move the spine. Reports often name it to locate a finding or to confirm the bone looks normal after a knock.
Also: back bump, bony spine of vertebra, spine bump
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Spondylolisthesis
One of the bones in the spine has shifted forward, backward, or sideways relative to the bone below it, so the stack no longer lines up perfectly. The slip is often small and stable, but a larger shift can narrow the spinal canal or pinch a nerve, causing back pain or symptoms down a leg.
Also: anterolisthesis, degenerative spondylolisthesis, isthmic spondylolisthesis
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Spondylosis
A general term for the slow, age-related wear of the spine — drying cushions, small bony spurs, and stiffer joints. It is the back's version of grey hair: nearly universal after middle age, often visible on scans of people who feel completely fine, and usually a description of normal ageing rather than a disease.
Also: arthritis of the spine, cervical spondylosis, degenerative disc disease
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Tarlov cyst
A small, fluid-filled sac that forms along a nerve root near the base of the spine, most often in the sacrum. The vast majority are silent, incidental findings picked up on imaging done for another reason, and only a small fraction ever grow large enough to cause symptoms.
Also: meningeal cyst, perineural cyst, sacral Tarlov cyst
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Thecal sac
A fluid-filled membrane tube that runs inside the spinal canal, holding the spinal cord, nerve roots, and cerebrospinal fluid. Radiologists use it as a landmark, checking whether nearby discs or bone are pressing on it. Its own tissue is not usually diseased — it simply outlines the space around the nerves.
Also: dural sac, dural tube, spinal thecal sac
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Thoracic kyphosis
The natural forward-curving shape of the middle section of the spine, running from the base of the neck down to the bottom of the ribcage, which gives the upper back its normal gentle rounded profile. A healthy amount of this curve is expected on every scan; only an exaggerated or reduced curve is unusual.
Also: hyperkyphosis, kyphotic curve, rounded upper back
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Vacuum disc phenomenon
Tiny pockets of gas trapped inside a worn spinal disc, seen as a dark streak or bubble on a CT scan. It's a sign the disc has lost some of its normal cushioning over time, and despite the alarming name, it's one of the more reassuring findings a spine report can contain.
Also: disc gas, gas in the disc, intradiscal gas
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Vertebra
A single backbone — one of the small, stacked bones that build the spine. You have around 33 of them running from the base of the skull to the tailbone. On a report it is simply naming a level of the spine, the way a street number names a spot along a road. The word itself is just anatomy.
Also: back bone, backbone bone, spinal bone
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Vertebral body
The solid, weight-bearing front block of each backbone. It is the chunky, cylinder-shaped part of a vertebra that stacks up to carry your body's load, with cushioning discs sitting between each one. On a report it is just naming which part of the spine bone a finding sits in. The term itself is plain anatomy.
Also: body of vertebra, front of the vertebra, spine bone block
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Vertebral endplate
The flat top and bottom surfaces of each spinal bone, where the bone meets the cushioning disc that sits between vertebrae. These thin caps of bone and cartilage anchor the disc in place and let nutrients pass into it. Reports often name them when describing wear, height, or changes next to a disc.
Also: bony endplate, disc endplate, endplates
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Vertebral hemangioma
A benign cluster of small blood vessels growing inside a spinal bone (vertebra), found incidentally on many routine scans. Despite sitting inside bone, it is not a bone tumor and almost never causes problems. The vast majority need no treatment and no follow-up at all.
Also: bone hemangioma, haemangioma of vertebra, hemangioma of the spine
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