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.
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Basal ganglia
A cluster of structures sitting deep inside the brain, on both sides, that help coordinate smooth, planned movements and certain types of learning and habit. They are routinely checked on every brain scan because they are a common site for small strokes, mineral deposits, and changes seen in some long-standing conditions.
Also: caudate putamen globus pallidus, deep brain nuclei, deep gray matter
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Brainstem
The stalk-like lower part of the brain that connects the larger brain above to the spinal cord below. It runs the basic, automatic functions the body cannot live without — breathing, heart rate, blood pressure, swallowing, and the level of wakefulness. Every brain scan checks this region carefully because of how vital it is.
Also: brain stalk, brain stem, lower brain stalk
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Cerebellum
The smaller, rounded part of the brain tucked under the back of the larger hemispheres, just above where the neck meets the skull. It coordinates balance, posture, and the smooth timing of movements. Radiologists mention it routinely on brain imaging because it is one of the standard structures they check on every scan.
Also: balance center of the brain, cerebellar, hindbrain coordinator
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Cerebral atrophy
A general shrinking of brain tissue, with widened grooves on the surface and slightly larger fluid spaces in the centre. A small amount is a normal part of getting older. Larger amounts, or shrinkage that does not match a person's age, can be linked to specific neurological conditions and are usually viewed alongside symptoms.
Also: age-related atrophy, brain atrophy, brain shrinkage
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Cerebral edema
Extra water inside or around the brain tissue, making part of the brain look swollen on a scan. It is a reaction to many things — a bruise, a stroke, an infection, a tumour, or surgery — rather than a diagnosis by itself. How much swelling there is, and what is causing it, decides how worrying it is.
Also: brain edema, brain swelling, cerebral oedema
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Infarct
An area of brain tissue that has been injured or has died because its blood supply was cut off, usually by a blocked artery. On imaging it shows up as a patch of tissue that no longer looks like its healthy neighbours. The size and location decide how the symptoms appear and how the team responds.
Also: brain attack, cerebral infarct, infarction
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Intracranial
An adjective meaning inside the skull. It describes the location of something — a structure, a finding, or a process — rather than what that thing is or whether it is a problem. The word appears constantly in brain reports because radiologists use it to point at where something sits.
Also: inside the brain cavity, inside the skull, intracranial compartment
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Intracranial hemorrhage
Blood that has leaked inside the skull, either into the brain tissue itself or into one of the spaces wrapped around it. It is an important and time-sensitive finding because fresh blood takes up room the brain does not have to spare. Exact location, size, and cause shape how urgently it has to be treated.
Also: ICH, bleeding in the brain, brain bleed
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Mass effect
A phrase radiologists use when something inside the skull is taking up extra room and pushing on the brain tissue or fluid spaces nearby. It is a description of crowding, not a diagnosis on its own. The cause — swelling, bleeding, a tumour, or a fluid pocket — and how much pressure it creates is what matters most.
Also: compression effect, local mass effect, mass-like effect
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Mastoid air cells
Tiny honeycomb-like air pockets inside the bone just behind each ear, connected to the middle ear. They normally contain air and help regulate pressure in the ear. Because they sit right next to the brain, every head CT or MRI looks at them and notes whether they are clear or contain fluid.
Also: ear bone air spaces, mastoid, mastoid bone
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Midline shift
A sign on brain imaging that something on one side is pushing the brain's central structures over toward the other side. It almost always points to swelling, bleeding, or a mass that needs attention soon. The amount of shift, measured in millimetres, is one of the strongest cues to how urgent the situation is.
Also: brain shift, deviation of the midline, mass effect with midline shift
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Paranasal sinuses
Air-filled spaces in the bones of the face around the nose, lightening the skull and warming and moistening the air you breathe. They sit in the forehead, behind the cheeks, between the eyes, and deep inside the head, and they all drain into the nose. Brain and head scans routinely include and comment on them.
Also: ethmoid sinus, facial sinuses, frontal sinus
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Periventricular
A descriptive term meaning "around the fluid-filled spaces in the middle of the brain." It points to the region of brain tissue that lies just next to the ventricles, where a finding has been seen. The word itself only marks the location — what matters is what is found there.
Also: around the brain's fluid spaces, around the ventricles, next to the ventricles
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Subarachnoid hemorrhage
Bleeding into the thin, fluid-filled space that wraps around the brain, between two of its protective layers. It is a time-sensitive finding because the blood sits in the same space as the cerebrospinal fluid and can quickly affect the whole brain. The cause and the amount of bleeding decide how it is treated.
Also: SAH, aneurysmal bleed, bleed under the arachnoid
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Sulci
The grooves on the outer surface of the brain, between the raised folds. They are a normal part of how the brain is built — the wrinkled surface packs a much larger sheet of tissue into the limited space of the skull. Radiologists describe how deep or wide these grooves look as part of every brain scan.
Also: brain folds, brain grooves, cerebral sulci
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