The one-line answer
An MRI report is written by one specialist to another. It is dense, cautious, and full of words that sound alarming out of context. The single most useful thing to know is that most reports contain one or two findings that look scary in isolation and mean very little once your consultant puts them next to your symptoms. This guide walks through the twelve terms UK patients most often Google after opening the PDF, and explains what each one actually signals.
If you have just had an MRI scan and are staring at a paragraph of Latin, radiology jargon and cautious hedging, read on. None of what follows replaces a conversation with your referring clinician, but it should stop the middle-of-the-night panic that most reports trigger.
'Unremarkable' / 'No acute abnormality'
This is the phrase every patient wants to see and almost no patient recognises. "Unremarkable" does not mean the radiologist glanced at the images and gave up. It means they looked carefully, at every sequence, and found nothing worth flagging. "No acute abnormality" is the same idea with a specific time frame - nothing new, nothing urgent, nothing that needs action today.
If your report uses either phrase for the body part being investigated, the scan itself is reassuring. Your symptoms may still need explaining, but the imaging has ruled out the serious structural causes it was ordered to look for.
'Hyperintense' and 'hypointense'
These two words describe brightness on the image, nothing more. Hyperintense means brighter than the surrounding tissue on the sequence being described. Hypointense means darker. The catch is that MRI runs several different sequences (T1, T2, STIR, FLAIR, diffusion), and the same tissue can be bright on one and dark on another.
Water and cerebrospinal fluid, for example, are hyperintense (bright) on T2 and hypointense (dark) on T1. That is completely normal. A hyperintense signal is only meaningful when the radiologist tells you which sequence and which tissue - "T2 hyperintense signal within the medial meniscus", for instance, points to a possible tear. On its own, the word tells you almost nothing.
'Signal change' / 'signal abnormality'
Signal change is a general-purpose radiology word for "this bit looks different to the tissue around it". It is deliberately vague because a signal change can mean anything from a healed old injury to inflammation to a genuine lesion. The report will usually add a location and a sequence, and often a suggested cause.
The key thing to remember is that a signal change on its own is a finding, not a diagnosis. Your consultant needs to marry it with your symptoms, your history and often another test before it means anything specific.
'Enhances' / 'post-contrast enhancement'
If your scan was done with gadolinium contrast, some of the report will discuss whether an area "enhances" after the injection. Enhancement means the tissue took up the contrast, which typically indicates increased blood flow. That can point to inflammation, infection, active demyelination, or a tumour with its own blood supply.
Not all enhancement is worrying. Normal structures like the pituitary gland, the mucosa of the sinuses and the walls of blood vessels enhance strongly because they are highly vascular. The report will separate normal enhancement from abnormal enhancement, and the pattern (ring, homogenous, patchy) matters as much as the fact of enhancement itself.
'Disc bulge', 'protrusion', 'extrusion'
These three words describe a spectrum of disc herniation, from mildest to most severe. A bulge is a diffuse outward push of the disc, usually broad and symmetrical. A protrusion is a more focal push where the disc wall is still intact. An extrusion is a more severe herniation where inner disc material has pushed out beyond the disc wall. A sequestration, the most severe, is a fragment that has broken off entirely.
Here is the piece patients rarely hear: bulges and small protrusions are extremely common in adults with no back pain at all. Studies of asymptomatic UK adults over 40 find disc bulges in more than half of scans. What matters is not the bulge itself, but whether it is compressing a nerve root or the spinal cord and whether your symptoms match. A finding of "L4/L5 disc bulge with no significant nerve root compression" in someone with mild backache is usually not the cause of the pain.
'Effusion'
An effusion is fluid inside a joint. On a knee, shoulder, hip or ankle MRI it is one of the most common findings and it usually means the joint is irritated. Small effusions can appear in normal joints after a long walk or minor injury. Larger effusions usually point to a specific cause - a tear, arthritis, infection or reactive inflammation - which the report will attempt to characterise.
An effusion on its own is not a diagnosis. It is a signal that the joint has been under stress, and the more useful information in the report is what else is present alongside it.
'Oedema' / 'bone marrow oedema'
Oedema means fluid within tissue. Soft-tissue oedema in muscle or fat is common after injury and usually resolves. Bone marrow oedema, however, is one of the terms in an MRI report that tends to genuinely matter. It is fluid inside a bone, and it points to something the bone is actively responding to - a stress reaction, an occult fracture, early arthritis, an infection, or an area of impact.
If your report describes bone marrow oedema, expect your consultant to correlate it with your symptoms, review the location carefully, and often order a targeted follow-up. It is not a diagnosis in itself, but it is rarely dismissed as nothing.
'Degenerative change'
Degenerative change is age-related wear. It is the single most common finding on adult MRI reports and it appears in almost every spine, knee and shoulder scan over the age of 40. Terms you might see alongside it include "spondylosis", "osteoarthritic change", "facet joint hypertrophy", "disc desiccation" and "endplate signal change".
None of these words are a diagnosis of anything sinister. They describe the normal biological ageing of joints and discs. Degenerative change can absolutely cause pain, but it is present in huge numbers of pain-free adults, so its mere presence on a scan does not automatically explain your symptoms. Your consultant will look for whether the degeneration is causing nerve compression, joint instability or synovitis before it becomes clinically meaningful.
