MRI is a powerful tool for assessing muscle disease. There are four main patterns seen on MRI of muscle: distribution, size/shape, T1 signal, and T2 signal. Increased T1 signal indicates fat or hemorrhage. Increased T2 signal shows edema. Common findings include patchy or diffuse fat/edema, atrophy, enlargement. Distribution patterns provide clues to specific diseases. For example, inflammatory myopathies typically cause symmetric edema in non-adjacent muscles while compartment syndrome causes edema between adjacent muscles. MRI is useful for diagnosing and monitoring muscle diseases.

1. MRI OF MUSCLE DISEASES
DR.SARATH MENON.R ,MD(Med.),DNB(Med.),MNAMS
DEPT.OF NEUROSCIENCES,
AIMS,KOCHI

2. INTRODUCTION – A PATTERN APPROACH
 MRI -powerful tool to assess the severity, distribution,
and progression of muscle injury and disease
 Muscle’s response to a pathological insult is limited to
only a few patterns on MRI, and non-specific.
 MR appearances of muscle into 4 main pattern
descriptors:
 (1) distribution;
 (2) change in size and shape;
 (3) T1 signal
 (4) T2 signal

3.  T1W sequences - muscle architecture and anatomy, in reference to
normal surrounding fat.
 Hemorrhage and abnormal fat deposition (e.g., fatty muscle atrophy or
lipoma) assessed on T1W
 T2W or STIR- characterize muscle edema.
 Gradient echo-presence of hemosiderin, detect old injury
 Contrast enhancement with gadolinium –
-differentiating between a cystic or solid mass
-biopsy approach
-areas of acute degenerative activity
-identifying an abscess or necrotic tissue.
 Normal muscle –intermediate/low signal intensity on all (MRI)
pulse sequences
MRI OF NORMAL MUSCLE

4. NORMAL MUSCLE MRI
•
Normal muscle is quite symmetrical.
•The outside borders tend to be smooth and convex, so no bulging
•Muscle should have low signal on all sequences
•On T1-weighted images you will see fat in the muscle in very predictable patterns, with either linear, branching or feathery distributions,
depending on the architecture of the muscle

5. PATTERN VARIABLE 1-DISTRIBUTION
 muscle presence
 location of findings in a muscle or muscle compartment,
 contiguous vs. noncontiguous disease,
 symmetry,
 and involvement of the adjacent subcutaneous fat and
fascia

6.  Diabetic muscle ischemia - muscles of the anterior thigh and
posterior calf.
 Denervation edema - asymmetric distribution, as changes reflect
the distribution of a specific nerve
 Diabetic neuropathy- involves the tibialis anterior & intrinsic
muscles of the feet
 Dermatomyositis/Polymyositis- muscles of the anterior thigh and
posterior calf , lower >> upper limbs, and proximal > distal muscles
 Inclusion-body myositis -the anterior thigh in isolation;
more distally particularly in the forearm flexor compartment
 Duchenne & Becker muscular dystrophies,
the pelvic girdle and proximal thighs - diffuse and symmetric or asymmetric
fashion
later stages, the calf and shoulder girdle are also involved.
relative sparing of the gracilis, sartorius, semimembranosus,and
semitendinosus muscles

7. (a) Axial proton density and (b) coronal fat suppressed T2W images show decreased muscle
bulk and hyperintense T2 signal in the anterior compartment of both thighs. The left side is
more severely affected than the right. Mild edema is also seen in the left anterior
subcutaneous fat.The differential considerations include dermatomyositis, polymyositis, and
diabetes

8. Axial T1W image demonstrates complete fatty replacement of the deep
head of the supinator muscle (arrow) implying chronic denervation change
of posterior interosseous nerve entrapment syndrome.(denervation
myopathy)

9. PATTERN VARIABLE 2: MUSCLE SIZE & SHAPE
 T1W sequences- distinction between muscle & fat.
 Gradient-echo sequences- demonstrating muscle -fascial
interfaces
 Abnormal muscle - normal, small, enlarged.
 comparison of contralateral or other surrounding muscles
 A smaller muscle = muscle atrophy
 Neighboring muscle –compensatory hypertrophy & bulk of the
muscle group may remain the same.eg; Polio,Traumatic injury
 If a muscle appears enlarged, T1W images-for abnormal fat
deposition pseudohypertrophy.
eg.Duchenne/Becker

10.  True muscle hypertrophy (fiber enlargement) - myotonia,
acromegaly,Hoffman syndromes, sarcoidosis,
amyloidosis,cysticercosis schistosomiasis
 Changes in muscle shape - trauma(such as a hematoma or tear
causing muscle fiber/ tendon retraction), herniation, or tumors.
 An important caveat is a slow-flow vascular malformation,-
disproportionately little mass effect and may therefore preserve
muscle size and shape.
 Most herniations occur in the leg, particularly herniations of the tibialis
anterior.
 Muscle herniating through a rent in the fascia is diagnostic on MRI

11. Chronic tear of the left medial gastrocnemius.
(a) Axial T1W image demonstrates atrophy and patchy increased fat content in the left medial
gastrocnemius (arrow).There is a T1 hypointense intrafascial collection deep to the muscle (*).
The left calf is larger than the right calf due to compensatory hypertrophy of the left soleus and
deep posterior compartmental muscles; there is also increased fatty infiltration of the right calf
muscles.
(b) Coronal fluid-sensitive image shows hyperintense signal of the collection (arrow), in keeping
with a resolving hematoma or seroma

12. PATTERN VARIABLE 3- T1W SIGNAL
 altered muscle T1W signal -always increased signal (T1
shortening) from fat.
 Hemorrhage in the methemoglobin state, proteinaceous
fluid, early calcinosis (hydroxyapatite deposition disease,
myositis ossificans, & calcium pyrophosphate dihydrate
deposition disease).
 T1W imaging patterns include:
 (1) patchy fat or marbling, representing early disease
 (2) complete fatty replacement of the muscle
 (3) focal fat or scar
 (4) post-traumatic hemorrhage;
 (5) loss of marbling from a mass or tumor recurrence.

13.  Patchy Fat/Marbling.
 Patchy fat replacement of muscle- an early stage of
completefatty replacement; it is seen in disease cause
muscle edema
 Vascular Malformations.
 Patchy fat can also be seen with intramuscular vascular malformations
 High flow AVM - a tangle of flow voids on T1W and T2W images &
hyperintensity on flow-sensitive gradient-echo images
 Low-flow AVM with venous components -serpentine structures with high
T2W and intermediate T1W signal intensity; internal septations and
striations may be present.
 Lymphatic components of vascular malformations appear cystic and
may demonstrate fluid–fluid levels.

14. Vascular malformation. (a) Axial T1W image demonstrates asymmetric enlargement of the left gluteus maximus
and medius muscles. There is mild increased signal intensity, disruption of normal fatty septae, and a nodular
contour at the interface of the muscle with the subcutaneous fat.
(b) Fat-saturated T2W image demonstrates corresponding prominent increased signal within the mass similar to
slow flow veins or fluid, which crosses myofascial planes between the left gluteus maximus and medius muscles.

15.  Complete Fatty Replacement.
 End-stage result of patchy fatty replacement
 complete old tendon tear; denervation including diabetic motor
neuropathy; end-stage or burned-out
dermatomyositis/polymyositis;long-standing disuse (e.g.,
immobilization); muscular dystrophies; and congenital myopathies
 Muscular Dystrophy
 Increased T1 signal = fatty infiltration , initially in gluteus
maximus & adductor magnus,followed by quadriceps,
rectus femoris,and biceps femoris.
 Signal changes spare gracilis, sartorius,
semimembranosus, and semitendinosus,which may
hypertrophy
 In the calf, the gastrocnemii are affected more severely
than other muscles.

16. MUSCULAR DYSTROPHY

17. On the T1-weighted image only the posterior muscles contain normal fat.
On the T2-weighted image there is edema of the quadriceps, which is a sign of
early muscular dystrophy

18.  Focal Fat.
 Lipoma- demonstrates pure fat signal on all pulse
sequences
 vascular malformation - curvilinear vascular channels
surrounded by fat
 scar tissue secondary to an old injury; or myositis
ossificans

19. Coronal T1W image of the right hand shows a well
circumscribed, homogeneous fatty mass in the abductor
pollicis brevis, displacing normal muscle tissue, a benign
lipoma.

20. MYOSITIS OSSIFICANS
 Vary with evolutionary phase of the mass
 Acute-well defined heterogenous signal intensity
rim enhancement and muscle edema
D/D- abscess,necrotic tumor,sarcoma
 Subacute- iso-hyper intense T1W
 Chronic – sharply marginated,no edema
T1W/T2W- fat signal seen centrally = bone marrow
Hypointense rim corresp. Cortical bone

21. Myositis ossificans/heterotopic ossification. (a) Axial unenhanced CT image of the proximal left thigh
demonstrates a well defined mass with peripheral calcification in the posterior subcutaneous tissues. (b) Axial
T1W image shows a hypointense rim corresponding to the calcification with higher signal centrally relative to
the thigh musculature Axial (c) proton density-weighted and (d) T2-weighted images with fat saturation show
high signal centrally and peripheral low T2 signal supporting chronic hemosiderin deposition or calcification.

22.  Focal Hemorrhage/Hematoma
 Parenchymal hemorrhage
 little mass effect and exhibits a hyperintense lacy, feathery
appearance on STIR or fat-suppressed T2W sequences.
Subacute intramuscular hematoma. Axial T1W image demonstrates a hematoma in the right
vastus intermedius (arrow). There is a hypointense rim with more hyperintense T1 signal
centrally, corresponding to encapsulated methemoglobin in the collection. Although a
hypointense rim is also seen with chronic hematomas, the presence of methemoglobin is
characteristic of a subacute hematoma

24.  Loss of Marbling.
 Hyperintense fat interposed between fibers gives muscle
its characteristic marbled appearance on T1.
 Loss of this marbled appearance - ominous finding-
raises suspicion for tumor

25. PATTERN VARIABLE4-T2W SIGNAL
 Muscle edema -hyperemia, congestion, post traumatic,
and tumor infiltration (tumorigenic),
 Muscle edema into 6 patterns seen on T2W images:
 (1) patchy focal edema
 (2) patchy edema throughout a single muscle
 (3) diffuse edema in a single muscle
 (4) edema in adjacent muscles
 (5) symmetric edema in non adjacent muscles
 (6) asymmetric edema

26. FOCAL EDEMA
 post traumatic,
 either secondary to incomplete muscle strain,
 the myotendinous junction
 Contusion-where the edema is located superficially
or at the muscle–bone interface

27. MUSCLE STRAINS
 3 grades
 Grade1- T2W hyper at myotendinous junction
TIW will be normal
 Grade 2- Grade1 + heamatoma
Grade 2 strain of the left hamstring tendon from its origin at the ischial tuberosity. (a) Sagittal proton-density weighted image of the left thigh shows
retraction of the muscle(semitendinosus) belly distally (*). Some tendinous fibers remain intact (arrow). (b) Coronal and (c) axial STIR images
demonstrate a large complex hematoma surrounding the central tendon (arrows). (d) Distally, the retracted left hamstring muscles demonstrate
diffuse edema on this axial T2W image with fat saturation, suggesting intramuscular hemorrhage.

28. GRADE 3
 Complete disruption of myo tendinous junction
 MRI –disrupted muscle fibres with extensive
edema(diffuse edema)
Inter/intramuscular heamtoma+

29. PATCHY EDEMA IN A SINGLE MUSCLE.
 trauma -muscle strains and contusions- focal
muscle or diffuse edema;
 pyomyositis, - (typically edema in adjacent
muscles)
 diabetic myopathy-
- denervation myopathy (typically diffuse edema in a
single muscle);
- diabetic muscle ischemia/infarction (symmetric
/asymmetric edema in either a single muscle or
multiple non adjacent muscles).

30. DIFFUSE EDEMA IN A SINGLE MUSCLE
 Acute focal atrophy such as a complete (grade 3)
muscle strain or acute denervation

31. DENERVATION RELATED MYOPATHY
 Hyperintense signal STIR/ T2W – due increase EC space
 Post contrast enhancement T1W
 Long standing, atrophy,fatty replacement – T1W
Denervation related atrophy of left-side quadriceps femoris muscle. Axial
STIR image shows both atrophy and residual muscle edema in subacute
phase of intraoperative damage of deep branch of femoral
nerve (arrow)

32. EDEMA IN ADJACENT MUSCLES
 deep venous thrombosis
 compartment syndromes,
 eosinophilic myositis,
 pyomyositis,
 peripheral neuropathy(may not be entirely
adjacent),
 Vascular malformations
 Radiation,
 Lymphoma.

33. COMPARTMENT SYNDROME
 T2W –subfascial hyper intensity within & between
adjacent muscles
 T1W- enlarged muscles & petechial hemorrhage
 Contrast fatsat T1W-
- avid enhancement in early phase
- enhance peripherally,central ischemia,necrosis in
late phase

34. Bilateral compartment syndrome. (a) Coronal STIR and (b) axial fat-suppressed T2W images show
extensive, patchy hyperintense T2 signal within and between muscles of the anterior compartments
bilaterally. (c) Axial postcontrast fatsaturated T1W image shows peripheral enhancement of the
anterior muscles and lack of central enhancement, in keeping with reduced perfusion and
myonecrosis.

35. PYOMYOSITIS
 Buttocks,pelvis,thighs
Early phase
 T2W/STIR- hyper intensity
 TIW-muscle enlarged,loss of marbling,hyperintense
 Late phase (abscess formation)
 T2W- hyperintense
 TIW- hypointense, wall- hyperintense
 Contrast T1W-ring enhancement with edema

36. pyarthrosis in right hip (arrowhead). Coronal STIR
image shows focal secondary infectious myositis
(arrow) in right quadriceps muscle adjacent to
infected hip joint. At this time, there is no abscess
formation

37. T1-weighted image with fatsat post
contrast
Fluid collections within the enhancing
muscle in a patient with pyomyositis

38. focal myositis presenting as painful
swelling of right thigh.
A and B, Coronal STIR (A) and fat-
saturated gadolinium enhanced
T1-weighted (B) images show
increased signal in focal distribution
along rectus femoris muscle on right,
suggestive of focal nodular myositis
(arrows).

39. SYMMETRIC EDEMA IN NONADJACENT
MUSCLES.
 usually symmetric muscles
 polymyositis and other inflammatory myopathies,
 delayed-onset muscle soreness (DOMS)
 Diabetes
 Drug induced

40. INFLAMMATORY MYOPATHY
 MRI-excellent tool
- early diagnosis
- Severity and extent of active disease
- Guidance for muscle biopsies
- Monitoring progression
- areas of fatty atrophy

41. POLYMYOSITIS/DERMATOMYOSISTIS
 Thigh-vastus lateralis,intermedius
 Subcutaneous edema-DM
 Edema- sorrounding muscle/muscle group
-TIW-ring like pattern
Chronic-fatty atrophy
Juvenile DM- inter/intra muscular calcifications

42. polymyositis. Note diffuse edema and inflammation of
obturator externus (arrowhead) and pectineus (arrow)
muscles on axial STIR image

43. chronic polymyositis. Note advanced fatty atrophy,
especially of quadriceps muscles (arrows), on unenhanced
axial T1-weighted

44. dermatomyositis. Axial STIR image shows diffuse hyperintensity in
some thigh muscles (arrowhead, vastus lateralis muscle).Note
also increased signal in subcutaneous tissue septa (arrow) and
skin thickening

45. Juvenile dermatomyositis. Whole-body
STIR image shows multifocal patchy
pattern of muscle edema and
inflammation (arrows)

46. DRUG INDUCED
administration of statins. Note atrophy and hyperintensity of thigh
muscles on axial STIR image (arrows).

47. INCLUSION BODY MYOSITIS
 Profound muscular atrophy
 Fatty atrophy
 More distal
 Extensors of knees,flexors of wrists,fingers
 Isolated anterior compartment of thigh

48. DELAYED ONSET MUSCLE SORENESS(DOMS)
 T2W/STIR –symmetric,feathery hyperintense signal
 Perifascial & intermuscular edema

60-year-old man days after excessive biking who has progressive myalgia in both legs, which is consistent with delayed
onset of muscle soreness.Note bilateral muscle edema on coronal STIR image involving especially quadriceps femoris muscles
Arrow in right thigh indicates vastus lateralis muscle; arrowhead shows edema of left vastus medialis muscle.

49. EDEMA IN NONADJACENT,NON SYMMETRIC MUSCLES.
 Diabetic myonecrosis
 medications,
 rolling crush injuries
 rhabdomyolysis.

50. MUSCLE INFARCTION & DIABETIC MYONECROSIS
 Lower extremity- anterior thigh & post.calf
 T1W- enlarged infarcted muscles,displaced fascial
planes.
- hyperintensity- hemorrhagic infarction
 T2W- diffuse.patchy,s/c,subfascial,intramuscular edema
 Contrast T1W
- diabetic muscle ischaemia
- region of enhancement,non mass-like rim enhancement
with central non enhanced- myonecrosis
-multiple non adjacent muscles

51. diabetic muscle disease/myopathy. (a) Axial fat-saturated T2W image of the calves -asymmetric, patchy edema in muscles of the
lateral, anterior, and posterior right calf with neuropathic muscle disease. (b) Axial fat saturated proton density image of the left
calf in type I diabetic with cellulitis, fasciitis, and ischemic myositis. There are skin thickening, subcutaneous edema, and focal
fluid collections surrounding the superficial fascia of the calf (arrows). Interfascial fluid tracks between the gastrocnemius and
medial soleus (arrowhead). Diffuse edema in the gastrocnemius and medial soleus without muscle enlargement favors ischemic
myositis. Coronal (c) fat-saturated T2W and (d) contrast-enhanced T1W images of another patient demonstrate patchy muscle
edema and enhancement throughout the left calf.

52. MUSCLE INFARCTION
Muscle ischemia/infarction. (a) Axial T2W image with fat saturation and (b) coronal STIR images
show a focal area of abnormal, non–mass-like signal hyperintense to normal muscle in the right
vastus lateralis. Contrast-enhanced (c) axial and (d) coronal T1W images with fat suppression show
predominantly peripheral enhancement with subtle enhancement centrally.

53. In the lower leg there are four compartments: the anterior, deep and superficial posterior compartment
and a small lateral compartment.
On the left T1W-images of a patient one month post trauma.
On the post-Gadolinium image the necrosis in the anterior and lateral compartment is seen.
The posterior compartment is normal

54. RHABDOMYOLYSIS
 T2W/STIR- diffuse hyperintensity
 Gradient echo-hemosiderin-hemorrhagic transfomation
diffuse edema of chest wall musculature as shown on coronal STIR image
along pectoralis muscles.

58. THANK YOU