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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6009_Библиотеки_им_академика_М_И_Перельмана.pdf
Muscle Denervation
KEY FACTS
TERMINOLOGY
• Secondary muscle injury resulting from denervation
following nerve injury
IMAGING
• Acute denervation
○ Muscle appears normal on T1WI
○ Diffusely increased signal intensity on T2WI, STIR
○ Mild, homogeneous enhancement with gadolinium
Peripheral Nerve and Plexus
• Chronic denervation
○ Fatty atrophy evident on T1WI
○ Muscle volume decreased
○ Denervation edema often persists for prolonged period
TOP DIFFERENTIAL DIAGNOSES
• Disuse atrophy
• Muscle trauma
• Muscle inflammation or infection
• Radiation myopathy
(Left) Coronal STIR MR shows
denervation edema st of the
trapezius, which is innervated
by the spinal accessory nerve.
This nerve can be traumatized
by carrying heavy loads on the
shoulder. (Right) Coronal T1WI
C+ FS MR in the same patient
shows uniform enhancement
st of the affected muscle.
Muscle tears, in contrast, have
a heterogeneous appearance.
PATHOLOGY
• Nerve tumor, infection, autoimmune neuritis, peripheral
neuropathy or injury
CLINICAL ISSUES
• Weakness, muscle volume loss in distribution of injured
nerve
○ May be painful
• Acute denervation may partially or totally recover
depending on nerve injury severity
• Chronic denervation changes permanent
DIAGNOSTIC CHECKLIST
• Distribution of muscle signal abnormalities indicates
location of nerve lesion
• Obtain fluid-sensitive sequence that shows muscle of
concern in cross section
420
(Left) Axial T2WI FS MR shows
a free muscle flap st to the
leg. The muscle shows severe,
diffuse edema with a few
streaks of fat interspersed.
This is an expected finding and
should not be confused with
infection. (Right) Coronal
T2WI FS MR shows
denervation edema st
throughout the intrinsic
muscles of the foot.
Denervation edema due to
diabetes primarily involves the
feet. It tends to be streakier
and less homogeneous than
denervation from other
causes.
Brachial Plexus Traction Injury
KEY FACTS
Peripheral Nerve and Plexus
TERMINOLOGY
• Synonyms: Brachial plexus stretch injury, brachial plexus
avulsion, avulsion pseudomeningocele
• Stretch injury or avulsion of ≥ 1 cervical roots, brachial
plexus
IMAGING
• Stretch injury: Enlargement, abnormal edema of neural
elements
• Avulsion: Abnormal CSF signal intensity within empty thecal
diverticulum
• Obstetric brachial plexus palsy: C5-C6 roots (Erb-Duchenne
palsy, 80%) > C8-T1 nerve roots (Klumpke palsy, 20%)
TOP DIFFERENTIAL DIAGNOSES
• Nerve sheath tumor
• Lateral meningocele
• Nerve root sleeve cyst
PATHOLOGY
• Adults: Majority posttraumatic injuries 2° to high-energy
force
• Infants: 2° to excessive traction on plexus during difficult
delivery (breech or forceps)
CLINICAL ISSUES
• Pain, paralysis of ipsilateral limb ± phrenic nerve palsy
• Complete brachial plexus avulsion produces useless "flail
arm"
• Clinical incomplete paralysis possible with complete root
avulsion(s) because of redundant muscle innervation from
multiple roots
DIAGNOSTIC CHECKLIST
• Familiarity with normal brachial plexus anatomy essential
for MR interpretation
• Muscle denervation pattern predicts abnormal nerves
(Left) Coronal graphic
demonstrates posttraumatic
avulsion of left C5-C8 nerve
roots ſt producing local
hemorrhage at the site of root
injury and associated
pseudomeningoceles. (Right)
Coronal T2WI MR in a patient
with posttraumatic paralyzed
"flail arm" demonstrates an
extensive extradural CSF
signal intensity collection
admixed with blood products
ſt, representing CSF leakage
following avulsion of multiple
nerve roots, displacing the
spinal cord to the right.
(Left) Coronal STIR MR in a
patient with severe brachial
plexus traction injury shows
avulsion pseudomeningoceles
of right C6, C7, and C8 roots
ſt. The C5 root is attenuated
with abnormally ↑ signal
(incomplete stretch injury) .
The avulsed nerve roots have
formed a "retraction ball" ,
with abnormal enlargement
and T2 hyperintensity of the
distal (denervated) plexus st.
(Right) Axial STIR MR confirms
the CSF signal and lack of
demonstrable neural elements
within the right C7
pseudomeningocele ſt.
421
Idiopathic Brachial Plexus Neuritis
KEY FACTS
TERMINOLOGY
• Parsonage-Turner syndrome
IMAGING
• Can affect any muscle innervated by brachial plexus
○ Most common: Rotator cuff, deltoid, biceps, triceps
• Denervation edema is earliest finding
○ Diffuse, homogeneous high signal on T2WI, STIR
throughout affected muscle
Peripheral Nerve and Plexus
• Fatty atrophy occurs in chronic denervation
○ Uncommonly seen
• Often muscles innervated by 2 or more different peripheral
nerves are affected
TOP DIFFERENTIAL DIAGNOSES
• Cervical radiculopathy
• Suprascapular nerve entrapment
• Brachial plexus neoplasm
• Brachial plexus or cervical nerve root avulsion
(Left) Coronal STIR MR shows
diffusely increased signal
intensity in brachial plexus
due to idiopathic brachial
neuritis. (Right) Coronal
oblique T2WI MR shows
denervation edema of the
teres minor ſt due to brachial
neuritis. Edema is
homogeneous and uniform,
and there is no disruption of
muscle fibers. Quadrilateral
space shows no evidence of
the mass involving axillary
nerve. Whenever denervation
edema is seen, a search should
be made for nerve mass or
extrinsic compression.
• Radiation neuritis/myositis
• Quadrilateral space syndrome
• Pancoast tumor
• Muscle injury
PATHOLOGY
• Often associated with viral or bacterial infection
• Can also be posttraumatic or postsurgery occurrence
CLINICAL ISSUES
• Sudden onset of pain, followed by weakness, paresthesias
• M > F
• Most cases resolve in 3 months to 2 years
• Physical therapy to preserve range of motion
DIAGNOSTIC CHECKLIST
• Often unexpected finding on shoulder MR performed to
evaluate weakness, pain
• Abnormal muscle signal often involves > 1 peripheral nerve
distribution
422
(Left) Coronal oblique T2WI
MR shows diffuse increase in
signal intensity throughout
superior fibers of infraspinatus
muscle st. The inferior portion
of the muscle is spared.
Unusual distributions of
denervation edema are
common in brachial neuritis.
(Right) Sagittal T2WI MR
shows diffusely abnormal
signal intensity in the
infraspinatus and
supraspinatus muscles st.
Differential diagnosis in this
case includes suprascapular
nerve entrapment.
Traumatic Neuroma
KEY FACTS
Peripheral Nerve and Plexus
TERMINOLOGY
• Amputation neuroma (stump neuroma)
○ Subtype of traumatic neuroma following traumatic or
surgical amputation
• Morton neuroma: Traumatic neuroma between metatarsal
heads
IMAGING
• Bulbous enlargement of nerve
• Enlargement of nerve fascicles
• Normal signal intensity on T1WI
• Intermediate to high signal intensity on T2WI, STIR
• Avid enhancement after gadolinium enhancement
• Any site of nerve injury or surgery
TOP DIFFERENTIAL DIAGNOSES
• Benign or malignant peripheral nerve tumor
• Perineural cyst
○ Eccentric to nerve, no enhancement
• Ganglion cyst
○ Associated with tendon, no enhancement
• Soft tissue metastasis or recurrent malignancy
• Neuritis
PATHOLOGY
• Secondary to nerve injury: Amputation, crush injury, deep
burns, minor trauma, nerve compression
• All elements of nerve present in neuroma in addition to scar
tissue
CLINICAL ISSUES
• Severe pain or paresthesias
• Arises 1-12 months after nerve injury
• As many as 1/4 of amputees develop stump neuroma
DIAGNOSTIC CHECKLIST
• May be mistaken for recurrent sarcoma
(Left) Coronal T1WI MR in a
patient status post aboveknee amputation for trauma
shows the sciatic nerve st
terminating in a large stump
neuroma . (Right) Coronal
STIR MR in the same patient
nicely demonstrates the stump
neuroma . The normal
sciatic nerve st is much less
visible than on T1WI, as it
blends with fat. T1W images
are best for locating normal
nerves, since the nerves' low
signal intensity is conspicuous
against the adjacent high
signal intensity fat.
(Left) Axial T1WI C+ FS MR in
the same patient shows
marked enlargement of the
abnormal sciatic nerve at the
neuroma site. The separate
tibial st and peroneal ſt
nerves are distinctly seen.
(Right) Surgical photograph of
a resected stump neuroma
illustrates bulbous
enlargement of a nerve stump
tip st gradually tapering
proximally into normal nerve.
423
Radiation Plexopathy
KEY FACTS
TERMINOLOGY
• Synonyms: Radiation-induced plexitis, radiation-induced
fibrosis
IMAGING
• Smooth, diffuse T2 hyperintensity ± enhancement of
multiple plexus elements
• Upper brachial plexus (BP) (C5-C7) > lower BP (C8, T1)
following radiation therapy (XRT) for breast and lung
Peripheral Nerve and Plexus
cancer, lymphoma
• Lumbosacral plexus following XRT for prostate, colorectal,
and gynecologic tumors and lymphoma
TOP DIFFERENTIAL DIAGNOSES
• Malignant brachial plexus infiltration
• Plexiform neurofibroma
• Plexus traction injury
(Left) Coronal graphic of the
left brachial plexus in a breast
cancer patient with skeletal
metastases following
radiation therapy
demonstrates diffuse swelling
of irradiated brachial plexus
elements ſt. Segmental
involvement of all neural
elements in the radiation field
is characteristic of radiation
plexopathy. (Right) Coronal
STIR MR (3 years post
radiation for breast cancer
with vague arm symptoms)
shows diffuse, smooth,
abnormal brachial plexus T2
hyperintensity ſt. No nodal
mass was evident.
PATHOLOGY
• Direct cell damage 2° to ionizing radiation and radiationinduced vascular damage to vaso nervosum
• Modified LENT-SOMA scale (brachial plexopathy)
○ Grade 1: Mild sensory deficits, no pain
○ Grade 2: Moderate sensory deficits, tolerable pain, mild
arm weakness
○ Grade 3: Continuous paresthesia with incomplete paresis
○ Grade 4: Complete paresis, severe pain, muscle atrophy
CLINICAL ISSUES
• Pain, paresthesia, motor deficits of ipsilateral extremity
• Prognosis variable; related to dose delivered to plexus,
severity of nerve injury
DIAGNOSTIC CHECKLIST
• Correctly diagnosis to avoid inappropriate additional
radiation therapy
424
(Left) Coronal T1WI C+ FS MR
(3 years post radiation for
breast cancer with vague arm
symptoms) reveals only mild
patchy plexus enhancement
ſt. No nodular mass lesion or
enhancement was present, a
finding that would imply
neoplastic infiltration. (Right)
Sagittal oblique STIR MR
shows that abnormal T2
hyperintensity in the upper
plexus ventral primary rami ſt
preserves fascicular
architecture. Plexus nodal
tumor invasion more
commonly involves the lower
plexus because of axillary
nodal location.
Peripheral Nerve Sheath Tumor
KEY FACTS
Peripheral Nerve and Plexus
TERMINOLOGY
• Grouping of benign and malignant primary tumors of
peripheral nerves
IMAGING
• Mass associated with peripheral nerve
○ Schwannoma: Round mass, eccentric to nerve
○ Neurofibroma: Fusiform, cord-like, or lobulated mass
centered on nerve
○ Plexiform neurofibroma: Arborizing tangle of lobular
masses
○ Malignant peripheral nerve sheath tumor: Round, ovoid,
fusiform, or lobulated
• Low signal intensity on T1WI, PDWI
• Intermediate to high signal intensity on T2WI, STIR
• Avid enhancement with gadolinium
• Muscles innervated by nerve often show denervation
changes
TOP DIFFERENTIAL DIAGNOSES
• Traumatic neuroma
• Hemangioma
• Neuritis
• Other soft tissue sarcomas
• Metastases, soft tissue
• Lymphoma
PATHOLOGY
• Malignant degeneration seen in neurofibroma but rare in
schwannoma
CLINICAL ISSUES
• Palpable mass, often painful
• May cause weakness in distribution of affected nerve
DIAGNOSTIC CHECKLIST
• Imaging cannot reliably distinguish between benign and
malignant nerve sheath tumors
(Left) Coronal T1WI MR
demonstrates a large mass st
arising from the peroneal
nerve ſt. The mass has the
same signal intensity as the
adjacent popliteal cyst .
(Right) Coronal PD FSE FS MR
in the same patient confirms
that both the tumor ſt and
fluid have a similar degree
of minimal signal
heterogeneity. It can be
challenging to discern these
tumors from cysts even with
MR.
(Left) Axial T2 FS MR reveals
marked T2 hyperintensity
characteristic of neural sheath
tumor in a large median nerve
mass ſt. Note the
characteristic target
appearance of plexiform
neurofibroma. (Right) Axial T1
C+ FS MR confirms the typical
heterogeneous, relatively
understated enhancement
(compared to schwannoma)
within the large median nerve
plexiform neurofibroma ſt.
425
Peripheral Neurolymphomatosis
KEY FACTS
TERMINOLOGY
• Synonyms: Peripheral neurolymphomatosis (NL), perineural
lymphomatosis
• Perineural plexus or peripheral nerve lymphomatous
infiltration
IMAGING
• Diffusely infiltrating plexus or peripheral nerve lesion in
patient with lymphoma
Peripheral Nerve and Plexus
○ Abnormal nerve T2 hyperintensity
○ Disruption/distortion of normal neural fascicular
morphology
○ Variable enhancement
TOP DIFFERENTIAL DIAGNOSES
• Peripheral nerve metastasis
• Chronic inflammatory demyelinating polyneuropathy
• Hypertrophic neuropathy
• Nerve/plexus stretch injury
(Left) Coronal STIR MR in a
patient with stage IV thoracic
lymphoma, progressive leg
atrophy, and pain
demonstrates abnormal L2-L4
nerve root and dorsal root
ganglia ſt hyperintensity and
enlargement. Also present is
concomitant abnormal
thickening and T2
hyperintensity of the right
lumbar plexus . (Right)
Axial T1WI C+ MR in the same
patient reveals abnormal
thickening and avid
enhancement of the infiltrated
right lumbar plexus ſt.
PATHOLOGY
• Perineural lymphomatous nerve infiltration produces
thickened neural elements
CLINICAL ISSUES
• Pain ± motor weakness, sensory deficit
• Progressive sensorimotor neuropathy ± plexopathy
• Relentlessly progressive; variable response to
chemotherapy, radiotherapy
DIAGNOSTIC CHECKLIST
• Careful evaluation of NL patients often reveals evidence for
subclinical systemic lymphoma
• Imaging findings are often subtle
○ Carefully scrutinize clinically abnormal nerves and plexi
for thickening, abnormal T2 signal
○ High index of suspicion important for recognition
426
(Left) Axial T1WI C+ FS MR in a
patient with non-Hodgkin
lymphoma, systemic
metastases with progressive
arm pain, and weakness
demonstrates an ill-defined,
enhancing infiltrative mass ſt
centered within the left radial
nerve neurovascular bundle
near the humeral spiral
groove. (Right) Sagittal
oblique T1WI C+ FS MR in a
patient with known lymphoma
and progressive left sciatic
neuropathy demonstrates
abnormal left sciatic nerve
enlargement and avid
enhancement ſt at the
piriformis muscle level.
Hypertrophic Neuropathy
KEY FACTS
Peripheral Nerve and Plexus
TERMINOLOGY
• Clinically and genetically heterogeneous group of inherited
disorders with focal or diffuse peripheral nerve
enlargement
• Hereditary motor-sensory neuropathy (HMSN)
○ HMSN I (Charcot-Marie-Tooth syndrome type I, CMT1)
○ HMSN II (neuronal-type peroneal muscular atrophy,
CMT2)
○ HMSN III (Dejerine-Sottas disease, hypertrophic
neuropathy of infancy, congenital hypomyelinating
neuropathy)
IMAGING
• Focal or diffuse fusiform peripheral nerve enlargement
○ Peripheral nerves ± intradural nerve roots
• Acute &/or chronic muscle denervation changes
• Best imaging tool: High-resolution MR neurography
TOP DIFFERENTIAL DIAGNOSES
• Guillain-Barré syndrome
• Chronic inflammatory demyelinating polyneuropathy
• Nerve sheath tumor
PATHOLOGY
• Hypertrophic nerve roots, peripheral nerves
• Histologic shows demyelination, remyelination + "onion
bulb" formations (HMSN I)
CLINICAL ISSUES
• Distal extremity muscle weakness/atrophy (motor >
sensory), foot deformities
• Back/lower extremity radicular pain ± myelopathy
• Sensory loss, focal tenderness, dysesthesias
DIAGNOSTIC CHECKLIST
• Consider HMSN when abnormally enlarged peripheral
nerves identified on MR
(Left) Coronal T1WI MR in a
patient with Charcot-MarieTooth and painful scoliosis
demonstrates convex left
scoliosis and bilateral
abnormal fusiform
enlargement of the extradural
spinal nerve roots and lumbar
plexus . (Right) Axial T2WI
MR in the same patient
confirms abnormal
enlargement and T2
hyperintensity of the bilateral
extradural lumbar nerve roots
as well as aberrant
enlargement of the intradural
cauda equina nerve roots ſt.
(Left) Coronal STIR MR
(unknown type, hypertrophic
neuropathy, left arm pain and
weakness) demonstrates
abnormal fusiform
enlargement of the left
proximal brachial plexus C7
and C8 roots/rami . (Right)
Coronal T1WI C+ FS MR in the
same patient of the left
brachial plexus confirms
fusiform enlargement and
diffuse homogeneous nerve
enhancement within the left
proximal brachial plexus C7
and C8 roots/rami .
427
Femoral Neuropathy
KEY FACTS
TERMINOLOGY
• Synonyms: Femoral neuropathy, femoral mononeuropathy,
femoral nerve (FN) palsy
• FN entrapment or injury 2° to direct trauma, compression,
stretch injury, or ischemia
IMAGING
• Nerve enlargement ± loss of internal fascicular architecture,
↑ T2 hyperintensity
Peripheral Nerve and Plexus
• Injury most common in psoas muscle body, iliopsoas
groove, or femoral canal
TOP DIFFERENTIAL DIAGNOSES
• Neoplastic FN infiltration
• Nerve sheath tumor
• Lumbosacral disc syndromes
• Lumbar plexopathy
(Left) Coronal graphic shows
the normal course of the
femoral nerve st relative to
the psoas muscle ſt and
inguinal ligament . The
femoral nerve produces
multiple peripheral branches
to the anterior thigh muscles.
(Right) Coronal STIR MR
(femoral neuropathy
postsurgical herniorrhaphy)
depicts marked enlargement
and T2 hyperintensity of the
right femoral nerve ſt, with
abrupt transition at the right
groin. In this case, the femoral
nerve was accidentally ligated
during herniorrhaphy.
PATHOLOGY
• Reported causes include self-retaining retractor, thigh
tourniquet, traumatic injury, heparin anticoagulation
(retroperitoneal hematoma), arterial catheterization
complication, obstetrical complication, diabetic neuropathy
CLINICAL ISSUES
• Acute symptom onset, pain/weakness in FN distribution,
diminished/absent knee jerk reflex, thigh muscle atrophy
• Severe back/groin pain (retroperitoneal hematoma)
• Recovery is rule over days → months
DIAGNOSTIC CHECKLIST
• Femoral neuropathy is uncommon
• Look carefully for lesion or hematoma in iliopsoas groove or
femoral canal
428
(Left) Axial STIR MR (femoral
neuropathy postsurgical
herniorrhaphy) through the
pelvis confirms that the right
femoral nerve ſt in the
iliopsoas groove is markedly
enlarged with discrete T2
hyperintense fascicles
(compared with the normal
left femoral nerve st). (Right)
Axial CECT (severe
hemophilia) depicts large left
iliacus and psoas ſt
hematomas. Femoral
neuropathy occurs from
compression of the adjacent
femoral nerve, which runs
along the psoas muscle and
iliopsoas groove.
Ulnar Neuropathy
KEY FACTS
Peripheral Nerve and Plexus
TERMINOLOGY
• Synonyms: Ulnar nerve (UN) entrapment, cubital tunnel
syndrome
• Partial fixation, compression, or distortion of UN
IMAGING
• UN enlargement ± abnormal T2 hyperintensity,
architectural distortion
• Most commonly occurs within cubital tunnel (elbow);
uncommon at Guyon tunnel (wrist) or brachial plexus
TOP DIFFERENTIAL DIAGNOSES
• Acute direct nerve trauma
• Idiopathic brachial plexitis (Parsonage-Turner syndrome)
• Nerve sheath tumor
• Enlarged perineural vein
• Medial epicondylitis
PATHOLOGY
• Edematous/indurated UN ± thickened retinaculum, fibrous
infiltration, fascicular atrophy/loss
• ± anconeus epitrochlearis, enlarged medial triceps head
CLINICAL ISSUES
• Symptoms range from mild transient paresthesias of 4th
and 5th digits → claw hand/digits, intrinsic muscle atrophy
• ± severe elbow/wrist pain radiating proximally or distally
DIAGNOSTIC CHECKLIST
• Focal nerve enlargement, abnormal T2 hyperintensity distal
to medial epicondyle
• Search for anatomic abnormalities (enlarged triceps medial
head or anconeus muscle, osteophyte, thickened
retinaculum)
• Electromyography: Helps localize most likely level of nerve
injury
(Left) Coronal graphic of the
right upper extremity
demonstrates the normal
course of the ulnar nerve ſt
(yellow). Vulnerable locations
to injury include the cubital
tunnel st at the medial elbow
and Guyon canal at the
medial wrist. (Right) Axial
T1WI MR of the right elbow
demonstrates mild abnormal
enlargement and rounded
configuration of the right
ulnar nerve within the
cubital tunnel.
(Left) Axial T2WI FS MR of the
right elbow demonstrates mild
enlargement and abnormal T2
hyperintensity of the right
ulnar nerve ſt with complete
loss of internal fascicular
architecture, indicating an
axonotmetic or neurotmetic
injury rather than the less
severe neuropraxic injury.
(Right) Axial T1WI C+ FS MR of
the right elbow confirms
diffuse abnormal
enhancement of the mildly
enlarged right ulnar nerve ſt.
Note also mild edema and
inflammation in the adjacent
soft tissues.
429