6::LE Entrapment Neuropathies

3 concepts

1) double crush syndrome = when a proximally squished nerve has a dec threshold for injury and is more susceptible to entrapment distally; hence not uncommon to find 2 sites of entrapment present simultaneously Spinal stenosis (example) = predisposes nerve to be entrapped again distally 2) Valleix phenomenon = opposite; now distal entrapped causes more prox nerve to be at risk; also 2 sites of entrapment 3) Selective muscle involvement = common; only 1 of the innervated muscles affected; sciatic nerve injury hits peroneal division (bc more superficial and has larger fascicles and is fixed 2 places), but not tibial division another example = common peroneal nerve hits deep peroneal nerve (bc closer to fibula head)more than superficial

1

3 major LE nerves: sciatic nerve, femoral nerve, obturator nerve.

Tarsal tunnel syndrome

3 mc causes: trauma (scarring sp sprain or fx), space-occupying lesions, foot deformities 30% have unknown cause varicosities, ganglia, anomalous muscles, and other masses can cause w mass-occupying lesions, a concomitant more proximal nerve entrapment (double crush syndrome) may be present Congenital foot (varus heel with forefoot pronation or valgus heel [less likely], pes planus, and tarsal coalition) and post-traumatic foot can stretch nerve Proximal migration of symptoms may be related to Valleix phenomenon or double crush syndrome pw intractable chronic heel pain and sensory loss of plantar foot medial calcaneal nerve is usually NOT involved, so no sensory loss along medial heel Motor loss in tarsal tunnel syndrome is less frequently described, bc intrinsic muscle weakness may be masked by nml extrinsic muscles

iliacus muscle syndrome

Compression of fem nerve mc under inguinal ligament, within the lacuna musculorum often iatrogenic injury (gyn procedures like hystero, pelvic surgery, hip surgery replacement, fem artery cath, arterial bypass

53 Medial plantar neuropathy

Denervation edema of arrow = FD brevis (FDB) asterisk = abductor hallucis

52 Medial plantar neuropathy

Denervation edema of asterisk = FD brevis (FDB) arrow = abductor hallucis

Nerve injury terms/definitions (spectrum)

Neurapraxia (early) = 1st deg nerve injury, early and reversible segmental conduction block wo axon disruption' range from transient ischemia to myelin sheath injury; usually resolves within hours, days, or months with no residual sequelae (aka like nerve TIA) Axonotmesis (mid) = 2nd deg nerve injury; more advanced nerve damage; focal axon disruption produces Wallerian degen distal to injured nerve; but the intact investing connective tissues around nerve allow axon regeneration (1-2 mm per day); prognosis still good; depending on distance btw site of nerve injury and muscle affected, this can resolve within weeks to months Neurotmesis (late/worst) = 3rd deg nerve injury; IRREVERSIBLE and complete axonal and connective tissue disruption; significant functional impairment and can also get neuromas (secondary to unsuccessful attempts at nerve regeneration)

17 Piriformis syndrome sp kicked horse in L buttock

P = engorged/edema'ed L piriformis (P) w edema in left sciatic nerve region white arrows = nml R piriformis

13 Lumbosacral plexopathy

T2FS w denervation femoral, obturator, and sciatic nerve distributions V = vastus muscle A = adductor mag arrows = hamstrings see inc sig in these (classic for sciatic aka a lumbar nerve)

24 obturator nerve

a = arrows = obturator nerves MEDIAL to acetabulum arrowheads = obturator vessels are adj b = arrows = obt nerves surrounded by fat

14 Plexiform neurofibromatosis

a = arrows and arrowheads = fusiform enlarged bilat scitatic nerves (plexiforms of them) b = "bag of worms" of R sciatic nerve (black arrow) white arrow = intramuscular neurofibroma in rectus femoris muscle (aka imag small IM nerve getting plexiform)

16 Surgically proven left piriformis muscle syndrome

a = P = enlarged piriformis displacing nerve (arrow) * = smaller reg R piriformis b = posterior view during surg, see piriformis indentation on sciatic nerve

31 common peroneal neuropathy due to hypertrophied biceps femoris

a = arrow = common peroneal nerve trapped btw biceps fem (white ast) and lat gastroc (black ast) b = arrows = denervation edema of antlat compartment

25 Acetabular metastasis w obturator neuropathy and denervation edema

a = asterisk = bright destructive acetabular mass medially displacing obturator NVI (arrowheads); aka push it AWAY from acetabulum (it rides next to it) b = acetabular mass (asterisk) medially displacing pelvic structures arrow = subacute denervation edema in obturator externus arrowheads = also denervation of adductor muscles (arrowheads) is noted

49 proliferative synovitis causing tarsal tunnel syndrome and medial plantar nerve denervation

a = asterisk = synovial mass in tarsal tunnel b = denervation edema in flexor digitorum brevis muscle (aka fed by medial plantar nerve) arrow = OA of tib-talar joint

8 Normal sciatic nerve

a = ax PD upper thigh black arrow = nml oval sciatic nerve ant to glut max (GM) white arrows = see how close they are to prox hamstring tendons b = ax PD mid thigh arrowhead = tibial division of sciatic nerve arrow = smaller peroneal divisions of sciatic nerve shows these in a common sheath before they diverge in prox knee

30 Common peroneal neuropathy due to varicosities

a = denervation atrophy of the anterolateral muscles (mostly ATT, see arrow) b = arrowheads = varicose veins next to peroneal nerves w arrow = denervation edema of ATT

34 dorsal ganglion causing deep peroneal neuropathy

a = oblique coronal arrow = gangliona dorsal to 2nd cuneiform (hence medial dorsal foot) asterisk = the 2nd cuneiform b = more distal coronal arrow = denervation of first dorsal interosseous muscle

44 tarsal tunnel (refers to both the prox and inf parts described)-normal in this pic

a = prox tunnel big arrow = tibial nerve (TD and nervous harry) arrowheads = tibia vessels (nerve medial to them) b = inf tunnel white and black arrows = med and lat plantar nerves deep to tibial vessels (arrowheads) not in pic: nml thin septa separate tunnel into multiple compartments

59 Third intermetatarsal Morton's neuroma

a/b = arrows = T1 and T2 interm sig Dumbbell mass (think fibrous, T1/2 interm/dark) c = enhances

56 inferior calcaneal nerve neuropathy (Baxter's neuropathy) by tarsal tunnel varicosities

a/b = asterisk = denervation atrophy of the abductor digiti quinti muscle c/d = asterisk = nml abductor digiti quinti muscle

Distal Foot Entrapment Neuropathies

aka entrapment of 1) medial calcaneal nerve 2) medial plantar nerve 3) lateral plantar and inferiro calcaneal (baxter's neuropathy)

63 base of 5th MT fx entrapping sural nerve

aka sural lives along lat foot

Lateral Plantar and Inferior Calcaneal (Baxter's) Neuropathy inf calc is first branch of lateral plantar nerve

also compressed disatl to tarsal tunnel get sensory def of lateral 1/3 foot sole and weakness of abd digiti minimi 50% time due to athletic activity (mc distance running) and secondary hypertrophy of abductor hallucis muscle they think 15% of athletesw chronic un-resolving heel pain is due to entrapped inf calcaneal nerve 3 entrapment sites: 1) Deep to or at fascial edge of hypertrophied abductor hallucis muscle 2) At medial edge of the quadratus plantae muscle, where the nerve changes from a vertical to a horizontal course 3) near the medial calcaneal tuberosity When entrap near med calcaneal tuberosity, its mc from adj inflammation due to heel spur or plantar fasciitis inferior calcaneal nerve squish pw intractable heel pain and burning sensation; hard to dx bc sensory loss not there till there's also more prox entrapment of lat plantar nerve

50 Accessory soleus muscle

arrow = accessory soleus muscle arrowhead = tibial nerve disp ant by it

55 Neuropathy of the inferior calcaneal nerve (Baxter's neuropathy)

arrow = atrophy of abductor digiti quinti incidental artifact from distal fibular fixation plate and screws

21

arrow = branch of saphenous nerve (lateral to sartorious); S for S saphenous nerve is branch of femoral nerve (diff than sciatic lineage) white arrowhead = tibial nerve (btw med and lat heads of gastroc) (branch of sciatic nerve) black arrowhead = common peroneal nerve (branch of sciatic); btw lat gastroc and biceps fem (peroneal nerve already split into deep and superficial branches here)

38 nerve sheath tumor causing proximal tibial neuropathy

arrow = bright nerve sheath tumor in soleus muscle black and white arrowheads = denervation edema in med and lat gastrocs

47 medial plantar nerve at Henry's knot

arrow = close proximity of nerve to knot (where FHL and FDL cross) use as landmark! (its behind the cross over)

54 Medial plantar neuropathy

arrow = denervation atrophy of the flexor digitorum brevis muscle

45 inferior calcaneal nerve

arrow = inf calcaneal nerve (runs up and down vertical) asterisk = quadratus plantae muscle is close to it (LAT to it) arrowhead = lateral plantar nerve is ant to it

36 nml superficial peroneal nerve

arrow = nerve in subQ fat after it has pierced the fascia

15 Amputation neuroma

arrow = neuroma in amputated R sciatic nerve black arrowhead = thickened nerve prox to neuroma white arrowhead = nml L sciatic nerve

61 normal sural nerve

arrow = sural nerve arrowheads = subQ vessels are superficial to it (ie sural nerve is deep to them)

37 Superficial peroneal neuropathy secondary to muscle herniation

arrowhead = fascial herniation of plongus abutting superficial peroneal nerve

20 normal femoral nerve in upper thigh

arrowheads = nml femoral nerve bundles LATERAL to femoral vessels

7 nml T1 bilat sciatic nerves

arrowheads = nml sciatic nerves arrow = slip of right piriformis muscle

57 Lateral plantar neuropathy

arrows = denervation of 1st, 2nd, 3rd interosseous muscles aka this is what it feeds

10 Sciatic neuropathy assoc w rhabdomyolysis

arrows = inc sciatic nerve sig inc muscle sigs

58 third interdigital Morton's neuroma

at confluence of terminal branches of med and lat plantar nerves

why is muscle denervation bright

bc intracell fluid moves to extracell (free water) due to muscle atrophy (w no change in total water content in muscle) inc blood perfusion to muscle may also contribute

48 Tarsal tunnel nerve sheath tumor

black arrow = bright nodule w dark center (target sign) white arrow = incidental peroneal tendon tenosynovitis

39 Proximal tibial neuropathy

black arrow = popliteus denervation white arrow = medial head gastroc denervation aka tibial nerves feed this

40 Tibia and common peroneal neuropathy due to traumatic spinal root avulsion

black arrow = popliteus denervation (innervated by tibial nerve) * = antlat muscles denervation (innervated by common peroneal nerve) white arrow = metal artifact in tibia and fibula

60

both tibial and peroneal contribute to sural nerve sural nerves lives in post lat calf

adductor canal

btw these muscles

29 Common peroneal neuropathy

by nerve sheath tumor a = arrow = nerve sheath tumor of common peroneal nerve b = arrow = ATT muscle denervation

MR T2 neurography selectively emphasizes fluid from nerves partially reversible nerve damage is inc T1 and T2 sig

chronic nerve damage has fatty infiltration and dec muscle bulk

Common Peroneal Nerve

comes off sciatic nerve in pop fossa, rides lat calf, then finish dorsal foot neuropathy usually occurs as the nerve crosses the fibular neck or as it pierces the peroneus longus muscle Extrinsic compression may be associated with intraneural and extraneural ganglia originating from the proximal tibiofibular joint

27

common peroneal nerve and its branches winding arnd fibula neck, deep to peroneus longus muscle

46

coronal oblique bleck and white arrows = nml MED and LAT plantar nerves in midfoot

denervation fluid vs other fluid causes (contusions, musculotendinous injuries, infection, rhabdomyolysis, and compartment syndrome)

denervation = diffuse (whole muscle involved), spares fascial planes btw muscles and adheres to the nerve distribution

12 Denervation edema sp resection of sciatic nerve tumor.

denervation edema in hamstring muscles (H) and adductor magnus (A)

5 sciatic nerve posterior view (in glut area)

descends in FRONT OF (anterior to) piriformis muscle and is above sup gemellus, obturator internus, inf gemellus, and quadratus femoris muscles

26 lateral femoral cutaneous nerve

dives and exits under inguinal lig (near ASIS); divides into ant branch (antlat thigh) and post branch (postlat thigh) after it passes ASIS; both branches penetrate fascia lata these branches divided prox to inguinal ligament in 25% ppl meralgia paresthetica aka lateral femoral cutaneous nerve neuropathy purely sensory nerve (L2, L3)

62 Sural nerve laceration

edema and obliteration of fat planes in sural nerve area (posterior lat calf)

Superficial Peroneal Nerve

entrapment mc as nerve pierces deep lower leg fascia fascia thickening, muscle herniation (mc plongus; may need plantar or dorsiflex imaging to see better) through fascia defect (see pic) which tents nerve are common causes numbness and tingling along lat calf and dorsal foot; spares 1st web space (bc deep peroneal nerve feeds that) sx mc 10-12 cm above ankle joint, where nerve exits deep fascia

Lateral Femoral Cutaneous Nerve

entrapped under inguinal lig or as perforates fascia lata use ASIS landmark to locate

Medial Plantar Nerve Entrapment

entraps DISTAL to tarsal tunnel can get at Henry's knot, btw navicular tuberosity superiorly and abductor hallucis muscle belly inferiorly jogger's foot = repetitive trauma to nerve in joggers who run w inc heel valgus and foot pronation pw heel and arch pain and numb medial plantar foot a secondary hallux rigidus is believed to be related to inc stress on 1st MTP joint w medial plantar nerve denervation

Obturator Nerve

feeds medial thigh muscles pass through obturator canal, divides into 2 branches that BOTH pierce obturator externus entrapment mc due to trauma and post-surgical injury to the inguinal area and pelvis pelvic tumors, including mets can cause obt neuropathy Groin pain in athletes assoc is impingement of ant obt branch DISTAL to obturator tunnel

Deep Peroneal Nerve

gives motor to extensor foot and toe muscles (ATT, EHL, EDL and peroneus tertius) and sensory of dorsal 1st web space entrapment sites include superior extensor retinaculum and, in the anterior tarsal syndrome, the inferior extensor retinaculum or talonavicular joint. (see later pic) deep peroneal travels in ant calf w tib at and vein; initially runs deep to EDL and distally deep to EDL and EHL; in ankle it goes under sup and inf ext retinacula and into ant tarsal tunnel tarsal tunnel = not true tunnel; flat space btw med and lat malleoli; boxed by ext retinaculum and talonav joint just above ankle joint, it divides into lat motor branch (feeds extensor digitorum brevis) and medial branch (mostly sensory, travels btw 1st and 2nd MTs to feed webbing of 1st space) use DP artery and ATA as landmarks to trace vessel

Tarsal tunnel syndrome cont

hard detect inc signal and size of tibial nerve and its branches bc they are small Denervation muscle change changes less common bc tarsal syndrome mc get sensory def only involved muscles vary based the tibial branch affected

11

huge hamstring tendon tear w secondary edema around sciatic nerve arrowhead = partial avulsion of conjoined tendon biceps and semiM muscles of the biceps and semitendinosus muscles arrows = tons of edema around the sciatic nerve

35 superficial peroneal nerve as pierces deep fascia of lat compartment

inversion injury can stretch the nerve

Tibial Nerve

largest division of sciatic nerve aka posterior tibial nerve come off sciatic nerve in pop fossa (sciatic divides into tibial and common peroneal nerve) and goes in post calf btw gastroc heads then into tarsal tunnel (medial ankle) innervates posterior stuff: plantaris, popliteus, gastrocnemius, soleus, PTT, FDL, FHL courses w PT artery and vein (use as landmarks) flexor retinaculum of tarsal tunnel (starts med mall and inserts on med tuberos ity of calcaneous) 3 terminal branches: (see later pic) medial calcaneal nerve medial plantar nerve lateral plantar nerve.

Lateral Femoral Cutaneous Neuropathy (Meralgia Paresthetica)

lateral femoral cutaneous nerve mc entraps at 2 sites: 1) under inguinal ligament 2) as perf fascia lata many causes = tumors, trauma (like asis avulsion), surgeries/ORIFs, etc causes sensory stuff (pain, burning, tingling, numb) along LAT thigh NO motor loss (no denervation or muscle atrophy)

sciatic nerve neuropathy cont

mc hits peroneal division and spares tibial division bc: peroneal fixed at 2 pts (sciatic foramen and fibular head; tibial only fixed at sciatic foramen), peroneal has larger fascicles and less protective connective tissue (easier to squish) and peroneal division is more superficial than tibial mc sign of sciatic neuropathy is foot drop from loss of ATT muscle (bc peroneal division) also loss of ankle and, foot eversion, toe extension (peroneal) also can be loss of toe flexion and foot inversion (tibial)

33

nml deep peroneal nerve at talonavicular joint white arrow = medial branch black arrow = lateral branch of deep peroneal nerve separated by dorsalis pedis vessels (aka peroneal nerve branches surround dorsalis pedis)

Common Peroneal Neuropathy (mc mononeuropathy in lower leg)

mc in knee region, mc as cross fibular neck or pierces peroneus longus muscle; when hit more commonly hits deep rather than superficial bc deep is more ant and med and has more direct contact w fibular head neuropathy of its branches is more distal in leg, ankle or foot can extrinsic comp after prolonged immobilization (like anesthesia), coma, drugs OD (sat night palsy; leg wake up dead after sleeping on it after drug) , after tons of weight lsos (slimmers paralysis), prolonged squatting (strawberry picker's palsy), casets that compress, tumors, osteochondromas slimmer and strawberry picker are bilat MR = denervated ant calf (deep peroeal) and lat calf (superficial peroneal) intraneuron or gen ganglion cysts are known to compress it

Morton's Neuroma

med and lat plantar nerves MERGE DISTALLY to make interdigital nerves; these pass btw MT bones mortons neuroma = intermetatarsal neuroma = fibrotic nodule caused by damaged interdigital nerve (interdigital aka btw toes aka mortons location) damage caused by nerve being entrapped against the transverse MT lig not true tumor, is djd fibrosis of epineurium and perineurium mc btw 2nd and 3rd spaces, but can be in any space mc middle-aged women in high-heeled shoes pw intermetatarsal pain, numbness, and sensory def that radiate to toes 80% Mneuromas assoc w forefoot deformities (hallux valgus, hammertoe, or pes planus) tx = conservative (shoe change), MT padding; etc; if no work, do neurectomy US can dx it (hypoechoic interMT mass) nerve only 1 mm and most symptomatic neuromas are over 0.5 mm MR = oval or dumbbell shaped low T1 and T2 sig (bc is fibrosis), and sometimes will enhance (variable, dont depend on it), u dont need MR to dx it; lesion in center of the NVI bundle, in interMT space on PLANTAR side of transverse MT lig remember its transverse size dpeends on body position (tans size impt bc lesions over 5 mm are sympto and better surg outcome when lesions they are 5 mm or bigger in trans (only 17% of mortons under 5 mm had good postop outcome)

NAVEL

nerves LATERAL to vessels

sciatic nerve neuropathy

neuropathy assoc w THA (especially revisions) mc hits peroneal nerve division sciatic nerve is largest nerve in body has 2 distinct divisions as exits greater sciatic foramen (tibial and peroneal) which are covered by common sheath exits ant to piriformis and post to sup gem, obt int, inf gem and quadratus femoris; continues to adductor mangus and short biceps fem in distal thigh it separates into tibial nerve and common peroneal nerve runs ant to piriformis and lat to iliac vessels piriformis syndrome and obturator internus muscle syndrome can cause usually spares hamstrings bc they innervate higher in thigh

Tibial Nerve cont

neuropathy types: Proximal tibial neuropathy = uncommon (pop fossa tumors); and rarely extrinsic compressed bc its deep in pop fossa; weak PLANTAR muscles and intrinsic muscles Tarsal tunnel syndrome Medial plantar neuropathy Lateral plantar neuropathy Morton's neuroma (interdigital neuropathy) Joplin's neuroma (medial plantar proper digital neuropathy) Distal foot entrapment neuropathies include: Medial calcaneal neuropathy Medial plantar neuropathy Lateral plantar nerve entrapment and entrapment of the nerve to the abductor digiti minimi Morton's neuroma = entrapped or ischemic interdigital nerve (is djd) Joplin's neuroma = entrapped plantar proper digital nerve (is djd)

MR Appearance of Medial and Lateral Plantar Neuropathy

not much MR info out there (not seen often on MR) medial plantar nerve signs: Abd hallucis and FDS denervation/atrophy first lumbrical and FH brevis denervation/atrophy TS of FDS/FHL henry cross lateral plantar nerve signs: Abductor hallucis hypertrophy and plantar fasciitis w medial calcaneal spur and adj ST edema (signs of entrapped first branch of lat plantar nerve aka baxter thing) incidental denervation and atrophy of abductor digiti quinti mc is a clinically missed entrapped first lateral plantar nerve branch dec bulk, fatty atrophy, and inc fluid signal of intrinsic foot muscles IN DM pt is due to peripheral neuropathy

23 normal obturator nerve

notice sciatic, femoral and obturator all come off lumbar spine it goes through obturator foramen

Medial Calcaneal Nerve Entrapment

occurs after it branches off tibial nerve and descends in fibromuscular tunnel btw the ant-med calcaneus and deep fascia of prox abductor hallucis pw chronic heel pain and dec sensation along medial heel pad tx = conservative, but if bad need to surg release deep fascia of abductor hallucis muscle

femoral nerve

originates from L2,3,4 feeds ANTERIOR thigh biggest branch is saphenous nerve (goes through adductor tunnel) (follows path of saphenous nerve) (which is where it gets entrapped)

Normal nerves do NOT enhance w contrast

partially reversible nerve damage is T1 and T2 bright; and now can enhance (from blood-nerve barrier changes and gad leaking into endoneurial space)

Piriformis Muscle Syndrome

piriformis muscle occupies large part of foramen as it goes from sacrum to greater trochanter shit affecting piriformis (and causing sx) = inflammation, spasticity (cerebral palsy), overstretching, lumbar lordosis (squish notch hole volume), trauma/hematoma there, anything, variations where sciatic PIERCES piriformis adductor magnus and hamstring denervation can be sign actually is rare in real life (is overcalled) MR = see asymmetry of piriformis muscles (sympto vs asympto side), atrophy of piriformis

9

piriformis pierced by normal variant peroneal division of sciatic nerve up near greater sciatic notch

Deep Peroneal Neuropathy

possible compression sites 1) inf edge of sup extensor retinaculum 2) mc entrapment syndrome (anterior tarsal syndrome),inf edge of inf extensor retinaculum or at talonav joint recurrent ankle sprains can stretch the nerve (esp at talonavicular joint) causes of compression: OPS, dorsal foot trauma, (soccer player) , hypertrophied extensor hallucis brevis muscle, os intermetatarseum at base of 1st MT, Tight-fitting shoes or ski boots ant tarsal syndrome mc get sensory deficits bc motor branch of deep peroneal nerve branched off prior to compression area see atrophy of extensor digitorum brevis muscle if compress prior to tunnel MR = ATA, EDL, EHL, peroneal tertius fatty atrophy see the cause (talonavicular OPs, 1st MT and 1st cuneiform OA and spurs, prominent os intermetatarseum, exuberant periostitis) Isolated extensor digitorum brevis denervation = entrapped lateral branch of deep peroneal nerve Bc of variable intrinsic muscles innervation of 1st web space, entrapped deep peroneal nerve may also demonstrate signal alterations in the first dorsal interosseous muscles (see Fig. 6.34B) and, less commonly, in lat head of flexor hallucis brevis and oblique head of adductor hallucis muscle tx = conservative or if bad, release extensor retinaculum

43 inferior calcaneal nerve (Baxter's nerve)

post view calcaneous it runs up and down vertical makes sharp 90 deg turn from vertical to horizontal as reaches calcaneous innervates abductor digiti minimi 3 sites of entrapment are from 1) hypertrophied abductor hallucis muscle 2) medial edge of quadratus plantae 3) medial calcaneal tuberosity aka shit along its course

3 49M w neuropathic foot pain

prox tibial entrapment sx resolved sp knee steroid injection arrow = T2FS loose body in pop muscle bursa arrowheads = it abuts NVI structures

Sural Nerve

pure sensory nerve made by merge of medial sural nerve (tibial nerve branch) and the smaller lateral sural cutaneous nerve (common peroneal nerve branch) (Fig. 6.60) variant is nerve coming from ONLY tibial or peroneal courses down midline calf, lat to achilles tendon, superficial and post to peroneal tendons behind med mall gives lat ankle and foot sensation to 5th toe base entrap mc 2/2 trauma (direct trauma or calc, talar, or 5th MT fx); can also traction in severe ankle sprain

joplin's neuroma

rare entrapped or compressed plantar proper digital nerve (terminal sensory branch arising from medial plantar nerve); pierces plantar aponeurosis post to tarsometatarsal joint and its branch feeds flexor hallucis brevis nerve can squish as crosses to first MT joint along plantar aspect of the hallux also bc nerve is superficial, its prone to repetitive trauma or chronic compression (by tight shoes or sports impacting 1st MTP joint like soccer, ballet) also see after hallux valgus repair pw pain, tingling, numbness, of medial and plantar 1st MT bone and 1st MTP joint

42

tibial nerve and its medial and lateral plantar nerve branches.

41 tarsal tunnel

tibial nerve give off inferior then splits into med and lat for plantar foot

Obturator Neuropathy

uncommon bc of deep location and protected by nearby muscles often by penetrating trauma or post surgical trauma adhesion of adductor brevis fascia can cause too basically anythign in the area compressing it can cause

28 normal peroneal nerves

white arrow = deep peroneal nerve black arrow = superficial peroneal nerve PL = both are DEEP to peroneal longus muscle

22 iliacus muscle tear causing femoral neuropathy

white asterisk = enlarged L iliac muscle black asterisk = enlarged L psoas muscle no see compressed femoral nerve I = nml R side P = nml right side

2 MR neurography

young pt w sciatic neuritis arrow = T2FS inc signal in sciatic nerve Note suppressed adjacent muscles and vessels aka T2 neurography; might be just as good as EMG but at present, there is little information on MR features of peripheral LE entrapment neuropathies