Lower Extremity Nerve Entrapments & EMG/NCT Basics. Mark Stovak MD University of Kansas SOM-Wichita

Transcription

1 Lower Extremity Nerve Entrapments & EMG/NCT Basics Mark Stovak MD University of Kansas SOM-Wichita

2 Basics Most nerves injured by compression Symptoms may be intermittent or positional Symptoms progress to constant when demyelination occurs Followed by axonal injury Symptoms: aching, burning, tingling, cramping, numbness, pain at rest or nighttime pain Valleix Phenomenon symptoms radiate proximal to the entrapment Double Crush Phenomenon nerve compressed in 2 different locations

3 Treatments Soft tissue mobilization/myofascial release NSAIDs Prednisone Shoe modification Stretching Steroid Injection Nerve Hydrodissection Neurolysis Surgical decompression

4 Nerve Conduction Test (NCT) Look for evidence of demyelination (conduction velocity slowing and conduction block) across likely affected segments of nerve, such as the common peroneal nerve at the fibular neck. Slowing = demyelination (more than axonal damage) Performed in combination with EMG May be normal despite injury unless performed 3-4 weeks after symptom onset May be normal despite an injury but may still exclude other diagnoses

5 Electromyography (EMG) Electromyography tends to be most important for the diagnosis of radiculopathy and plays a more confirmatory role in other disorders. Fibrillations (denervation) Positive sharp waves (denervation) Decreased sensory & motor amplitudes (axonal damage)

6 Sciatic Nerve Entrapments Sciatic Notch / Gluteal Region - Trauma (hip dislocation, fracture, or replacement), prolonged bed rest, deepseated pelvic mass, piriformis syndrome, wayward injection Mid- thigh - Femur fracture, mass, ischemic nerve infarction Most common location for a nerve infarction (vasculitis / atherosclerosis) is posterior mid-thigh

7 Sciatic Nerve Entrapments Pedal Pusher s Neuropathy with bilateral sciatic nerve palsies reported in unicyclists Divides into the common peroneal nerve, the tibial nerve, and the sural nerve within the popliteal fossa Symptoms involve all 3 distributions but usually affect the lateral division of the nerve affecting the common peroneal nerve most frequently Lose ankle jerk

8 Femoral Neuropathy Cross country skiing, gymnastics, bodybuilding Iliacus muscle hematoma, hip or pelvic fracture, hip replacement, prolonged lithotomy position, surgery Repetitive hip flexion/extension Passes under the inguinal ligament Quadriceps weakness; sensory loss over anterior and medial thigh extending down medial shin to arch of foot (saphenous) Lose knee jerk

9 Obturator Nerve Entrapment Medial thigh pain/parasthesias Nerve entrapped by fascia over the adductor brevis muscle Cancer, post-surgery, trauma

10 Genitofemoral Nerve Entrapment Soccer, Kickers, Hockey Players, Baseball, Softball Often entrapped/injured in the inguinal canal at the external oblique aponeurosis Particularly the genital branch Often treated with neurolysis during inguinal wall reinforcement

11 Ilioinguinal Nerve Entrapment Soccer, Kickers, Hockey Players, Baseball, Softball Often entrapped/injured in the inguinal canal at the external oblique aponeurosis Source of chronic nonspecific groin pain Often treated with neurolysis during inguinal wall reinforcement

12 Pudendal Nerve Entrapment Bicycle Seat Neuropathy Often in cyclists from bicycle seat pressure, horse back riding Scrotal or penile numbness, impotence but not just limited to male riders (often reported in females as well) Travels in Alcock s canal medial & posterior to the ischial tuberosity (between the ischium & obturator internus) Prove the diagnosis with a pudendal nerve block Change saddles or riding technique Lower seat while pointing the nose downward

13 Lateral Femoral Cutaneous Nerve Entrapment Meralgia Paresthetica Purely sensory nerve direct branch of the lumbar plexus Entrapped as it enters the thigh under the inguinal ligament Paresthesias of the anterolateral thigh Repetitive flexion/extension Weight belts, work belts, or obesity Block performed medial & inferior to the ASIS below the inguinal ligament

14 Saphenous Nerve Entrapment Surfers (football quarterback after a hit from a helmet, a runner & a swimmer) Usually affects the medial knee & leg Pure sensory branch of femoral nerve Often entrapped in Hunter s Canal (distal subsartorial canal) + laptop sign Can be injured during knee scope from medial portal

15 Sural Nerve Entrapment From sciatic nerve Runners, recurrent ankle sprains Posterior leg pain / paresthesias that radiate to the 4 th /5 th toes Lateral Sensory branch of the Common Peroneal Nerve Positive Tinel s at distal popliteal fossa Tight ribbons or elastic in dancing shoes

16 Common Peroneal Nerve Runners, leg crossing, kneeboard straps, knee dislocation, direct trauma, squatting (roofer), leg casts, chronic bed rest Foot drop (weak dorsiflexion & eversion)/steppage gait Paresthesias over dorsum foot & lateral leg (rarely pain) Location: neck of the fibula and rarely from a Baker s cyst

17 Superficial Peroneal Nerve Entrapped often by muscle herniations, fibula fracture, varicose veins, boots Tight inline or roller skates Associated with Lateral Leg Compartment Syndrome Pain/Paresthesias of the dorsal ankle, foot except for the web space of toes 1 & 2 Decompression highly successful

18 Deep Peroneal Nerve Entrapment Anterior Tarsal Tunnel Syndrome Boot Top Neuropathy Travels with dorsalis pedis Entrapped by the Superior Extensor Retinaculum (3-5 cm above the ankle joint) or Inferior Extensor Retinaculum (1cm above the ankle joint) or by the EHL and EHB tendons or by tight shoes or boots, key under the tongue of running shoes Associated with Anterior Compartment Syndrome

19 Tarsal Tunnel Syndrome Tibial nerve entrapment in the tarsal tunnel Fracture, RA, Idiopathic Must get imaging like an MRI to rule out a ganglion or soft tissue mass or tumor affecting the nerve whenever non-operative treatment fails

20 Tarsal Tunnel Syndrome Runners, basketball players, ballet dancers Posterior tibial nerve Posterior to the medial malleolus under the tranverse tarsal ligament Pain/paresthesias at the medial malleolus with radiation to the heel (medial calcaneal branch) & sole of foot (medial & lateral plantar branches), toe flexion weakness

21 Medial Plantar Nerve Entrapment Jogger s foot Entrapped at the Master Knot of Henry (abductor hallucis muscle fibro-osseous canal) Pain/burning at the medial arch of the foot into the toes 1-4 Mixed sensorimotor nerve that travels with the FHL May be confused with posterior tibialis tendonopathy or navicular stress fracture

22 First Branch of the Lateral Plantar Nerve Baxter s Nerve, Inferior Calcaneal Nerve, Nerve to the Abductor Digiti Quinti Muscle Usually entrapped by the quadratus plantae muscle and the abductor hallucis muscle Chronic dull pain at the heel No sensory component

23 Interdigital (Morton s) Neuroma Paresthesias between toes that radiates into the toes Most common between 3 rd /4 th the 2 nd /3 rd toes Common in tight-fitting pointed shoe wear Associated with MTPJ synovitis Positive Mulder s Click test/squeeze test Purely sensory nerve passes under the intermetatarsal ligament and is compressed during toe dorsiflexion

24 Bibliography Madden C., Putukian M., Young C., McCarty E. Netter s Sports Medicine. Saunders Elsevier O Connor F. et al. Sports Medicine: Just The Facts. McGraw-Hill Rutkove S. Overview of Lower Extremity Peripheral Nerve Syndromes. UpToDate. Jan. 7, Toth C. et al. Peripheral Nervous System Injuries in Sport and Recreation: A Systematic Review. Sports Medicine 35 (8)