Dorsal scapular nerve (C5): Compression site & risk factors: Scalene muscles due to cervical hyperextension/flexion, trauma. Si/sx: Winging of scapula on arm abduction.

Suprascapular nerve (C5-C6): Compression sites & risk factors: Suprascapular notch, spinoglenoid notch due to repetitive forward traction or trauma. Si/sx: Atrophy of supraspinatus and/or infraspinatus muscles, aching posterior shoulder pain. Dx: History, exam, EMG/NCS. Rx: Most spontaneously improve over time. Steroid injection/surgery for refractory cases.

Musculocutaneous nerve (C5-C6): Compression sites & risk factors: Within belly of coracobrachialis, between biceps brachii & brachialis; weight lifting, shoulder dislocation, or surgery. Si/sx: Weakness & atrophy of biceps brachii & brachialis, sensory loss over lateral forearm. Dx: History, exam, EMG/NCS. Rx: Generally recovers spontaneously; consider steroid injection for sxs; surgical decompression if persistent.

Radial nerve (C5-C8): Compression sites & risk factors: (1) Axilla: Crutches. (2) Spiral groove (Sat. night palsy; Honeymooner palsy): Compression/drunken sleep.
(3) Posterior interosseous nerve: RA, trauma, fracture, soft tissue mass, strenuous use of arm. (4) Superficial sensory branch (cheiralgia paresthetica): Wristbands, handcuffs. Si/sx: (1) Axilla: Weak triceps, brachioradialis, supinator, wrist/finger extension; sensory loss over entire extensor surface of arm, forearm, & hand. (2) Spiral groove: Weak brachioradialis, wrist/finger extension; triceps spared; sensory loss in dorsolateral hand, thumb, dorsal aspect of proximal digits II-IV. (3) Posterior interosseous nerve: Weak wrist/finger extension, extensor carpi ulnaris; variable forearm pain but no sensory loss. (4) Superficial sensory branch: Sensory loss in dorsolateral hand, thumb, dorsal aspect of proximal digits II-IV. Dx: EMG/NCS; MRI at compression site. Rx: For compression at axilla, spiral groove & posterior interosseous nerve, conservative Rx w/modification of activities & wrist splint; usually improves after 6-8 wk. For superficial sensory branch, sx usually self-limited.

Median nerve (C6-T1): Compression sites & risk factors: (1) Wrist (carpal tunnel syndrome; CTS) due to tenosynovitis, arthritis, trauma, repetitive use, vibrating tools; a/w DM, pregnancy, thyroid dz, gout, amyloid. (2) Forearm due to trauma, casting, venipuncture; may involve only anterior interosseous nerve (AIN) or more proximal median nerve. Si/sx: (1) Wrist/CTS: Paresthesias & pain in lateral palm & digits I-IV, sx worse at night, thenar atrophy, weakness of thumb abduction, Phalen, Tinel, Flick signs (poor se & sp). (2) Forearm: AIN syndrome w/weakness of flexion of distal phalanx of thumb & index finger & forming “OK” sign, normal sensation. Proximal forearm w/forearm aching, Tinel, weakness of pronation, flexion digits II-III, thumb abduction & flexion, median distribution numbness. Dx: EMG/NCS. Rx: CTS: Wrist splints, anti-inflammatory medications, PT, surgery for refractory cases or if thenar atrophy, steroid injections (only limited short-term benefit). Forearm: Conservative Rx, surgery if fracture/trauma or refractory sx & suspected entrapment.

Ulnar nerve (C8-T1): Compression sites & risk factors: (1) Elbow: Retroepicondylar groove or cubital tunnel due to elbow leaning, chronic stretch, trauma; (2) wrist (Guyon canal) in mechanics, cyclists, RA or degenerative dz of wrist joints, wrist fractures. Clinical features: (1) Elbow: Numbness of medial hand (dorsal & palmar aspect.) & digits IV-V. Atrophy of intrinsic hand muscles, weakness of flexion of wrist & digits IV-V, claw hand. Tinel sign at elbow, Froment sign. (2) Wrist: Numbness of palmar medial hand & digits IV-V, hypothenar or interossei atrophy. Rx: Conservative management w/rest, modification of activities, immobilization w/splint, or corticosteroid injections. In more severe cases, surgical decompression.

Lateral femoral cutaneous/meralgia paresthetica (L2-L3): Compression site & risk factors: Inguinal ligament due to tight clothing, obesity, DM, pregnancy, pelvic/abdominal mass. Si/sx: Sensory loss, burning, tingling in the anterior & lateral thigh from hip to knee. Dx: Hx & exam; NCS if unclear. Rx: Weight loss; rest; injection of local anesthetics or steroids; topical anesthetics, AEDs, tricyclics; rx underlying tumor if present.

Obturator (L2-L4): Compression site & risk factors: Obturator canal due to tumor, surgery, pelvic fracture, DM. Si/sx: Radiating pain & numbness of groin & inner thigh; weak hip adduction. Dx: EMG/NCS; CT or MRI pelvis to look for tumor. Rx: Conservative Rx; treat underlying tumor.

Femoral (L2-L4): Compression site & risk factors: Inguinal ligament due to lithotomy position, aortic or iliac aneurysms, retroperitoneal hematoma, trauma, pelvic/abdominal surgery. May be affected as forme fruste of lumbar radiculoplexus neuropathy due to diabetes or of idiopathic etiology. Si/sx: Weak hip flexion & knee extension, absent knee jerk. Dx: EMG/NCS. If suspect hematoma or unclear cause, CT abdomen/pelvis. Rx: Based on etiology. If due to lithotomy, trauma, position/stretch, then conservative Rx. If retroperitoneal hematoma, then surgical evacuation & discontinue anticoagulation/antiplatelet agents. If malignancy, then treat underlying tumor.

Sciatic (L4-S3): Divides into common fibular (peroneal) & tibial nerves. Compression sites & risk factors: (1) Gluteal region/sciatic notch due to immobilization, hemorrhage, iatrogenic injections. (2) Hip due to hip/femur fracture/dislocation or surgery. (3) Thigh due to immobilization, trauma, vasculitis, endometriosis. (4) Popliteal fossa due to Baker cyst. Si/sx: Pain down thigh, weakness of knee flexors & all muscles distal to knee; sensory loss of entire foot except over medial malleolus; absent ankle jerk; early si may mimic peroneal neuropathy as these fibers are preferentially affected. Dx: EMG/NCS. Rx: Identify & treat underlying cause, conservative therapy (PT, orthotics, pain control).

Common fibular (peroneal) nerve (L4-S1): Divides into superficial (L5-S1) & deep peroneal (L4-S1) nerves. Compression site & risk factors: Fibular neck; due to leg crossing, squatting/trauma. Si/sx: (1) Common peroneal: Weakness of foot dorsiflexion & eversion, sensory loss in dorsum of foot. Variable Tinel at fibular head. (2) Superficial peroneal: Sensory loss of lateral part of leg & dorsum of foot except for web space between first & second toes. Weak ankle eversion. (3) Deep peroneal: Sensory loss of web space between first & second toes. Weak ankle dorsiflexion. Dx: EMG/NCS. Rx: Conservative Rx. Relieve underlying compression. Ankle-foot orthosis, splints.

Tibial nerve (L4-S2): Compression sites & risk factors: (1) Popliteal space due to Baker cysts, trauma, nerve tumors, entrapment. (2) Tarsal tunnel due to ankle fracture, tenosynovitis/RA, ill-fitting shoes, tumors. (3) Foot due to trauma, tumors. Si/sx: (1) Popliteal space: Weakness w/inversion & plantar flexion of foot & toes, sensory loss in sole & lateral foot. (2) Tarsal tunnel: Sensory loss, burning pain of plantar foot; atrophy of intrinsic foot muscles. Pain w/percussion below medial malleolus (Tinel sign). (3) Foot: Pain, paresthesias, & numbness in sole of foot. Dx: EMG/NCS. Rx: Conservative therapy; steroid injections for sx relief, or surgical decompression.

Guillain-Barré syndrome: Si/Sx: Ascending, predominantly motor paralysis; may progress to respiratory failure; evolves over days-wks; pain in hips, thigh, & back; reduced vibratory & position sensation; reduced tendon reflexes (normal in 10%); facial diplegia often occurs (>50%), autonomic instability; paresthesias in toes & fingers; may be preceded by Campylobacter, EBV, CMV, Mycoplasma. Variants: (1) Acute inflammatory demyelinating polyneuropathy (AIDP; classical demyelinating form). (2) Descending form (facial/brachial onset). (3) Miller Fisher syndrome: Ophthalmoplegia w/ataxia & areflexia. (4) Acute motor & sensory axonal neuropathy or “axonal GBS”: Worse prognosis & slower recovery. (5) Acute motor axonal neuropathy. Ddx: Spinal cord dz/myelopathy, necrotizing myelopathy, carcinomatous meningitis, poliomyelitis, brainstem dz, neuromuscular disorders such as myasthenia gravis or botulism, myopathy, critical illness polyneuropathy, porphyria, acute hypophosphatemia. Dx: Primarily a clinical diagnosis. LP: High protein, few cells (<10) = albuminocytological dissociation, present in ˜50% of pts in 1st wk of sx & ˜75% by 2 wk. If increased cell count (>50), consider GBS in setting of alternative dx such as Lyme dz, HIV, neurosarcoidosis, CNS lymphoma, or leukemia w/nerve infiltration. EMG/NCS: Demyelination except in axonal variant. MRI: Gadolinium enhancement of cauda equina roots. Labs: May be abnormalities in LFTs, EKG, hyponatremia due to SIADH. Abs: Anti-GQ1b (Miller Fisher variant). Rx: Close VS monitoring, NIFs, FVCs. If NIF < -20, FVC < 1.5 L or downward trend, consider intubation; monitor electrolytes. Consider plasmapheresis or IVIg. Plasmapheresis: Exchange 200-250 mL/kg of plasma in 4-6 treatments qod; IVIg: 0.4 g/kg/d × 5 days. Adverse effects: Rarely ARF, proteinuria, aseptic meningitis, anaphylaxis if IgA deficient, headache, rash, thromboembolic events (Ann Neurol 2001;49:694).

Chronic inflammatory demyelinating polyneuropathy: Si/Sx: Slowly progressive, motor > sensory sx in both proximal & distal muscles. Weakness must be present >2 mo. Generalized hyporeflexia or areflexia, can have nerve root enlargement. May be a/w HIV, MGUS, plasma cell dyscrasias, hepatitis, inflammatory bowel dz, Hodgkin lymphoma. Dx: Labs/x-ray: Chem10, CBC, LFTs, ESR, HIV, SPEP, UPEP, immunofixation, skeletal bone survey for evaluation of underlying systemic disorder. EMG/NCS: Multifocal demyelination & partial conduction block. CSF: Albuminocytological dissociation (see GBS for same ddx if cell count is high). Nerve biopsy: May reveal demyelinating or axonal changes. Usually not necessary. MRI: lumbosacral roots may reveal gadolinium enhancement. Rx: IVIg 2 g/kg over 2-5 days monthly for 3 mo. If
sx improve, may continue IVIg 1 g/kg at intervals depending on dz response, generally every 1-2 mo. Prednisone started at 60-80 mg for 2-3 mo followed by a slow taper as tolerated (5-10 mg/mo or the lowest possible dose that controls the neuropathy). May add a second-line steroid-sparing immunosuppressive agent (e.g., azathioprine, mycophenolate mofetil, methotrexate). Plasmapheresis biweekly initially & then individualized (Ann Neurol 1994;36:838; Ann Neurol 2001;50:195).

Multifocal motor neuropathy: Si/Sx: Progressive, asymmetric, predominantly distal limb weakness (90% are in the distal upper extremity), muscle cramps, fasciculations, & atrophy over months-years. Depressed tendon reflexes. May be confused w/ALS but absent UMN sx. Dx: EMG/NCS: Persistent focal motor conduction block or other features of demyelination in motor responses. CSF: Protein usually normal but may be slightly increased. Abs: IgM anti-GM1 ab in ˜20% to 80% of pts. Rx: IVIg per rx of CIDP (Neurology 2000;55:1256). Cyclophosphamide 1 g/m2 IV qmo × 6-8 mo may be of use in some nonresponders to IVIg. Unclear efficacy of rituximab. No benefit of steroids or plasma exchange.

Acute sensory neuronopathy: Si/Sx: Sensory ataxia, areflexia, numbness, variable pain. No weakness. May be GBS variant, or a/w cancer, HIV, Sjögren syndrome, pyridoxine toxicity, or idiopathic. Dx: CSF: Protein may be elevated. EMG/NCS: Absent/reduced sensory amplitudes w/normal motor studies. Rx: May treat w/IVIg as per GBS.

Critical illness polyneuropathy (CIP): Si/Sx: Acute or subacute neuropathy in the setting of sepsis/SIRS, steroids & paralytic use, multiorgan failure. Most cases are actually critical illness myopathy as opposed to CIP. Often diagnosed w/failure to wean from ventilator. Predominantly motor weakness & mild sensory sx. Dx: EMG/NCS: Primary axonal process w/early denervation. Normal CSF. Rx: Physical therapy.