Paraneoplastic Syndromes

Peripheral Nerve Anatomy

A. See also

Peripheral Neuropathy p. 93 .

B. Spinal level by disc

Figure 10 . Dermatomes and peripheral nerve territories . (From Patton HD, et al. Introduction to Basic Neurology . Philadelphia: Saunders; 1976, with permission.)

P.90

C. Spinal level by function

• 1. Movement :

  • a. Neck : C1-4.

  • b. Diaphragm : C3-5.

  • c. Shoulder : Abduction and lateral rotation are C5. Adduction and medial rotation are C6-8.

  • d. Elbow : Flexion is C5-6. Extension is C6-8.

  • e. Wrist : C6-8. Extension = radial n. Flexion = median + ulnar n.

  • f. Hand : Finger abduction and adduction are ulnar nerve (C8-T1). Grip is median nerve. Finger extension is radial nerve.

  • g. Thumb test : Can tell radial, median, and ulnar nerve lesions by thumb movements. Mnemonic is RUM : R adial extends, U lnar adducts, and M edian abducts. Flexion + extension = in plane of the palm; abduction + adduction = at right angles to the palm.

  • h. Intercostals : T2-9.

  • i. Abdominals : Upper is T9-10. Lower is T11-12.

  • j. Hip : Flexion is L2-4, adduction is L3-4, abduction is L5-S1.

  • k. Knee : Extension is L2-4; flexion is L4-S1.

  • l. Foot : Dorsiflexion is L4-S1; plantar flexion is S1-2.

  • m. Bladder, anal sphincter : S2-4.

• 2. Sensation :

  • a. Arm : Shoulders: C4; inner forearm: C6; outer forearm: T1; thumb: C6; fifth finger: C8.

  • b. Leg : Front of thigh: L2; medial calf: L4; lateral calf: L5; fifth toe: S1; midline buttocks: S3.

D. Spinal level by nerve

• 1. See also : p. 95 for sx of common entrapment syndromes.

  Figure 11 . The brachial plexus. (From Warwick R, Williams P. Gray's Anatomy . 35th ed. London: Churchill Livingstone; 1973, with permission.)

• P.91

  
  

• 2. Brachial plexus : C5-T1.

  • a. Plexi :

    • 1) Upper plexus : C5-6. Deltoids, biceps, supra- + infraspinatus.

    • 2) Middle plexus : C7.

    • 3) Lower plexus : C8-T1.

  • b. Cords : Upper-mid-lower plexi recombine to form three cords; lateral and medial cord then recombine to form median nerve.

    • 1) Lateral cord (from upper + middle plexus) forms musculocutaneous nerve, lateral anterior thoracic nerve, median nerve.

    • 2) Posterior cord (from upper, middle, and lower plexus) forms radial nerve, axillary nerve, and subscapular nerve.

    • 3) Medial cord (from lower plexus) forms ulnar nerve, medial cutaneous nerve, median nerve.

• 3. Nerves of arm : Note that any weakness of both flexors and extensors or of all intrinsic hand muscles implies that the lesion cannot be a mononeuropathy.

  • a. Long thoracic nerve : C5-7. Serratus anterior. Test: scapula wings when pt presses arm forward against a wall.

  • b. Axillary nerve : C5 -6. Deltoid, etc. Test: abduct arm >90 degrees.

  • c. Musculocutaneous nerve : C5 -6. Biceps.

  • d. Radial nerve : C5-8, esp. C7 . Extensors (triceps, wrist, and finger), supinator, brachioradialis.

  • e. Median nerve : C6-T1. Flexors except ulnar: most forearm flexors, flex. dig. superior ; all pronators. Hand: LOAF muscles ( L umbricals 1 and 2, O pp. pollicis, A bd. poll. brev., F lex. poll. brev.).

  • f. Ulnar nerve : C8-T1. Flexor digitorum profundus 3 and 4, flexor carpi ulnaris. Most of intrinsic hand (except LOAF muscles above): thumb adductors and flexors, interossei, lumbricals 3 and 4, hypothenar muscles.

• 4. Leg :

  • a. Femoral nerve : L2-4.

    • 1) Function : Extend knee.

    • 2) Muscles : Iliopsoas, quadriceps, sartorius, rectus femoris.

  • b. Obturator nerve : L2-4.

    • 1) Function : Adduct leg.

    • 2) Muscles : Adductor longus, brevis, and magnus; gracilis, pectineus .

  • c. Sciatic nerve (tibial and peroneal nerve): L4-S2.

    • 1) Function : Extend and abduct hip, flex knee, all foot mvts.

      • a) Deep peroneal nerve : Extends toes and ankle.

      • b) Superficial peroneal nerve : Everts foot.

      • c) Tibial nerve : Superficial tibial flexes foot; deep tibial flexes toes.

    • 2) Muscles : Semitendinosus and semimembranosus, biceps femoris, gastrocnemius, soleus, foot muscles .

E. Spinal level by reflex