Neurology - Spinal Nerves Map

*Home

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Cervical Plexus

  • C1 -C8

Thoracic Plexus

  • T1 - T12

*Cervical Plexus

  • C1 -C8

*Thoracic Plexus

  • T1 - T12

*Notes - Spinal Nerves

  • all Cervical spinal nerves exit above the vertebrae
  • C8 is the dividing spinal nerve
  • there are ONLY 7 C vertebrae
    --> C8 is below vertebra 7
  • all spinal nerves starting at T1 and below exit below the vertebrae
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*LumboSacral Plexus

  • contain both the sacral and lumbar plexeses

Lumbosacral Radiculopathy = Nerve Compressions

  • SCIATICA = nonspecific term for compression of the lumbosacral nerve roots
  • usually below L2
    --> L5 and S1 are most common\
  • L5 = "foot drop and big toe drop"
    --> deep peroneal = big toe + deep in the cracks sensation
    --> superficial peroneal = dorsiflexion
  • S1 = achillies reflex
    --> "1 2 BUCKLE my SHOE"

Sacral Plexus

  • S1 - S5

*Sacral Plexus

  • S1 - S5

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Lumbar Plexus

  • L1 - L5

*Lumbar Plexus

  • L1 - L5

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  • L1 = Inguinal
    --> NOT involved in sciatia
  • L2 = front thigh
  • L3 = outer thigh
  • L4 = knee
    --> "on all 4s" = knee reflex
  • L5 = "foot drop and big toe drop"
    --> deep peroneal = big toe + deep in the cracks sensation
    --> superficial peroneal = dorsiflexion
  • S1 = achillies reflex
    --> "1 2 BUCKLE my SHOE"

*Sciatica

  • SCIATICA = nonspecific term for compression of the lumbosacral nerve roots

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*Brachial Plexus

  • C5 - T1

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Brachial Plexus --> think of REAL truckers and their J BRAKES (= brachial plexus)


"REAL Truckers Drink COLD BEER" (at rest stops)

  • roots, trunks, divisions, cords, branches

"REAL Truckers TIP HIGH and play the LOWERING CLAW GAME at rest stops"

  • Upper trunk lesion = "waiter's tip / ERBs palsy"
    --> behind back (arm extended / internally rotated / pronated)
  • Lower trunk lesion = CLAW hand

*Phrenic Nerve

  • comes from C3,c4,c5

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*straight leg raise test for spinal radiculopathy

  • tries to pinch the nerve to recreate the pain

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*Pudendal Nerve

  • from S2,s3,s4
  • pudendal nerve responsible for the "anal wink" reflex
    --> "s3,s4 = Winks Galore"

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Pudendal Nerve Injury after pregnancy

  • from stretching of the pelvis can cause damage

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*Reflexes of the Cervical Roots

  • C1 - C8

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Posterior Chord

*Radial nerve


MOTOR

  • ALL extensors of ENTIRE posterior arm
  • triceps
  • all posterior forearm extensors


SENSATION

  • back of the arm
  • back of the hand for 1st 3 1/2 digits
    --> behind the median front coverage

Radial nerve "wrist drop" vs "finger drop"

  • Radial nerve "wrist drop" = radial groove fracture
    --> higher up so wrist affected
  • Radial nerve "finger drop / Saturday night palsy/screwdriver palsy" = supinator canal nerve compression
    --> lower down so only the fingers are affected

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*Radial nerve sensation
SENSATION

  • back of the arm
  • back of the hand for 1st 3 1/2 digits
    --> behind the median front coverage

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*Axillary nerve


MOTOR

  • deltoid muscle


SENSATION

  • ?

Axillary nerve sensation
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Axillary nerve Motor
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Lateral Chord

Medial Chord

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Lateral Pectoral Nerve

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*Median Nerve

*Musculocutaneous Nerve

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Medial Pectoral Nerve

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*Obtuator Nerve

  • origin = L2, L3, L4
  • Motor innervation = obtuator muscle
    -->
  • Motor innervation = adductor muscles
    --> after obtuator canal divides into anterior and posterior branches to supply the 3 adductor muscles
    --> adductor brevis, longis, magnus
  • Anatomy Course = posteromedial to IlleoPsoas muscle in pelvis
    --> exits the pelvis through
  • Dermatomes = just above the knee on inner thigh

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*Obtuator Foreman and Canal

  • OF is the big foreman in the anterior o the pubic tubercle
  • Obtuator membrane covers most of it
    --> has a tiny hole in the obtuator membrane where the obtuator nerve anterior and posterior branches exit the pelvis

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*Abdominal Nerves

  • suprapubic areas sensation = illeohypogastric nerve

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*Pubic and Supra Pubic Innervation

  • Pubic sensation = illeoinguinal
  • Suprapubic sensation = illeohypogastric
    --> note the HYPOGASTRIC GI area
    --> named after the ILLEO HYPOGASTRIC nerve that supplies innervation there

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*illeohypogastric Nerve

  • Suprapubic sensation = illeohypogastric
    --> note the HYPOGASTRIC GI area
    --> named after the ILLEO HYPOGASTRIC nerve that supplies innervation there
  • suprapubic catheder
    --> this is the nerve that would sense pain when putting a supr pub catheder in

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*illeoinguinal Nerve

  • Pubic sensation = illeoinguinal

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illeohypogastric Nerve injury - after appendectomy


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Clinical Cases

Clinical Case

Clinical Case

Notes:

  • note that

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*Pelvic autonomic nerves

  • note the prostatic plexus and cavernous nerves to the penis for Point and Shoot erection go together
  • so radical prostatecomy has a risk of erectile dysfunction since you may take the parasympathetic cavernous nerves to the CORPUS CAVERNOSUM

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*DIRTY USMLE


UPPER EXTREMITY NERVES

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*Femoral Nerve

  • femoral nerve part of the lumbar plexus
  • think it is in front and above the sciatic nerve branches = tibial and fibular

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*Ulnar nerve


MOTOR




SENSATION
-

Ulnar nerve
MOTOR
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*Lateral Cutaneous Femoral Nerve = LCFN

  • comes from L2L3
    • NO motor
    • Sensory ONLY to the lateral thigh

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*Sciatic Nerve

  • from the sacral plexus
  • gives off the 2 major nerve branches that reach the foot
    --> tibial and peroneal = fibular nerves
  • Tibial nerve
    --> posterior calf muscles = 2x gastrocnemius, pantaris, soleus
    --> plantar flexion
  • common peroneal = fibular nerve
    --> superficial peroneal = eversion + most sensation
    --> deep peroneal nerve = dorsiflexion + INVERSION

*common peroneal = fibular nerve

  • splits into Deep and superficial branches of peroneal nerve
  • note the peroneal = fibular nerve wraps around the top head of the fibula
    --> common compression site or tear from fractures of fibula
  • superficial fibular branch = gives sensation to the dorsum of the foot
  • deep fibular branch = gives mottor innervation to anterior muscle of leg that cause dorsi flexion of the foot
    --> get foot drop when injured

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*Superficial peroneal nerve


MOTOR innervation:

  • 3 major foot INVERSION muscles = fibularus BLT
    --> anterior tibialis
    --> fibularis longus
    --> fibularis tertius

SENSATION innervation:

  • MOST sensation to the dorsum of the foot
    --> just NOT DEEP and around the big toe = Deep peroneal nerve

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*Inversion / Eversion


Inversion:

  • title the Pantar Plane IN

Eversion:

  • title the Pantar Plane EVERT

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*Deep peroneal nerve

  • deep fibular branch = gives mottor innervation to anterior muscle of leg that cause dorsi flexion of the foot
    --> get foot drop when injured

MOTOR innervation:

  • 1 + 3
  • 1 major dorsiflexor
    --> anterior tibialis
  • 4 LBs extensors of digits
    --> extensor digitorum longus
    --> extensor digitorum brevis
    --> extensor hallicus longus
    --> extensor hallicus brevis

SENSATION innervation:

  • ONLY sensation the small space between the hallicus and 2nd digit

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*Foot drop in Common peroneal nerve injury

  • from trauma to fibular neck or casts applied too tight

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*tibial nerve

  • goves off the cutaneous sural nerve branch
  • divides into posterior tibial nerve

*tibial nerve

  • tibial nerve injury
    --> can't do the tippy toe PLANTAR FLEXION

MOTOR innervation:

  • ALL major plantarflexion muscles in leg + foot INVERSION (along with deep peroneal nerve)
    --> anterior tibialis
    --> fibularis longus
    --> fibularis tertius
  • also innervates the flexor hallicus longus

SENSATION innervation:

  • ONLY plantar!!
    --> rest is fibular = deep + superficial

*tibial nerve MOTOR innervation:

  • ALL major plantarflexion muscles in leg + foot INVERSION (along with deep peroneal nerve)
    --> anterior tibialis
    --> fibularis longus
    --> fibularis tertius
  • also innervates the flexor hallicus longus

SENSATION innervation:

  • plantar region of the foot

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*Tom dick and Nervous Harry:

  • go around the medial maleolus

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*tibial nerve SENSATION innervation:

  • plantar region of the foot

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  • INVERSION - The tibialis posterior, innervated by the tibial nerve, receives its main segmental innervation from L5. This muscle provides the majority of ankle INVERSION.
  • If ankle EVERSION is weak, the lesion involves more than the common peroneal nerve.