Anatomy of Spinal Nerves

Question 1

How is the organisation of peripheral nerve cutaneous innervation different from dermatomes?

Answer 1

Nerves have more than one spinal nerve root so overlap into more than one true dermatome

Question 2

What is the posterior peripheral cutaneous nerve innervation of the neck?

Answer 2

The posterior rami of C2-8

Question 3

What is the anterolateral periphera cutaneous nerve innervation of the neck?

Answer 3

Sensory branches of the cervical plexus = lesser occipital nerve (C2), great auricular nerve (C2-3), transverse cervical nerve (C2-3), supraclavicular nerve (C3-4)

Question 4

Where is the nerve point of the neck?

Answer 4

Just above the midpoint of posterior border of sternocleidomastoid = sensory nerves of cervical plexus

Question 5

What is the peripheral nerve cutaneous innervation of the upper anterolateral trunk?

Answer 5

Intercostal nerves = become subcostal nerves at T12

Question 6

What is the peripheral cutaneous nerve innervation of the lower anterolateral trunk?

Answer 6

Iliohypogastric and ilioinguinal nerves

Question 7

What is the peripheral cutaneous nerve innervation of the back?

Answer 7

Posterior rami

Question 8

What is the peripheral cutaneous innervation of the anatomical snuffbox?

Answer 8

Supplied by cutaneous branches of the radial nerve = belongs to C6 dermatome

Question 9

What nerve innervates the badge patch?

Answer 9

The axillary nerve (C5-6) = badge patch is landmark for C5 dermatome

Question 10

What is relevant about the peripheral cutaneous nerve innervation of the medial arm?

Answer 10

Innervated by T1-2 anterior rami = important for referred pain from the heart

Question 11

What happens when you test the peripheral cutaneous nerves?

Answer 11

APs conducted along axons into spinal nerve into the posterior roots and rootlets
APs arrive at posterior horn and are conducted via an ascending tract to the primary somatosensory cortex

Question 12

What are the main myotomes that should be examined for the function of their motor axons?

Answer 12

Cervical plexus (C1-4) = neck postural and strap muscles, diaphrgam
Brachial plexus (C5-T1) = muscles of upper limb, extrinsic back muscles
T2-L3 = intrinsic back muscles, intercostal muscles, anterolateral abdominal wall muscles 
Lumbosacral plexus (L1-S4) = muscles of lower limbs, perineal skeletal muscles

Question 13

How do you test the upper limb myotomes?

Answer 13

Shoulder = abduction (C5), adduction (C7)
Fingers = flexion (C8), extension (C7), ab/adduction (T1)
Elbow = flexion (C5-6), extension (C7-8)
Wrist = flexion and extension (C6-7)

Question 14

How do you test the lower limb myotomes?

Answer 14

Hip = flexion (L2-3), extension (L5-S1)
Knee = flexion (L5-S1), extension (L3-4)
Ankle = dorsiflexion (L4-5), plantar flexion (S1-2), inversion (L4)

Question 15

What happens when you want to initiate movement in a myotome?

Answer 15

APs generated in primary somatomotor cortex then conducted via UMN axons to corticospinal tract
Reach anterior horn to stimulate LMNs and conduct through spinal nerve and into named nerve

Question 16

What does the spinal cord reflex depend on?

Answer 16

The integrity of the arc pathway

Question 17

What is an example of a monosynpatic reflex arc?

Answer 17

Occurs each time skeletal muscle is stretched = reflex muscle contractions controlled by descending pathways

Question 18

What do lesions in the monosynaptic reflex arc cause?

Answer 18

UMN lesions cause spasticity

LMN lesions cause flaccidity

Question 19

What is the underlying pathology of paralysis?

Answer 19

Lack of functioning motor nerve

Question 20

What is the underlying pathology of spasticity?

Answer 20

Due to descending controls not working