Neurology Shorts

Question 1

What nerve roots supply all the small muscles of the hand?

Answer 1

C8/T1

Question 2

What is the pathology in clawing of the ring and little finger?

Answer 2

Weakness in the lumbrical muscles; ulnar nerve lesion

Question 3

Wasting of first dorsal interosseous and abductor digiti minimi - where is the lesion?

Answer 3

Ulnar nerve

Question 4

Isolated wasting of the abductor pollicis brevis - where is the lesion?

Answer 4

Median nerve

Question 5

Hand of benediction - where is the lesion?

Answer 5

Proximal lesion of the median nerve.

Question 6

How to test for weakness of the flexor pollicis longus and flexor digitorium profundus and where is the lesion that affects those nerves?

Answer 6

• Ask the patient to form an “O” with the thumb and index finger. If there is weakness of the distal flexors, it will adapt this shape (see pic)
• It is the weakness of the proximal median nerve

Question 7

What muscles should be examined in hand wasting and what are some differentials?

Answer 7

abductor pollicus brevis

abductor digiti mini

1st dorsal interroseous

Ddx: nerve root/plexus lesion, Horner’s syndrome, avulsion of root, syringomyelia, tumour, trauma, MND, peripheral neuropathy

Question 8

Nerve roots of reflexes:

• Biceps
• Brachioradialis
• Triceps

Answer 8

Biceps: C5/6

Brachiradialis: C5/6

Triceps: C6/7 (mainly C7)

Question 9

Musculocutaneous:

1. Nerve roots
2. Motor functions
3. Sensory functions

Answer 9

1. Nerve roots: C5, 6, 7
2. Motor: brachialis, ciceps, coracobrachialis
3. Sensory: lateral half of the anterior forearm, and a small lateral portion of the posterior forearm

Question 10

Axillary nerve:

1. Nerve roots
2. Motor function
3. Sensory function

Answer 10

1. C5, 6
2. Teres minor and deltoid muscle
3. Inferior region of the deltoid

Question 11

Median nerve:

1. Nerve roots
2. Motor function
3. Sensory function

Answer 11

1. C6 - T1
2. Most flexors in the forearm, thenar muscles, 2 lateral lumbricals
3. Lateral aspect of the palm, lateral 3 and half fingers on the angerior surface of the hand

Question 12

Radial nerve:

1. Nerve roots
2. Motor function
3. Sensory function

Answer 12

• C5-T1
• Triceps, muscles in the posterior compartment of the forearm
• Posterior aspect of the arm and forearm and posterolateral aspect of the hand

Question 13

Ulnar nerve:

• Nerve roots
• Motor function
• Sensory function

Answer 13

1. C8/T1
2. All muscles of the hand aside from the thenar muscles and 2 lateral lumbricals, flexor carpi ulnaris (flexion of the hand) and medial half of the flexor digitorum profundus (mass action muscle that flexes at the DIP)
   
   1. e.g. cannot abduct and adduct fingers
3. Median palmar and dorsal hand area + 1.5 median fingers both sides

(note everything else in the anterior forearm is innervated by the median nerve)

Question 14

Difference in flexor digitorium profundus vs flexor digitorium superficialis:

1. Innervation
2. Clinical testing

Answer 14

1. The median 2 digits of FDP are innervated by the ulnar nerve where as the rest of the anterior forearm muscles are innervated by the median nerve
2. Test FDP by isolating the DIP for testing. Test the FDS by immobilising the other 3 digits so it stops the mass action of the FDP.

Question 15

What causes wasting of one hand, loss of reflexes in the arm and a dissociated sensory loss (loss of pain with preserved fine touch) in a half cape distribution on the same side)?

Answer 15

Intrinsic lesion of the cervical and upper thoracic cord (e.g. syringomyelia)

Question 16

How to test for myotonia in the hands?

Answer 16

Ask the patient to make a tight fist and then open the fingers as rapidly as possible. If the fingers unfurll slowly, they have myotonia

Question 17

What is the most common cause of wasting of the small muscles of the hands?

Answer 17

Old age and arthritis (should have preserved muscle power in the muscles)

Question 18

What is the most common cause of the wrist drop?

Answer 18

Compression of the radial nerve in the spiral groove

Question 19

What muscles extend the wrist?

Answer 19

Extensor carpi radialis longus (C5/6 radial nerve)

Extensor carpi ulnaris (C7/8 posterior interosseous radial nerve)

Question 20

What wrist extensor does the posterior interosseous nerve innervate and what are the causes of lesions?

Answer 20

Extensor carpi ulnaris - weakness of finger extension w radial deviation on wrist extension

No sensory loss

Mononeuritis multiplex/simplex or any cause or nerve entrapment

Question 21

What nerve roots supply wrist extension?

Answer 21

C5/6 supplies extensor carpi radialis longus

C7/8 supplies extensor carpi ulnaris

Question 22

Investigatins of mononeuritis multiplex

Answer 22

NCS

EMG

CSF protein

Bloods tests for diabetes, hIV, HCV, ANCA, campylobacter, anti=GM1 and GQ1b antibodies, sarcoidosis

Question 23

How to separate radial nerve injury vs C7/8 nerve root injury?

Answer 23

Radial nerve would affect brachioradialis

Question 24

Deltoid innervation nerve roots

Answer 24

C5/6

Question 25

What is the action and nerve root innervation of the supraspinatus?

Answer 25

First 20 degrees of should abduction C5/6

Question 26

What is the action of the infraspinatus and the innervation?

Answer 26

External rotation of the shoulder Suprascapular nerve C5/6

Question 27

What is the innervation of the trapezius?

Answer 27

Spinal accessory nerve C3/4

Question 28

What is the action of serratus anterior and its innervation?

Answer 28

Scapular fixation and rotation Long thoracic nerve C5/6/7

Question 29

Most likely cause of unilateral proximal upper limb weakness?

Answer 29

Nerve roots/peripheral nerve/brachial plexus

Question 30

General inspection of proximal weakness

Answer 30

- Skin for heliotrope rash around eyes, cheeks, fingers, elbows and knees for dermatomyositis - Joints for subluxation of the humerus - Wasting (deltoid and scapula) - Face - horner's, ptosis, facial droop - Fasiculations

Question 31

Ddx for weakness of all proximal uscles of the arms and legs

Answer 31

Polymyositis, dermatoyositis, myasthenia gravis

Question 32

Selective weakness and wasting of proximal muscles of the arms and legs - differentials

Answer 32

Muscular dystrophy, spinal muscular atrophy, inclusion body myositis Test facial movements and eye closure!