Lecture 5: Peripheral Neuropathies

Question 1

How can radiation injury vs. neoplastic etiology be differentiated on the basis of involvement and pain in terms of brachial plexopathy?

Answer 1

• Radiation injury: upper trunk, lateral cord, painless
• Neoplastic: medial cord, painful (breast and lung)

Question 2

What are 6 motor signs/sx’s of peripheral nerve disease?

Answer 2

• Distal weakness
• Cramps
• Muscle fasciculations (twitching)
• Atrophy
• ↓ DTRs
• Reduced tone

Question 3

What are sx’s of a small unmyelinated fiber neuropathy?

Answer 3

• Pain
• “Burning” dysesthesias
• Paresthesias
• Temperature sensation abnormalities

Question 4

What will be seen on skin biopsy in a small (unmyelinated) fiber polyneuropathy?

Answer 4

↓ epidermal nerve fiber density

Question 5

Weakness in shoulder abduction with loss of sensation in the lateral arm is seen with lesion of what nerve root?

Answer 5

C5

Question 6

Weakness in shoulder abduction + elbow flexion with sensory loss in the 1st and 2nd digit is due to lesion of what nerve root?

Answer 6

C6

Question 7

Sensory loss in the medial calf + weakness in hip flexion and knee extension is due to lesion of which nerve root?

Answer 7

L4

Question 8

Sensory loss in the lateral calf/dorsum of foot + weakness in hamstrings + foot dorsiflexion, inversion, and eversion is due to lesion of what nerve root?

Answer 8

L5

Question 9

What is the dermatomal distribution for T1?

Answer 9

Medial forearm

Question 10

When diagnosing a plexopathy which 2 muscle can help identify proximal lesions?

Answer 10

• Rhomboids (Dorsal Scapular n. - C5)
• Serratus Anterior (Long thoracic n. - C5)

Question 11

What are the negative vs. positive sx’s associated with a large (myelinated) fiber peripheral neuropathy?

Answer 11

• Negative: ↓ vibration + ↓ joint position sense + arreflexia + ataxia + hypotonia
• Positive: tingling + pins and needles + numbness

Question 12

Which median mononeuropathy is associated with an insidious onset of diffuse/dull ache about th proximal forearm (rarely acute or sharp)?

Answer 12

Pronator Syndrome

Question 13

Pronator syndrome will have associated sensory loss where in the hand?

Answer 13

Diffuse numbness of hand, mostly 2nd-3rd fingers

Question 14

Which median nerve mononeuropathy is associated with an abnormal pinch sign w/ normal sensation?

Answer 14

Anterior Interosseous Syndrome

Question 15

What is a common site in the elbow and wrist contributing to ulnar mononeuropathy?

Answer 15

• Elbow: between medial epicondyle and olecranon
• Wrist: Guyon’s canal

Question 16

Which muscle and motion of the thumb will be impaired in ulnar mononeuropathy?

Answer 16

ADductor policis = weak thumb ADduction = Froment Sign

Question 17

What is the most common site for radial mononeuropathy to develop; presents with what deficit?

Answer 17

• Spiral groove of the humerus
• Presents with wrist drop due to paresis of extensor ms. of the wrist, finger, and thumb
• Elbow extension is SPARED!