Mononeuropathies, Spinal Cord Lesions

Question 1

Features of radial nerve lesion

Answer 1

• C5- C8
• Wrist and finger drop (wrist flexion normal)
• Triceps loww (elbow extension loss) if lesion above the spinal groove
• Sensory loss over the anatomical snuffbox
• Finger abduction appears to be weak because of the difficulty of spreading the fingers when they cannot be straightened

Question 2

Notes on median nerve lesions

Answer 2

• C6 - T1
• **Supply
• **All muscles of the forearm except flexor carpi ulnaris and half of the flexor digitorum profundus
• LOAF muscles of hand - lateral two lumbricals, opponens pollicus, abductor pollicus brecis, flexor pollicus brevis
• **Clinical features
• **Loss of APB with lesion at or above the wrist: pen touching test - with hand flat ask the patient to abduct the thumb vertically to touch your pen
• Loss of flexor digitorum sublimis with a lesion in or above the cubital fossa: Ochsner’s clasping test - ask patient to clasp hands firmly togetherl the index finger on the affected side fails to flex
• Sensory loss over the thumb, index, middle and lateral half of the ring finger (palmar aspect only)

**Causes of carpal tunnel syndrome
**Idiopathic
Arthropathy - RA
Endocrine - hypothyroidism, acromegaly
Pregnancy
Trauma and overuse

Question 3

Notes on ulnar nerve lesions

Answer 3

• C8 - T1
• Wasting of the intrinisc muscles of the hanf (except the LOAF muscles)
• Weak finger abduction and adduction (loss of interosseous muscles)
• Claw like hand - higher the lesion - less deformity
• Froment’s sign - ask patient to grasp a piece of paper between thumb and lateral aspect forefinger with each hand, the affected thumb will flex (loss of thumb adductor)
• Sensory loss over the little and medial half of ring finger (both plantar and dorsal aspects)

Question 4

Differentials for wasting of the small muscles of the hands

Answer 4

1. Nerve lesions - median and ulnar nerves, brachial plexus lesions, peripheral motor neuropathy
2. Anterior horn cell disease - MND, polio, spinal muscular atrophies
3. Myopathy - dystrophia myotonica - forearms more affected than the hands, distal myopathy
4. Spinal cord lesions - syringomyelia, cervical spondylosis with compression of C8 segment, tumour
5. Trophic disorders - athropathies (disuse), ischaemia including vasculitis, shoulder0hand syndrome

Question 5

How to distinguish a ulnar nerve lesion from a C8 root/lower trunk brachial plexus lesion

Answer 5

**C8 lesion
**Sensory loss extends proximal to the wrist
Thenar muscles involved

**C8 vs lower trunk brachial plexus
**Difficult to distinguish clinically but think of lower trunk brachial plexus if Horner’s syndrome or axillary mass

Question 6

Notes on femoral nerve lesions

Answer 6

• L2, L3, L4
• Weakness of knee extension (quadriceps paralysis)
• Slight hip flexion weakness
• Preserved adductor strength
• Loss of knee jerk
• Sensory loss involving the inner aspect of the thigh or leg

Question 7

Notes on sciatic nerve lesions

Answer 7

• L4, L5, S1, S2
• Weakness of knee flexion (hamstrings)
• Loss of power in all muscles below the knee causing a foot drop, patient may be able to walk but can’t stand on toes or heels
• Knee jerk intact
• Loss of ankle jerk and plantar response
• Sensory loss along the posterior thigh and total loss below the knee

Question 8

Notes on common peroneal nerve lesions

Answer 8

• L4, L5, S1
• Foot drop and loss of foot eversion only
• Sensory loss (minimal) over the dorsum of the foot
• Normal reflexes

Question 9

How to distinguish between a common peroneal nerve lesion vs L5 radiculopathy/lesion

Answer 9

Foot drop in both, In both eversion lost
L5 lesion - inversion also lost (intact with common peroneal nerve lesion)

Question 10

Notes on upper cervical spinal cord lesions

Answer 10

1. Upper motor neurone signs in upper and lower limbs
2. Paralysis of the diaphragm occurs with a lesion above C4

Question 11

Notes on C5 spinal cord lesion

Answer 11

1. LMN weakness and wasting of rhomboids, deltoids, biceps and brachioradialis
2. UMN signs affect the rest of the upper and lower limbs
3. Biceps jerk is lost
4. Supinator jerk is inverted

Question 12

Notes on C8 spinal cord lesions

Answer 12

1. LMN weakness and wasting of the small muscles of the hands
2. Upper motor neurone signs in the lower limbs

Question 13

Notes on mid thoracic spinal cord lesions

Answer 13

1. Intercostal paralysis (cannot be detected clinically)
2. Loss of upper abdominal reflexes at T7 and t8
3. UMN signs in the lower limbs
4. Sensory level on the trunk (often missed)

Question 14

Notes on T10-T11 Spinal cord lesion

Answer 14

1. Loss of lower abdominal reflexes and upward displacement of the umbilicus on contraction (Beevor’s sign)
2. Upper motor neurone signs in the lower limbs

Question 15

Notes on L1 Spinal cord lesions

Answer 15

1. Cremasteric reflex loss (normal abdominal reflexes)
2. Upper motor neurone signs in the lower limbs

Question 16

Notes on L4 Spinal cord lesions

Answer 16

1. LMN weakness and wasting of the quadriceps
2. Knee jerk lost

Question 17

Notes on L5 and S1 spinal cord lesions

Answer 17

1. LMN weakness of knee flexion and hip extension (S1) and abduction (L5), plus calf and foot muscles
2. Knee jerk present
3. No ankle jerk or plantar response
4. Anal reflex present

Question 18

Notes on S3 and S4 spinal cord lesions

Answer 18

1. No anal reflex
2. Saddle sensory loss
3. Normal lower limbs

Question 19

Nots on subacute combined degeneration of the cord (B12 deficiency)

Answer 19

1. Symmetrical posterior column loss (vibration and position sense) causing an ataxic gait
2. Symmetrical UMN signs in the lower limbs with absent ankle reflexes; knee reflexes may be absent but more often exaggerated
3. Peripheral sensory neuropathy (less common and mild)
4. Optic atrophy (occasionally)
5. Dementia (occasionally)

Combination of upper motor neurone signs causing an extensor plantar respnse with peripheral neuropathy causing loss of knee and ankle jerks if distinctive

Question 20

Causes of extensory plantar response with loss of ankle jerk

Answer 20

1. Subacute combined degeneration of the spinal cord
2. Conus medullaris lesion
3. Combination of upper motor neurone lesion with cauda equina compression or peripheral neuropathy
4. Syphilis (taboparesis)
5. Friedreich’s ataxia
6. Diabetes (uncommon)
7. Drenoleukodystrophy

Question 21

Notes on Brown Sequard Syndrome

Answer 21

Hemisection of the spinal cord
**Motor changes
**UMN below the level of the lesion on the same side
LMN signs at the level of the lesion on the same side

**Sensory changes
**Pain and temperature loss on the opposite side of the lesion (the upper level of sensory loss is usually a few segments below the level of the lesion)
Vibration and proprioception loss on the same side
Light touch often normal
There may be a band of sensory loss on the same side at the level of the lesion

**Common causes
**1. Multiple sclerosis
2. Angioma
3. Glioma
4. Trauma
5. Myelitis
6. Postradiation myelopathy

Question 22

Causes of disoociated sensory loss

i.e. Spinothalamic loss only, dorsal column loss only

Answer 22

**Spinothalamic
**1. Syringomyelia
2. Brown Sequard (contralateral)
3. Anterior spinal artery thrombosis
4. Lateral medullary syndrome (contralateral to the other signs)
5. Peripheral neuropathy (e.g. DM, amyloid, Fabry)

**Dorsal column
**1. Subacute combined degeneration of the cord
2. Brown sequard syndrome (ipsilateral)
3. Spinocerebellar degeneration (Friedreich’s)
4. Multiple sclerosis
5. Tabes dorsalis
6. Sensory neuropathy or gangliopathy e.g. carcinoma
7. Peripheral neuropathy from DM or hypothyroidism

Question 23

Sensory dermatomes on the upper limb

Answer 23

• C5 supplies the shoulder tip and outer part of upper arm
• C6 supplies the lateral aspect of forearm and thumb
• C7 supplies the middle finger
• C8 supplies the little finger
• T1 supplies the medial aspect of the upper arm and elbow

Question 24

Dermatones on the lower limbs

Answer 24

• Stand on S1
• Big toe pushes the door with L4

Question 25

Specific sensory changes associated with major nerves of upper limbs

Answer 25

Question 26

Notes on brachial neuritis

Answer 26

• AKA neuralgic amyotrophy/Parsonage Turner syndrome/inflammatory brachia plexopathy
• Inflammation in brachial plexus - can be post-infecitous/vaccintation or inheritied
• Severe shoulder pain at onset, followed by weakness often around shoulder girdle. Sensory loss often outer upper arm
• Infraspinatus and serratus anterior most commonly affected