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Year 4 - PAN > Neurology - Disorders of peripheral nerves II > Flashcards

Neurology - Disorders of peripheral nerves II Flashcards

1
Q

Mononeuropathy

A

= Disease where a single peripheral nerve is affected

Mononeuritis multiplex = many single peripheral nerves are damaged one by one (specifically if 2 or more peripheral nerves)

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2
Q

What systemic illnesses can cause mononeuropathy or mono neuritis multiplex?

A

“WARDS PLC”

  • Wegener’s
  • AIDS/ Amyloid
  • Rheumatoid
  • Diabetes
  • Sarcoidosis
  • PAN
  • Leprosy
  • Cancer (carcinomatosis)
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3
Q

Entrapment mononeuropathies

A

Caused by damage to the nerve where it passes through a tight space - e.g. median nerve under flexor retinaculum of the wrist

Often related to conditions such as acromegaly, myxoedema, and pregnancy where soft tissue swelling occurs

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4
Q

Location of the brachial plexus

A

Brachial plexus is formed from the anterior rami of C5-T1

It is located in the posterior triangle of the neck between the anterior and middle scalene muscles

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5
Q

Name the 4 motor branches that the brachial plexus gives off

A

1) Nerve to rhomboids
2) Long thoracic nerve (of Bell) - innervates serrates anterior
3) Pectoral nerves - to pectoralis major
4) Suprascapular nerve - to supraspinatus and infraspinatus

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6
Q

What causes an upper plexus lesion affecting C5 and C6? What name is given to this condition?

A

Causes:

  • Traction of the arm during birth
  • Violent falls on the side of the head and shoulders - e.g. motor cycle accidents

= Erb-Duchenne palsy

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7
Q

Where is the sensory loss in Erb-Duchenne palsy?

A

C5 and C6 dermatome - lateral aspect of the upper arm and radial side of the forearm

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8
Q

Explain the clinical features of an upper plexus lesion

A

Damage to C5 and C6 causes paralysis of the deltoids, short muscles of the shoulder, and the elbow flexors -brachialis and biceps

Biceps is also a powerful supinator of the forearm so the arm hangs down by the side and the forearm is pronated with the arm facing backwards (due to unopposed supination and extension) like a waiter hinting for a tip - this is Erb-Duchenne palsy

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9
Q

What are the features of a lower plexus lesion affecting T1?

A

T1 supplies the intrinsic muscles of the hand

Hand assumes a clawed appearance because of unopposed action of the long flexors and extensors of the fingers:

  • extensors insert into the bases of the proximal phalanges and EXTEND the MCP joints
  • flexors insert onto the middle and distal phalanges FLEX the IP joints

Lower plexus lesion affecting C8 and T1 caused by upward traction on the arm (e.g. forcible breech delivery) is called Klumpke’s paralysis

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10
Q

What is thoracic outlet syndrome?

A

Rare condition where a structure (e.g. cervical rib or fibrous band) compresses both the brachial plexus and the subclavian artery (which also passes between the anterior and middle scalene muscles in front of the plexus)

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11
Q

Signs and symptoms of thoracic outlet syndrome

A

Symptoms:

  • Pain in the neck and shoulder
  • Paraesthesia in the ulnar forearm (made worse by lifting heavy weights)

Signs:

  • Sensory loss in T1 distribution
  • Wasting of intrinsic hand muscles
  • Evidence of vascular compression (i.e. unilateral Raynaud’s, pallor of the limb on elevation, loss of radial pulse in arm on abduction and external rotation of the shoulder - Adson’s sign)
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12
Q

What is brachial neuritis?

A

Common disorder sometimes associated with:

  • Viral infection (EBV, cytomegalovirus)
  • Vaccination
  • Strenuous exercise

Clinical features:

  • Acute onset with preceding shoulder pain
  • Weakness is usually proximal
  • Sensory findings are minor
  • Loss of reflexes
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13
Q

Differential diagnoses to consider in brachial neuritis

A

DDx - painful weak arm:

  • Cervical spondylosis
  • Cervical disc disease
  • Brachialgia due to local bursitis
  • Polymyalgia rheumatica
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14
Q

Features of Pancoast’s tumour

A

= Involvement of the plexus by apical lung tumour (usually squamous cell carcinoma) - lower plexus affected

Causes wasting of intrinsic hand muscles, paraesthesia along ulnar border of the forearm, and Horner’s syndrome

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15
Q

Causes and features of a long thoracic nerve palsy

A

Long thoracic nerve supplies serratus anterior

Caused by:

  • Diabetes
  • Strapping the shoulder

Features:
- Winging of the scapula (when arms are stretched in front)

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16
Q

Causes and features of a suprascapular nerve injury

A

Suprascapular nerve innervates infraspinatus and supraspinatus muscles

Caused by:

  • [as for long thoracic nerve], plus
  • Carrying heavy objects over shoulder

Features:

  • Weakness in abduction of the arm (supraspinatus)
  • Weakness in external rotation of the arm (infraspinatus)
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17
Q

What are the features of an axillary nerve palsy?

A

Axillary nerve (direct branch of the posterior cord) supplies deltoid and teres minor

Caused by:
- Shoulder dislocation

Features:

  • Weakness of shoulder abduction between 15-90 degrees
  • Sensory loss over the outer aspect of the shoulder
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18
Q

What are the causes of a radial nerve injury?

A
  • Injury in the axilla by the pressure of a crutch (“crutch palsy”)
  • Falling asleep with the arm resting over the back of a chair (“Saturday night palsy”)
  • Fractures of the humeral shaft
  • Fractures of the radial head - damages the posterior interosseous branch
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19
Q

What is the distinguishing feature of a radial nerve palsy and a posterior interosseous nerve palsy?

A

Radial nerve palsy causes wrist drop because of paralysis to ALL wrist extensors

Damage to the posterior interosseous nerve leaves extensor carpi radialis longus intact (it is supplied by the radial nerve above its division) which is powerful enough to maintain wrist extension

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20
Q

Where is the sensory loss in a radial nerve palsy?

A

Anatomical snuff box

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21
Q

Where can the ulnar nerve be damaged?

A
  • Arcade of Struthers (a musculofascial band proximal to the medial epicondyle)
  • Epicondylar groove (point where it passes between the 2 heads of flexor carpi ulnaris)
  • Exits flexor carpi lunaris in the forearm
  • Guyon’s canal (between the pisiform and hamate bones)
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22
Q

Features of ulnar nerve damage at the wrist

A

All intrinsic muscles of the hand (except the 2 radial lumbricals) are paralysed so the hand assumes the clawed position like that seen in Klumpke’s palsy

Clawing is slightly less intense in the 2nd and 3rd digits because of their intact lumbricals supplied by the median nerve

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23
Q

What are the features of ulnar nerve damage at the elbow? How does this differ from wrist lesions?

A

Flexor digitorum profundus to the 4th and 5th fingers is paralysed so that the clawing of these 2 digits is less intense than a division at the wrist

Paralysis of flexor digitorum ulnaris results in a tendency to radial deviation at the wrist

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24
Q

Why does the sensory loss in ulnar nerve injuries differ depending on whether it is at the wrist or above the wrist?

A

High division of the ulnar nerve (anywhere above a hands breadth above the wrist) leads to sensory loss over the ulnar side of the hand and small and half of the ring finger on both the palmar and dorsal aspect

If damage to the ulnar nerve occurs at the wrist (most common place) then sensory loss is limited to the palmar aspect of the ulnar side of the hand and the ulnar one and a half fingers with sparing of the dorm of the hand - this is because the dorsal branch of the ulnar nerve is given off about one hands breadth above the wrist and is therefore spared

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25
Q

Causes and features of a musculocutaneous nerve palsy

A

Causes:

  • Humeral fracture
  • Systemic causes (“WARDS PLC”)

Features:

  • Weakness of elbow flexion (supplies anterior arm compartment) and forearm supination
  • Sensory loss over the lateral border of the arm
  • Absent biceps reflex
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26
Q

Where is the median nerve most vulnerable to damage?

A

Median nerve can be damaged by supracondylar fractures but is most vulnerable at the wrist (e.g. lacerations, carpal tunnel syndrome)

27
Q

What intrinsic hand muscles are innervated by the median nerve?

A

Most of the intrinsic hand muscles are innervated by the ulnar nerve, only 4 are innervated by the median nerve - “LOAF”

  • 2 radial lumbricals
  • Opponens pollicis
  • Abductor pollicis brevis
  • Flexor pollicis brevis
28
Q

Characteristics of median nerve injury at the wrist

A

Only the thenar muscles (except adductor pollicis) and the radial 2 lumbricals are paralysed and wasting of the thenar eminence occurs

Sensory loss is over the radial 2 and a half fingers, thumb and radial 2/3 of the palm

29
Q

Characteristics of median nerve injury above the elbow

A

If median nerve is damaged at the elbow there is serious muscle impairment

  • Pronation of the forearm is lost
  • Wrist flexion is weak and accompanied by ulnar deviation since this now depends on flexor carpi ulnaris and the ulnar half of flexor digitorum profundus
30
Q

Carpal tunnel syndrome

A

= Most common entrapment neuropathy

More frequent in women and results from median nerve entrapment under the transverse carpal ligament at the wrist

Median nerve is accompanied by 9 tendons in the carpal tunnel

31
Q

What are the symptoms of carpal tunnel syndrome?

A

Remember “wake and shake”

  • Aching pain in the hand and arm (especially at night)
  • Paraesthesia in the thumb, index and middle fingers all relieved by dangling the hand over the edge of the bed and shaking it
  • Weakness of thumb abduction (abductor pollicis bravis)
32
Q

Signs of carpal tunnel syndrome

A

Phalen’s test = maximal wrist flexion for 1 min may elicit symptoms

Tinnel’s test = tapping over the nerve at the wrist induces tingling

33
Q

What causes carpal tunnel syndrome?

A

Famous “median traps”:

  • Myxoedema
  • Enforced flexion (e.g. Colles’ splint)
  • Diabetic neuropathy
  • Idiopathic
  • Acromegaly
  • Neoplasms (e.g. myeloma)
  • benign Tumours (e.g. lipomas)
  • RA
  • Amyloidosis
  • Pregnancy
  • Sarcoidosis
34
Q

Volkmann’s contracture

A

Contracture affecting the hand following ischaemia and fibrosis and contraction of the long flexor and extensor muscles of the forearm

1) Flexors are bulkier than the extensors so their fibrinous contraction is greater and the wrist is flexed
2) Long extensors are inserted into the proximal phalanges; their contracture extends the MCP joints
3) Long flexors are inserted into the distal and middle phalanges; their contracture flexes the IP joints

35
Q

Nerve roots comprising the lumbar plexus

A

T12 - L5
It is located in the substance of the psoas major muscle with the important branches being the femoral and obturator nerves

36
Q

What is the location of the femoral and obturator nerves relative to the psoas major muscle?

A

The femoral nerve is located lateral to the psoas major muscle - it passes underneath the inguinal ligament laterally together with the femoral artery

Obturator nerve is located medial to psoas - it passes through the obturator foramen to innervate the medial thigh compartment muscles (thigh adductors)

37
Q

What nerve roots compose the sacral plexus? Where is it located?

A

The sacral plexus is composed of the anterior rami of nerve roots L4 - S3, each root dividing into anterior and posterior divisions

There is some overlap with nerve roots of the lumbar plexus - specifically L4 and L5 join to contribute the “lumbosacral trunk”

The plexus is located on the posterior wall of the pelvis, overlying the piriformis muscle

38
Q

What are the main branches of the sacral plexus?

A

The L4L5S1S2 posterior divisions form the common peroneal nerve

The L4L5S1S2S3 anterior divisions form the tibial nerve

Both of these nerves fuse to form the sciatic nerve - this nerve then splits in the popliteal fossa into its constituent nerves

Posterior divisions of S2S3 form the pudendal nerve

39
Q

What causes lumbosacral plexus syndromes?

A

Proximity of the plexus to important abdominal and pelvic structures makes it vulnerable to damage from disease

E.g.

  • Trauma following surgery - e.g. hysterectomy, lumbar sympathectomy, or during labour
  • Compression from abdominal masses - e.g. aortic aneurysm
  • Infiltration from pelvic tumour
40
Q

In general what are the features of upper and lower plexus lesions?

A

Upper plexus lesions: (femoral + obturator)

  • Weakness of hip flexion and adduction
  • Anterior leg sensory loss

Lower plexus lesions: (sciatic)

  • Weakness of posterior thigh muscles (hamstrings)
  • Weakness of foot muscles
  • Posterior leg sensory loss
41
Q

What causes a femoral nerve palsy?

A
  • Fractures of the upper femur
  • Congenital dislocation of the hip
  • Psoas muscle abscess
  • Haematoma in the psoas muscle
  • Systemic causes
42
Q

Features of a femoral nerve palsy

A

Femoral nerve supplies the anterior thigh muscles (all 4 heads of quadriceps, iliacopsoas, sartorius, pectineus)

  • Weakness of hip flexion
  • Weakness of knee extension (wasting of thigh muscles)
  • Loss of knee jerk reflex (L3L4)
  • Sensory loss over anterior and medial aspects of thigh
43
Q

Causes of obturator nerve damage

A
  • Same as for femoral nerve
  • Labour
  • Compression by hernia in the obturator canal
44
Q

What are the features of an obturator nerve palsy?

A

Obturator nerve innervates the medial thigh compartment (obturator externus, gracilis, adductor muscles including half of adductor magnus)

  • Weakness of external rotation and ADduction
  • Loss of adductor reflex
  • Sensory loss limited to innermost aspect of the thigh
45
Q

What is the course of the sciatic nerve?

A

The nerve descends between the ischial tuberosity and the greater trochanter of the femur

In the thigh it innervates - biceps femoris, semimembranosus, semitendonosus and half of adductor magnus

In the popliteal fossa it divides into its component parts - the common peroneal and the tibial nerve

46
Q

What causes sciatic nerve damage?

A
  • Congenital or traumatic hip dislocation
  • Penetrating injuries
  • Iatrogenic from misplaced IM injection
  • Entrapment at the sciatic notch
  • Systemic causes of mononeuropathy
47
Q

Features of sciatic nerve damage

A
  • Weakness of hamstring muscles and loss of knee flexion
  • Distal foot and leg muscles also affected
  • Sensory loss involves outer aspect of the leg
  • Absent ankle reflex
48
Q

Describe the course of the common peroneal nerve

A

Nerve arises from the division of the sciatic nerve in the popliteal fossa

Has a close relationship with the head of the fibula, which it winds around anteriorly

It divides into superficial and deep branches as well as giving off a purely sensory which blends with fibres from the tibial nerve forming the sural nerve (sensation to the dorsum and lateral aspect of the foot)

49
Q

Causes of common peroneal nerve injury

A
  • Fracture of the fibular head
  • Pressure from kneeling or crossed legs
  • Systemic causes
50
Q

What are the features of a common peroneal nerve injury?

A

Common peroneal nerve splits into a superficial and deep branches

Superficial branches supply the peroneal muscles (these are primarily foot evertors and located in the lateral compartment of the legs)

Deep branch supplies the extensor muscles (extensor digitorum longus and extensor hallucis longus in the anterior leg compartment)

  • Weakness of dorsiflexion and foot eversion
  • Patient walks with a “foot drop”
  • Sensory loss over dorsum and lateral aspect of the foot
51
Q

What does the posterior tibial nerve supply?

A

Posterior tibial nerve arises from the division of the sciatic nerve in the popliteal fossa and descends behind the tibia terminating in the medial and lateral plantar nerves

Sensory branch contributes to the sural nerve

It innervates the superficial and deep posterior compartment muscles - gastrocnemius, soleus, tibialis posterior, flexor digitorum longus, flexor hallucis longus

52
Q

How can the posterior tibial nerve get damaged?

A
  • Trauma in the popliteal fossa
  • Fracture of the tibia
  • Systemic causes
53
Q

Features of posterior tibial nerve damage?

A
  • Weakness in plantar flexion and inversion (tibialis)
  • Patient cannot stand on toes
  • Sensory loss involves sole of the foot
  • Ankle reflex is lost
54
Q

Tarsal tunnel syndrome

A

= entrapment of the posterior tibial nerve behind the medial malleolus as it passes under the flexor retinaculum

Produces burning pain in the sole of the foot

Diagnosed by prolonged sensory conduction velocity

55
Q

Ptosis, down and out gaze and a fixed dilated pupil is most likely to be caused by a lesion to which cranial nerve?

A

III

56
Q

What are the features of a 4th cranial nerve palsy?

A

Defective downward gaze leading to vertical diplopia.

57
Q

Loss of facial sensation and deviation of the jaw to the side of the lesion indicates a lesion to which cranial nerve?

A 
V (trigeminal)
Other features include:
- trigeminal neuralgia
- loss of corneal reflex 
- paralysis of mastication muscles
58
Q

What are the features of a 6th cranial nerve palsy?

A

Defective ABduction leading to horizontal diplopia

59
Q

What are the features of a 7th cranial nerve palsy?

A

Flaccid paralysis of the facial muscles
Loss of corneal reflex (efferent)
Loss of taste (anterior 2/3 of tongue)
Hyperacusis

60
Q

Nystagmus and vertigo indicate a lesion to which cranial nerve?

A

VIII

61
Q

What are the features of a lesion to the 9th cranial nerve?

A

Hypersensitive carotid sinus reflex

Loss of gag reflex

62
Q

Lesions to the vagus nerve involve

A

Uvula deviates AWAY from the site of the lesion

Loss of gag reflex

63
Q

What are the features of a lesion to the 11th cranial nerve?

A

Weakness turning head to the contralateral side

64
Q

If the tongue deviates towards the side of the lesion it indicates damage to which cranial nerve?

A

XII

Year 4 - PAN (43 decks)

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