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PERIPHERAL NEUROPATHIES Flashcards

1
Q

What is peripheral neuropathy?

A

A broad term that refers to any disorder of the peripheral nervous system

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2
Q

Types of peripheral neuropathies?

A

Polyneuropathy
Radiculopathy
Plexopathy
Mononeuropathy
Mononeuritis multiplex

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3
Q

What is polyneuropathy?

A

Generalised damage to multiple peripheral nerves
Distal nerves are usually affected most prominently
Often symmetrical e.g. glove and stocking

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4
Q

What is radiculopathy?

A

Symptoms related to the involvement of a specific spinal nerve root

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5
Q

What is a mononeuropathy?

A

Damage to a single peripheral nerve

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6
Q

What is mononeuritis multiplex?

A

Simultaneous involvement of at least 2 separate nerves

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7
Q

Causes of peripheral neuropathy?

A

Diabetes
Alcoholism
Vitamin B12 deficiency
Guillain-Barré syndrome
Porphyria
Lead poisoning
Charcot-Marie-tooth syndrome
Chronic inflammatory demyelinating polyneuropathy
Diphtheria
Amyloidosis
Uraemia
Leprosy

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8
Q

What are the 3 major mechanisms of peripheral neuropathy?

A

Axonal degeneration - damage to nerve axons. Usually causes symmetrical polyneuropathy with weakness
Wallerian degeneration - damage to nerve axon due to lesion or physical compression. Commonly seen in mononeuropathies with the portion of the nerve dista to compression affected e.g. carpal tunnel syndrome
Demyelination - degeneration of myelin sheath

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9
Q

Most common cause of polyneuropathy?

A

Diabetes mellitus - causes “glove and stocking” distribution

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10
Q

Causes of acute polyneuropathies?

A

Guillain-Barré syndrome
Vasculitis
Toxins
Critical illness

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11
Q

What typically causes chronic polyneuropathies?

A

Diabetes mellitus
CKS - caused by uraemia. Very common
Herediatary neuropathies
Alcohol excess
HIV/AIDs
Neoplasia - particuarly myeloma - caused by infiltration or paraneoplastic
Lupus
Iatrogenic - isoniazid and phenytoin

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12
Q

What classically causes demyelinating polyneuropathies?

A

Guillain barre syndrome (a post-infective demyelinating peripheral neuropathy)
Chronic inflammatory demyelinating polyneuropathy
Charcot-Marie tooth disease

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13
Q

What classically causes axonal degeneration polyneuropathies?

A

Diabetic neuropathy
Alcoholic neuropathy
Toxic neuropathies e.g. lead

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14
Q

Examples of motor polyneuropathies i..e damage to motor nerves

A

Chronic demyelinating inflammatory polyneuropathy
Guillain-Barré syndrome
Charcot-Marie-tooth syndrome

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15
Q

Examples of sensory polyneuropathies i..e damage to sensory nerves

A

Diabetes mellitus
Alcohol excess
CKD
Paraneoplastic syndromes

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16
Q

How does diabetes polyneuropathy typically present?

A

Distal, symmetrical, polyneuropathy with predominant sensory loss
As it progresses, motor function may also be lost

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17
Q

Pathophysiology of nerve damage in diabetes?

A

Perisstent hyperglycaemia leads to oxidative stress which causes nerve damage
Damage to vasa nervorum also leads to nerve damage

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18
Q

What is the most common hereditary peripheral neuropathy?

A

Charcot-Marie-tooth disease

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19
Q

What is Charcot-Marie-tooth disease?

A

A collection of peripheral neuropathies due to an inherited mutation that results in predominantly motor loss
No cure
Onset 5-15

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20
Q

Features of Charcot-Marie-tooth disease?

A

Predominantly motor peripheral neuropathy!!

Muscle weakness in feet, ankles and legs
There may be a history of frequently falling or sprained ankles
Foot drop + Pes cavus+ Hammer toes + high stepping gait
Peripheral sensory loss
Distal muscle atrophy “inverted champagne bottle legs”
Hyporeflexia
Hypotonia
Fatigue

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21
Q

What is Guillain-Barré syndrome?

A

An immune-mediated demyelination of the PNS often triggered by an infection
Causes progressive, ascending neuropathy
Rare

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22
Q

How does Guillain-Barré syndrome typically present?

A

Often 2-4 weeks post-infection

Initial symptoms: back/leg pain in the initial stages

Others:
Rapidly progressive, symmetrical, ascending limb weakness
Paraesthesia in lower limbs and hands - mild
Issues with balance and coordination
Reflexes reduced or absent

Can affect chest causing respiratory issues
Can be cranial nerve involvement - diplopia, facial nerve palsy, oropharyngeal weakness
Autonomic involvement can occur - urinary retention and diarrhoea

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23
Q

What most commonly triggers Guillain-Barré syndrome?

A

Campylobacter jejuni

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24
Q

Investigtaions for Guillain-Barré syndrome?

A

Nerve conduction studies - will show decreased motor nerve conduction velocity due to demyelination, prolonged distal motor latency, increased F wave latency

Lumbar puncture - will show rise in protein with normal WBC

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25
Why can Guillain-Barré syndrome be life threatening?
It can cause autonomic instability and hypoventilation due to respiratory muscle weakness
26
What is chronic inflammatory demyelinating polyneuropathy?
An acquired immune-mediated cause of polyneuropathy - demyelination of PNS
27
Presentation of chronic inflammatory demyelinating polyneuropathy?
Symmetrical sensorimotor polyneuropathy (motor symptoms predominate) in proximal and distal muscle groups Can be slow progressive, acute or cause radiculopathies
28
How does vitamin B12 deficiency induced polyneuropathy present?
Distal, symmetrical sensory polyneuropathy
29
What can happen in severe cases of vitamin B12 deficiency?
Subacute combined degeneration of the spinal cord
30
What is Subacute combined degeneration of the spinal cord?
Impairment of the dorsal columns, lateral corticospinal tracts and spinocerebellar tracts due to vitamin B12 deficiency
31
Features of Subacute combined degeneration of the spinal cord?
dorsal column involvement: distal tingling/burning/sensory loss is symmetrical and tends to affect the legs more than the arms impaired proprioception and vibration sense lateral corticospinal tract involvement: muscle weakness, hyperreflexia, and spasticity upper motor neuron signs typically develop in the legs first brisk knee reflexes absent ankle jerks extensor plantars spinocerebellar tract involvement: sensory ataxia → gait abnormalities positive Romberg's sign
32
Sensory features of polyneuropathy?
Burning sensation Paraesthesia Sensory loss (touch, pain, temperature) Ataxia Loss of light touch Loss of vibration Loss of proprioception
33
Motor features of polyneuropathy?
Weakness Reduced/absent reflexes Hypotonia Fasciculations Muscle atrophy Muscle cramping Deformity (e.g. pes cavus, clawing)
34
What is used to confirm peripheral neuropathy?
Electrodiagnostic tests (electromyography and nerve conduction studies)
35
Management of polyneuropathy?
Treat underlying cause e.g. avoid alcohol, vitamin B12 replacement, BG control in DM Neuropathic pain medications Other Tx but specialist
36
What can cause an acute, rapidly progressive polyneuropathy with predominant weakness?
Guillain-Barré syndrome
37
Most common type of radiculopathy?
Lumbosacral radiculopathy L1-S3
38
Types of radiculopathy?
Cervical C1-C8 Thoracic T1-T12 Lumbosacral L1-S3
39
What is a dermatome and a myotome?
Myotome: a collection of muscles innervated by a single spinal nerve root Dermatome: an area of skin supplied by a single spinal nerve root
40
Myotome for shoulder elevation?
C4
41
Myotome for shoulder abduction?
C5
42
Myotome for elbow flexion?
C6
43
Myotome for elbow extension?
C7
44
Myotome for thumb extension?
C8
45
Myotome for finger adduction?
T1
46
Myotome for hip flexion?
L1/L2
47
Myotome for knee extension?
L3
48
Myotome for ankle dorsiflexion?
L4
49
Myotome for great toe extension?
L5
50
Myotome for ankle plantar flexion?
S1
51
Pathophysiology of radiculopathies?
Degenerative changes in spine cause impingement of spinal nerve roots Importantly spondylosis
52
What are skeletal radiculopathes?
Degenerative spondylotic changes in the intervertebral discs and facet joints = impingement of spinal roots = radiculopathy Or disc herniation Commonly there is an inciting event such as falls, bending over, trauma
53
What are non-skeletal radiculopaties?
Caused by non-skeletal things e.g. DM, infections, inflammatory conditions, vasculitis, mass lesion etc
54
Aetiology of Lumbosacral radiculopathies?
Degenerative disease of the spine most commonly - often acute in association with movement or trauma
55
Clinical features of Lumbosacral radiculopathy?
Radicular pain Sensory symptoms e.g. paraesthesia or anaesthesia Muscle weakness in affected myotome Most commonly affects L5 so acute back pain that radiates down the lateral aspect of the leg to the foot, sensory changes over lateral aspect of the lower leg and dorsum of foot, weakness in foot dorsiflexion big toe extension and foot inversion/eversion
56
Sciatica vs radiculopathy?
Sciatica is a non-specific clinical description of pain affecting the back or leg. The sciatic nerve is formed by a combination of nerve roots L4, L5, S1, S2, S3 Sciatica is a clinical manifestation of Lumbosacral radiculopathies however the term is used generally to reference lower back pain that may be non-radicular in origin so its important to determine exactly what the patient means when they say they have sciatica
57
Clinical features of thoracic radiculopathy?
Radicular pain that starts in the back and radiates around the chest in a linear pattern Paraesthesia and anaesthesia in the same dermatology Sudden back movements or increases in thoracic pressure may precipitate Radicular pain
58
Clinical features of cervical radiculipathy?
Neck, shoulder, arm pain associated with sensory changes and muscle weakness
59
Diagnosing radiculopathy?
MRT and CT spine Electrodiagnostic studies
60
Causes of brachial plexopathy?
Contact sport Difficult birth - Erbs’ palsy, Klumpke’s paralysis RTA Neuralgic amyotrophy Thoracic outlet syndrome
61
Causes of mononeuritis multiplex?
Systemic causes Most commonly vasculitis Remmeber by WARDS PLC: Wegeners Amyloidosis Rheumatoid arthritis Diabetes Sarcoidosis Polyarteritis nodosa Leprosy Cancer
62
Investigtaions to determine the cause of peripheral neuropathies?
FBC: may show macrocytosis Renal function: to assess for CKD HbA1c: to assess for DM TFT: to assess for hypothyroidism Immunological e.g. protein electrophoresis for myeloma Autoimmune tests for connective tissue diseases Virology: hepatitis C, syphilis, Lyme disease Heavy metals: copper na clear Vitamins: B12, folate, pyridoxine Imaging: MRI, CT US Nerve biopsy is rarely performed Genetic testing for hereditary causes
63
Aetiology of mononeuropathies?
Most commonly compression Transduction e.g. knife injury Ischaemia e.g. vasculitis, DM Others: infections, inflammation, radiation, metabolic
64
Most common cause of median nerve neuropathy?
Carpal tunnel syndrome
65
Sensory function of median nerve?
Palmar and distal dorsal aspects of lateral 3.5 digits, central palm
66
Motor function of median nerve?
Anterior forearm In the hand it innervates the thenar eminence and 2 lateral lumbricals - remmeber as 2LOAF (2 lateral lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis)
67
Most common upper limb mononeuropathy?
Carpal tunnel syndrome
68
Causes of carpal tunnel syndrome?
idiopathic pregnancy Obesity Endocrine - hypothyroidism and acromegaly oedema e.g. heart failure lunate fracture rheumatoid arthritis They cause compression of the median nerve in the carpal tunnel
69
Symptoms of carpal tunnel syndrome?
Pain/pins&needles in thumb, index and middle finger Symptoms may ascend Patient shakes hand to obtain relief - classically at night Weakness of thumb abduction
70
Examination findings for carpal tunnel syndrome?
Weakness of thumb abduction Wasting of thenar dominance Tinel’s sign - tapping causes paraesthesia Phalen’s sign - flexion of wrist causes symptoms
71
How to do the phalen manoeuvre?
ask the patient to hyperflex both hands and hold dorsal surfaces together. This should be held for 1 minute. A positive test for carpal tunnel syndrome leads to pain and/or paraesthesia in the distribution of the median nerve
72
How to do the tinel test?
percuss over the median nerve just proximal to the carpal tunnel. A positive test for carpal tunnel syndrome leads to pain and/or paraesthesia in the distribution of the median nerve
73
Management of carpal tunnel syndrome?
6 week trial of conservative treatment if symptoms are mild to moderate - corticosteroids injection and wrist splints at night If severe symptoms or symptoms persists then surgical decompression can be done (flexor retinaculum division)
74
Sensory function of ulnar nerve?
Palmar and dorsal aspects of the medial 1.5 digits and adjacent palm
75
Motor function of ulnar nerve?
2 muscles of the anterior forearm: Flexor carpi ulnaris and flexor digitorum profundus Motor innervation to all intrinsic muscles of the hand except the LOAF muscles
76
Causes of ulnar neuropathy?
THINK ELBOW Compression at elbow (most commonly) or wrist as nerve travels through cubical tunnel in elbow and guyon’s canal at the wrist Causes include trauma, prolonged elbow flexion, direct pressure i.e. leaning, osteophyte formation due to arthritis, prolonged use of hand tools
77
Clinical features of ulnar neuropathy?
Sensory loss or paraesthesia over little finger and medial side of ring finger Hand weakness Muscle wasting over hypothenar eminence or interossei muscles Claw hand deformity if severe
78
What is claw hand?
Hyperextension of the 4th and 5th metacarpophalangeal joints with flexion at the interphalangeal joints
79
Sensory function of radial nerve?
Dorsal aspect of lateral 3.5 digits Skin of posterior and outer surface of arm and forearm
80
Motor function of radial nerve?
The radial nerve has important function for several muscles in the arm: Triceps brachii Extensor carpi radialis longus Brachioradialis Anconeus Extensor muscles of forearm
81
Causes of radial neuropathy?
Mid-humeral fractures (radial nerve is particularly vulnerable to compression as it wraps around the posterior surface of the mid-humerus along the spiral groove) Saturday night palsy - place arm over chair for a long time leading to pressure injury - usually when drunk
82
Symptoms of radial nerve neuropathy?
Wrist drop Weak finger extension Weakness in brachioradialis - Sensory loss and paraesthesia over dorsum of hand
83
Sensory function of axillary nerve?
small oval-shaped patch of cutaneous skin on the lateral aspect of the shoulder. This is often known as the ‘regimental badge area’. It also carries sensory information from the glenohumeral joint (i.e. the shoulder joint).
84
Motor function of axillary nerve?
Deltoid Teres minor Lateral head of triceps brachii
85
Aetiology of axillary neuropathy?
Trauma - shoulder dislocation or proximal humeral fracture
86
Clinical features of axillary neuropathy?
Sharp sensory loss over lateral shoulder Weakness may be present Pain - often due to the aetiology e.g. dislocation
87
Sensory and motor functions of the superficial peroneal nerve?
Sensory: skin over the anterolateral aspect of the lower limb and dorsum of the foot Motor: muscles in the lateral compartment of the leg (fibularis longus and fibularis brevis)
88
Sensory and motor functions of the deep peroneal nerve?
Sensory: first dorsal webspace (i.e. between the big and second toe) Motor: muscles in the anterior compartment of the leg (Tibialis anterior, extensor hallucis longus, extensor digitorum longus)
89
What causes common peroneal neuropathy?
Trauma/injury to the knee External compression e.g. tight splint, tight plaster, habitual leg crossing Prolonged pressure e.g. immobility
90
Clinical features of common peroneal neuropathy?
Foot drop - due to weakness of dorsiflexion at ankle Sensory loss of paraesthesia over dorsum of foot and lateral shin
91
Sensory function of the tibial nerve?
Skin of posterolateral lower leg (sural nerve), lateral foot and sole of foot
92
Motor function of the tibial nerve?
Posterior compartment of the foot Intrinsic muscles of the foot
93
Aetiology of tibial neuropathy?
Compression as the nerve passes under the transverse tarsal ligament in the ankle e.g. fracture or dislocation of ankle Others: inflammatory arthritis, tumours, large bakers cyst
94
Clinical features of tibial nerve neuropathy?
Paraesthesia, pain and numbness over the sole of the foot - worse at night or after prolonged standing Tinels test positive Atrophy of intrinsic muscle sof foot in chronic cases Foot deformities due to this weakness- pes planus, pronated foot, abnormal gait
95
What is meralgia paraesthetica?
Pain or sensory loss over the anterolateral thigh
96
What causes Meralgia paraesthetica?
Neuropathy of the lateral femoral cutaneous nerve (a small sensory nerve supplying cutaneous tissue over the anterolateral portion of the thigh) Commonly due to entrapment as the nerve passes under the inguinal ligament Risk factors: diabetes, mellitus, obesity, older age, pregnancy, tense ascites, trauma, surgery, sports e.g. gymnastics Can also be iatrogenic after surgical procedure or result from a neuroma
97
Symptoms of Meralgia paraesthetica?
Burning, tingling, coldness, or shooting pain Numbness Deep muscle ache Symptoms are usually aggravated by standing, and relieved by sitting They can be mild and resolve spontaneously or may severely restrict the patient for many years.
98
Which drugs are most likely to cause peripheral neuropathy?
some types of chemotherapy for cancer, especially for bowel cancer, lymphoma or myeloma some antibiotics, if taken for months, e.g. metronidazole or nitrofurantoin phenytoin if taken for a long time amiodarone and thalidomide
99
ABCDE of peripheral neuropathy?
Alcohol B12 deficiency Cancer Diabetes and drugs Every vasculitis
100
What palsy causes wrist drop?
Radial nerve palsy
101
2 common drugs that cause polyneuropathy?
Isoniazid and phenytoin

NEUROLOGY (16 decks)

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