PERIPHERAL NEUROPATHIES Flashcards
What is peripheral neuropathy?
A broad term that refers to any disorder of the peripheral nervous system
Types of peripheral neuropathies?
Polyneuropathy
Radiculopathy
Plexopathy
Mononeuropathy
Mononeuritis multiplex
What is polyneuropathy?
Generalised damage to multiple peripheral nerves
Distal nerves are usually affected most prominently
Often symmetrical e.g. glove and stocking
What is radiculopathy?
Symptoms related to the involvement of a specific spinal nerve root
What is a mononeuropathy?
Damage to a single peripheral nerve
What is mononeuritis multiplex?
Simultaneous involvement of at least 2 separate nerves
Causes of peripheral neuropathy?
Diabetes
Alcoholism
Vitamin B12 deficiency
Guillain-Barré syndrome
Porphyria
Lead poisoning
Charcot-Marie-tooth syndrome
Chronic inflammatory demyelinating polyneuropathy
Diphtheria
Amyloidosis
Uraemia
Leprosy
What are the 3 major mechanisms of peripheral neuropathy?
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
Most common cause of polyneuropathy?
Diabetes mellitus - causes “glove and stocking” distribution
Causes of acute polyneuropathies?
Guillain-Barré syndrome
Vasculitis
Toxins
Critical illness
What typically causes chronic polyneuropathies?
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
What classically causes demyelinating polyneuropathies?
Guillain barre syndrome (a post-infective demyelinating peripheral neuropathy)
Chronic inflammatory demyelinating polyneuropathy
Charcot-Marie tooth disease
What classically causes axonal degeneration polyneuropathies?
Diabetic neuropathy
Alcoholic neuropathy
Toxic neuropathies e.g. lead
Examples of motor polyneuropathies i..e damage to motor nerves
Chronic demyelinating inflammatory polyneuropathy
Guillain-Barré syndrome
Charcot-Marie-tooth syndrome
Examples of sensory polyneuropathies i..e damage to sensory nerves
Diabetes mellitus
Alcohol excess
CKD
Paraneoplastic syndromes
How does diabetes polyneuropathy typically present?
Distal, symmetrical, polyneuropathy with predominant sensory loss
As it progresses, motor function may also be lost
Pathophysiology of nerve damage in diabetes?
Perisstent hyperglycaemia leads to oxidative stress which causes nerve damage
Damage to vasa nervorum also leads to nerve damage
What is the most common hereditary peripheral neuropathy?
Charcot-Marie-tooth disease
What is Charcot-Marie-tooth disease?
A collection of peripheral neuropathies due to an inherited mutation that results in predominantly motor loss
No cure
Onset 5-15
Features of Charcot-Marie-tooth disease?
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
What is Guillain-Barré syndrome?
An immune-mediated demyelination of the PNS often triggered by an infection
Causes progressive, ascending neuropathy
Rare
How does Guillain-Barré syndrome typically present?
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
What most commonly triggers Guillain-Barré syndrome?
Campylobacter jejuni
Investigtaions for Guillain-Barré syndrome?
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
Why can Guillain-Barré syndrome be life threatening?
It can cause autonomic instability and hypoventilation due to respiratory muscle weakness
What is chronic inflammatory demyelinating polyneuropathy?
An acquired immune-mediated cause of polyneuropathy - demyelination of PNS
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
How does vitamin B12 deficiency induced polyneuropathy present?
Distal, symmetrical sensory polyneuropathy
What can happen in severe cases of vitamin B12 deficiency?
Subacute combined degeneration of the spinal cord
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
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
Sensory features of polyneuropathy?
Burning sensation
Paraesthesia
Sensory loss (touch, pain, temperature)
Ataxia
Loss of light touch
Loss of vibration
Loss of proprioception
Motor features of polyneuropathy?
Weakness
Reduced/absent reflexes
Hypotonia
Fasciculations
Muscle atrophy
Muscle cramping
Deformity (e.g. pes cavus, clawing)
What is used to confirm peripheral neuropathy?
Electrodiagnostic tests (electromyography and nerve conduction studies)
Management of polyneuropathy?
Treat underlying cause e.g. avoid alcohol, vitamin B12 replacement, BG control in DM
Neuropathic pain medications
Other Tx but specialist
What can cause an acute, rapidly progressive polyneuropathy with predominant weakness?
Guillain-Barré syndrome
Most common type of radiculopathy?
Lumbosacral radiculopathy L1-S3
Types of radiculopathy?
Cervical C1-C8
Thoracic T1-T12
Lumbosacral L1-S3
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
Myotome for shoulder elevation?
C4
Myotome for shoulder abduction?
C5
Myotome for elbow flexion?
C6
Myotome for elbow extension?
C7
Myotome for thumb extension?
C8
Myotome for finger adduction?
T1
Myotome for hip flexion?
L1/L2
Myotome for knee extension?
L3
Myotome for ankle dorsiflexion?
L4
Myotome for great toe extension?
L5
Myotome for ankle plantar flexion?
S1
Pathophysiology of radiculopathies?
Degenerative changes in spine cause impingement of spinal nerve roots
Importantly spondylosis
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
What are non-skeletal radiculopaties?
Caused by non-skeletal things e.g. DM, infections, inflammatory conditions, vasculitis, mass lesion etc
Aetiology of Lumbosacral radiculopathies?
Degenerative disease of the spine most commonly - often acute in association with movement or trauma
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
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
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
Clinical features of cervical radiculipathy?
Neck, shoulder, arm pain associated with sensory changes and muscle weakness
Diagnosing radiculopathy?
MRT and CT spine
Electrodiagnostic studies
Causes of brachial plexopathy?
Contact sport
Difficult birth - Erbs’ palsy, Klumpke’s paralysis
RTA
Neuralgic amyotrophy
Thoracic outlet syndrome
Causes of mononeuritis multiplex?
Systemic causes
Most commonly vasculitis
Remmeber by WARDS PLC:
Wegeners
Amyloidosis
Rheumatoid arthritis
Diabetes
Sarcoidosis
Polyarteritis nodosa
Leprosy
Cancer
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
Aetiology of mononeuropathies?
Most commonly compression
Transduction e.g. knife injury
Ischaemia e.g. vasculitis, DM
Others: infections, inflammation, radiation, metabolic
Most common cause of median nerve neuropathy?
Carpal tunnel syndrome
Sensory function of median nerve?
Palmar and distal dorsal aspects of lateral 3.5 digits, central palm
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)
Most common upper limb mononeuropathy?
Carpal tunnel syndrome
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
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
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
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
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
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)
Sensory function of ulnar nerve?
Palmar and dorsal aspects of the medial 1.5 digits and adjacent palm
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
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
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
What is claw hand?
Hyperextension of the 4th and 5th metacarpophalangeal joints with flexion at the interphalangeal joints
Sensory function of radial nerve?
Dorsal aspect of lateral 3.5 digits
Skin of posterior and outer surface of arm and forearm
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
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
Symptoms of radial nerve neuropathy?
Wrist drop
Weak finger extension
Weakness in brachioradialis -
Sensory loss and paraesthesia over dorsum of hand
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).
Motor function of axillary nerve?
Deltoid
Teres minor
Lateral head of triceps brachii
Aetiology of axillary neuropathy?
Trauma - shoulder dislocation or proximal humeral fracture
Clinical features of axillary neuropathy?
Sharp sensory loss over lateral shoulder
Weakness may be present
Pain - often due to the aetiology e.g. dislocation
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)
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)
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
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
Sensory function of the tibial nerve?
Skin of posterolateral lower leg (sural nerve), lateral foot and sole of foot
Motor function of the tibial nerve?
Posterior compartment of the foot
Intrinsic muscles of the foot
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
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
What is meralgia paraesthetica?
Pain or sensory loss over the anterolateral thigh
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
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.
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
ABCDE of peripheral neuropathy?
Alcohol
B12 deficiency
Cancer
Diabetes and drugs
Every vasculitis
What palsy causes wrist drop?
Radial nerve palsy
2 common drugs that cause polyneuropathy?
Isoniazid and phenytoin
