Neuropathies Flashcards
What is a mononeuropathy
Lesions of individual peripheral or cranial nerves
From which nerve roots is the median nerve formed of?
C6-T1
What is the function of the median nerve
Precision grip
Which muscles are innervated by the median nerve
Lumbricals
Opponens pollicis
Abductor pollicis brevis
Flexor pollicis brevis
What syndrome results from compression of the median nerve at the wrist?
Carpal tunnel syndrome
Describe the symptoms of carpal tunnel syndrome
Aching pain in the hand and arm especially at night and paraesthesia in the thumb, index and middle fingers
Relieved by dangling hand over the edge of the bed and shaking it
May be sensory loss and weakness of abductor pollicis brevis and wasting of the thenar eminence
Light touch and 2 point discrimination and sweating may be impaired
What causes carpal tunnel
Swelling or compression of the tunnel - myxoedema, prolonged flexion (colles splint), acromegaly, myeloma, local tumours, rheumatoid arthritis, amyloidosis, pregnancy, sarcoidosis
What tests are requested in carpal tunnel
Neurophysiology - confirms the site of the lesion and severity
Phalens test - Maximal wrist flexion for 1 minute
Tinnels test - tapping over the nerve on the wrist can induce tingling
How is carpal tunnel syndrome treated?
Splinting
Steroid injections
Decompression surgery
What is tarsal tunnel syndrome
Unilateral sole pain, following tibial nerve compression
Which nerve roots form the ulnar nerve
C7-T1
What is the ulnar nerve vulnerable to?
Elbow trauma
What are the signs of ulnar nerve damage
Weakness/wasting of medial wrist flexors, interossei and medial 2 lumbricals (claw hand - more marked wrist lesions with digitorium profundus intact). Hypothenar eminence wasting, weak 5gth digit abduction and 4th, 5th DIP joint flexion, sensory loss over medial 1 and half fingers and ulnar side of the hand
Where does compression of the ulnar nerve most commonly happen?
The epicondylar groove or at the point where the nerve passes between the two heads of flexor carpi ulnaris.
May also less commonly occur at the Guyon’s canal (between pisiform and hamate bones)
How are ulnar nerve mononeuropathies treated?
Rest and avoid pressure on the nerve
Elbow splinting at night time to prevent flexion >60
Splint for the hand may prevent permanent clawing
For chronic neuropathy or if splinting fails, a variety of surgical procedures have been tried. Decompression in situ or medial epicondylectomies are effective in 50% but many will recur
What is the function of the radial nerve?
Opens the fist
Which nerve roots form the radial nerve?
C5-T1
How may the radial nerve become compressed?
Compression against the Humerus
How do you test for radial nerve compression?
Wrist and finger drop with elbow flexed and arm pronated
Sensory loss is variable - the dorsal aspect of the root of the thumb - anatomical snuffbox is more reliably affected
Which muscles are involved in radial nerve compression?
Brachioradialis Extensors Abductor pollicis longus Supinator Triceps
What is the function of the phrenic nerve
Supplies the diaphragm
Which nerve roots form the phrenic nerve
C3,4,5
What do lesions of the phrenic nerve cause?
Orthopnoea with a raised hemidiaphragm on CXR
What causes lesions of the phrenic nerve?
Lung cancer TB Paraneoplastic syndrome Myeloma Thyoma Cervical spondylosis/trauma Thoracic surgery Infections - HZV, HIV, Lyme disease Muscular dystrophy
Describe brachial plexus compression symptoms
Pain/paraesthesia and weakness in the affected arm in a variable distribution
What causes brachial plexus compression?
Trauma Radiotherapy Prolonged wearing of a heavy rucksack Cervical rib Thoracic outlet compression Neuralgic amyotrophy
Which nerve roots form the lateral cutaneous nerve of the thigh?
L2-3
What does compression of the lateral cutaneous nerve of the thigh cause?
Meralgia paraesthetica
Describe the symptoms of meralgia paraesthetica
Anterolateral burning thigh pain
Where is the compression of the lateral cutaneous nerve of the thigh
Entrapment
Which nerve roots form the sciatic nerve
L4-S3
What causes sciatic nerve mononeuropathy
Pelvic tumours
Fractures to the pelvis or femur
What symptoms do lesions of the sciatic nerve cause
Lesions affect the hamstrings and all the muscles below the knee (foot drop) with loss of sensation below the knee laterally
Which nerve roots form the common peroneal nerve
L4-S1
Where does the common peroneal nerve originate
From the sciatic nerve just above the knee
Where is the common peroneal nerve often damaged
Often damaged as it winds round the fibular head
What are the signs of common peroneal nerve damage
Foot drop
Weak ankle dorsiflexion/eversion
Sensory loss over dorsal foot
Where does the tibial nerve originate?
From sciatic nerve just above knee
Which nerve roots form the tibial nerve?
L4-S3
What do lesions of the tibial nerve cause?
Inability to stand on tiptoes (plantarflexion of the foot), invert the foot or flex the toes with sensory loss over the sole
What is mononeuritis multiplex
Involvement of 2 or more peripheral nerves
What causes mononeuritis multiplex
DM Connective tissue disease Vasculitis Sarcoidosis Amyloidosis Leprosy
Which investigation is used to define the anatomic site of lesions in mononeuritis multiplex?
EMG
What are polyneuropathies
Motor and/or sensory disorder of multiple peripheral or cranial nerves
Usually symmetrical, widespread and often worse distally
How are polyneuropathies classified?
Chronicity
Function
Pathology
How are polyneuropathies diagnosed?
History - time course, nature of symptoms, preceding/associated events, travel, alcohol and drug use, STIs and FH
Which conditions result in palpable nerve thickening
Leprosy
Charcot marie tooth
What investigations are done in polyneuropathies
FBC ESR U&Es LFT TSH B12 Electrophoresis ANA ANCA CXR urinalysis LP and specific genetic tests for inherited neuropathies Lead level Antiganglioside antibodies Nerve conduction studies distinguish demyelinating from axonal causes
Describe sensory neuropathy
Numbness, pins and needles, paraesthesia, affects glove and stocking distribution, difficulty handling small objects. Signs of trauma, joint deformation
Diabetic and alcoholic neuropathies are typically painful
Which disorders is sensory neuropathy common in
DM
CKD
Leprosy
Which disorders is motor neuropathy common in
Guillian barre syndrome
Lead poisoning
Charcot Marie Tooth disease
Describe the symptoms of a motor neuropathy
Progressive, weak or clumsy hands, difficulty in walking (falls and stumbling), difficulty breathing (decreased vital capacity)
What are the signs of a motor neuropathy
LMN lesion
Wasting and weakness more marked in the distal muscles of hands and feet (foot or wrist drop)
Reflexes are reduced or absent
Describe the symptoms of cranial nerve polyneuropathy
Swallowing/speaking difficulty
Diplopia
How are polyneuropathies treated?
Involve physio and OT
Foot care and shoe choice are important in sensory neuropathies to minimize trauma
Splinting joints helps prevent contractures in prolonged paralysis
In Guillian barre - IVIG helps
Vasculitis causes - steroids and immunosuppressants
Neuropathic - amitriptyline, duloxetine, gabapentin or pregabalin
What is autonomic neuropathy
Sympathetic and parasympathetic neuropathies may be isolated or part of a generalised sensorimotor peripheral neuropathy
What causes autonomic neuropathy
DM Amyloidosis Guillian Barre Sjogrens HIV Leprosy SLE Toxic Genetic Paraneoplastic
List some signs of sympathetic autonomic neuropathy
Postural hypotension
Decreased sweating
Ejaculatory failure
Horner syndrome
List the signs of parasympathetic autonomic neuropathy
Constipation Nocturnal diarrhoea Urine retention Erectile dysfunction Holmes Adie pupil
List some autonomic function tests
BP - Postural drop of >20/10mmHg is abnormal
ECG - A variation of <10bpm with respiration is abnormal
Cystometry - Bladder pressure studies
Pupils - Instil 0.1% adrenaline dilates if post-ganglionic sympathetic denervation, 2.5% cocaine dilates if normal, 2.5% methacholine constricts if parasympathetic
Paraneoplastic antibodies - AntiHU, antiYO, antiRI, antiamphysin, anti CV2, antiMA2
What does primary autonomic failure occur with?
Alone or as part of multisystem atrophy or with parkinsons disease
