Peripheral Neuropathies Flashcards
What is carpal tunnel syndrome
Compression of the median nerve passing through the carpal tunnel in the wrist
What are the nerve roots of the median nerve
C6-T1
What are the two primary causes of compression in Carpal Tunnel Syndrome?
- Swelling of the contents (e.g., tendon sheaths due to repetitive strain).
- Narrowing of the carpal tunnel.
Which branches of the median nerve responsible for sensory innervation of the hand are affected in carpal tunnel syndrome
- recurrent branch
- palmar digital nerves
What are some key risk factors associated with Carpal Tunnel Syndrome? (5)
- Age 40-60
- Female
- High BMI
- Pregnancy
- Diabetes, hypothyroid, acromegaly
Give 3 causes of carpal tunnel syndrome
- rheumatoid arthritis
- oedema
- pregnancy
How does Carpal Tunnel Syndrome typically present in terms of symptom onset and characteristics?
- Onset: gradual, initially intermittent and often worse at night
- numbness, paraesthesia, pain in thumb, index and middle finger
Describe signs that would indicate carpal tunnel syndrome on examination
- weakness of thumb abduction (abductor pollicis brevis) - difficulty opening jars
- wasting of thenar eminence (NOT hypothenar)
- Tinel’s sign: tapping causes paraesthesia
- Phalen’s sign: flexion of wrist causes symptoms
Which part of the hand is typically spared in Carpal Tunnel Syndrome, and why?
The palm is usually spared because the palmar cutaneous branch, responsible for its innervation, does not travel through the carpal tunnel.
What is considered the diagnostic test of choice for Carpal Tunnel Syndrome and what would be a positive finding?
Electromyography (EMG).
* motor + sensory: prolongation of the action potential
What are the management options for Carpal Tunnel Syndrome?
6-week trial of conservative treatments if the symptoms are mild-moderate:
* wrist splints (particularly useful in pregnancy) +/- steroid injections
Severe/ persistent symptoms:
* surgical decompression
What structure is divided in the surgical management of carpal tunnel syndrome
The flexor retinaculum, aka the transverse carpal ligament
What is the most common mononeuropathy
Carpal tunnel syndrome
What are the nerve roots of the radial nerve
C5-T1
What group of muscles does the radial nerve mainly innervate in the hand
motor: Extensor muscles of the hand
sensory: dorsal aspect of the hand (this does not apply to the little finger and part of the ring finger)
How does a radial nerve palsy present
Wrist drop
What are the nerve root of the ulnar nerve
C8, T1
What does the ulnar nerve supply sensory innervation to
medial 1 1/2 fingers (palmar and dorsal aspects)
How would damage of the ulnar nerve at the wrist present
- ‘claw hand’ - hyperextension of the MCPJ and flexion at the distal and proximal IPJ of the 4th and 5th digits
- wasting and paralysis of hypothenar muscles
- wasting and paralysis of intrinsic hand muscles (except lateral two lumbricals)
What are the two most common causes of foot drop
- common peroneal nerve lesion
- L5 radiculopathy
What is peripheral neuropathy
Reduced sensory and/or motor function in peripheral nerves
Give 5 causes of peripheral neuropathy
Alcohol
B12 deficiency
Cancer and CKD
Diabetes and Drugs
Vasculitis
Name 4 drugs that can cause peripheral neuropathy
- Amiodarone
- vincristine
- nitrofurantoin
- metronidazole
What is the typical presentation of peripheral neuropathy
- Numbness and tingling in hands/feet
- Muscle weakness
- Loss of balance
Describe the characteristic distrubution of polyneuropathy pathology
Usually symmetrical and starts distally - glove and stocking distribution
Give 3 pathological mechanisms resulting in peripheral neuropathy
- Demyelination
- Axonal degeneration
- Nerve compression
Give 4 peripheral neuropathies that predominately cause a motor loss
- Guillain Barre - motor
- Charcot Marie Tooth
- lead poising
- diphtheria
Give 4 peripheral neuropathies that predominately cause a sensory loss
- diabetes
- alcoholism (sensory-> motor)
- Vit B12 deficiency
- Uraemia
How are polyneuropathies managed
- Treat the underlying cause
- Physio
- Podiatrist
- Analgesia for neuropathic pain (e.g. amitriptyline, pregabalin)
What is mononeuritis multiplex
group of disorder that involve damage to at least two separate peripheral nerves
What commonly causes mononeuritis multiplex
vasculitis
* Microscopic polyangiitis
* Polyarteritis nodosa
* Eosinophilic granulomatosis with polyangiitis
What is the typical distribution of sensory loss in diabetic neuropathy?
‘Glove and stocking’ distribution, with the lower legs affected first.
What is the first-line treatment for diabetic neuropathy?
Amitriptyline, duloxetine, gabapentin, or pregabalin
- if one doesn’t work, try another
What is used as ‘rescue therapy’ for exacerbations of neuropathic pain in diabetic neuropathy
tramadol
What topical treatment can be used for localized neuropathic pain in diabetic neuropathy (e.g., post-herpetic neuralgia)?
topical capsaicin
How should resistant diabetic neuropathy be managed
pain management clinics
